SB 349
.K8 The University of Chicago
‘Copy 1
VEGETATION AND REPRODUCTION WITH
SPECIAL REFERENCE TO
THE TOMATO
A DISSERTATION
SUBMITTED TO THE FACULTY
OF THE OGDEN GRADUATE SCHOOL OF SCIENCE
IN CANDIDACY FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY
DEPARTMENT OF BOTANY
BY
EZRA JACOB KRAUS anp HENRY REIST KRAYBILL
Private Edition, Distributed By
THE UNIVERSITY OF CHICAGO LIBRARIES
CHICAGO, ILLINOIS
Reprinted from
STATION BULLETIN 149, OREGON AGRICULTURAL COLLEGE
January 1918
The University of Chicago
VEGETATION AND REPRODUCTION WITH
SEC TAL RE PERENCE LO
THE TOMATO
A DISSERTATION
SUBMITTED TO THE FACULTY
OF THE OGDEN GRADUATE SCHOOL OF SCIENCE
TN CANDIDACY FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY
DEPARTMENT OF BOTANY
BY
EZRA JACOB KRAUS anp HENRY REIST KRAYBILL
Private Edition, Distributed By
THE UNIVERSITY OF CHICAGO LIBRARIES
CHICAGO, ILLINOIS
Reprinted from
STATION BULLETIN 149, OREGON AGRICULTURAL COLLEGE
January 1918
Station Bulletin 149
January, 1918
Oregon Agricultural College
Experiment Station
Vegetation and Reproduction with
Special Reference to the Tomato
BY
E. J. KRAUS and H. R. KRAYBILL
CORVALLIS, OREGON
The regular bulletins of the Station are sent free to the residents of Oregon who request them
STATION STAFF
Board of Regents of the Oregon Agricultural College and
Experiment Station
Hon. J. Ke Wearnmrrorn, President -.. t:.5-(--ereh ce ermacrcs tea eae ae eG Albany
Fees IN (aul gl Voyensnoh SNOW ICTA facnisoos pe ugppecesouuy auEcncuTo ro sodpavaknoapaacone as ase s6 00) Corvallis
FETT Omd Gla Ua 20'S aia) aed ase HL Baga ce bce weap Sonoda Cuasmon apg bak moe ieee Sagas Asn BSST McCoy
ELON? die RDHBON MYRRSq,.0 0002 one rece cen ca) aia es eae et ee gee ees Portland
Hon. James WitHYCOMBE, Governor AAA ANH TC ond cule anapa cr aGear oddone ASSN Salem
Hon. J. A. CHURCHILL, State Superintendent of Public Instruction.............-+++-.+++0+> Salem
WH OuGomis Secretary. of Statens. er site ce eye nical eae penetra clad Cina a Salem
PENCE, Master of the State Grange.......------+---+-ssssssse trees Oregon City
SORT. (CHIRAL 181, We hedcnsso.chs0 2800 Ss eguunnoDaddtosemuDGEsameRDooSeds Fanea5e0R POLE Portlan
fee nen nea Soap adaga Gp cooR sds do LOOatasaO0 34 La Grande
TG NE MAIS SAWIOO DCOGK. a yee eile cai eee alsa oe Corvallis
TEIGSG Jab, Wong Dorm labs AVI IN ono oe soso de oopeascunococeconeceoresoadaaneoedanmoalsose sa] 5S0 5 Wellen
ETN GM CORNWALL Ar ecm ee eee ee aA ete In aa ne Portland
Administration
We Palceaith a DJs elolOn snpasupysadaonascpasen naman pequdaDecocagzososgpopoarbadsnesodeh Ser" President
JA IzL Glas th aeID loan bey ona dooeacduandosneroocanadoanoan {ang dens bos SODA ESCO SEO. Director
TDM Ba SW ase ABE Seay. Wel Snes cosnur doo cop asanemobecanpAsshonghednesoo > SauPC.t phe ee Ade Editor
MAGEAWORKINGR Go nee eeer Sere er ence or ees iene rnin iersscc ra ieee Secretary to Director
Department of Animal Husbandry
BT ROTTER Se eee sae ria see ie etotets tote ole et one eictes ole hace rem Chief in Animal Husbandry
TDR las poisn UO Su isin bocce couepEooondomsc sso Ono uODD IU OGr: Assistant Professor in Animal Husbandry
OP WEN fanclon plan isle suaceodu sea AnesoouboansodsDDUD OUTED anOH Sou aoL Assistant in Animal Husbandry
Department of Bacteriology
T. D. Beckwith, M. Si.c-.5-2-- sos ecte ec: ee NECA Sree ead Chief in Bacteriology
Department of Botany and Plant Pathology
TEs 18 1sVwaseh IM bsho, cuobeeeanboassquerseposD os asacunecty SoD: Chief in Botany and Plant Pathology
WIL ADS Nilo Wig tsienoesscososceooedongUssobooC Research Assistant in Botany and Plant Pathology
W. M. Arwoop, Pu. D..........:.+:-0:+5+---+-4 Associate Professor in Botany and Plant Pathology
W. EL LAWRENCE, B. S.....5..-02-00- ees ones Assistant Professor in Botany and Plant Pathology
(Oe IN. Onapaisis Ne Nhe poo oneccoucnodcpsocmodes ‘Assistant Professor in Botany and Plant Pathology
Department of Agricultural Chemistry
Tis We JNA WT el Bwisin pouppeadonanocodGeocuscodcdcoCEnERS HOD SS aS on 5s Chief in Agricultural Chemistry
18% 18hy INGEN TOKNA ey ilshodosocsaqcboboolconoceno ange 2 Research Assistant in Agricultural Chemistry
Teh (Gs iitnuaiie By Sonn ceogossouspodoascddodamepsposor Research Assistant in Agricultural Chemistry
N/a yuls tannic [Ses EnapouodssonsondcosDoUc Dads CoapeH Research Assistant in Agricultural Chemistry
Department of Dairy Husbandry
TDs WE, ISNA RANG I Gp IN yaneane Seen assondboadeh cocoa sun poapESOp ORE COR aE RE Chief in Dairy Husbandry
Wi, 1D), Chitosan, INE IS) peaooscsusne doonoss pad opoonUcDossS Assistant Professor in Dairy Husbandry
12 i Daarol N= b Jeena ob eoous pened cbObD ab UdosnoSs OSDLOK GNC cule Assistant in Dairy Manufacturing
Te NW NEE aN bya is apepocbonccoocodso na pseconssncEe DSO SMuaE Pood ‘Assistant in Dairy Production
Department of Domestic Science
ltahipal Graal ane Cane dee uae smonsoodconsadeosuSooNCodou Chet Research Assisiant in Domestic Science
Department of Drainage and Irrigation
Vi ableton pot Til bs keh dan Be ep enr doobodeodonne shod opacomaSgRDOOUr or Chief in Drainage and Irrigation
Department of Entomology
OA GRAS ATi Sheena eee sa ecnoncaosodadnoeo sUaDOM Ono pO) cag vRnanG Og ey: Chief in Entomology
Anibal fol rev Giisborriwacyy Joy tSooon DocasajoonnonurouDDSocoOnIaso ou Do GoD Research Assistant in Entomology
THe JN, IbTHsaTOIDS WWD Vo pop doco no pana nemoc ous ocUOOoDOOUDDSSAnES HUGE Research Assistant in Entomology
leno ve CHInDS Ba Shores see ee bee er eiecirasts Entomologist, Hood River, Acting Superintendent
Department of Farm Crops
(GWU hair aed oi Soe deaeeaadddabaas dodndsnon ald soc door so o0n Hen TOBR AEE See Ie Chief in Farm Crop
18 hae iSters ainsi ls SB bgc abe oconanbnseuvadundomnooodooDbarcaDaa ego eo Expert in Vetch Investigations
Jy Sienapo ty USpN isaae go neunon me ooadarooboucupuoe so bO CORO OG HDS Assistant Professor in Farm Crops
Department of Horticulture
(Ol, 1h Jbpayaity IN Ip Sb ape oompovoseabodsocdssoconOSHOareDbHOr Vice-Director, and Chief in Horticulture
Ni faalg2. | GUSTIN TDI ikl Sin gnome peenndddenpoondsdscopcs coodbe do ncoR Aten A yop SS ISOS IA SA Pomologist
IDE IB acGai Gabi Ds0id Danes sn ddassacnnedpoccosenbouoD OD OonD On Sct Professor of Horticultural Research
RCMB OU OUETS Be Serene cre tees ee ere Fa eel ele Ce hte cna rae Professor of Olericulture
IDE 1, ancora Uy Bnpnaodooosoper eopsboorsu coo o00GeR0EE Assistant Professor of Horticultural Products
TN 1 TBYNite eb ND SRE Bu anepodendcseduDosdnecbuoD ga mmccTop OUR AD RO Research Assistant in Horticulture
GUG@HBROWNGB oN Socceroos eists ety rrraos Research Assistant in Horticulture, Hood River
Department of Poultry Husbandry
ANIES) DRYDEN oo ce ate ac oe rere tosets eerie mie lorasbetere ee etal eee chreaa Chief in Poultry Husbandry
Department of Soils and Farm Management ’
1Sb) ID tors apenas hong ads one dnoconacmdaneeDbutDdaituboc ana Tt Chief in Soils and Farm Management
(ChAT Shap ant oul Shy ge ene pRoasdd odopapope oon oop DbamEa bE Oa INar Spo EEN Ss Associate Professor in Soils
Department of Veterinary Medicine
12a Re Shaver aD SAVigih' Geverneer Sens badnvoUoDencousomnboos soca enannalcs Chief in Veterinary Medicine
Rospert WITHYCOMBE, B.5S......-.------ Supt. Eastern Oregon Branch Experiment Station, Union
D. E. StepHens, M.S.............--665 .Supt. Sherman County Dry-Farm Br. Exp. Station, Moro
Te) AWG Nannon NiinSbosooooddeccasoocoscoo cDN Supt. Umatilla Branch Experiment Station, Hermiston
1H. (Cpeboretea eos pomonbasnonpooens oodDocce Supt. Southern Oregon Branch Exp. Station, Talent
L. R. BrerrHavrt, B. S........----2eee eee Supt. Harney Co. Branch Experiment Station, Burns
A. BE. ENGBRETSON, B.S.....-..--eeeeeer ees ‘Act. Supt. John Jacob Astor Br. Exp. Station, Astoria
*On leave of absence.
TABLE OF CONTENTS
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(Grermnie alles See eee en late ses Aenean hates Sp ae Mac recites nate tena tayo Mar Secen ars 38
Samplingsand preservation of samples... 2.00406 3.45. w sata 38
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FOREWORD
This bulletin is one in the series of those issued in connection with the in-
vestigations on the problem of pollination of the pomaceous fruits which have
been in progress at this Station for a number of years. Most of the ideas ex-
pressed are the direct result of such studies. After having made extended
morphological and histological investigations, and finding in them, as yet,
little more than a confirmation of the already well-recognized microscopic sit-
uations, it appeared that physiological and bio-chemical investigations must
be made to establish a true basis for determination of the factors involved,
particularly so when the variable and conflicting evidence of a wide range of
experiments was considered. With this general idea in mind, Mr. E. J. Kraus
was granted a leave of absence in order to continue these investigations while
studying in the Department of Botany at the University of Chicago. While
he was there, it was possible for him to secure in this work the cooperation of
Mr. H. R. Kraybill, who was at that time on leave of absence from the Depart-
ment of Agricultural Chemistry of the Pennsylvania State College. This bulletin
is the result of the cooperative efforts of Messrs. Kraus and Kraybill and
has been submitted by them in fulfillment of the thesis requirements for the
degree of Doctor of Philosophy from the University of Chicago.
Because of the nonavailability of fruit trees, it was necessary in carrying
out the studies, to use some other plant. After considering a wide range of
species, the tomato was finally selected, since in its general responses in vege-
tation and fruit setting it accords very closely to those observed in apple and
pear trees; and moreover, with few exceptions, the plants are self fertile under a
wide range of environmental modifications, but can be rendered barren or
sterile.
C. I. Lewis,
Chief, Division of Horticulture.
Hegetation and Reproduction with
Special Reference to the Comain
(Lycopersicum esculentum Mill.)
By E. J. Kraus and H. R. Kraysiuu
INTRODUCTION
The question of the differentiation of sexually reproductive parts, blooming,
fruit setting, and fruit development has been a topic for investigation and
speculation for many years. It has been approached in many different ways.
Much has been learned; many facts remain unexplained and without correla-
tion; not a few facts are still to be established. More recently the influences
of self- and cross-pollination in various plants, particularly those of com-
mercial importance, have been taken up for serious study. The whole subject
is so vast that these studies must naturally concern themselves with special
phases of the problem. It has been necessary to do much simple testing
throughout a wide field and variety of plants under varying conditions.
Morphological, anatomical, and histological investigations have been and
still are necessary for the determination of the exact structures involved.
Physiological studies must be extended and utilized in order to arrive at any
final explanation of the conditions observed or the determination of their
means of regulation. Not one of these types of study can be spared as a
means of finally bringing the problem within the limits of practice.
More specifically the work with plants of commercial importance has
dealt and must still deal with the determination of so-called affinities or
compatibilities between plants in so far as fruit setting and seed development
are concerned. This naturally has led to an investigation of the parts and
processes concerned in fertilization, seed and fruit development, and their
interrelation. While many of the results have simply furnished microscopic
details of what was already well known macroscopically, yet some facts were
added. There is still a wide opportunity for such work. Some insight into
the mechanism and processes of abscission has been gained; much more is
needed. The value of physiological studies can scarcely be over emphasized,
but these of necessity must be so detailed and thorough, considering the
multiplicity of factors involved, that at best individual investigations can
cover only restricted fields.
Pending the more definite working out of details through any one or all of
the foregoing methods, the very fertile field of established agricultural and
horticultural practice is open for study. Whether such practices are good or
bad from the commercial viewpoint, they furnish many suggestions that
5
may be correlated and interpreted in connection with the available results of
controlled investigations. The material reported and the viewpoints expressed
in this paper embody some of the results of such a study undertaken in con- °
nection with the fruit-setting problem, in so far as it concerns higher plants.
Four general conditions of the relation of nitrates, carbohydrates, and
moisture within the plant itself, and the responses apparently correlated
therewith, will be discussed. These are:
(1) Though there be present an abundance of moisture and mineral
nutrients, including nitrates, yet without an available carbohydrate supply
vegetation is weakened and the plants are non-fruitful;
(2) An abundance of moisture and mineral nutrients, especially nitrates,
coupled with an available carbohydrate supply, makes for increased vegeta-
tion, barrenness, and sterility;
(3) <A relative decrease of nitrates in proportion to the carbohydrates
makes for an accumulation of the latter; and also for fruitfulness, fertility,
and lessened vegetation.
(4) A further reduction of nitrates without inhibiting a possible increase
of carbohydrates, makes for a suppression both of vegetation and fruitfulness.
This analysis is not intended, in any way, to convey the idea that only
these compounds—carbohydrates, nitrates, and moisture—are concerned in
vegetation and fruitfulness, but that the study in hand is principally con-
cerned with them and the response resulting from an alteration of their relative
proportions within the plant. It would be extremely difficult also to draw
rigid lines between any particular class and the one next to it; since they
intergrade insensibly one into another and yet, generally speaking, are
recognizably distinct.
GENERAL DISCUSSION
In any discussion concerning vegetation and fruit setting, it is necessary
to keep clearly in mind their interrelation as plant functions. One is prone
to think of them as diametrically opposite expressions, whereas in fact no
sharp and clear line can be drawn between them. There is perhaps a pos-
sibility of drawing a definite line of division between the production of true
gametes and vegetation, but there are plenty of cases on record, in which
seeds, and particularly fruits, are regularly produced with scarcely even an
approach at gamete differentiation. It is granted that fruits are intimately
associated with gametic reproduction in the higher plants, but that does not
in any sense remove them from the category of vegetative structures. The
most that can be claimed is that they are merely specialized structures,
occupying a position between truly vegetative organs and gametes, and that
in discussing them they must be regarded from both points of view.
It is really necessary that this situation be brought out clearly, since in
some of the work dealing with the question of fertility and sterility in plants
the conclusions are based on an inspection and record of the number of fruits
produced rather than the number of viable seeds or preferably seedlings.
This point is discussed in greater detail later.
6
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A study of the comparative morphology of fruits reveals the fact that
widely different structures may enter into the conspicuous or edible portion.
The parts which may be concerned are axis, bract, pedicel, torus, calyx,
petal (rarely), stamen, and carpel. The mature fruit may consist of any
particular one, several, or all these parts separated and distinct, or firmly
united. One structure or group of structures may develop out of all pro-
portion to others, resulting in the wonderful range of fruit types already well
known. But the point is, that whatever the nature or whatever the appear-
ance of the fruit, it is a specialized vegetative part generally concerned with
the production of seed; this seed in itself actually may be an entirely sporo-
phytic structure.
There is a wide range in the external expression of the capacity of plants
to produce fruits and seeds. There are many varieties of plants, representing
wide ranges of families and orders, which produce mature fruits entirely
without seeds or in some cases functional ovules, while other varieties within
the same genus under identical conditions fail to mature fruits unless embryo-
containing seeds are present. To discuss this situation two classes are made.
I. Barren forms are those which entirely fail to produce flowers or fruit-
like structures, shed such structures at an early period, or fail to develop
them to maturity.
II. Fruitful forms are those which do produce and mature fruits, whether
such fruits do or do not contain seeds.
There are three types of this condition. (1) The first is best designated
by the term parthenocarpy, in which there is a development of the fruit wholly
independent of any pollination of the stigmas or fertilization of the ovules.
As a matter of fact, in many parthenocarpic forms, development within the
ovules does not proceed beyond the mother-cell stage. The term refers to
the development of fruit structures other than the seeds. (2) The second
class comprises forms in which development of the flesh proceeds only if
pollination of the stigmas has taken place. Usually also fertilization takes
place, but there is an abortion of the embryos at a more or less advanced
stage. In spite of the fact that seed formation is thus eliminated, fruit de-
velopment continues to a normal, though frequently early, maturity. (38) The
third type of development is that following normal pollination, fertilization,
and seed development or that occurring in apogamous forms. The terms
sterile and fertile have at times been confused with, and used in place of,
barren and fruitful. In this discussion these terms will be used in the limited
sense as already suggested by Kraus (28).
Sterile forms are those which produce no viable seeds, either because of
failure of gametic union, abortion of the embryo, or embryos resulting from
a gametic fusion. Fertile forms are those which produce viable embryos
resulting from a gametic union.
The terms fertile and fertility are extraordinarily confused in the literature.
On the one hand they have been used to designate a condition of fruitfulness
with little or no regard for the idea of production of new individuals, while
8
Fig. 2.—Vegetative fruits of the d’Anjou pear, collected at Corvallis, Oregon. Such fruits were
of fairly common occurrence at the tips of vigorously vegetative branches in the fall of 1917. These
fruits were entirely vegetative structures with well-defined growing points; many intermediate forms
were also found.
Fig, 3.—Fruits of the Bartlett pear. Though markedly deformed, they are truly reproductive in type.
on the other hand they have served to convey the idea of great reproductive
capacity frequently without regard to the manner or method of the origin of
the offspring. Again, an organism has been considered fertile if it produced
new individuals through seed, without reference to the exact origin of the
embryos. In the present discussion, the term fertility is limited to the
production of viable embryos through the union of true gametes. This
limited view really excludes a number of seminally reproductive forms, in
fact all cases of apogamy and vegetative apogamy and parthenogenesis, using
the term parthenogensis to mean the development of an embryo from a haploid
egg without fusion with a male nucleus. Whether this truly occurs in plants
is still a matter for investigation, but cases of apogamy and vegetative
apogamy are found with sufficient frequency to cast doubt on some records
of supposed fertility and to warrant a careful investigation of this point in
any form studied.
It seems better, therefore, when not using terms specifically to speak of
the reproductive capacity of plants rather than their fertility. Even this
terminology leaves much to be desired, though there is little to be gained from
mere multiplicity of terms. There is a very closely graded series from vege-
tative reproductivity to true sexual (gametic) reproductivity, the only sharp
line of separation being the differentiation of true gametes and fertilization.
Thus plants may be multiplied by stems, leaves, or roots, not at all modified
from the average structure; by these same organs distinctly modified, such as
bulbs, tubers, fleshy roots and the like, or by seeds, the embryos of which
have resulted from sporophytic budding or vegetative apogamy. It is worthy
of note, that when stems or leaves are used as cuttings for vegetative propaga-
tion a larger percentage of them will produce roots and continue growth
provided they are not too soft or succulent, but allowed to harden; the con-
ditions for hardening are in a broad way much the same as those which make
for the differentiation of fruit-producing parts. This will be considered later.
A discussion of fruit production is naturally tied up with the question of
fertility and sterility. The sense in which these terms are used has been
pointed out; from that viewpoint some records of fertility in plants have
really been records of self-fruitfulness or at best vegetative apogamy. A recent
paper by Stout (41) discusses at some length several reports and suggested ex-
planations of fertility and sterility; it is therefore unnecessary to discuss that
matter here. Stout adds many instances of self and cross-fertility, and
intersterility in Cichoriumintybus, a condition which Gardner (9) also found to
be the case of several varieties of the sweet cherry, (Prunus avium) in Oregon.
Stout states that the sterility probably is due to physiological incompatibility,
but that ‘“‘to what degree such incompatibilities involve pollen-tube growth,
irregular fusions of gametes, or embryo abortion, has not been adequately
determined.’’ It would be particularly interesting to know the extent of
embryo abortion in the forms which he studied. In the apple, sterility,
unless it be otherwise in varieties not yet investigated, is due almost wholly
toembryo-abortion, as previously pointed out by Kraus(28). Such degeneration
also occurs in Oenothera (Davis[6]), in certain tobacco hybrids (Goodspeed [12]),
11
cherry, almond, pear, plum, and tomato. It will probably be found to occur
in a very wide range of species.
Now th’s type of sterility is of particular significance since the degree of
embryo abortion varies, to a very marked extent, with different varieties and
particularly with environment, using this term in its broader sense. It is
also a fact that many varieties of fruits, particularly those which are fleshy,
show a marked correlation between flesh and seed development; but such a
correlation varies greatly according to the variety of fruit, and even within
the same variety, depending upon environment or as sometimes stated, ‘‘upon
the vegetative vigor of the plant.’’? There are plenty of instances, however,
of entirely seedless fruits, which develop either parthenocarpically or as a
condition of self-fruitfulness. Vegetative vigor itself is probably really
nothing more nor less than a response to environment. In other words, mere
vegetative extension and fruitfulness are not separate and distinct functions
of the plant but each is an external expression of an internal condition. One
is much too inclined to interpret plant functions as desirable or undesirable
from a commercial or practical viewpoint rather than a physiological one.
On the former basis it is desirable that fruit plants be producing fruit and at
the same time making sufficient vegetative extension to distribute such fruit
over a large producing surface or to provide area for the production of future
crops, whereas from the physiological viewpoint each plant can be regarded
as an expression of an adjustment to its surroundings, or in the process of
adjustment, whatever its condition. Such an expression may be evident only
as a rapid vegetative extension, the formation of reproductive parts, or a
combination of the two in varying degrees. Now the commercial grower
seeks the most profitable combination of the two. Each has come to interpret
for himself what is most desirable; but few growers have any considerable
knowledge of the means of regulation. It is well recognized that it is not
necessarily only the greatest number of fruit buds or even of fruits that is
most desirable, but also the quality, and with perennial forms, continued
production.
What, then, are the factors or conditions which make for vegetative
extension and those which make for fruitfulness? While it is not possible as
yet to define the exact effects or functions of specific substances, still it is
possible to point out some very definite relationships of some of them, which
will aid in a better understanding of the problem and certainly be of value
from the standpoint of practice.
One of the fallacious notions nearly as ancient as horticulture itself is
embodied in the statement that any condition which seriously threatens the
life of a plant, induces a realization in such an individual that it is about to
die, and therefore it becomes markedly reproductive in order to perpetuate
itself. This point is brought out here merely because such ideas are still
being taught and perpetuated and actually made the basis for investigation
and recommended practices. In any case, in deference to any possible vital-
istic ideas, it may be said that whatever may be the conception of a plant,
12
its responses are readily modifiable and any preconceived determination on
its part may be altered by environmental change.
One frequent error in much of the experimental work relating to pro-
ductivity in plants, has been the attempt to interpret an external response
in the light of the specific external conditions imposed with but little or, in
many instances, no attempt to discover or analyze the internal changes con-
cerned. Frequently important factors have been neglected entirely. In some
experiments the apparent limiting factor, or factors, under investigation have
played a lesser part in determining the final result than others which were
unobserved or given no consideration. Now it is more than probable that
there may be groups of external influences, any one or all of which produce
much the same internal response, and other groups which may produce
diametrically opposite results. In other words, external conditions may
either augment or largely destroy the effect of each other. It might be difficult,
then, without knowing the medium through which action has been transmitted,
to determine any specific cause merely from the evidence of some external
effect frequently associated with it. That this is the case is apparent in
plenty of published accounts, though they need not be considered here. All
this means that it is absolutely essential to have a thorough knowledge of the
internal changes, conditions, or compounds developed in response to the
several external conditions or factors to which plants may be subjected, then
the correlation of these, and finally a determination of the external response
to these internal conditions.
In this connection it is worth while to consider the oft-repeated objection
to the carrying on of experiments under abnormal conditions. Really after
all the idea of just what constitutes normality frequently varies with the
experince of the individual experimenter. The normal state is generally the
average condition, and the conception of what constitutes the average
condition too frequently is based on what is most valuable from an aesthetic,
applied, or commercial standpoint. The effect of an essential element or
factor in any set of imposed conditions can best be studied only by varying it
from the average, greater and less, and noting the changes or responses induced.
The growing of plants under ‘“‘abnormal”’ conditions must remain one of the
most valuable experimental methods.
Coming then to a consideration of the factors concerned in fruit setting, it
is well worth while to examine briefly a few of the reports of experiments in
various fields that are designed to provide an insight into the problem. These
experiments will be examined largely from the viewpoint of the relations
existing between the nitrate-carbohydrate-moisture conditions within the
plant and the associated vegetative or reproductive responses as detailed in
the introductory paragraphs.
RELATIONS TO PRACTICE
I. Cultivation and Companion Cropping. Two of the principal effects
claimed to be the result of tillage are the retention of moisture in the soil
and the increase in the amount of available plant foods, including nitrogen.
13
It is particularly interesting to consider certain orchard practices and note
the absurdity of attempting to follow any specific practice universally, without
due regard to local conditions, or a knowledge of the factors operating. It is
now realized quite generally that fruit plantings under very diverse cultural
conditions may be equally productive. The idea that the soil must be kept
in a state of intense cultivation each succeeding year is not valid for all con-
ditions. There are plenty of instances in which no cultivation, and even sod
mulch have proved to be the best commercial practices to induce and maintain
the fruiting condition. Plantings on so-called rich moist lands often tend to
remain vegetative, if thorough summer tillage is given and leguminous cover
crops are grown, but become abundantly fruitful if cultivation is lessened, or
a crop of grain, or other non-leguminous crop, is grown between the trees.
In one region, the most successful practice to bring the trees into bearing at
an early age may be to interplant with corn or other crops; whereas, in another,
clean cultivation supplemented with leguminous cover crops turned into the
soil or even the addition of animal or mineral fertilizers, may be considered
to be the best orchard management. Thus there are many and varied recom-
mendations, each has its supporters, and of course its application. It is
unnecessary even to attempt to record all or a considerable portion of them.
The point is Just this, through every one of these practices some condition is
changed and that change is either an increase or a decrease of some substance
or substances in its relative proportion to others. It is notso much the
absolute amounts as the proportions. If, then, it is possible to determine what
internal relationships are required for one type of response and what for
another, what factors operate and how they operate to modify such relation-
ships, then the correlation of these findings will aid in establishing rational
agricultural practices. Thus on the one hand it may be desirable to increase
nitrates and moisture, within the plant; whereas in another it may be essential
to decrease one or both of them. This general idea is not new, but seems
to be lost sight of all too frequently. It is quite as essential to know what is
present in the body of the plant itself, its extent and environment, as to know
what nutrients are in the soil. As a simple example, light and temperature
conditions suited to a rapid photosynthesis, on the one hand, or a slow one, on
the other, with identical soil conditions, will result in widely different responses
in the plant. Or, again, identical conditions influencing photosynthesis with
different soil conditions will result in equally wide variations. All conditions
are operating all the time. It is not easy to be sure of every environmental
condition and interpret an external result as a response to some one particular
external condition imposed.
Since the moisture and nitrate relations particularly are being considered
in this article, reference is made to the findings of several investigators.
Pickering (3) reports on a comparison of trees growing in sod and tilled
land. In general his results favor cultivation, though on the whole the
moisture is greater under grass by 3%. There is no record of the condition of
nitrates. He attributes the injurious effects to toxins from the grass rather
than to soil nutrients.
14
Hedrick (17) records experiments which sbow an appreciable gainin moisture
in favor of cultivated plots in comparison with those in sod. He considers
the amount of moisture removed by the grass an active agency in decreasing
moisture under sod. ‘‘As a consequence of the reduced water supply in the
sod plot, there is a reduced food supply; for it is only through the medium of
free water that plants can take in food. Analyses show that the differences
between the actual amounts of plant food in the two plots are very small.”
Gourley (13)has determined both soil nitrates and moisture in his experiments
on trees in sod as compared with those in clean culture. He found that on the
average there was about 33% greater moisture under sod, but on the
reverse that nitrates were appreciably higher under conditions of tillage than
under sod. The trees receiving clean culture were superior in growth and
fruit production. One plot (IX), which received nitrate fertilizer, averaged
higher both in nitrates and moisture but did not show a greatly increased
yield over another plot (V) showing less nitrates and less moisture. The
nitrate fertilizer was applied in June. It is therefore a fair question to ask
whether the nitrate really was available to the trees, and whether indeed there
was sufficient moisture for its utilization by the trees. This will be considered
further under the discussion of fertilizers and irrigation.
In a later report (14) by the same writer, particular attention is called to a
third treatment; namely, tillage and cover crops, under which treatment
there is an increase in moisture and nitrates in the soil and in the annual
average growth, though it is stated that the increase in moisture content is
“searcely sufficient to account for the difference in growth.’’ The yield of the
sod plots is less than half that of the other two. It is concluded that; (1)‘‘under
a good system of tillage nitrates were usually present in excess of the needs of
the trees,’ and (2) ‘‘moisture was not the limiting factor in the sod plots.”
It would be of considerable interest to know if the yield in the plots high in
nitrates could be increased by the application of additional moisture and to
determine the effect of a nitrate application to the sod plots early in the season.
A great array of tillage experiments with various crops and with varying
results might be adduced; the purpose in citing those above has been to give
an example of the studies which are being made with orchard fruits relative
to soil treatments and the changes in relations of moisture and nitrates.
Now, it is not argued for a moment that other nutrients and sanitary con-
ditions are not important in relation to growth studies. The point with
which we are concerned is the fact that certain vegetative and reproductive
responses are closely associated with a variation in the nitrate and moisture
relations. Thus the meens of regulation of these two factors and a knowledge
of their function within the plant, are of prime importance. On the one hand
it may be commercially advantageous to increase one or both of them in order
to render the ultimate crop more abundant or profitable, while on the other
hand, it may be desirable to decrease them for the same purpose. Much
depends on the type of response desired, it might be vegetative or it might
be reproductive, depending on the crop grown and upon its state of develop-
ment. Furthermore, an intercrop or cover crop might be of such a nature
15
that through shading and reducing the light intensity, the photosynthetic
activities of any specific crop might be profoundly changed, a condition
certainly as fundamentally important in interpreting plant response as soil
environment. The kind of tillage, intercrop or cover crop adopted, therefore,
will be determined by its influence on any one or all these factors at least.
Gourley gives some analyses of the plants in bis experiments, more especially
the carbohydrates. ‘‘In alternate-bearing trees we find a heavier deposition
of reserve food material in the storage tissues when the tree has formed fruit
buds. As starch, this is mainly found in the medullary rays and pith.’ No
determinations of the nitrates within the plant tissues are given but, “It
appears in this soil that nitrate formation of from 20 to 40 parts per million of
dry soil as an average for the growing season is essential for the maximum
vigor of the trees and abundant fruit-bud formation, and that above this an
excess will not of itself increase the growth or number of fruit buds formed.’’
It would be interesting to know what would be the result of increasing nitrates
and moisture simultaneously, or of an application of nitrates very early in
the season.
In this connection, it is a common experience to find very great increases
in yield or in the number of fruit buds formed during the first one or two
seasons of tillage following the sod-mulch system, provided of course that the
tree roots have not been severely injured. This may be due to the fact that
excess carbohydrates are frequently stored in plants suffering from lack of
nitrates, the plants being in the fourth condition previously enumerated;
namely, feebly vegetative and low in fruit production. When nitrates and
moisture were rendered available and taken into the plant, the stored carbo-
hydrates would be drawn upon and utilized in vegetative extension and the
production of fruiting parts. This is the third condition described. Theoreti-
cally by further additions of nitrate and moisture the second condition could
be attained, and practice has often shown this to be the case. By artificially
restricting the available carbohydrates or preventing their formation, the
first condition can be induced. While this condition is not generally likely
to be met with in practice, yet one means of producing it is through heavy
pruning. This situation is discussed at length in connection with pruning
practices.
II. Nitrogenous Fertilizers. It is not the purpose of this paper to enter
into the discussion of the use of fertilizers. A vast amount of experimentation
has been done, much is still required. One cannot question that each and
every one of the essential elements is a limiting factor in crop production;
they are that by definition. The main criticism to be offered on much of the
work, however, is that it has concerned only external results, sometimes with
but little indication of how they were produced. It is absolutely essential that
future work shall take into account internal changes and the relations of these
to observed results. Much more information is needed on the role of any
essential element in its varied relations to processes of water absorption,
respiration, carbohydrate formation, translocation and storage, protein
synthesis, and any number of other plant functions. Such determinations will
16
come closer really to answering fundamental questions than a record of pounds
of fertilizer applied and yield in bushels per tree or per acre, no matter of how
great practical or local significance such records may be.
Here it is our purpose merely to note afew experiments which are of interest
from the viewpoint of a nitrate-carbohydrate relationship as previously
proposed. Russel (89) concisely sums up the general effects of nitrogen as
follows:
“The normal nitrogenous food of plants is, however, a nitrate, and there
is a close connection between the amount supplied and the amount of plant
growth, which is well shown in Hellriegel and Wilfarth’s experiments.
“The increasing effects produced up to a certain point by successive
increments of nitrogen may be due to the circumstance that the additional
nitrate not only increases the concentration of nitrogenous food in the soil,
but also increases the amount of root; 1. e., of absorbing surface, and of leaf;
i. e., assimilating surface. The process thus resembles autocatalysis, where
one of the products of the reaction acts as a catalyser and hastens the reaction.
The increase does not go on indefinitely because some limiting factor steps in.
“The effect of nitrogen supply on the grain is very marked. (In the ex-
periments cited), it is seen that the grain formed, when nitrogenous food is
wholly withheld, is only two-thirds of the normal weight per individual. The
first addition of nitrate causes a marked rise in the weight per grain and the
proportion of grain to total produce, but successive additions show no further
rise. Indeed other experiments prove that excess of nitrogenous food causes
the proportion of grain to fall off somewhat. The leaf and the general charac-
ter of growth are affected to a much greater extent. Nitrogen starvation
causes yellowing of the leaf, especially in cold spring weather, absence of
growth, and a poor starved appearance generally; abundance of nitrogen, on
the other hand, leads to a bright green color, to a copious growth of soft,
sappy tissue, liable to insect and fungoid pests (apparently because of the
thinning of the walls and some change in composition of the sap) and to re-
tarded ripening; the effects resemble those produced by abundant water
supply. A series of plants receiving varying amounts of nitrate are thus at
somewhat different stages of their development at any given time, even though
they were all sown on the same day those supplied with large quantities of
nitrate being less advanced than the rest. If they could all be kept under
constant conditions till they had ripened, this difference might finally dis-
appear; but in crop production it is not possible much to delay the harvest
owing to the fear of damage by autumn frosts, so that the retardation is of
great practical importance. Seed crops like barley that are cut dead ripe are
not suppled with much nitrate, but oats, which are cut before being quite
ripe, can receive larger quantities. All cereal crops, however, produce too
much straw if the nitrate supply is excessive, and the straw does not commonly
stand up well, but is beaten down or ‘‘lodged”’ by wind and rain. Swede and
potato crops also produce more leaf, but not proportionately more root or
tuber, as the nitrogen supply increases; no doubt the increased root would
follow, but the whole process is sooner or later stopped by the advancing
season—the increased root does in fact follow in the case of the late-growing
mangold. Tomatoes, again, produce too much leaf and too little fruit if they
receive excess of nitrate. On the other hand, crops grown solely for the sake
of their leaves are wholly improved by increased nitrate supply.
“.. . The actual increase of growth brought about by successive incre-
ments of nitrogenous food depencs on the amount of water and other nutrients,
on the temperature, and so on; any of these may act as limiting factors.”’
Hartwell (15), inreporting on starch congestion accompanying certain factors
which retard plant growth, states that many different factors, correlated in
17
each case with retarded growth, were found to be associated with an accumula-
tion of starch in the above-ground portion of plants. The omission from
the manures of nitrogen, as well as of phosphorous, was associated with a
marked depression in the growth of vines, and it may be seen that in general
this was accompanied by a greater accumulation of starch than where the
complete manure was used. A deficiency of available potassium in the soil
was usually accompanied by an accumulation of starch in the potato vines.”
In general, an increase in the amount of the available nitrogen caused an
increase in growth but a decrease in the average amount of starch in the vines.
In one experiment, comparing the various amounts of nitrogen applied with
the starch stored, the results were not uniform throughout the growing season,
starch storage being greater in late July and very appreciably less, especially
in the heavily nitrogen-fertilized plots, in August and September. No ex-
planation is given; but a statement of the condition of growth at this time
would have been very desirable.
It seems as unnecessary to account for the accumulation of starch as a
pathological condition, as it does to assume that its absence could be con-
sidered such a condition in highly vegetative plants. Though the author
suggests it as an improbability, yet it is as legitimate to assume that the
lack of utilization of starch, or the substances from which it is synthesized, is
just as much the cause of retarded growth as that the retarded growth causes
the starch accumulation, though why this should be referred to as a patho-
logical condition is not entirely clear. Retarded growth and starch ac-
cumulation would be the expected results if the carbohydrates were not
utilized in vegetative extension or the production of reproductive portions.
The nitrate fertilizer experiments of Lewis and Allen (29) are of especial
interest when considered from the viewpoint previously expressed. Their work
consisted in applying to apple trees in declining vigor nitrate of soda, either
as a spray on the trees themselves or as crystals or a spray on the ground.
There was little difference in result in relation to the method of application,
but a very decided difference depending upon the time of application. To
quote:
“Orchards in a somewhat run-down, or devitalized condition; namely,
those which are making very little vegetative growth, either in twig or leaf,
those which have thin, yellow leaves and weak fruit buds—are greatly
benefited by the use of nitrogen. In such cases this fertilization produces
2 vigorous wood growth, causes the leaves to become thicker and greener,
produces more and larger fruit, and thus restores the trees to normal vitality.
There is an indication that some of the so-called pollination troubles have
been due to the fact that while the fruit buds and spurs might have sufficient
energy to blossom, they did not reserve food enough to mature fruit. One of
the most striking results obtained from the use of nitrogen has been in the
increased percentage of set.
“It has been startling to notice the rapidity with which nitrogen in an
available form gives results. Nitrogen added in March causes a larger per-
centage of set of fruit in April, an immediate change in the character of the
foliage, and a stimulation of the wood growth.
“With about six pounds of nitrate of soda applied to the ground around
each mature fruit tree, one secures about a pound of actual nitrogen. Such
18
an amount is sufficient to restore the trees to their natural vigor. Indications
are that in many cases this amount of nitrogen added two years in succession,
causes an over stimulation, shown by too heavy a foliage development, too
strong wood growth, and a production of too many over-large specimens
of fruit.
“The experiments in 1915 indicate clearly that the fertilizer should be
applied during the early part of March—that if we wait until May, which
has been the custom in applying nitrates, we recieve very little benefit from
such fertilization the year the nitrates are applied. This is due to the fact
that the seasons are too dry to cause the proper dissolving of these fertilizers
in time to be of assistance. The fact that the nitrogen has such a marked
effect on the percentage of set means, moreover, that it should be applied
before the trees bloom.
“Our experiments in 1915 indicate clearly that the best method of applying
nitrate of soda to orchards is to spread the dry crystals broadcast on the
ground under the trees, harrowing soon after applying. In 1914 the indications
were that it paid to spray the nitrate on the trees, but investigations this year
showed that the real reason why we secured better results from spraying in
former years was due to the fact that nitrogen sprayed on the trees was dis-
solved and reached the roots, whereas the nitrates spread on the ground were
added in May instead of March, and were therefore of little value. We believe
that this year’s experiments indicate very strongly that the nitrogen will be
of value to the trees only when it reaches the roots. Further experiments
will be conducted, however, to confirm these conclusions.”’
Further experiments as reported by Lewis and Brown (80) have tended
to confirm these conclusions. While no chemical analysis of the plant
tissues has been made either before or since the nitrate applications, yet
the general observed responses are so precisely similar to those in the tomato
experiments, to be detailed later in this article, that some suggestions may
not be out of place. It is more than likely that the trees described as lacking
in vegetative vigor and possessing small yellowish leaves and weak, slender
fruit buds were very low in nitrates and high in carbohydrates, especially
starch. Brief examinations of the twigs and branches of trees of similar
appearance and from the same locality show this to be the case. This being
true, the trees would be in a state of low vegetation due to a lack of
nitrates sufficient to permit the utilization of the carbohydrates in any ex-
tensive formation or development of vegetative or reproductive parts. This
accumulation of carbohydrates, however, when nitrates are added to the soil
and sufficient moisture is available to permit their being taken into the trees,
is drawn upon and is made over into other compounds and structures. Depend-
ing, then, upon the amount of nitrates and moisture available in relation to
the stored carbohydrates and those subsequently synthesized, the type of
growth response would vary. Very large amounts of available nitrate,
moisture, and carbohydrates would thus result in vigorous vegetative exten-
sion; proportionately smaller amounts of moisture and nitrates, in varying
degrees of vegetative extension and reproduction; and very small amounts, in
feeble vegetation and feeble fruit production. On the other hand, if the
carbohydrate supply was very limited, even though nitrates and moisture
were abundant, then the growth might be expected to be weakly vegetative
and scarcely or not at all reproductive or fruitful.
19
In the experiment just previously cited and in many others dealing with
nitrate fertilization, the above range of final results in growth and yields has
actually been recorded. Unfortunately, in the majority of these experiments,
no analyses of the plant tissues themselves are available; so that it is not
possible directly to analyze the results according to the foregoing suggestions.
It may be hoped, however, that in some of the future experiments analyses
may be made in order to test these suggested relationships.
III. Pruning. A consideration of the factors involved in pruning in
relation to fruit setting is particularly interesting, since by pruning, the
organism itself is profoundly altered in its relation to its general environment,
which usually is not greatly modified. It may be supposed that a plant at
any particular time represents the result of all the environmental forces
acting upon it, and it is either in a state of equilibrium with such forces or in
a state of becoming so adjusted. The response following pruning is largely
a process of regeneration. The type of such regeneration, whether of simple
vegetative parts or parts closely associated with reproduction, is of the
greatest practical significance, and any knowledge leading to a possible control
of such responses is highly desirable. Top pruning is a most direct and
speedy method of influencing the carbohydrate conditions in a plant.
Pruning practices are almost as many and as varied as the number of
individuals who grow plants. While there are almost endless varieties of
types and combinations of types, yet through all run two fundamental ideas,
the one to direct, maintain, decrease, or increase the vegetative extension of
the plant, the other to maintain or increase flowering or fruitfulness. Fre-
quently vegetation and fruitfulness are regarded as opposing plant functions.
While at first thought this seems to be the case, it can hardly be the true
situation; rather, vegetative extension and fruitfulness are intimately as-
sociated one with another. Reproduction may be vegetative or gametic.
Beginning with clearly vegetative parts used for reproductive purposes, a
closely graded series may be constructed, through slightly modified parts
such as off-shoots, bulbs, and the like, sporophytic budding, apogamy to
parthenogenesis (if in the limited use of the term this really occurs in plants)
and true gametic reproduction. The main point to be borne in mind is that
there are not two entirely antagonistic functions, but rather extremes of
possible expression, and that between these extremes, all sorts of gradations
may exist. To say that a plant becomes markedly reproductive because its
life is threatened is indeed begging the question.
Pruning practices concern both roots and tops of plants. Much more work
has been done and many more results recorded regarding the latter than the
former, probably because of the ease of handling and observation. The
comparatively limited experiments on root pruning, for the most part have
been recorded and interpreted on the basis of the responses of the tops.
Lacking an abundance of specific chemical analyses of the plant tissues in
connection with pruning experiments, much of the following discussion must
be based on inference. The conditions imposed and responses recorded,
however, agree so closely with similar circumstances and results in the
20
experimental work detailed later in this article that the specific, suggested
explanations seem worth presenting.
One of the most general statements regarding pruning of fruit trees is that
heavy dormant pruning increases vegetation, that trees should be pruned to
cause them to grow more vigorously. The inaccuracy of this general state-
ment has been pointed out, particularly in three reports. The Duke of
Bedford and Pickering, found in comparing trees 12 years of age that heavily
pruned trees were 16 percent lighter than moderatly pruned trees, while those
unpruned were 20 percent heavier than those moderately. pruned. Alderman
and Auchter (1) found that young trees lightly winter pruned as compared
with those heavily pruned were taller and broader, made longer total growth,
grew branches which were longer and larger, had larger trunks, and exhibited
a tendency toward earlier bearing as indicated by flower-bud formation.
Gardner (11) in experiments in winter, winter-and-summer, and no pruning on
young trees found that on the average the unpruned tree increases in size as
rapidly as, if not a little more rapidly than, the tree that is winter pruned
only or both winter and summer pruned.
In the case of the older trees, ‘‘not in a very vigorous condition,’’ Alderman
and Aucher report, as a result of heavy and light pruning, an exact reversal
of fruiting habits from those in the younger trees. ‘‘Both the Arkansas and
the York Imperial varieties produced distinctly larger crops on the heavily
pruned blocks than on the lightly pruned blocks. This sharp distinetion in
bearing habits between vigorous young trees and middle-aged trees of subnormal
vigor is of interest. Middle-aged is only a relative term. In New York
where apples are still in their prime at thirty-five years of age, fifteen-year old
trees would be considered young. In the Shenandoah Valley the commercial
orchards generally start their decline at twenty-five to thirty years of age
and fifteen to twenty years is truly middle age. We know that neglected
orchards which have not produced crops of any consequence for years will
frequently be greatly benefited and stimulated into fruit production by a
heavy pruning. To besure such trees are abnormal, but it will be noticed that
the trees in this orchard made but four inches of terminal growth in the year
before the experiment began, and that since that time they have averaged
from seven to nine inches for one variety and from four to five for the other.
This result would indicate that at the beginning the trees were somewhat
below normal in vigor, but under better cultural methods their average
condition had improved. The writers are of the opinion that, from the stand-
point of fruit production, vigorously growing trees would have made a
somewhat different response to the treatment than did the ones in the test.’’
Both Kraus (27) and Gardner (10) have pointed out that the thinning out of old
massive spurs in pears, apples and prunes, results in a much greater tendency
of the fruit buds to mature fruit. In brief, to prune ‘“‘judiciously’’ in order
to maintain the desired balance between fruiting and vegetation, is a very
general recommendation, but how many of those who make the recommenda-
tion understand what factors are involved in producing the results?
Now, why these apparently diverse results from similar practices? An
21
analysis of some of the internal conditions affected and their relation to external
response may aid in obtaining a clearer view of the situation. In the first
place whatever may be the character of the storage in the top under any
condition, it is self evident that some will be removed from any future use
by the tree if any pruning whatsoever is practiced. Considering now the
responses during the growing season on the basis of the suggested idea of a
moisture, carbohydrate, nitrate relationship, it may be assumed that at the
actual time of pruning the soil moisture and nutrients themselves would
neither be increased nor decreased whatever the practice, though the amount
utilized later by the tree would be profoundly modified. On the contrary,
any pruning practice would certainly mean a decrease in the amount of storage
materials actually remaining as a part of the plant, and in large measure also
the future synthesis of such material, so that the relation of the nutrients in
the plant to those in the soil about it have been profoundly disturbed. That
is to say, top pruning, whatever its nature, would decrease particularly the
available carbohydrates and other stored substances in relation to the soil
moisture and nutrients; root pruning would not only do the same thing but in
addition would tend to prevent, in considerable degree, the possibility of
absorption of materials from the soil. As will be pointed out later also, in
the more detailed experiments on tomatoes, the amounts of moisture and
nitrates which are absorbed and used in growth are dependent upon the
available carbohydrates either in storage or those being derived from
photosynthetic activity.
Thus, as previously pointed out, the four general types of response related
to the varying nutrient conditions, could be expected from pruning practices
as well as any other practice which would tend to modify them. If, for
example, either because of lack of storage or photosynthetic activity, the
carbohydrate supply were greatly reduced, even though there were an abun-
dance of available moisture and nitrates, then blooming and fruit production
are very greatly decreased, and vegetation is also restricted. The suppression
of vegetation in itself is absolutely no reason why fruitfulness should follow. *
Again, if moisture, nitrates, and carbohydrates all are abundant, these
would be utilized in rapid vegetative extension, with little tendency toward
the formation of specialized reproductive parts or the storing up of large
quantities of carbohydrates, as long as growth was active. This condition
differs from the preceding in the availability of the carbohydrates. If, then,
a pruning of any type were given to trees or plants with meager carbohydrate
reserves or means for their continued synthesis, even though the nitrogen and
moisture conditions are unchanged, there would be a tendency for decreased
vegetation and fruiting. That this is the actual situation is evidenced by the
recorded results of many investigations, especially those dealing with young
or so-called vigorously growing plants.
A third condition exists when there are available nitrates, moisture, and
carbohydrates, but the latter are synthesized in excess of the quantities which
*(The effects of etiolation naturally suggest themselves, but these seemingly must be rather
sharply separated from the discussion at hand.)
22
are utilizable in simple vegetativeextension. Insuch cases growth is expressed
both as vegetative extension and specialized reproductive parts, either as a
sort of balance or as an expression in favor of the one type or the other. Com-
pared with the preceding condition, actual vegetative extension is apparently
less. It is this condition which is of greatest commercial interest to fruit
growers. It is an ideal condition to have trees making some vegetation each
year, thus increasing and maintaining bearing area coupled with abundant
fruit production. This nicety of balance can be and is maintained through
many orchard practices, expecially such soil treatments as will regulate nitro-
gen and moisture conditions, and such top treatments as can be managed
through pruning. Sometimes no cutting whatsoever may be needed, but
generally some is required. The desired results of such cutting might be to
suppress all growth in one portion, encourage growth in another, or to maintain
a balance between purely vegetative parts and reproductively modified parts
in still others. These conditions could be regulated by severe or light cutting
depending upon the relative abundance of the carbohydrates, nitrates, and
moisture, pruning furnishing the most ready practical means of regulating the
form.
A fourth condition is most frequently encountered in very old trees, in
those which are growing in impoverished or dry soils, or in those which have
sustained certain types of injury which virtually amount to a ringing or
girdling. In these cases vegetative extension is notably depressed, the foliage
small and generally light colored, and there is usually an increased tendency
toward flowering, accompanied or not, as the case may be, with fruit develop-
ment. In many instances there is actually a relative decrease in the pro-
duction of flowers. If this condition is due to a relative lack of nitrates or
moisture or both in proportion to the available carbohydrates, then it might
be expected that if the former were increased, there would be first a tendency
toward increased vegetation and fruiting, but on increasing these amounts
more and more, a response wholly vegetative would finally result. Such
increase could be brought about either by some top pruning which directly
removes stored carbohydrates, or by increasing the available nitrates and
moisture by the application of nitrogenous fertilizers and cover crops with
or without irrigation, as the case may be. Both these methods and their
gross results are well known and established in practice. In general, it may
be added that for most tree fruits, a combination of the two is most useful,
since if the available nitrogen is very low, to secure results by pruning alone,
the potential bearing area must be so greatly reduced that the trees are no
longer commercially profitable. On the other hand, the application of
fertilizers or cover crops only without some pruning may result in a loss of
some of the most profitable bearing area by over-crowding or the development
of fruit of a poor commercial grade.
With this viewpoint and suggestions as a starting point, it is of interest to
consider the recorded results of several investigations.
There is a wide range of opinion among horticulturists in general regarding
the response due to summer pruning; that is, pruning when the plants are in
23
actual foliage. Formerly it was stated that summer pruning induced fruitful-
ness, This view is changing, due to the accumulation of results of accurate
experimentation. One might expect much the same results from summer
pruning as from winter pruning, and such is not far from the true situation.
There is absolutely no question but that growth or vegetation may be de-
cidedly decreased by cutting in full leaf but it must be remembered also that
fruitfulness is not a necessary accompaniment of reduction of vegetation.
It may be quite as much associated with an increase as with a decrease, as
previously pointed out.
Summer pruning differs in one marked essential from dormant pruning,
especially when the plant in question is leafless in its dormant stage, in that
the former removes not only whatever nutrients are in the portion cut away,
but also removes an appreciable portion of the carbohydrate synthesizing area.
It must be remembered, however, that while some leaves are removed entirely,
yet in some portions of the tree, other leaves may be exposed to the light to
a greater extent. In other words the decrease in synthesizing power may or
may not be entirely equal to the leaf area removed. Again, moisture and
nitrates are apt to be present in smaller quantities during the mid-summer
growing season than in spring, so that they, as well as a restriction of carbo-
hydrates, would act as limiting factors to growth. With these facts in mind,
whatever else has been said of dormant pruning in the ratios of nitrates and
moisture to carbohydrates in relation to growth, applies equally forcibly in
summer pruning.
The term summer pruning has been used to include a wide variety of
pruning practices followed out during the summer months, such as a thinning
out and heading back relatively early or late in any given season or at several
times during the season, removing water sprouts or large limbs, or merely
pinching the tips of branches. At times it has been employed in connection
with winter pruning. Much of the disagreement between the interpretations
of investigations is because of different methods employed. Actually, so far
as can be deduced from the data available, the results are remarkably well
agreed.
Batchelor and Goodspeed (2) have reported on summer-pruning practices.
The data recorded permit only a suggested interpretation of the results.
There are many possible combinations of causes operating. The greater
average length of 100 twigs in each case, does not indicate whether the winter
and summer pruned trees actually accumulated more total volume of growth
than the unpruned trees. The mere weight of the fruit produced also leaves
doubt as to the general fruit-bud situation, the percentages of blossoms setting
fruit, where the functioning spurs occur, and other points, It is quite probable
that as the authors suggest, the decreased fruit production is due to a reduced
area of fruit-bearing wood removed by the summer pruning. ° At least, if fruit
buds were stimulated as a result of the thinning (pruning), they were not
sufficient in number or quality to compensate for those removed. It is not
possible to judge these results as they stand on the nitrogen, moisture, carbo-
hydrate relations, for lack of sufficient data.
24
Alderman and Auchter (1) report on summer-pruning experiments, which in
net result of fruit production approximate those just previously discussed.
The experiments included heavy, moderate, and light pruning in the form of
a heading back and thinning out. The light pruning evidently was almost
entirely in the nature of thinning. A proper relation, however, was always
maintained between the heavy, moderate, and light pruning. In one orchard
the degrees of difference in pruning were secured entirely by varying the
amount of branch thinning.
“Tn all orchards dormant pruning took place between March 20 and April
4 of each year. The summer pruning practiced was of virtually the same type
as the dormant pruning and in amount of wood removed corresponded closely
with the moderate dormant pruning. The early summer pruning was per-
formed in 1912 between May 25 and May 31, but in the last two years was
shifted to June 9 to 11, as the earlier pruning seemed to be much too early.
The midsummer pruning took place each year between July 8 and 15, while
the repeated summer pruning was simply a combination of the early and
midsummer prunings and took place on the dates mentioned. In this region
fruit-bud formation in the apple begins from June 20 to July 1. Early summer
pruning was performed just previous to this period and midsummer pruning
just following it after the period of most rapid growth was completed . . .In
the case of the winter and summer pruning, the trees were headed back in
the winter and about one-half of the wood was thinned out. In the summer
time, the other half of the wood was thinned out and the suckers were removed.
In the case of the repeated summer pruning it was attempted to do the same
amount of pruning at each date. The sum of these two prunings made about
the same as the moderate dormant pruning and left the trees pruned in about
the same condition as regards shape, etc.”
The results of the experiment to test the effects of seasonal pruning upon
the first five years’ growth of trees ‘“‘show that the trees pruned heavily in the
dormant season made by far the longest average terminal growth. The sum-
mer-pruned trees made a longer growth than the trees pruned lightly in the
dormant season, but did not make quite as much growth as did the moderately
pruned trees.’’ But the authors made a measurement of the total as well as
“average’’ growth produced in the year 1915 and the result ‘‘shows that
summer pruning has checked decidedly the growth of the trees as regards
total amount of new wood produced.’’ In general the authors concluded that
in this experiment, summer pruning has checked tree growth and has delayed
and decreased fruit production. Other experiments on trees five and six years
old showed that ‘‘on young trees bearing their first crops summer pruning
has reduced both vigor and fruitfulness.”’
These results are not at all out of harmony with the general ideas expressed
regarding dormant pruning. The thinning out of the branches in summer
in all probability removed more in the way of potential fruit-bud area, stored
nutrients, and the potential carbohydrate synthesizing area, than was com-
pensated by admitting light and air into the remaining leaves and branches.
Naturally a decreased total growth should be expected since it is also quite
likely there was less available nitrate and moisture at the time of summer
pruning as compared with the amounts present earlier in the season. The
greater average length of terminal growth in the heavy dormant and the
summer- and winter-pruned trees is not out of keeping with the general idea,
25
but as the authors themselves pointed out, this does not mean greater total
growth, but rather the contrary. In fact, quite a point is made of the fact
that lightly pruned trees showed a strikingly greater increase in trunk
diameter, branch diameter, size of top, and total annual growth than those
which received annual heavy dormant pruning. This result could readily
be explained as the result of limiting the available carbohydrates in the
pruned trees. The moisture and nitrate conditions in the soil would not be
materially changed by the mere removal of branches in itself, and if these
were in excess of what would be utilized in increasing growth in the heavily
pruned tree because of the limiting of the carbohydrates, then in the unpruned
tree where such limit had not been imposed, total growth should be greater.
If, however, the carbohydrates synthesized were in excess of the amount which
might be utilized in simple vegetative extension, 1t might be expected that the
character of growth would be progressively changed toward the reproductive
type, as already pointed out.
It is in experiments of this kind that the value of the study of the parts
remaining after pruning, and the conditions and changes induced in them
becomes apparent and are of even greater importance than what has been
removed. Any attempt to measure vigor by growth response alone is unsafe.
One of the greatest hindrances to advance in the study of the whole pruning
problem has been segregation of growth, blooming and fruiting responses as
if they belonged in different categories or were due to antagonistic fundamental
causes. It seems much more helpful to an understanding of the problem to
regard these responses as being due not so much to many distinct and separate
causes, but rather to modifications or different combinations of a few, often
closely associated or even inter-dependent.
Some recent work reported by Gardner (11) deals with asomewhat different
phase of summer pruning in apples. The work was done on young trees, not
yet in bearing. The summer pruning consisted of a more or less severe heading
back and thinning out in early summer, removing from 55 to 78 percent of the
season’s growth. The winter pruning of these same trees removed from 53
to 72 percent of the late short growth formed for any particular year. From
the winter-pruned trees 64 to 79 percent of the growth of any current year was
removed. Some trees were unpruned. This type of summer pruning generally
results in a putting forth of branches below the cut. These branches may
attain a length of but afraction of an inch or of many inches before the dormant
season. If not of such length that they would interfere with the future ideal
form of the tree, these shoots are not headed back in winter. If this secondary
growth is profuse, it is often thinned out. Evidently this type of pruning is
not quite the same as that reported by Batchelor and Goodspeed or by
Alderman and Auchter.
“The data relating to shoot growth indicate that on the average the un-
pruned tree increases in size a little more rapidly than the trees that are
winter pruned only, or that are both winter and summer pruned. Its average
annual shoot growth is less but it loses none of this by pruning and bence its
net increase is greater. Broadly speaking there is but little difference in
increase in size between trees that are winter pruned only, and those that are
26
both winter and summer pruned. The summer-pruned trees lose more shoot
growth from pruning, but they produce nearly enough more to compensate
for the additional loss.’
The greater size of the unpruned tree is in keeping with the results of
Alderman and Auchter. The same suggestions as were made on their ex-
periments are entirely applicable here.
“While there is considerable variation between individual trees in the
units of shoot growth they made in 1915 for each unit of 1914 shoot growth,
there is shown no general tendency for the more severely pruned trees to
produce more shoot growth for each unit of last year’s growth than the less
severely pruned trees. In fact, the average for the varying degrees of severity
of pruning shows a slight tendency in the opposite direction. In other words,
the evidence tends to show that at least in the case of young apple trees that
have not yet produced many spurs, the amount of shoot growth they produce
one season is much more closely correlated with the amount they made the
preceding season than with the amount removed by winter pruning.”’
“Study of the data presented indicates that on the average there is little
or no relation between the severity of the early summer pruning given these
trees and their subsequent response in shoot growth. Individual trees of any
of the varieties might be selected for comparison that would seem to show
that heavy early summer pruning results in a more rapid shoot growth than a
lighter summer pruning. Conversely other individuals might be selected that
would seem to indicate an opposite tendency. The averages, however, clearly
show that amount of later summer -shoot growth following the summer pruning
here described is much more closely correlated with the amount of early shoot
growth already possessed by the tree at the time of summer pruning than
with the pruning itself. This would indicate that while on the average early
summer pruning, like winter pruning, does not check rate of shoot growth, it
results in a check to increase in size of tree because rate of growth is not
accelerated; and that the heavier the summer pruning the greater is such a
check. Attention is called to the facet, however, that the early summer
pruning did not check the increase in size of the trees (as measured by shoot
growth) to a degree greater than a correspondingly heavy winter pruning.”
An examination of the actual figures upon which this statement is based
shows some wide departures from this general conclusion; so wide in fact that
it is questionable if it is safe to venture an explanation of the results expressed
only as a general average. It is essential that something more be known
regarding the condition of the individual trees and branches as well as their
length. Professor Gardner has told the writers that in his experiments the
degree or state of maturity of the branches is a very great factor in determining
response from this type of summer pruning. Now degree of maturity is really
another way of expressing the evident differences resulting from different
conditions of nutrition. Since for the purposes of this discussion the main
interest centers in the nitrate, moisture, and carbohydrate conditions, and
since no determinations of these substances are at hand, it is only possible to
offer conjectures as to the possible causes of the results recorded. The relative
state of development of the several trees or branches is an indication of the
relative amounts of the substances mentioned which are present or available.
How these influence growth has already been pointed out, but a few additional
examples may be mentioned here. Now a branch which is very vigorously
vegetative at the time of heading back is in itself an indication that it is
receiving these nutrients in the proportions which produce such growth, and
27
on the other hand one which has made little vegetative extension, and has
perhaps already developed a terminal bud indicates totally different pro-
portions. What the response of any branch or tree will be after heading back
will depend upon how these relationships are changed. Such heading back
during the active growing season will exert its greatest limiting influence in
carbohydrate synthesis, in much the same manner as does defoliation. The
conclusion naturally follows that if the carbohydrate supply were decreased
below the amount that could be utilized in maximum vegetative extension,
considering the amounts of other compounds present, then growth would be
decreased. If on the other hand the moisture-nitrate relations were such
that there was not an active vegetative extension, but a surplus of carbo-
hydrates (simple or complex), then a moderate heading back, which would
tend to remove some of the latter, would result in a vegetative response until
balanced relations were again restored. But as stated, if such heading back
were so extensive that carbohydrate starvation effects were introduced, then
vegetative activity would not result because of that fact itself, no matter what
the nitrate-moisture conditions. In similar manner the entire range of results,
already ascribed to the nitrate-moisture-carbohydrate relationships, might
be expected. Actual experiments bear out such expectations remarkably well.
Several other results reported by Gardner are of interest. All may be
interpreted on the general hypothesis previously stated. ‘‘There seems to
be a close correlation between increase in trunk circumference at any period
during the summer and the leaf area possessed by the tree at that particular
time.’’ It should be remembered that young actively growing trees were
used in the experiments.
“Summer pruning of the type described affords a direct stimulus to fruit-
spur formation. Some of the buds on the basal portions of the shoots that
are left after the summer pruning almost invariably grow out into fruit spurs
during the latter part of the summer. Those that remain dormant during
the latter part of the summer are just as apt to develop into spurs the following
year as similarly situated buds on shoots that are not summer pruned.
“The later summer shoot growth of the summer-pruned trees is very
productive of fruit spurs the season following itsformation. A high percentage
of its buds develop into spurs. Herein, apparently, lies the chief gain in fruit-
spur production from the summer pruning. On the trees that are winter-
pruned only, there is no growth to correspond with it. There is little or no
relation between the severity of the summer pruning and the number of spurs
to each unit of shoot length that remains.”
The outstanding facts of particular interest in these experiments are that
the winter- and summer-pruned trees are very similar in the amount of growth
accumulated, and that the summer-pruned trees produce larger numbers of
fruit spurs, more in fact than those which have been winter pruned only.
That the unpruned trees average greater total growth than those pruned, is
another instance of greater accumulations through non-removal of any reserve.
For the most part the type of summer pruning practiced removes only the
terminal portions of the branches, the portion which in active growth, as most
of these branches are at the time, contains least of the storage carbohydrates,
28
if there are any present. But since such a pruning does remove considerabe
synthesizing area, it may prove seriously devitalizing in its effects.
That there should be increased fruit spur formation on the summer-pruned
trees is in accord with the general ideas expressed, since the new growth is
only slightly or not at all cut back. There would be little or no removal of
stored materials, so that the adjustment for fruit buds is more quickly estab-
lished. (It should be borne in mind, however, that fruit spurs and fruit buds
are not one and the same thing, and that the mere development of fruit buds
does not necessarily mean fruit development.)
Magness (31) has also called attention to the fact that in this method of sum-
mer heading ‘‘the form of the summer-pruned shoot, which allows many axillary
buds to be left at the time of the following winter pruning, accounts for the
greatly increased number of spurs in trees that have received regularly an
early summer heading back.’ In a later report on defoliation experiments,
Magness (82) gives more concrete evidence bearing on the cause of such increased
fruit-spur production. His summary is so suggestive that it is worth repeating
in full:
“The study of the relation of fruit-bud and leaf-bud formation and develop-
ment of leaf area, as shown by the results following the removal of leaves, may
be summarized as follows:.
“7. Fruit-bud initiation will not take place, and fruit buds will not form
in most varieties in the absence of a fair amount of leaf area in the tree.
‘2. Leaf area in one part of the tree will usually not supply food material
to the buds in another part to the extent necessary to cause them to become
fruit buds. Defoliating one-half of a tree has little influence upon the un-
defoliated portion, but that part which is defoliated functions as it would if
all the leaves had been removed from the whole tree.
‘3. Food material stored in the tree through the dormant season is
apparently stored largely in the tissue adjacent to the leaves in which it was
manufactured. This is shown by the fact that the defoliated portion of a
tree does not develop as strongly and well during the spring following the
treatment, as does the undefoliated portion.
“4. Removing the same number of leaves, without any pruning, has
practically the same effect upon the fruit-bud formation for the immediate
year following, that a summer pruning, removing leaves from the same position
would have.
‘5. Buds on one-year wood, in areas from which the leaves have been
removed are slower in starting out into growth, and make a weaker growth
the following spring than do other buds on the same shoots not defoliated
This is more noticeable in some varieties than in others.
“6. One shoot seems to be very largely independent of other shoots about
it so far as fruit-bud formation is concerned. It is apparently largely de-
pendent upon its own leaves for nourishment. ;
“7, Removing leaves from individual spurs tends to prevent the formation
of fruit buds upon those spurs, although it does not entirely check the develop-
ment of flower parts. ores
“8, On those spurs which form fruit buds, notwithstanding defoliation,
the blossoms are, on the average, considerably later in opening in the spring.
“9, Axillary buds of the Wagener seem to be almost entirely dependent
upon the immediate subtending leaf for the carbohydrate supply with which
they are nourished. Removing the subtending leaf entirely prevents fruit-bud
formation. Buds so treated either remained entirely dormant during the
29
following growing season or pushed out into very weak growth. Very few of
them showed a development approaching normal.
“10. Microscopic examination of buds, both defoliated and undefoliated,
taken at intervals during the summer, show little influence of the defoliation
so far as development is concerned. No buds were studied that were taken
later than September 12.
“11. There is very decided decrease in the number of calcium oxalate
crystals deposited in the tissues of defoliated as compared to undefoliated
buds. This may be indicative of a small supply of soluble carbobydrates and
general slow metabolism in the bud tissue.
“12. Injury to the bark on the trunk of the tree very greatly stimulated
fruit-bud formation. This injury brings about very different conditions of
nutrition in the tree from those produced by defoliation, for by preventing
the normal flow of elaborated foods to the roots, the supply in the top of the
tree is greatly increased by the injury of the bark.”
The evidence as to the influence of carbohydrates on fruit-bud formation
is particularly direct. The extremely close relation between the behavior of
any bud relative to its immediate leaf area emphasizes such an influence still
further, and is of great practical significance. It is unfortunate that no direct
measurements of the various nitrogenous compounds are available, but it
should be recalled that, for the most part, young vegetative trees were used, so
located that there was a copious supply of soil nitrates. One tree of the
Glowing Coals variety which had a severe trunk injury developed a little
more than one-third as many fruit buds on the defoliated half as on the non-
defoliated half, though the former produced much weaker bloom clusters the
following spring. Magness has suggested that the conditions of nutrition in
this tree caused an initiation of floral primordea somewhat in advance of the
defoliation because of the relation of the elaborated foods in the tops. This
is no doubt true, and the elaborated foods were probably carbohydrates for
the most part. Of course this behavior resembles that of artificially girdled
individuals, but the contrast in performance of the defoliated and non-
defoliated halves bears out the general conclusion even more clearly.
One other set of resultsreported by Drinkard (7) is particularly significant,
when examined from the viewpoint previously expressed regarding growth
behavior and fruit production. Some of his conclusions together with a
suggested analysis follow:
1. “Spring pruning of the branches of the trees at the time of growth
resumption had a tendency to discourage the formation of fruit buds, but there
was apparent stimulation of wood growth in the trees.”
_An explanation for this result has already been given. The apparent
stimulation resulting from severe heading back is an indication that nitrogen
rather than carbohydrates was a limiting factor to vegetation.
2. “Summer pruning of the branches of the trees the latter part of June,
when fruit buds normally begin to show differentiation, checked wood growth
the year in which the summer pruning was done, and greatly stimulated the
formation of fruit buds as was shown by the bloom and crop of fruit the fol-
lowing year.”’
Without more complete data on the exact location of fruit buds and the
full behavior of these trees, a complete explanation of the results is impossible.
Still it is interesting to note some of them. Compared with the check trees
and the spring- and fall-pruned trees, the average circumference of these
30
summer-pruned trees was less, the number of fruit buds formed was not greatly
in excess of the checks, though decidedly greater than the spring-pruned trees.
It may be suggested that the carbohydrates were present or being manu-
factured in proportions relative to the available nitrogen, sufficient for copious
fruit-bud initiation and development in those trees which received no pruning
treatment. If so, then an early spring pruning would tend to reduce these
from the standpoint of storage and subsequent synthesis. At this time, also,
soil moisture and nitrates could be expected to be somewhat higher than at
the time of summer pruning. The natural growth expression would be
vegetative, provided that lack of carbohydrates were not a limiting factor, and
the results indicate that they were not. It certainly would have been possible
tomake themso. A pruning given later in the summer would likewise remove
some stored carbohydrates and of course synthesizing area, but at that time
soil nitrates and moisture were probably relatively less so that a strong
vegetative response would not be anticipated. Increased fruit-bud formation
over the checks would be expected in this particular case only if the carbo-
hydrate supply were relatively greater, which might have been the case, since
the amount of leaf area removed may have been compensated by the admission
of more light to the parts remaining, and by the new leaves developed. Such
carbohydrates as were synthesized were not used up in vegetative extension,
since these trees made very short growth in annual shoots. This is a par-
ticularly interesting case in which it would be extremely desirable to know
something of the relative proportions of the several substances under con-
sideration. Under the present circumstances they can only be surmised.
These suggestions should be considered in connection with the next point.
“Root pruning on April 238, at the resumption of growth in the absence of
spring pruning, did not give as much stimulation to fruit-bud formation as
the same treatment applied at later dates. Apparently this was too early
for the full effects to be felt by the trees. Root pruning when the foliage was
fully developed, and when the fruit buds began to become differentiated, in
the absence of spring pruning of the tops, produced very marked stimulation
in fruit-bud formation. At these three times the treatment retarded wood
growth and foliage development in the current and succeeding year and the
trees suffered from the treatment.
“Severe root pruning at the time of growth resumption in the spring
(April 23), at the time the leaves were well developed (May 381), and at the
beginning of fruit-bud differentiation (June 23), when accompanied by or
preceded by spring pruning of the branches, produced some stimulation in
fruit-bud formation. Another series of experiments showed that the spring
pruning did much to off-set the effects of the root pruning. The root-pruning
treatment retarded wood growth in the current and succeeding year; the leaf
area of the trees was reduced and the trees showed injury from the treatment.’’
The results expressed in the two preceding paragraphs can best be analyzed
together. A root pruning would be expected to reduce the intake of moisture
and of mineral nutrients including nitrates. Of course the earlier in the season
performed, the earlier some result would be produced in the top, though the
results might not be quite the same under the two conditions. A root pruning
when the foliage is fully developed and the fruit buds are beginning to become
differentiated would mean decreased moisture and nitrate intake, whereas
3l
carbohydrate synthesis would continue, assuming of course that such pruning
is not so severe as to result in actual death of the tops. Without sufficient
moisture and nitrates to utilize the carbohydrates in forming other compounds
or in vegetative extension, they would tend to accumulate, with the resultant
types of expression of vegetation and fruiting already enumerated from scarcity
to marked fruit-bud production, even to the suppression of fruit-bud pro-
duction, fruiting, and vegetation. On this basis it readily follows that, other
conditions of root pruning and the like being the same, a spring pruning of
the branches, which would decrease the materials already in storage and to a
degree the subsequent amount of foliage developed, should tend to influence
fruit-bud formation to the same extent that it modifies the relations of the
carbohydrates to the moisture and nitrates. In the experiments under
consideration fruit-bud formation for the most part was greater when the root
pruning was not accompanied by branch pruning, but not necessarily so.
Theoretically there should be a point where fruit-bud formation on root-
pruned branch-pruned trees should be relatively greater than on those which
had been root-pruned only. That is, such a condition would exist when the
root removal had so reduced the possibilities of absorption that it would be
necessary to decrease the carbohydrates in proportion to the nitrates in order
to promote growth. Inthe scheme already proposed this would mean a change
from the fourth to the third condition. Such a situation is actually indicated
in the fruit-setting records in the experiments under consideration. It should
be brought out also, that a branch pruning removes many buds likely to develop
into fruit spurs, whereas these remain when no pruning is given, so that a
comparison based on numbers of fruit buds only, seems hardly a just one.
“Ringing at different seasons when accompanied or preceded by spring
pruning of the branches produced no noticeable stimulation of fruit-bud
formation.
“Ringing at the time growth was resumed in the absence of spring pruning
did not stimulate fruit-bud formation. The treatment was given too early.
Ringing at the time the foliage was fully developed in the absence of spring
pruning gave the best results; however, when the treatment was given at the
time the fruit buds began to become differentiated, there was some stimulation
of fruit-bud development.’’
All these results would be expected in accordance with the general ideas
proposed. There is little question that ringing would result in an accumula-
tion of carbohydrates above the girdle, if they are being manufactured in
excess of the amount utilizable in connection with the moisture and nitrates
available. The same series of results would be expected as from root pruning
or as from limiting the nitrate or nitrate and moisture supply. The situation
is Just the reverse of root pruning in which nitrate and moisture intake were
limited through reducing the absorbing medium, but the same net result in
the relation of carbohydrates to nitrates is gained by holding the carbohydrates
in the top even though the root conditions are not mechanically changed.
It would seem that if moisture and nitrate intake were not limited that growth
should be little changed. A question may be raised here, however, in regard
to the possibilities of moisture and general mineral intake when the carbo-
hydrate supply is prevented from reaching the roots. There are reasons and
32
evidence for believing that the actual root extension is decidedly diminished
by such carbohydrate limitation, and there is also quite likely a change in
the power of the roots to absorb mineral nutrients. In any case such analyses
as have been made do show an accumulation of carbohydrates above a girdle,
generally in direct proportion to the severity of the ringing, whether there is
also a limitation of nitrate intake remains to be determined. Thus a ringing
when the trees were in full leaf might be expected to result in a more rapid
accumulation of carbohydrates and in larger quantities than when such leaf
surface were small or if the girdle healed before the leaf surface became larger.
The relative amounts of moisture and nitrates available in the soil earlier or
later in the growing season are also important factors to be considered. It is
easily possible to make a girdling so severe that fruit-bud formation, blooming,
fruiting, and growth are all seriously diminished. The whole range of growth
responses resulting from the nutrient relations as previously proposed can be
produced.
“Stripping at different seasons when accompanied by or preceded by
spring pruning, had no stimulative effect on fruit-bud formation. The effects
of stripping were offset by those of spring pruning. Stripping at the three
seasons already mentioned, in the absence of spring pruning stimulated fruit-
bud formation uniformly.”’
Stripping in its effects, is like ringing or girdling, except that it is less
severe. What has been said for the latter will apply equally well to stripping.
HISTORICAL
There are many references in botanical and general agricultural literature
dealing with a suggested relationship between plant responses and the avail-
ability of elaborated or non-elaborated food. Some of these make no further
explanations or suggestions regarding the particular nature of these foods,
others roughly classify these compounds as mineral or organic nutrients, while
still others fix upon specific compounds as related to specific responses. In ad-
dition to specific references already mentioned in this article, several others
are of special interest. Up to the present time, at least, Klebs (21, 22, 23) has
been one of the most active contributors to definite knowledge on this subject.
He has worked with algae, fungi, and the higher plants. In the lower forms
he has shown that by controlling the environmental conditions it was possible
to cause the plants to remain in a vegetative condition, to produce zoospores
or to reproduce sexually. He has demonstrated that much the same results
could be secured in the higher plants as, for example, Sempervivum Funckii.
(24). In amore recent paper (25) he has brought together the results of nu-
merous investigations which have shown that the environmental conditions
very largely determine whether a plant shall remain in a vegetative condition
or become sexually reproductive. The controlling factors were found to be a
reduction in the supply of nutritive salts (especially those which are nitro-
genous) and an increase in the intensity of light, the efficiency of the illumina-
tion being responsible for the formation of organic substances, such as carbo-
hydrates.
33
It has been observed for a long time that most tropical trees show an altera-
tion of growth and a rest period. This has quite often been attributed to some
inherent heredity character. Klebs, (26) however, has regarded this condition
as a result of external conditions acting upon the specific hereditary character
of the plant. Each plant is supposed to possess certain hereditary possibili-
ties in the way of expression of growth and reproduction, and the probable form
which results will depend upon the surrounding conditions. Klebs has con-
cluded that, since growth depends upon a large number of factors, any one of
which may be a limiting factor, rest can be secured by suppressing any one of
these factors toa minimum. Intense photosynthesis, producing a large supply
of carbohydrates in case salts are not present in sufficient amounts, may result
in rest.
Crocker (5) in reviewing the foregoing work by Klebs, has stated the follow-
ing: “It seems that Klebs has established his general contention of the dual
determination of periodicity in these forms, but there are some minor concep-
tions that are less happy.
“He classifies all nutrient salts together as if they all have the same effect
upon the course of development, while agriculturists have fully demonstrated
that nitrates and phosphates in some respects have opposite effects. He im-
plies that salts have their effects mainly as nutrients (building materials),
while the extensive work on antagonism probably deals with general physical
or colloidal effects, and there is evidence that metallic ions are of importance in
catalysis. Moreover, it is not yet known whether high nitrate supply induces
vegetation and succulence through materials, (proteins, etc.) built from it, or
through its lyotropic effects, and whether the partly contrasting effects of
phosphates depend upon the first or second condition. Periodicity in salt ab-
sorption which has been observed in trees and grains is also minimized. It
seems evident that to get far back of the general proposition which Klebs has
apparently proved, there is need of a careful study of internal conditions of the
plant, anatomical, chemical, and microchemical, as well as the application (by
injection or otherwise) of various salts and carbohydrates and products manu-
factured from them to be sure of the effective agents.”’
This summary very accurately defines the present status of the whole prob-
Jem and opens up the field of future attack. Some other references are of special
significance in furnishing additional facts for interpretation of the nutrient
relations in the plant itself.
Fischer (8) has studied the starch and sugar transformations ina wide range
of plants taken at various periods during the year. He did not differentiate
between vigorous and non-vigorous individuals, but has distinguished between
starch storeres and fat storers. He found that the stored starch underwent
marked changes, and that such transformations are closely associated with the
formation of glucose.
Leclere du Sablon (40) has investigated the carbohydrate reserves in the
stem, root, and leaves of girdled and non-girdled pear trees three or four years
of age. He found that by autumn there were greater reserves in the leaves but
smaller amounts in the roots of the decorticated trees. Analyses of the stems
indicated little difference. The chlorophyll, however, was less abundant in
the leaves of the decorticated trees; such leaves were in general recognizable
by their yellow color. It was suggested that there seemed to be a sort of regu-
34
lation of the assimilatory function; the products of chlorophyll assimilation
not having their normal outflow thus encumbering the leaves, and causing a
diminution in the production of chlorophyll.
Hedrick (16) has reported ringing experiments with tomatoes and chrysan-
themums. Commercially this practice was not asuccess. There was actually
a decrease in the weight of fruit produced on the ringed tomato plants, and the
root development of both the tomato and chrysanthemum plants which had
been ringed was markedly decreased. i
Remy (38) has given results of the analyses of apple and pear trees used in
fertilizer tests. Those trees from which nitrogen was withheld were markedly
unfruitful. He has stated that a nitrogen content of at least 1.25% of the dry
substance of the leaves is essential to fruit-bud formation, and that the flower-
ing and fruiting condition is far more sensitive to variations in nitrogen supply
than to potash, phosphoric acid, or lime.
Petri (86)* has reported experimental studies on fruit setting in the olive.
His observations are of particular interest. He has suggested that the abortion
of the developing flowers and ovaries in the olive is due in large measure to a
lack of sufficient supply of nitrogen in the plant tissues, and that this really
constitutes a cause for sterility inthat plant. A deficiency of nitrogen relative
to the carbohydrate supply represents a stimulus to abundant formation of
flowers, but if the available nitrogen supply goes below a certain limit, the
flowers remain sterile because of incomplete development of the ovary. Lack
of moisture in soil may be a cause of sterility, due to the lack of absorption of
nitrates. His investigations are limited, but tend to bear out his conclusions.
A later report (37) has confirmed and somewhat extended his former state-
ments. He found that fertile branches of olive contained 2.119% to 2.370% N
of dry weight, whereas those not setting fruit contained from 0.720 to 0.924%.
“Tn normal conditions of vegetation the inception of the reproductive phase
coincides with a relative prevalence of the products of assimilation over those
that are derived in whole or in part from the mineral nutrients. Naturally
this particular nutritive relation may be established both by an increase of the
assimilatory function of the leaves and by a diminution of the absorbing roots.”
Petri has taken special pains to point out that the mere formation of floral
parts does not necessarily indicate the capacity of any plant for fruit produc-
tion, and that the nutritive relations for fruitfulness do not necessarily coin-
cide with the extreme fluctuations under which ‘‘the simple differentiation of
the reproductive organs’”’ occurs. ‘‘The same deficiency of nitrogen which in
many cases determines an abundant flowering, may also impede the develop-
ment of the ovary when it goes beyond a certain limit. Likewise the deficiency
of water in the soil may frequently stimulate the formation of abundant flowers
and yet constitute a cause of arrest of the growth of the female organs.’ That
sterility may be due to conditions of nutrition as well as heredity was also
pointed out.
Hartwell (15) has reported on work with potatoes and mangels in which he
attempted to determine the effects of potassium in relation to starch assimila-
*The writers are indebted to Dr. Sophia H. Eckerson, of the Department of Botany of the
University of Chicago, for a careful translation of the original articles by Petri.
30
tion. He has stated that, ‘‘A deficiency of available potassium in the soil was
usually accompanied by an accumulation of starch in potato vines,’’ and that
“Many different factors, correlated in each case with retarded growth, were
found to be associated with an accumulation of starch in the above-ground
portion of plants.”’
Hibino (20) has reported on his investigations in ringing. Among other
things he found that in the ringed individuals above the wound there was an
increase in organic and inorganic reserve materials. In the case of decortica-
tion only these consisted of starch, reducing sugar, ether extract, and ash; if
wood ringing was performed these were non-reducing sugar, proteins, crude
fiber, and tannins. There were no estimates of nitrates, the total nitrogen de-
terminations having been calculated to proteins.
Recently the relation of nitrogenous fertilizers in connection with mottle-
leaf in citrus trees has been receiving much attention. Briggs, Jensen, and
McLane (4) have reported in connection with their investigations of this sub-
ject that ‘“‘groves which for some years had received only the ‘complete’ ferti-
lizers in general use in the areas studied were badly mottled in all cases, so far
as observed in these studies. This was also the case where sodium nitrate was
used alone or as the principal fertilizerforsome years. . . . Norelationwas
found between the percentage of leaves mottled and the total nitrogen content
in the soil in either the orange groves or the lemon groves studied.’’ McBeth
(33) has found that ‘‘mottled orange leaves have a higher moisture content
than healthy leaves of the same age from the same tree. The nitrogen content
of mottled leaves is also generally higher than healthy leaves. Extreme mot-
tling is frequently associated with a high nitrate content, but the correlation
is by no means an invariable one.”’ The relation between nitrates and mottle
leaf still remains to be established definitely.
MATERIAL AND METHODS.
Experimental.
In the present work with tomatoes, we were interested mainly in a compara-
tive study of the internal conditions in plants which were setting fruit, and
those which were not, particularly with reference to the presence of total nitro-
gen, nitrates, moisture, and carbohydrates, and the relations between them.
Since our work was to deal largely with the conditions within the plant, we
made little effort to determine the exact quantities of nutritive or other ele-
ments in the soil in which the plants were grown, beyond a knowledge that the
supply was abundant or restricted in any particular case.
Materials. The tomato was selected as material for investigation because
of the ease with which this plant can be handled and grown under green-house
conditions, because it is clean cut in its fruit-setting responses to any set of
conditions imposed, and because it is readily available in any quantity.
36
All the plants used, with the exception of one lot, were of the Lorillard
variety and were raised from seed. The seeds were first sown in loam soil, the
seedlings pricked off into individual two-inch pots containing rich potting soil
and when they had made a height of some three or four inches, the most uniform
plants were selected for transfer to any particular set of conditions which it
was desirable to employ. For the most part the plants used were stocky,
actively growing, and without external evidences of flower buds when they
were selected for transplanting.
For the sand cultures ordinary white quartz sand was used. This was free
from organic matter but was not subjected to any particular treatment or
washing before being used. It contained considerable quantities of iron.
Without added nutrients the plants did not grow init. This sand was used as
a medium in which to grow plants subjected to a very low supply of nitrates.
It was not desired in any case completely to eliminate them from the soil. A
thin layer of cotton batting was put in the bottom of each pot before filling it
with sand so as to prevent the latter from being washed through when the
plants were watered. After filling the pots a porous battery cup was sunk into
each, allowing about one-half inch to protrude above the surface of the sand.
A large, flat cork was fitted into the opening. The nutrient solutions were
poured into these cups and allowed to seep out into the sand. In this way the
taking up of the nutrient solution by the pot itself and its later appearance as
an efflorescense on the rim and sides, was almost entirely avoided. The roots
of the growing plants formed a solid mat about the cups.
The nutrient Knop’s solution employed in connection with the sand cultures
was made up as follows:
Aveen\Vinonesnummi stiliatery.c-mensteee can ers: sate a Sele saraeene aos 2%
Dibasie potassimm-ephosphatessaascee aaa aes ae 2%
IPOGASSHIMBMTbT A Gemeente ei ot iat cre cress Riva sence Serer eete 2% :
Bee Calcitimeaomitratesee es ie tise a cie ceeoe cee ae 8%
For use, equal parts of A and B were diluted one to seven with tap water and
then mixed. Some precipitate was always formed, but this did not in any way
seem to interfere in the use of the porous cups. Every three weeks the cups
were scraped out with a scalpel and the accumulated sand and precipitate,
which is always but little, dug into the sand about the plant. In some cases
this was not done; not the slightest difference was observed in the plants in the
two cases.
When the plants were transferred to the pots containing sand, all the soil
and adhering particles of organic matter were washed from the roots with great
care. The plants were then placed in the sand about one-half inch deeper than
they stood originally. This is desirable because a large part of the roots pre-
sent at the time of transfer die back, but new ones are produced very quickly
from the stem.
The particular conditions for any particular lot or series of plants are given
in connection with the analysis of the same, but there are some general condi-
tions which will apply to all of them. No special precautions were taken re-
37
garding the general green-house conditions. So far as possible a temperature
suitable for growing tomatoes was maintained, the light conditions of course
varied with the season and external conditions, but care was taken that all
plants in any lot or series were uniformly subjected to the same general condi-
tions. The plants were grown in ordinary ten-inch to twelve-inch earthenware
pots. Every pot, however, was placed in a granite-ware basin, which served
the double purpose, first, of preventing the roots which came through the bot-
tom of the pots from coming into contact with any soil in the benches on which
the plants stood, or the leeching of any material from such soil into the pots,
and second, it was possible to maintain a uniform condition of moisture in the
several pots. For the most part our effort was to maintain, in each basin,
when the pot was in it, a depth of about one inch of water. Of course imme-
diately after watering this level was often higher, and sometimes it was a trifle
lower; but the soil was not permitted to become dry in any case, except in the
experiment where the soil was intentionally allowed to dry out. Water from
the Chicago Municipal supply was used throughout all the experiments and in
making up the nutrient solutions.
Chemical.
Sampling and Preservation of Samples. In order to obtain uniform samples
in so far as it was possible, a number of plants were selected from any given lot
which was to be sampled. After cutting the plants off just above the surface
of the ground the leaves were removed, those from the upper half being kept
separate from those of the lower half of the plant. The leaves were then cut
into pieces about two inches long, and 100 grams weighed out for each sample.
The stems were then cut into two-inch pieces and weighed. The samples were
placed in large wide-mouthed glass-stoppered bottles and taken at once to the
laboratory.
Enough 95% alcohol was added to each sample to insure a concentration of
about 75%. In all cases except the first few lots of samples 0.25 gr. of precipi-
tated CaCO ; was added in order to neutralize any acids which might be present.
After heating for one hour on a steam bath at 70° to 75° C. the samples were
placed away until they could be analyzed.
It might seem as though there would be sufficient loss of moisture to cause
error from the time the samples were cut up until they were weighed, but
Table I will illustrate that such was not the case. In Table I, samples 1, 2,
and 3 were taken without cutting the plants and samples 4 and 5 were weighed
from a composite of the plants which had been cut into two-inch pieces. The
moisture in sample 6 is calculated from the determinations of series M, upon
the basis that there was twice as much green weight in the leaves as in the stem,
a ratio which was noted when the samples were taken. The other samples
were taken from the same lot and at the same tims as series M.
Extraction of theSamples. After the samples had been allowed to stand for
at least several weeks, the aleohol extract was poured off and filtered into a liter
flask. The residue was then transferred to a pyrex beaker. Small amounts of
38
— | a
TaBLE I.—SHOWING THE DETERMINATIONS FOR MOISTURE IN W HOLE PLANTS
AND THOSE CUT INTO SMALL PIECES.
Sample Character of Percentage
Material of moisture
Reeser Sa Sten fm uae, Soe ectee Matas <tAegole terns silos sire Whole plants 91.17
PAs oie LORE ea ROTA Men LO EIA TORTS ACI ce REED SARE Whole plants 91.06
8}, ba Bernd SEN ERY eo Eoin imal eR ene poe Whole plants 91.40
(OS CUED EE An RE Se nC ena see Sette soe Cut into 2-inch pieces 91.61
DO remeerete arena aerate, neierahcneak are eae Staion bye sseracs Coes esc Cut into 2-inch pieces 91.65
Gyre Sick crt cwtran rere ates cic eteach Te neicaaeia eine eaieees From sample extracted 91.63
Series M
warm 80% alcohol were added and allowed to cool and then filtered into the
liter flask. After repeating this operation until there were about 900 ¢.c. in
the flask the residue was dried upon a steam bath and then transferred to a
small weighed beaker. All of the extract remaining in the original beaker was
transferred to the filter and the filter paper was washed carefully. The ex-
tract in the flask after coming to room temperature was made up to a liter and
then stored away in a tightly stoppered glass bottle. After the residue was
air dried it was weighed, ground finely in a mill, and then weighed out into
one-fifth sample and one-twentieth sample aliquots.
Total Nitrogen. Fifty cubic centimeters of the extract, representing
1/5) of the original sample were placed in a Kjeldahl flask and placed upon a
steam bath to drive off the aleohol. An aliquot of the residue representing
1/59 of the sample was then added and the total nitrogen determined by the
Kjeldahl method modified to include nitrates.
Nitrate Nitrogen. The nitrrte nitrogen was determined by a modification
of the Schulze (42) method very similar to that used by Mitchell, Shonle, and
Grindley (34). The method was checked up with a sample of potassium ni-
trate of known strength.
Carbohydrates. Two hundred cubic centimeters of the extract represent-
ing!/,of the sample were placed in a beaker and the alcohol driven off upon a
steam bath. An aliquot of the residue representing 1/; of the sample was
placed upon a filter paper and extracted with 200 c.c. of warm water (80°-40°C.)
in successive small portions. Such an extraction completely removed all the
free-reducing substances and sucrose. The extract of the residue was used to
transfer the extract from the alcohol solution to a 250 ¢.c. volumetric flask. The
extract was then neutralized when necessary with NaOH and cooled to room
temperature. The solution was cleared with just sufficient basic lead acetate,
then made up to volume and without standing longer than to allow the precipi-
tate to settle, was filtered through a dry filter paper into a dry vessel. Two
hundred cubic centimeters of the filtrate were placed in a 250 c.c. volumetric
flask and sufficient saturated Na,SO, solution was added to precipitate any
very slight excess of lead. This solution was made to volume and after stand-
ing until the lead was completely precipitated was filtered through a dry filter
paper into a dry flask. This solution was used for the determination of free
reducing substances and the easily hydrolyzable non-reducing disaccharides
39
(sucrose*). The residue from the water extraction was used for the determina
tion of polysaccharides (starch*).
Free-Reducing Substances. Twenty-five or fifty cubic centimeters of the
cleared extract were used for the determination of the free-reducing sub-
stances.
Sucrose. Seventy-five cubic centimeters of the extract were placed in a
100 c.c. volumetric flask. Five cubic centimeters of HCl(sp.gr.1.19) were added
slowly and then the flask was placed in a water bath at 70° so that the solution
reached 65° to 70° at the end of 314 minutes and was kept at 69° C. for 6/2 min-
utes longer. The flask was then removed, cooled, neutralized, cooled to room
temperature, and made up to 100 ¢.c. After being filtered through a dry filter
paper into a dry flask 25 or 50 c.c. were used for the determination of the reduc-
ing power.
Polysaccharides. The residue from the water extraction was boiled with
150 c.c. of water and 15 c.c. of HCl (sp. gr. 1.125) in a two-liter flask with a re-
flux condenser for two and one-half hours. After neutralizing to litmus with
NaOH the solution was transferred to a 250 c.c. flask. After clearing with
basic lead acetate and deleading with Na.SO,, 25 c.c. of the solution was used
for the determination of the reducing power.
The reducing power of all of the carbohydrate solutions was determined by
a combination of the Munson and Walker method and the Bertrand method.
The reduction was carried out under the conditions of the Munson and Walker
method and the tables of this method were used (43). The determinations of
the amount of reduced copper were carried out by the Bertrand method.
The results have all been calculated and expressed as dextrose. While this
does not give absolute results for the different carbohydrates, such results are
none the less comparative. Any reliable method for a more definite differen-
tiation of the carbohydrates would have consumed so much time that it would
have been impossible to cover so wide a range of material. It seemed wiser,
therefore, to make a general survey now and to defer a more minute study until
a later time.
General Statement. The free-reducing substances represent the total re-
ducing power of the extract before hydrolysis, expressed as dextrose. Sucrose
represents the increase in reducing power due to the hydrolysis under the con-
ditions given for the determination of sucrose. The results are expressed as
dextrose. While this may not give absolute results for the amount of sucrose
it does give the relative amounts of sucrose or substances which are hydro-
lyzed with the same degree of ease. A sample of pure maltose was sub-
jected to the same method of hydrolysis and no measurable increase of reduc-
tion due to the hydrolysis was detected. Starch is expressed in terms of dex-
trose. Although the method used for the determination of starch is not abso-
lute and includes any polysaccharides which are hydrolyzed under the condi-
tions imposed with the production of reducing substances, it should be kept
in mind that the term is used with that significance. The substances included
in addition to the starch are those which are hydrolyzed with about the same
*The terms ‘’sucrose” and ‘‘starch’’ are used throughout this discussion with the significance indi-
cated in the paragraphs under the ‘‘general statement.”’
40
degree of ease. Micro-chemical tests show an abundance of starch grains
where the determinations for starch are high and scarcely any starch where
the quantitative methods show very low amounts. It is quite probable that
the polysaccharides hydrolyzed by this method are made up of starch in a
large part.
Moisture and Dry Weight. One hundred cubic centimeters of the alcohol
extract were evaporated to dryness upon a steam bath and then dried to con-
stant weight in a vacuum oven at 78°C. From this weight the total dry weight
of the extract was calculated. The total dry weight of !/; of the residue was
determined by drying under the same conditions as mentioned above. The
moisture was then determined by difference.
Microchemical.
The principal substances tested for microchemically in all the experiments
were free-reducing substances, starch, and nitrates, to a lesser extent deter-
minations of calcium, potassium, oxalates, and chlorides were also made. All
the analyses were made immediately after cutting the fresh material and bring-
ing it into the laboratory. All tests were made in triplicate, at least.
The following were the three principal tests employed:
Free-reducing Substances. Fliickiger’s Reagent made up of a minute quan-
tity of copper tartrate placed in a drop or two of 15% to 20% NaOH was used.
When the copper tartrate was completely dissolved and mixed with the sodium
hydrate, thin sections were cut from the material to be tested, immediately
placed in the solution, and a cover glass added. The preparations were then
placed on a water bath at about 90°C for one hour. Comparisons were based
on the relative number and size of the dark brown granules of copper oxide
precipitated.
Tests based on osazone formation were entirely unsatisfactory for the to-
mato tissue.
Nitrates. The reagent used was made by dissolving 0.1 grams diphenyla-
mine in 10 grams 75% sulfuric acid. Fresh sections were placed on a slide,
covered, and the reagent run in from the side of the cover. <A blue color indi-
cated the presence of nitrates. Very satisfactory comparisons were obtained
by noting the intensity of the coloration.
Starch. The well-known test, iodine-potassium iodide solution was em-
ployed, and the peculiar granular nature of the starch noted.
Anatomical Methods.
For the anatomical studies both fresh and preserved material was used.
Some of the stems were cut in parafine though for the most part material hard-
ened in alcohol was cut sufficiently well on a sliding microtone without previous
imbedding of any kind. For the more detailed studies the material was stained
in Safranin and Griibler’s Lichtgriin and mounted in balsam.
41
PRESENTATION OF DATA
Chemical.
Experiment II. The plants from which samples of Series A and E were
taken were of the variety Ponderosa. They were grown in ordinary greenhouse
soil in 2!4-inch pots, and at the time of transplanting were about five inches
tall, slender, somewhat yellowed, and showing flower buds.
On June 14, 1916, they were transplanted in the greenhouse to a ground bed
about two feet in depth, of fresh cow manure which contained considerable hay
and straw but without the admixture of any soil whatsoever. Ordinarily these
conditions would be considered wholly unfitted for the growing of tomato
plants, but within several days, the young plants took onahealthy green color
and began to grow vigorously, though most of the blossom buds fell off before
or immediately after blooming.
The samples constituting series A were taken July 25 at 9:30 a.m. ona clear
day. The plants were then about four feet high, had a good green color, were
flowering fairly well but had failed to set fruit.
The samples constituting series E were taken September 8, at 9:30 a. m.
during fairly clear weather. The plants were still distinctly vegetative, about
five to six feet high, beginning to turn somewhat yellow, and although they
blossomed freely, scarcely any fruit was produced. The analyses are given in
Tables II, III, IV, and V. Because the variation in dry matter of the plants
grown under different conditions and in different parts of the plant is great, it
seemed wise to give the results calculated to both the dry weight and to the
green weight.
These plants of this series were high in moisture, total nitrogen, and nitrate
nitrogen and low in total dry matter, sucrose, and polysaccharides, and fairly
high in free-reducing substances. In the stem, going from the top to the bot-
tom, the total nitrogen decreased and the polysacchrides, free-reducing sub-
stances, and total dry matter increased. In the leaves this relation of total
nitrogen and nitrate nitrogen to free-reducing substances is the opposite, but
with the polysaccharides the same relation holds as was found in the stems.
TABLE II.—SeEnrtzes A.
All results computed to a dry-weight basis except moisture and dry matter.
Material Upper leaves Lower leaves Upper stems Lower stems
one First | Second]| First | Second || First | Second|| First | Second
deter. | deter. || deter. | deter. deter. | deter. || deter. | deter.
C7, 07. O7. O7. Oo O07. Oo7 OF.
oO /O /0O /O oO
IMoIsturetacenae cerca OORT Mee canes 91.25 90.88 932291. Ail) cicteerets O17 0)e ees
DryeMatter seas ssercaeee 9.89 oan 8.75 9.12 (G57 6 Neng Peactadton SES0% |laaeee
Total Nitrogen........... 5.02 5.06 3.36 3.41 1.81 1.76 1.74 1.78
Nitrate nitrogen.......... Be ers Sah ee et he Pe ee || pale na llltoa aac
Free-reducing substances. 1.92 1.97 2.21 2.73 2.08 2.20 ib ilit siti
SUCTOSC sane er 0.00 0.00 0.00 0.00 0.53 ORO? ol\| Nees |e eee
Starch-crsscreue onesies Bi 908 le eee eO9e | |\cisorenrs 7.90 7.90 8.43 8.26
TasBLeE III.—SeErizgs A.
All results computed to a green-weight basis.
Upper leaves Lower leaves Upper stems Lower stems
Material
First | Second || First | Second || First | Second|| First | Second
deter. | deter. || deter. | deter. || deter. | deter. || deter. | deter.
% % % % % % % %
IMOISturenses ca. eeic an seo SORT ale eke 91.25 90.88 93529) meres: ONeill ee acne
DD rvAMeattenar deme eicee ORSOUA a aks 8.75 9.12 6.71 nia aoe eC ors mae
Motalinitrogenk-eas..-2 0.496 0.500 (ei Geaauc 0.121 0.118 0.144 0.147
Nitrate nitrogen.......... Fora e || SCTE all | eee Reese Al | Meaaemerc aaa hs ane || | peter eeal wena
Free-reducing substances. 0.189 0.194 O228h ieee 0.139 0.147 0.092 0.092
SUCRE AGabe asco Oreo: 0.000 0.000 0.00 0.00 0.055 ONOZT a); See eee ll sears
Sbanchignsseac tats tess ec ORGS25i (ea sere | leew ets tall a eeecte 0.5301} 0.5301)) 0.699 0.685
Experiment V. For this experiment seeds of the Lorillard variety were
sown July 29, 1916. The young plants when large enough to handle were trans-
planted to a rich loam soil in 2!4-inch pots, watered as required, and forced
along rapidly until they were from six to eight inches high. By September 1,
the plants were thrifty and healthy and just beginning to show flower buds.
On this date most of them were taken out of the pots in which they were grow-
ing and the soil washed carefully from the roots. They were then transplanted
to three different conditions of nitrogen supply.
1. Those from which the samples of series G and B were taken were trans-
planted to ten-inch pots containing a soil mixture of one-half clay loam, one-
fourth sand, one-fourth well-rotted manure. They were given an abundance
of moisture, and well exposed to the light. They grew rapidly, were dark green
and succulent and produced many blossoms, most of which fell off soon after
opening.
Series G was collected on September 28 at 10:00 a. m. on a fairly clear day.
At this time, the plants were about three feet tall, decidedly vigorously vegeta-
tive and yet somewhat fruitful. The foliage was large and dark green, the
stems of large diameter and succulent, particularly the upper two-thirds.
Series B was collected on October 12, at 10:00 a.m. on a slightly cloudy day.
These plants were still dark green and vigorous, had set a few more fruits than
those in series G above, were somewhat taller, the foliage not quite so dark
green and the stems were more firm and less succulent.
Tasie VI.—SERIEs G.
All results computed to a dry-weight basis except moisture and dry matter.
Upper leaves Lower leaves Upper stems Lower stems
Material
First | Second || First | Second || First | Second |) First | Second
deter. | deter. || deter. | deter. |} deter. | deter. || deter. | deter.
% % % % % % %o %
IMOISGUKEH=P erence eer leno 4ol ol erereererers OI64), ilcioen OH O8 ll sessbo 93066) alle ceria
Dryamiatierneteacievacch ocr Shoo we |e teres Sx OOm Almere An OANA let ee GkS4ee eee
Motalonitrozenk sates 5.58 5.34 4.03 4.01 3.10 3.26 2.76 2.51
Nitrate nitrogen.......... 0.64 0.64 (Det all ees 0.57 0.55 0.73 0.71
Free-reducing substances. 3.27 3.30 2.20 2.18 3.16 3.15 0.88 0.80
SUCTOSE fxcaeeaeiacit oe aasis 0.46 0.41 0.00 0.00 0.07 0.07 0.00 0.00
Starcheewe. cicsso ete 8.40 8.46 6.18 6.04 6.43 6.64 10.44 10.64
43
1L0°T S60 °T 6620 te (0) Meo ISP 0 0&6 °0 9260 208°0 #68 0 898°0 CEVA trae Sate, onli ls opi aebc heat ah A Se Lp SS Yoreys
960°0 S00 LL0°0 £90 0 00°0 00°0 es 000°0 00°0 000°0 200°0 CTO ROR line eins ate yaaa SEhE eeceee nr op tetiae + es0r0ng
8° 0 cer 0 1逰0 GEE 0 £920 GF 0 8ST 0 T9T'0 2cg¢°0 69€°0 F6r 0 (G70) ee "7+" ""*S90UBISqNs SUIONpes-9L J
S100 gT0°0 620°0 0£0°0 G00 SOKO ls || een 900°0 6600 S100 ; : ““WOSOIPU O}BIZIN,
ye ies Let 0 210 est 0 6L1T'0 6410 6960 Gcc'0 GLE 0 GLE 0 “Wes01}1U [BJO],
Asi Be 066'6 “sess | Qge-g tress | Q7e+g Press | QT OT reese | ORE OT Distt teeter eeeeere ses csenesagqqeur SIG
Stee 010'06 vse | gga -T@ --->+ | g6g-eg || -----: | ogg-es || -----: | o92°68 Firetree eee ee reese ress eeeress maging
% % % % % % % % % %
‘rajap | “rejep ‘rejep | “1ejop ‘Iojop | ‘Jeep || “1ejyep | ‘1ejep || “re}ep | ‘10jep
puoseg | ysitq || puoseg | ysarq || puooeg | ysarq || puooeg| ysarq || puoseg | 4ysunq
[e197 8]
SUIO}S IOMO'T SUI0}S O[PPI]L suiays teddy) SOABOT IOMO'T SOABZ O[PPTL soave] reddy
‘sispg jy bian-waatB D 07 payndwod sz)nsas 1)¥
“WY SaluagQ— A al1avV
GL OT 96° OT 936 NG yp OF L 616 ST'6 68°2 G0'8 9F LZ 0g 2 7" Gores
Le°0 9F°0 060 690 00°0 (0); ye 00°0 00°0 00°0 10°0 &1'0 fea coOlONS
69°F bE FP L8°¢ 88'¢ 06°¢ GL & Zo°T 09'T 6P SE 19°€ SOF [TY 28 Sc marten ee ee NP ak ve ‘Se0UB]SqNs SUIONpol-soly
S10 STO FE 0 98°0 ¢9°0 SO), = [ne 20°0 1Z°0 ST 0 1Z°0 620 OT USSR! HERS LIN
mie LET 6F T 6L 1 GL% GL% 69°S Go's 19'¢ #9'€ Ors eps “"**"TesOI}U [BOT
wee eee 66'6 wee 9¢'8 HORA 1¢°9 eee ee Z1 ‘OL ee eee $2 OL Cary $9 IT Pee PODGORO CUMIN A00 ANCA [
eSB EE 10°06 ero FF 16 ahess 6re6 || cc 88°68 |] oo B68 ee 98°88 Pits ress ees eeeseeeees Qmastong
% % % % % % % 7) % % % %
‘Ieyep | ‘1ojep ‘Iejep | “rejep ‘rajyop | ‘rojep || -soyep | ‘sojep |} ‘soyop | -sez0p || ‘sojep | -1oj0p
puoossg | 4sinq |} puoveg] 4sanq || puovsg| ysarq ||puooeg}] ysatq ||puoveg] 4ysiTq || puod.g] 4saty
[ele
Sulo}s IOMOT SUI0}S O[PPI]L suieys reddy SOABOT IOMO'T SOABI O[PPIT serve] roddyQ
daqqput hap pup ainjsrowu ydaoxa sispg Jybran-hap v 07 pajndwuod sznsas 1) V
"WY SHIMHQ— AT ATAV],
Tasie VII.—Serizs G.
All results computed to a green-weight_basis.
Upper leaves Lower leaves Upper stems Lower stems
Material
First | Second || First | Second || First | Second || First | Second
deter. | deter. || deter. | deter. deter. | deter. || deter. | deter.
% % % % % % N %
IMOISGures-cencecce cee MO lcAoOlalh tite ntc O164.0 1 | eaercr 95.060 ites BbOROOOE linc ameiee
Dryomatterscossens o 2c. ek G10) Il) ceowoe 8.360 a 4.940 3 GO|; oseone
Total nitrogen............ 0.477 0.456 0.336 0.335 0.186 0.161 0.201 0.159
Nitrate nitrogen. . oH 0.054 0.055 0.083 SACRA 0.028 0.027 0.046 0.045
Free-reducing substances. 0.279 0.282 0.183 0.182 0.156 0.155 0.055 0.050
NUCEOSO Neate acim eae 0.039 0.0385 0.00 0.000 0.007 0.000 0.000 0.000
Starches one sees secs 0.718 0.723 0.512 0.505 0.317 0.328 0.661 0.674
TaBLe VIII.—Senrtzs B.
All results computed to a dry-weight basis except moisture and dry matter.
Upper leaves Lower leaves Upper stems Lower stems
Material
First | Second || First | Second |) First | Second || First | Second
deter. | deter. || deter. | deter. deter. | deter. || deter. | deter.
OF. 7, oF. 7. OF. G O7, oF
/0 7/0 /O /O /O. ca 7/0 /O
IMoisturessascecte ee oe i | COSC wll, sees BORA A ence 91.17 89.76 a
Dry matter. . eh ouae 13.23 Mean eLORoo nate 8.83 : 10.24 ;
Total nitrogen. . 3.31 3.30 2.24 2.14 2.08 2.07 0.96 1.16
Free-reducing substances. 3.26 Beil 3.66 3.65 8.06 8.03 6.67 6.65
ISUCTOSGHr keene crs eens 0.00 0.00 0.00 0.00 1.84 1.88 4.01 4.05
Starch pie rast ce ns ae 12.04 12.27 7.00 T12 (eo (se) 8.54 8.41
TABLE IX .—SrEnrtrEs B.
All results computed to a green-weight basis.
Upper leaves Lower leaves Upper stems Lower stems
Material
First | Second|| First | Second || First | Second || First | Second
deter. | deter. || deter. | deter. deter. | deter. || deter. | deter.
07. OF. C7. O07. OF. O07 OF. OF.
7O /O 70 70 (0) (0) oO 40
WIOISGUTG yee anes Clie) || Soeare 8944008) ee. 91.170 ; CANO || ae geas
Dry matter.. Se S25 0e| ere ee NOSTAO We Saas 8.830 102405 eee
Total nitrogen.. 0.437 0.436 0.236 0.226 0.183 0.182 0.098 0.118
Free-reducing substances. 0.431 0.424 0.386 0.385 0.711 0.709 0.683 0.681
Sucrose. . er Pe tent Coe 0.000 0.000 0.000 0.000 0.163 0.166 0.410 0.414
Starchin pres ee 1.593 1.623 0.739 0.751 0.650 0.647 0.874 0.861
2. Those from which series H and C were taken were transplanted to twelve
inch pots containing quartz sand. Each pot received 350 c.c. of diluted Knop’s
solution at each of five applications as follows: September 2, September 8,
September 28, (after sampling), September 30, October 9. Following the
transplanting the plants soon began to grow fairly rapidly, but the leaves were
grayish green in color, stood out stiffly from the stems, felt firm and harsh
rather than succulent to the touch; the stems were erect, small in diameter,
tough, and scarcely at all succulent except perhaps at the apical one-sixth.
There was an abundance of bloom and many of the earlier flowers set fruit
readily, though the later ones failed to do so in as great proportion.
45
Series H was collected September 28 under the same conditions as series G
above. At that time the plants were about two feet tall, blooming abundantly,
and setting at least two-thirds of the blossoms, some of the larger young fruits
were about one inch in diameter.
Series C was collected October 12 at 10:00 a. m. on a slightly cloudy day.
At this time the plants were still blooming abundantly but were setting only
one-half or less of the blossoms, were more gray in appearance, the lower leaves
slightly yellowed, and the stems more stiff and firm. In general, the plants
could be characterized as only moderately vegetative.
TABLE X.—SERIES C.
All results computed to a dry-weight basis except moisture and dry matter.
Upper leaves Lower leaves Upper stems Lower stems
Material
First | Second || First | Second || First | Second || First | Second
deter. | deter. || deter. | deter. deter. | deter. || deter. | deter.
% Te Ge. iN ee NRG ae No
Moisture paecceee cere SOMO] et leeemecr: SORGSia | Mer antese OSHO2z ha ame 86324: 51 eee
Diryematiersaneeeeere ae: A OOS Sees 110 S259 eee SSS ote eer es 13). 06. |e
Totalinitrozen se. sess. see Zo 2.06 3.16 2.87 1.65 1.48 1.36 132
Nitrate nitrogen.......... 0.14 0.138 0.06 0.05 0.07 0.07 OF036n|) =eeeee
Free-reducing substances. 3.10 Oeil 0.75 0.73 6.82 6.73 4.57 4.54
WIUCROSE Pact eieran secrere eter 0.43 0.32 153 I 2e o.Ld 3.51 4.58 4.37
DStarchis ose eee eee 125) 11.25 12.20 11.70 9.83 10.00 10.75 10.92
3. Those from which series I and D were taken were treated exactly as
those in H and C except that potassium nitrate was omitted from the nutrient
TABLE XI.—SERIES C.
All results computed to a green-weight basis.
Upper leaves Lower leaves Upper stems Lower stems
Material
First | Second || First | Second || First |Second |} First | Second
deter. | deter. deter. | deter. deter. | deter. || deter. | deter.
9% % Vows %o % % % %
MIO SH adecocse Saude sond| eAUlON lo oease SORGSOM eee SO2620)|eeanees 8622408 | sees
IDIAY ATEN esc ospAesouessce || JUICED Ion sece LOFS200|iaeein S80" eee BIEN |) sone sp
Motalimitrozenweodee ee 0.277 0.247 0.326 0.296 0.187 0.168 0.187 0.181
Nitrate nitrogen.......... 0.017 0.015 0.006 0.006 0.009 O2009))||aneee 0.005
Free-reducing substances. 0.371 0.384 0.077 0.075 0.776 0.765 0.623 0.624
SUCTOSC hence eee 0.051 0.038 0.157 0.182 0.358 0.399 0.630 0.601
Starchisservoneee series 1.347 1.347 1.259 1.207 0.669 0.674 1.479 1.503
|
solution and instead of calcium nitrate, one-half the amount was substituted
with calcium chloride. The nutrient solution therefore was without nitrates
except those contained in the water supply.
Series I was collected September 28 under the same conditions as G and H.
The plants were twelve to eighteen inches tall, yellowish except at the tips, the
lower leaves having fallen or about to fall on many of the specimens, the stems
comparatively small in diameter but distinctly firm and woody to the touch.
There were no blossoms or fruit, though there was an occasional weak blossom
46
cluster only partly developed. Commonly the plants would be spoken of as
distinctly sickly in appearance.
Series D was taken at the same time and under the same conditions as series
Band C. At that time the plants were little or not at all taller than on Sep-
tember 28, light yellow, many were without lower leaves, the stems were more
firm to the touch and practically no blossom clusters were present.
Series F was made up of plants which had been left undisturbed in the small
pots in which they were growing and collected for analysis September 8 at 10:00
a.m. on a clear day.
TaBLE XII.—SeErtzgs D.
All results computed to a dry-weight basis except moisture and dry matter.
Whole plant Whole plant
First sample Second sample
Material
First Second First Second
deter. deter. deter. deter.
; % % % %
IN ORAVIND 9 an coo OD EO OU TAR Ob Care ee : Sordi. Mlhesso secre SAE 56” alk een eae
Drverratiteney semen arc iie ere sic eta ieee aaa TABOR ee et ie 1a 2 St ee etnies
Motalenibrorenss) is onerclon ase cles eid mere QSOS Ge tne oe (tye etl It AAAS Aopitis
Nitratenatrogcenk cescmcrnsnccin see aerate (ORO | Mallitscamcce O00" © elle k eee a
Free-reducing substamces..................... 6.41 6.43 4.57 4.45
DUICLOSO RPE race ane eic ie le aiisinse otersitiat oe aes (Jaiy-A ee bine Wlattenicn a's Byatt isi" Milena eee. cre
SIGH. Saagune SOOM ECE So mC SEE mane Siersicrotanane 21.04 20.97 1923 ie Soll echeseerecaise
Tas_Le XIJI.—Sertzs D.
All results computed to a green-weight basis.
Whole plant Whole plant
Material First sample Second sample
First Second First Second
deter. deter. deter. deter.
To % % %
IW IGTELGUENS oo dep eab acades Senn Oe Boa eborosrEcons S45 60K S| bs todays] ON Oia Pons eee Best
ID FATEH) anon oie tame eGo BG enon ioenreae 1544.0) | eee 1 Ot ea atl hearers pee hain
PROCAIPNIELOLOEM Gee ann ee sote ee ee ae crores: Qcibit. “ill Saneokoote O3Seau |Percerence
INabratemiutroeseni ncmncce cere scetas trees ONOOO Mes Pera enyes O00 Breese eee
Free-reducing substances........-............ 0.706 0.688 0.954 0.957
SUGCKOSG tart coke tite c ase ontarststecs wlsallia tego stette OL GI Whe ae ee O89 7 Ome lt aero:
Starcheerotee mn tetas myth aipoeern acne NO Te sally treoesaeeet 3.133 3.122
TasLeE XIV.—Srenrtiss F, H and I.
All results computed to a dry-weight basis except moisture and dry matter.
Whole plant Whole plant Whole plant
Series F. Series H. Series I.
Material =
First Second First Second First | Second
deter. deter. deter. deter. deter. deter.
% % % % % %
IMOIStUTE:fmcaraarisn: ciclecles sya sere OD a6 Due bal |laleletecnrd cts OO OT a eek ss SE: 80805. 0 |eoseeceee
ID rye MECH Psst ocoeeeaao BoE acme oom Breet ti) Stetepe all |. Se aecatecey 14.05 SEAS or
sRotalimctnrosenkar sami: & een criss QNSSe) lhe Nears 2 3.00 2.99 1.78 1.70 x3
INitratemmitrogen....s.2.0.+. cee. 0.52 0.53 0.15 0.18 0.00 0.00
Free-reducing substances....... 2.01 2l'5 0.88 0.79 4.01 4.00
Sucrose 0.00 ~ 0.00 0.17 0.26 Pa 1.20
Sbanchiner mete peices ose carne 8.54 8.40 4.06 3.99 15.66 15.70
TaBLE XV.—SeEnriss F, H, ann I.
All results computed to a green-weight basis.
Whole plant Whole Plant Whole plant
Series F. Series H. Series I.
Material
First Second First Second First Second
deter. deter. deter. deter. deter. deter.
% % % % % %
IMOIstitest eeecse ee eet eed |e oe GOO lenses 90512025 eases 855950! ee ocean
Dryzmatteryacieeceeee eee MBOOk A|ecetctetye 97880). | sacaeees 1420506 |) Same
Motalenitrorent sense ee ae (OPH? Wgrranee = 0.296 0.295 0.250 0.238
Nitrate nitrogen........ wees 0.038 0.039 0.015 0.018 0.000 0.000
Free-reducing substances....... 0.147 0.158 0.086 0.078 0.563 0.562
SUCTOSOS si ese deck Sores 0.000 0.000 0.016 0.025 0.170 0.168
Starche cance cece eae 0.627 0.617 0.401 0.394 2.200 2.206
Series G. The analyses show that compared with the other two series H
and I the plants of series G were high in moisture, total nitrogen, and nitrate
nitrogen, and, compared with series I, are low in free-reducing substances,
disaccharides, polysaccharides, and total dry matter. It is difficult to com-
pare with series H where the differences are not so marked because the whole
plant was taken as a sample in the lattet case. In the stems of series G going
from top to bottom there is considerable difference in total nitrogen and nitrate
nitrogen. There is also an increase in polysaccharides and a decrease in free
reducing substances. It is apparent, however, that the plants of series H are
low in moisture, nitrate nitrogen, and total nitrogen and are higher in total
dry matter.
Series I. Compared with the vegetative plants of series G they are much
lower in total nitrogen. The free-reducing substances, sucrose, polysacchar-
ides, and total dry matter are very much higher than in series G. Here again
no comparison can be made upon the different parts of the plant because whole
plants were used to make up the sample.
Series B. In composition the plants in series B resemble the plants of
series G except that the stems of the latter are higher in moisture and total
nitrogen and lower in disaccharides, and total dry weight. In the stems of
the plants themselves in series B there is an increasing gradient from top to
bottom in total dry matter, sucrose, and polysaccharides and a decreasing
gradient in total nitrogen and free-reducing substances. In the leaves there
is no such relation between nitrogen and carbohydrates.
The plants of series C compared with series B were less vegetative and more
fruitful. In the stems of series C there is a decreasing gradient from top to
bottom in moisture, free-reducing substances, and nitrate nitrogen, and an in-
creasing gradient in total dry matter, sucrose, and polysaccharides. The total
nitrogen is about the same in the upper and lower portion of the stems. In the
leaves there is no such relation between nitrogen and carbohydrates.
Series D. Compared with series B the plants were low in moisture and total
nitrogen and high in sucrose and polysaccharides. Nitratesareabsent. Since
whole plants were taken to make the samples, no comparisons can be made be-
tween the different parts of the plant itself.
48
Series F. The analyses show that the plants were high in moisture and
nitrate nitrogen and fairly high in total nitrogen. The free-reducing sub-
stances and polysaccharides were low, and sucrose was absent.
While not recorded for analysis it is worthy of note that at the close of this
experiment a few pots containing plants which had received no nitrates still
remained. To each of these, 100 c.c. of a one percent calcium nitrate solution
was added. Within four or five days the stems of these plants began to turn
green, the terminal leaves became darker green and expanded, and terminal
axial growth was rapid. This result is of interest more particularly in indi-
cating that the reason for the slow growth previously was the lack of nitrate
rather than some other essential element or the presence of some harmful salt
in the modified nutrient solution.
Experiment VI. The seed for this lot of plants of the Lorillard variety was
sown October 20, 1916. On October 30 the plants were transplanted to three-
inch pots of rich, fertile soil and on December 11 the plants were transplanted
to the three different conditions of soil nitrogen supply; namely, quartz sand
without nitrogenous fertilizer, quartz sand with Knop’s solution, and to a rich
potting soil composed of clay loam one-fourth, sand one-fourth, well-rotted
manure one-half. The analyses were listed under series J, K, and L. No
analyses were finally made of the plants which were transferred to sand and
given no nitrogenous fertilizers so they are not listed below.
Series J is made up of plants collected about 2:00 p. m. December 138, 1916,
which were still in the three-inch pots of rich soil. The day was clear. At
that time the plants were growing vigorously, about four to six inches tall,
dark green, sturdy and succulent, without visible blossom buds. It was hoped
to use the analyses of these plants as a basis for study of variation in the later
analyses of plants grown with large and small soil-nitrogen supply.
Series K was collected at the same time and under the same conditions as
series L. Following transplanting, the plants had been grown in the rich pot-
ting soil noted above, but the moisture supply was limited. Instead of main-
taining a constant supply in the granite-ware pans in which the pots had been
placed, the pots were watered only at intervals as needs seemed to require in
order to keep them above the wilting point. The plants were about three to
three and one-half feet tall, growing moderately vigorously, the foliage was large,
anddark green. Each plant had two or three blossom clusters of good size and
one to several fruits. Compared with series L, the plants were much the same
except that they gave the general impression of being greener and more stocky
in every way.
Series L was collected February 16, 1917, at 2:00 p. m. on aclear day. The
plants had been grown in twelve-inch pots containing quartz sand. ‘To each
pot had been added 350 c.c. Knop’s solution diluted one to seven on each of the
following dates—December 11, 18, January 8, 18, 22,29. At the time of collec-
tion the plants were from three to three and one-half feet tall, moderately vege-
tative, the leaves large and green, somewhat drooping, those at the base some-
what smaller and lighter in color, the lower two-thirds of stem firm, green, the
49
upper one-third succulent.
There were several blossom clusters of good size,
and two to five fruits to each plant, though a number of blossoms had fallen
without setting.
TABLE XVI.—SERIES J.
All results computed to a dry-weight basis except moisture and dry matter.
Whole plant
First sample
Material
First Second
deter deter
; % %
MOIsture i scaaea cs eens er ac RIE Ooo OS. 44 Bee eee
Dryimatters seater oes eer ere 6756). all teteree ee
shotalmitrogenss eer nee een eee SeGlie = WMecageeacss
INitratemibroz ene ene een neers ORSON AA ene sce
Free-reducing substances....................-. WS7il 1.57
SUCTOSESstin5.)cnerne SO ae eae eee O80." 9 ll, Shee eee
Starch. sry eae eee erences 12.98 12.62
Whole plant
Second sample
First Second
deter deter.
% %
O38 RBs iene een
6282) | eee
Bi45% alle eee
LS 70s |e eee
0275s Seal ee eee
13.13 13.20
Series J. The plants were high in moisture and fairly high in total nitro-
gen and nitrate nitrogen and low in free-reducing substances, sucrose, and total
dry matter.
Series K. Compared with series L, they are higher in moisture and in total
nitrogen, but slightly lower in sucrose, polysaccharides, and total dry matter.
TaBLE XVII.—SeErI1Es J.
All results computed to a green-weight basis.
Whole plant
First sample
Whole plant
Second sample
Material
First Second First Second
deter deter deter. deter
: % % % %
Moisture $9.2 Ape eictase os neve aaa oe 932440) | acte seco OSRT80K- ap setae
Dry matter....... Me TEAR OR oe GeOGOW leone 65820 wile
Total nitrogen..... Pa entre so aoa CN a EES O22 82% nee see 0.2282) IE eRe
Nitrate mitrogen:.s-eeere ern mente oe eceer OFO59) © Al ec ase s wilh S Seka oa el | eee eee
Free-reducing substances..................... 0.116 0.103 Od22% > || Saas
SUCKOBON hers etre. neta Saleen onl eee DANGY (Es etoncbarcc OO51 | Riera ene
CATCH eee tye aren oe eer Ra ae 0.851 0.828 0.895 0.900
TABLE XVIII.—SeErtigs K.
All results computed to a dry-weight basis except moisture and dry matter.
Upper leaves Lower leaves Upper stems Lower stems
Material
First | Second First | Second First | Second First | Second
deter. | deter. deter deter. deter deter deter. | deter
é % % % % % % % %
Moisture scene cace mre ts on 00tan | eaeee OU 26h ee ee O3F 16 Ra ltsoanees Co) Patsy Aiea [wees Sie sic
IDA FIN AS coopacnnnucoool| LO-CeE Il cadens 8.74 ae O48Si alee eae S18 See
Motalimitrogentaeepeee een let OS 3.96 2.84 2.56 2.52 2.43 1.31 1.30
Nitrate nitrogen..........] 0.04 0.04 0.09 0.13 0.17 0.14 0839s eee
Free-reducing substances.| 3.06 Bolly ercid 1.82 11.30 11.30 3.07 3.16
Sucrosetas. 52... teen ose D5 Ngi|| eee Ou92e Nite es ne OnS2rlnetsee 1.85 1.60
Starch? ways eee eee lone 14.49 2.28 2.08 5.41 5.09 8.97 8.40
TasLe XIX .—Smrtzs K.
All results computed to a green-weight basis.
. Upper leaves Lower leaves Upper stems Lower stems
Material
First | Second First | Second First | Second First | Second
deter. | deter. deter. | deter. deter. | deter. deter deter.
; % % % % % q % %
IMGIEDETOCMO ose atic 8O0GE "| We. Js OLE | eae G3ELG yale nae snl ToIkeo es ieee
ID nvematiertay- ec reiece 1094) Ailsa 8 bate || ers cee (late: Bate (ie mes tialtse il en peroce:
Total nitrogen... 0.441 0.483 0.248 0.224 0.172 0.166 0.107 0.106
Nitrate nitrogen... 0.004 0.004 0.008 0.012 0.012 0.009 QRO3 205) eee
Bie educing substances.| 0.335 0.347 0.154 0.159 0.774 0.773 0.251 0.259
Sucrose. . er ested (tL OOM ee eats | OROSO) || eeee. OR0560 eee 0.151 0.1381
Starchpretecsepnetrrt cir 1.654 1.585 0.195 0.181 0.370 0.348 0.734 0.687
TABLE XX.—
SERIES L.
All results computed to a dry-weight basis except moisture and dry matter.
Upper leaves Lower leaves Upper stems Lower stems
Material
First | Second First | Second || First | Second || First | Second
deter. | deter. deter. | deter. deter. | deter. deter deter.
% % % % % % % %
MOISTURE hermes ecice nisl SOL Obea||, miele SSPo0EM |eeeeae SOROO May ete 882270 silane
IDIAy TMENAR NE soopsecoueoees|| VeRO) Wl Zecene 1 5Oe Yl eee: OMTOE Mle (nares Nl), ceeecc
Total nitrogen. . Shoo OBO 2.78 2.51 1.69 1.59 97 1)
Nitrate nitrogen... O03 Wl takee 0.16 0.13 0.06 0.07 0.52 0.47
Free-reducing substances.| 2.47 2.46 3.00 3.00 9.22 9.20 5.20 5.40
Sucrose. . BS atersee ovsreverers 1763 2.06 1.39 1.42 3.39 3.05 4.39 4.44
Starch......... keane |CLoe38. 18.39 4.15 4.17 8203 8.29 13.64 13.40
TABLE XXI.—SERIES L.
All results computed to a green-weight basis.
| |
Upper leaves Lower leaves Upper stems Lower stems
Material
First | Second || First | Second || First | Second || First | Second
deter. | deter. deter. | deter deter deter. || deter. | deter.
; % % % % % % % 70
IMOISHURE Aceon kas eee SOMLOOM |e SSEO00M|preceiee fA) 9 Sook ac 8822708 een cee
DiGpyam attereeeeene eee. 1329000 pees THEO || osc LO SOON |Reeaeee WTB I Saoce
Total nitrogen. . 0.464 0.468 0.319 0.288 0.170 0.160 0.113 0.132
Nitrate nitrogen.. OROOSH | Saseee 0.019 0.015 0.006 0.007 0.061 0.055
Big feducing substances. 0.343 0.342 0.344 0.344 0.930 0.929 0.610 0.633
Sucrose. . Seca pare dare 0.239 0.286 0.159 0.162 0.342 0.356 0.514 0.520
Starches ee pres ns eee 7) {59533 2.505 0.476 0.480 0.861 0.837 1.600 1.572
Within the stems from top to bottom there is a decreasing gradient in moisture,
total nitrogen, and free-reducing substances and an increasing gradient in suc-
rose, polysaccharides, and total dry matter.
Experiment VII. For this experiment seeds of the variety Lorrillard were
sown February 2, 1917, and the young plants transplanted to two and one-half-
inch pots of richsoil February 14, 1917. On March 10 these plants were from four
to five inches tall, stocky, and green, but in need of repotting. Some showed
small flower buds clearly. On this date the plants were transferred to ten-
inch pots containing rich soil.
which follow.
51
Further treatments are described in the series
Series M. The plants in the series were grown from March 10 to March 23
in ten-inch pots in a soil mixture of clay loam one-fourth, sand one-fourth, well
rotted manure one-half, and were copiously watered. Two plants were grown
in each pot. At the time of sampling they were eight to ten inches tall, dark
green with full heavy foliage, succulent, vigorous, and usually showed a well-
developed bud cluster, none of the single buds of which showed any yellow of
the corolla. Generally one of the two plants was taken from each pot though
in some instances both were removed. (The plants remaining were used in
series Q and R.) The samples were taken at 2.00 p.m. ona clear day. The
analyses of these plants are used for comparison with those collected later in
the other series of this experiment.
TaBLE XXIJ.—SrEnrixzs M.
All results computed to a dry-weight basis except moisture and dry matter.
Leaves of whole || Leaves of whole || Stems of whole || Stems of whole
plant plant plant plant
First sample Second sample First sample Second sample
Material : — -—---
First | Second|} First | Second |} First | Second || First | Second
deter deter deter. | deter. || deter. | deter. || deter. | deter
i % % % % % % % To
Wikies soadooaecenupooce || USGI Wong GO S24 ||| ansee 94516)" lh eens 93°94) |b-c Rae
Dryemattensn nace ee aoe CRG T IER leanense 6 OeiGr le ements eto ey wigs S2 620635 |pemeere
Motalmnitrogen., o.- 51.0. ye Ur lg eee etre SHODDY Illes hetoe PRI | ence tetre 2204: cal) a cae
Nitrate nitrogen.......... OR76- |b O50) al eerie DO 2 ll ects, ere 1e63%y ieee
Free-reducing substances. 2.08 2.05 1.30 1.40 OF 8054 ones a ne De ee ee
SUCTOSEStecpeeerc ee nee De Sie eerecvetees 1204S | cercr O46) sees 5 106 4| saree
Starchiere Mew nea eee roy mle 2D ina llostrsonce TOGO 2 neers ORSOM SI emma 3.08 3.05
TasLE XXIII.—Szrnrizs M.
All results computed to a green-weight basis.
Leaves of whole || Leaves of whole || Stems of whole || Stems of whole
plant plant plant plant
First sample Second sample First sample Second sample
Material First | Second || First | Second]|| First | Second || First | Second
deter. | deter. || deter. | deter. deter. | deter. || deter. | deter.
% %o % % % % % %
IMOIStuTeNaacecr eer elo. O Lm eee SOR 24 Sess OA S16). aes OSE 94. ule Stee
Diryemsattenwye-ecereene D239 MN orlenckext O76: Wie eae 52 84~ ale ethene HANG Wl ceoace
Motalmiutrorensaas 6 oases (8S MI cee ee (evs |b Sasonc OF1GOR eee OFV789|eaeeeee
Nitrate nitrogen.......... (OAS Ih ooops OR046a1F eee OOS || Seeane O2098s |i eases
Free-reducing substances. 0.195 0.192 0.126 0.136 050467 |eseeee OL075s | (eaeecer
Sucrose a shoe ee OMMOS HI Serccuse OSLO Speers OROZ6N aac QUOC Sah erasecc
Starches eecmenass coe LAOH san an HE lerenen 0.051 0.049 0.185 0.186
Series O. On March 10, 1916, some of the plants mentioned in series M
were removed from the pots in which they were growing, the soil particles care-
fully and thoroughly washed from the roots, and then they were transplanted
to ten-inch pots containing quartz sand. Two plants were put in each pot.
On April 11 and April 19 each pot was given 350 ¢c.c. of nutrient solution free
from nitrogen. After being transplanted, the plants wilted appreciably but
recovered within two days. While there was some continued axial elongation,
52
“TBI ‘ZZ YoU poydeisojoyg “J Seeg pesoduroo yorys syuvyd jo edueg—'F “sty
growth was decidedly checked, the lower leaves became yellow and fell, though
for the most part the blossom clusters expanded and in some cases set one or
two fruits. The stems became yellow, very tough and woody, and stood erect
with no tendency to tip over. Samples were collected for analysis April 16 at
2:00 p.m. on a partly cloudy day. At this time the plants were about sixteen
inches high, erect, light green, the lowermost leaves brown and dry, and in
some cases already fallen; the upper leaves gray green, small, the stems becom-
ing yellow, woody, even well above the middle, and scarcely at all succulent,
the second blossom clusters small and not setting to form fruit.
TaBLE XXIV.—Seniss O.
All results computed to a dry-weight basis except moisture and dry matter.
Upper leaves Lower leaves Upper stems Lower stems
Material —_
First | Second || First | Second}! First | Second |} First | Second
deter. | deter. || deter. | deter. || deter. | deter. || deter. | deter.
x % % % % % % % %
Moisture........ ST ec Ml SOU AO |! eee S6x000 4 fee eee S6s98ie leone 842625 |||, eee
Diya attereeseeeee ‘ 18.60 Pee ici 14200 Wi seee SSO 2a rere 152385 Ae races
Total nitrogen..... enc Oe I ZAW) 1.73 1.12 1.20 0.90 0.96 0.80 0.83
Nitrate nitrogen..... . 0.00 0.00 0.00 0.00 0.00 0.00 0.007 0.002
Free-reducing substances. 3.65 3.72 4.02 4.08 9.20 9.23 9.05 8.96
Sucrose........ ee 1.05 0.78 0.86 0.80 4.00 4.08 6.31 5.70
Starchytacset ear eeie pee 31.76 31.85 16.20 15.90 17.98 18.51 22.96 22.51
I
Series P. On March 10 the plants in this series were taken from the pots in
which they were growing, the soil carefully washed from the roots, and, they
were then transplanted to twelve-inch pots containing quartz sand. Each pot
TABLE XX V.—SERIES O.
All results computed to a green-weight basis.
Upper leaves Lower leaves Upper stems Lower stems
Material
First | Second || First | Second |) First | Second || First | Second
deter. | deter. || deter. | deter. deter. | deter. || deter. | deter.
O7 7. OF G7. OF. € O7 OF.
BESAC 70 /0 /0 /0 70 /0 7/0
Morstulemenreeenintrn S1i24.0) | Eevee GLO) Ws ieasc 86298 Sealer. S462) Wwe eeonrers
IDV Ne mboosouncsnoos |} sod) «| aooncc WANS al| Gaoece USOT | eres 15.38 Rae
Motallmitrogent-see ence 0.316 0.323 0.156 0.168 0.117 0.125 0.123 0.127
Nitrate nitrogen.......... 0.000 0.000 0.000 0.000 0.000 0.000 0.002 0.0004
Free-reducing substances. 0.679 0.692 0.563 0.572 1.197 1.201 1.392 1.378
Sucrosesssjssnoae eee 0.195 0.145 0.121 0.112 0.521 0.531 0.970 0.875
Stancheerees epee ana 2 5.909 5.925 2.269 2.226 2.340 2.409 3.531 3.461
received an application of Knop’s solution diluted one to seven on each of the
following dates: March 10, March 17, March 24, April 2, April 19. An abun-
dance of moisture was supplied at all times. On April 16 the samples were col-
lected under the same conditions as series O. At this time the plants were
eighteen to twenty-four inches high, erect, bright green in color, the leaves
standing out stiffly from the stems except the lowermost, which were also some-
what yellowed; each plant had set several fruits.
54
TABLE XXVI.—Srniss P.
All results computed to a dry-weight basis except moisture and dry matter.
Upper leaves Lower leaves Upper stems Lower stems
Material
First | Second || First | Second || First | Second || First | Second
deter. | deter. |} deter. | deter. deter. | deter. || deter. | deter.
’ % % % % % % % %
IMGISCUTE Ms eateecserecter: otistes, | Oe UO2ialy ates Sie Zie ell fase; OORS2 i eer ae: Sal Zt eae ares
GA ene e +t D598 rec iliorstes, sacs WA A papas ORB Urs ecm US Sia eee:
Total nitrogen. . Sees 2.74 2.80 2.28 2227 1.75 1.91 1.25 1.07
Nitrate nitrogen. . 0.02 0.03 0.12 0.09 0.21 0.13 0.16 0.18
Free-reducing substances. 2.60 2.53 2.08 2.08 8.33 8.31 7.78 7.80
SUCEOSC aenevyee Ailcinacn aes O85 |) Seaewe 0.26 0.27 0.85 1.06 3.58 3.45
Starches seas cemcternes 25.38 25.58 12.65 12.36 8.70 8.54 11.20 11225
TasBLE XXVII.—SeErtzs P.
All results computed to a green-weight basis.
Upper leaves Lower leaves Upper stems Lower stems
Material
First | Second || First | Second|| First | Second || First | Second
deter. | deter. || deter. | deter. || deter. | deter. || deter. | deter.
: % Yo % 70 % % % %
IMOIStUTe err rate eee (Ce SeaO er lk once. Sion |e enn: SOR82eeener Sota SR Yer
Dive at terescecsccis <r: Us SIe o|| Caren 122%, alperetae ORT Sie il) cere 11.88 B a
Total nitrogen. . erent 0.438 0.447 0.280 0.278 0.160 0.175 0.148 0.127
Nitrate nitrogen. : 0.003 0.004 0.013 0.011 0.019 0.011 0.018 0.021
Free-reducing substances. 0.416 0.404 0.255 0.254 0.764 0.763 0.924 0.927
Sucrose. . Se, Sere ete ORO4S3 | eee OOS] eeeete 0.078 0.098 0.425 0.410
STAT Chee tin oe 4.055 4.087 1.553 1.517 0.798 0.784 eel il sSBy/
Series Q. The plants of this series were transferred on March 10 from small
pots exactly as in series M previously described. In fact, that series simply
represents an earlier collection from the same group of plants. An abundance
of moisture was provided at all times. The plants grew very rapidly, the
leaves became large and green, and the stems of large diameter and very succu-
lent. Samples were taken at the same time and under the same conditions as
those in series O. At that time the plants in the present series were eighteen
TasLe XXVIII.—Sertzs Q.
All results computed to a dry-weight basis except moisture and dry matter.
Upper leaves Lower leaves Upper stems Lower stems
Material First | Second || First | Second} First | Second |) First | Second
deter. | deter. deter. | deter. deter. | deter. deter. | deter.
% % % % % To % Zo
IMOISGUTO Nsom ies Gee POOR 4On Ml eur evs OOPS wsoge QAS7 ON aly canna: 93230 mn Eee
nya aoveiaee ernie seas 1 SP te eee SOROS Uline: Beary al tater ee GAGE Tete
Motal mitrogenias.... 25... 4.38 4.43 33.815) 3.51 Biaex/ 3.08 2.46 D4 593}
Nitrate nitrogen. . ; 0.32 0.25 0.92 0.83 2.05 Spas 1.54 1.56
Free-reducing substances. 1.04 1.04 0.68 0.50 3.225 3.18 15 1.29
SUCrOse pista aneteeehene <5 OFS TP sees 0.47 0.30 0.17 0.24 1.43 1.65
Starchoper ses cs cue ene 12.65 12.83 4.95 5.10 1.02 1.10 IFAS tA Pace
Or
Or
TasBLE XXIX.—SERIEs Q.
All results computed to a green-weight basis.
Upper leaves Lower leaves Upper stems Lower stems
Material First | Second || First | Second|} First | Second || First | Second
deter. | deter. || deter. | deter. || deter. | deter. || deter. | deter.
: % % % % % % % %
Moisture’s.ccncn clear icton alee Ora Gums | mseitecers QUOD Ss see 94791. dee CBee) iP Sancnc
Dryamiattberieee see ee Ome a eer 8398) 8 jae aves Gea ll eee he O64 ees
Motalinitrogentercseo sees 0.505 0.511 0.301 0.315 0.170 0.160 0.163 0.168
Nitrate nitrogen.......... 0.036 0.029 0.082 0.065 MOE |\- Secon 0.102 0.103
Free-reducing substances. 0.151 0.151 0.060 0.045 0.169 0.165 0.100 0.085
Sucrosesta.heceaeceeteneee 020395 eeeree 0.027 0.042 0.008 0.012 0.095 0.109
Starch a hen mse seee 1.458 1.478 0.444 0.458 0.053 0.057 O2095 5 | ieee
to twenty-two inches tall, very dark green and succulent, the leaves large, soft,
and with a decided tendency to droop, the stems green, of large diameter, suc-
culent, and scarcely at all woody to the touch above the lower one-fourth, with
the result that the plants required stakes to support them. The plants were
blooming freely but at this time none of the blooms had set, all having fallen
soon after the fading of the corolla.
Series R. The plants in this series correspond in every way to those in
series Q except that each plant when taken for a sample, bore from two to five
TaBLE XXX.—SeEnrtss R.
All results computed to a dry-weight basis except moisture and dry matter.
Upper leaves Lower leaves Upper stems Lower stems
Material
First | Second || First | Second|}| First | Second || First | Second
deter. | deter. || deter. | deter. || deter. | deter. || deter. | deter.
t % % % % % % % %
Moisture intact cs ey OOOO el | eee Dee) alll caaado OB) ll soot on 9085 5ie5 eee
IDAZTOENNIGGonogocpoaouoe |p Lue Y/ | Seance OF 63a peers ish Die Pater ethsc 9:45) i\\ eerie
Motalinitrogenseepeseesen 4.13 4.06 DSOO Mlle eer Delia inte we 1.61 155)
Nitrate nitrogen.......... 0.16 0.15 0.17 0.20 artite Il, Seca 0.36 0.42
Free-reducing substances. 1.31 1.39 0.53 0.51 bald 4.91 4.13 4.10
Sucrose enasnnctieee ee 0.58 0.49 0.12 0.14 0.64 0.86 1.47 1.50
Starchtencesncseceemeren abdeos 17.67 0.00 0.00 1.16 1.19 0.51 0.52
TaBLe XXXI.—Sertss R.
All results computed to a green-weight basis.
Upper leaves Lower leaves Upper stems Lower stems
Material
First | Second || First | Second|| First | Second || First | Second
deter. | deter. || deter. | deter. || deter. | deter. || deter. | deter.
: % % % % % % % %
WGN s coodobdio cddocds ||, eenGe |} comands 90.37 Stee tl POOF DO lad | Ree GORDO | eee
Dryemattere. eee A Te |e see OR GRY Wl Gae sao G50) eee as O45 ieee ee
Motalimitrogenk.-ssenae 0.473 0.466 OF280) | ee cere || eereentere 0.176 0.152 0.144
Nitrate nitrogen.......... 0.018 0.017 0.016 0.019 O09 Uh aceres 0.034 0.039
Free-reducing substances. 0.150 0.160 0.050 0.048 0.333 0.319 0.390 0.387
Sucrose..... Heder Gabo 0.066 0.056 0.011 0.013 0.041 0.056 0.138 0.142
Starcheyecm ecm oss 1.987 2.026 0.00 0.00 0.075 0.077 0.047 0.048
56
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SIF LEP LLG LL°% 60°F 60°F 80°% 60°% 10°% 26°T 00° 90°€ "* sooueisqns SuULONpoel-oady
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puossg | 4Sity || puooeg | ysimy || puoosg]| ysutq || puooseg]| ysutq || puosvsg| 4ysinq || puoosog | ysung
— [Boye yy
SU19}8 IAMO'T SUI0}S OT PPI, sues reddy SOABO] IOMOT SOAB9] O[PPI] saavet reddy
“wayoul hip pun ainjsrowm ydaoxa sispq ry bran-hup D 07 pajndwoo szjnsaL 1). V
'§ SHIUAGO— TTX XX @I1EV I;
57
fruits ranging in size from that of large peas to good-sized walnuts. The object
in taking this sample was to determine if any differences in analysis could be
detected between purely vegetative and vegetative-reproductive plants grown
under identical conditions.
Series S. The plants in this series were treated exactly like those described
in series O. In fact the plants in this lot which are mentioned as having been
cut back, are the remaining bases of those which constituted series O, up to
April 23, on which date the plants were carefully knocked from their pots and
with the least possible disturbance, roots and adhering sand mass were trans-
ferred to larger pots in which there was a soil mixture of one-fifth sandy clay
loam and four-fifths well-rotted manure. At this time the plants which had
not been cut back had changed very little from the condition described for
April 16, but those which had been cut back to within an inch or two of the sand
surface, in the majority of cases had developed one or two sprouts from one-
quarter to one and one-half inches long. These sprouts were gray green, slen-
der, and woody. Within three days following the transfer to rich soil, the
stems and tip leaves began to assume a much brighter green color. Growth
was resumed almost immediately at the tips, the new leaves pushed out vigor-
ously, and became large, soft, and dark green, the stem developed above the
tip following the transfer was much larger in diameter than that below it, was
dark green, succulent, and more densely clothed with glandular hairs. Later
the old lower stems also became very dark green, showed a decided secondary
annular growth coupled with a strong tendency to develop adventitious roots.
The plants bloomed profusely and began to set some fruit though most of the
blooms fell as soon as the corolla faded. Many of the plants developed axillary
shoots. In general, plants which had not been cut back, produced much more
new growth than those which were cut to stubs. All the samples were of
plants which had not been cut back. The samples were taken for analysis on
May 12, 1917, at 2:00 p. m. on aclear day. By that date the plants had made
from four to six inches of terminal growth which was very succulent and green,
were producing many flower clusters, a few of which had begun to bloom, and
the whole stem had again become green. The sample was divided into three
portions, (1) tips made up of the new growth, (2) middles, which included the
upper halves of the plants as they were before transplanting and (3) bases, the
lower halves of the same plants.
TABLE XXXIV.—SeEniEs N.
All results computed to a dry-weight basis.
Leaves of first lot Leaves of second lot
7.195 gr. dry weight 7.591 gr. dry weight
Material
First Second First Second
deter. deter. deter. deter.
O7. OF. OF. OF.
7O 70 /0 70
Lotalimitrozentsy cy perce aoee nce rk: Cee 1.14 1.02 0.81 0.64
INI tra temitropenener ee ere tier etree ONO4 5 or ae 0222: |) tetas
Free-reducing substances..................-.- 2.07 2.03 Bia ile/ 3200
SUCTOSC® sho ctevaratie Steroe les Seis irene Poaroteve rare NST 0.00 0.00 O04 ls oe seree
Stare baat se cee ye roe tie eRe aren 5.26 5.00 7.78 7.97
58
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SPINA [BUS oY, [NJ JINAj-uoU pues ‘9AT}BOBOA ‘SNOIOSIA ‘0 SOLIOg WOLF JUBT ‘YYSII 4B ‘[NJZMAJ PUB SNOIOSIA ‘yY SoLleg U0IJ FURL 9AI}eJUESOIdAI “4Jo, JY—'E “SLT
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Ul UMOIS ‘(C) SolIog UOT; SyuB]d oAtze}UOsSoIdod ‘QUST ye SUOTN[OY s,douyy YIM pezi[i}10y PU’ PUBS UL UMOIS ‘gq SoLIEg UOT] yURTA OATyeIMASaIdoI ‘V8, IW—9 “SIq
Series N. This series is made up of the leaves which fell from the plants
in series O. Sample 1 represents those leaves which fell first and sample 2 a
later collection.
The relatively high amounts of nitrate nitrogen present compared with the
total nitrogen content is worthy of note.
Series O. Compared with series Q and R the plants in this series are very
low in moisture, fairly low in total nitrogen, and very much higher in free-re-
ducing substances, sucrose, polysaccharides, and total-dry matter. Nitrates
were absent with the exception of a trace in the lower stems. Within the stems
from top to bottom there is a decreasing gradient in moisture and an increasing
gradient in free-reducing substances, sucrose, polysaccharides, and total-dry
matter.
Series P. The plants of this series compared with series Q and R are lower
in moisture, total nitrogen, and nitrate nitrogen and are higher infree-reducing
substances, sucrose, polysaccharides, and total-dry matter. Within the stems
from top to bottom there is a decreasing gradient in moisture, total nitrogen
and free-reducing substances and an increasing gradient in sucrose, polysac-
charides, and total-dry matter. Within the leaves this relation does not hold.
Series Q. The plants of this series compared with those of series R, are
slightly higher in moisture, total nitrogen, and nitrate nitrogen, and lower in
free-reducing substances, sucrose, and total-dry matter. Within the stems of
series Q from top to bottom there is a decreasing gradient in moisture, total
nitrogen, nitrate nitrogen, and free-reducing substances and an increasing
gradient in sucrose, polysaccharides, and total-dry matter. In series R within
the stem from top to bottom there is a decreasing gradient in moisture, total
nitrogen, nitrate nitrogen, and free-reducing substances and an increasing
gradient in sucrose and total-dry matter.
Series S. The analyses of the plants in this series show that the middle
stems and leaves which are comparable to the upper stems and leaves in series
O have changed very little in percentage of total nitrogen expressed upon the
green weight. They have increased in moisture and nitrate nitrogen and have
decreased very much in total-dry matter, free-reducing substances, sucrose,
and polysaccharides. Comparing the lower leaves and stems of series O with
those in series S it is evident that there is a slight increase in total nitrogen,
nitrate nitrogen, and moisture and a decided decrease in free-reducing sub-
stances, sucrose, and polysaccharides.
DISCUSSION.
Several points stand out clearly after a study of the foregoing data. It is
particularly interesting to note that the interrelation of nitrogenous and carbo-
hydrate substances in the leaves themselves is very variable in the several
series and that these relations are frequently quite the reverse of those in the
stems. This result might be anticipated perhaps from the general knowledge
61
; “JT6L ‘62 [Ady peydvrsojyoyg ‘s}od yout-uo4 ur [je ere syuvld oyy, “97 [Ay Bq IN “AOSTA o[qBropIsuod TFT poynoids oavy seAres
-o1 YoIvys SUSI YIM g ULS}URId ey, “peAvoep sey synods ou pey Yorys yued Joqzo oy} Ysnoyy Y}MOLS poppe e[qBiepIsuoo sMoYs JuBLd ouO ‘> UT “APponD
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squvld ey) !yoeq yo Udt_M SUC] SoyOUT J[eY-9UO puv OU yNoe o10M YURI BuO UO Synords Om} OY} O UT ‘aseq oy} 78 synods ou pey Vy ULSs}UL[d oy, “(0 Selieg wWory
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of photosynthesis. It will be better in any future studies of the reserves in
leaves to collect samples after the plants have had a period in the dark as well
as from plants which have had several hours of exposure to sunshine.
The tomato stem is interesting in its general anatomical makeup. The
structure is brought out in the drawings from sections of vegetative and non-
vegetative stems, taken from the same general location in both types of plants.
In addition to the usual structures there is present an internal phloem and
what appears to be an internal xylem. The internal phloem in the average
stem is nearly equal in amount to the external, and does not differ greatly
whether such stems are vegetative or non-vegetative, whereas the internal
xylem cells show decidedly greater thickening in the non-vegetative stems. In
one of the later experiments for which we did not secure analyses, a number of
the plants were completely girdled by removing a half inch ring of cortex near
the base of each. At the time of ringing, these plants were actively growing
and the first noticeable change was a vigorous development of a callous-like
tissue at various points within the girdled area. The plants did not seem to
suffer greatly from this treatment, and after about a week they began to form
roots above the girdles. Some of these stems were collected for microscopic
examination and it was found that the internal phloem within the girdled area
had greatly increased in amount; in some instances being present in from five to
ten times as great an extent as in the portions which had not been decorticated.
The diagrams (figure 14) also show that the xylem in proportion to the pith, is
much greater in the non-vegetative than in the vegetative stems. In fact the
greater diameter, succulence, and brittleness of the vegetative stems is due to
the very large size of the pith and pith cells in proportion to the xylem tissue,
and the tough, woody nature of the non-vegetative stems is due to exactly the
reverse conditions.
In connection with the larger size of the leaves and stems of the vegetative
plants as compared with the reproductive and the non-vegetative non-repro-
ductive plants, it is worth while to call attention to the work of Gourley (13)
and of Heinicke (18, 19). Gourley has suggested that larger leaf surface is as-
sociated with fruit-bud formation. While this is true to a certain degree, yet
it is amatter of common knowledge that the largest leaves are frequently borne
on the most vigorous vegetative plants, so that increased leaf area in itself does
not necessarily accompany the attainment of the fruiting condition though it
may be a correlated factor. That this and several other correlations listed by
Gourley are thoroughly appreciated by him, is indicated by the fact that he
states that ‘a good growth is not antagonistic to a good yield but rather they
go hand in hand.’’ Heinicke has emphasized the importance of the size and
diameter of conducting tissue and sap densities in connection with increased
fruit setting. Whether such increase in the percentage of fruit set is due to
larger size of conducting tissue is really open to question. No doubt there is
a close correlation between them but each is probably dependent upon some
other cause back of both of them rather than that the latter follows as a result
of the former. It is certain that at least some of the conditions of nutrition
which result in the production of the small spurs are likewise those which make
63
for decreased fruit setting and development, and the large spur is rather an ac-
companiment of increased fruitfulness than its cause. Many similar correla-
tions between growth and fruit production have been pointed out by various
workers in connection with pruning problems. In the work of Lewis and Allen
on nitrate of soda fertilization, the percentage of setting was greatly increased
the first season the nitrate of soda was applied, not because there was any im-
mediate appreciable increase in size of the spur, but because of the change in
the conditions of nutrition from which greater vegetation followed as an essen-
tial consequence. Theoretically and practically this change in nutrition could
be so great, that the response is simply vegetative without an increase of fruit
production. The means which Heinicke employed, such as sawing partially
through limbs, pruning, etc., in order to limit the amount of sap which any
given number of spurs could receive, would modify the quality of such sap
quite as much as its quantity. Both these factors must be taken into consid-
eration in interpreting the results obtained. In fact, girdling, even such as
sawing partly through limbs, has been found to increase fruitfulness and fruit
setting in some instances. It has even been recommended in practice as a
means of causing over-vigorous trees to become fruitful. These apparently
conflicting results are not difficult to interpret. If the carbohydrate factor
relative to the nitrogenous factor were already higher than that which would
make for maximum fruit setting, then pruning would tend to reduce the carbo-
hydrates and thereby increase fruitfulness; whereas sawing through, as the
analyses of Hibino have shown, would tend to increase them still further and
a decrease in fruitfulness might be expected. If on the contrary the nitro-
genous factor were relatively too high, then exactly the reverse results from
the same practices might be expected, since pruning would tend still further to
decrease carbohydrates, whereas the sawing would tend to increase them. It
would be interesting to know the differences in composition of the sap corre-
lated with the differences in its density, and the relation this has to the devel-
opment of the abscission layer. How to regulate such composition in practice
is of prime importance.
From our experiments with tomatoes and from much corroborative evidence
from general observed conditions throughout a wide variety of plants, it seems
quite likely that nitrates play a very important part in the development of the
abscission layer, especially in vegetative plants; whereas relatively higher
carbohydrate content makes for continued development of the vascular strands
of the pedicel and the strengthening of their connection with the fruit spur.
This would be in keeping with the finding of greater thickening of the xylem
cells in various parts of the plant under the same conditions, and yet, as is well
known and was clearly evident in our work, a very marked abscission of fruits
and blossoms occurs also when the carbohydrate content is relatively very
high. While several possible explanations present themselves, little would be
gained by theorizing before much more precise information on the actual chem-
istry of the abscission of fruits is at hand, for many of the factors apparently
involved in foliar abscission seem to differ widely from those connected with
the dropping of fruits.
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It was observed throughout the experiments that as the plants became less
vegetative, the leaves began to lose their fresh green color, to turn gray green
and finally yellowish, In spite of this fact, carbohydrate storage in the stems
continued. In the very vegetative stems, small plastids containing chloro-
phyll were to be found in the cortical cells and in the pith cells even to the
center of the largest stems and especially toward the tips. When the available
nitrogen in the soil was limited, either by drying out the soil or withholding
nitrogenous fertilizers, the plants began to turn yellow. This was accompan-
ied by a complete disappearance of the green pigment from the plastids within
the cortical and pith cells, and apparently the disappearance of many of the
plastids themselves, especially when deposition of starch grains within the
cells became rapid. On supplying nitrate to the soil, such plants as were non-
vegetative first began active growth at the stem tips. This was associated
with a greening of the smaller, younger leaves and a very rapid disappearance
of the starch grains from the pith cells of the stem, first near the tip and then
progressively down the stem to its very base. Plastids again began to appear
in these cells and later took on a bright green color. These plastids were es-
pecially abundant in the cells of the newer growth produced after the applica-
tion of nitrate fertilizer, but also occurred in the cells of the older growth.
Throughout all of our experiments the plants grown with an abundant sup-
ply of available nitrogen were distinctly vegetative and non-fruitful. These
plants as a whole were higher in total and nitrate-nitrogen and lower in free-
reducing sugars, sucrose, and polysaccharides than were the distinctly non-
vegetative plants. Within any given plant, especially those which were grown
most vigorously and rapidly, the nitrate content was generally greater in that
part of the stem which was the more vegetative. When the plants were not
excessively vegetative, however, the total nitrogen was higher in the more
vegetative portions, but the nitrate readings were greater in that portion of
the plant where the starch content was also higher. It may be remarked that
there was some disagreement between the quantitive chemical analyses and
the microchemical analyses for nitrates; by the latter method the greatest
quantity of nitrates was always indicated in the most actively growing portion
of any given stem; whereas this relation was found to be variable according to
the quantitive macrochemical methods. Just how to account for this or what
the significance of it may be, must be left for future investigations. The gen-
eral condition of an association of higher total nitrogen and nitrates with in-
creased vegetation is in most instances valid, especially in the comparison of
the stems as a whole in the various series.
There were some wide variations in the amounts of carbohydrate present
in the different types of plants. The greatest fluctuation was in the amount
of free-reducing substances. These were generally highest in the stems of the
less vegetative plants, when considered as a whole, but within the stems them-
selves they were sometimes more, sometimes less in the more vegetative por-
tions. Disaccharides and polysaccharides were far less variable in relation
to any specific vegetative conditions of the stems, either as a whole or in any
given portion of it, than were the free-reducing substances. Generally an in-
al
pee TPT Py ee
Hage. 15 and 16.—Diagrammatic cross sections of stems to show relative development of pith
(dotted), xylem (converging lines), phloem (solid black) and bast (circles) in Series O (S), Series P
(K) and Series Q (V).. The numbers 1 to 4 indicate region of stem from which section was taken in-
cluding base, lower middle, upper middle, and tip.
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Fig. 14.—Cross sections of feebly vegetative (Series O) and vegetative (Series Q) stems of tomato,
The greater development of the xylem tissue inthe former is very noticeable. Though not indicated.
the development of the pith tissue in the latter was very much greater. CO, collenchyma; END,
endodermis; B, bast; Ex PH, external phloem; CA, cambium; SEC X, secondary xylem; PX, pri-
mary xylem; IPH, internal phloem; P, pith cells; IX, internal xylem.
vere
Fig. 17.—Diagrammatic cross sections of stem of typical plant from Series S. Sections 1 and 2
are from the base and what was the top of the plant before transferring to rich soil; both show a dis-
tinct second growth in the secondary xylem. Sections 3 to 6 are taken at points about five centi-
meters apart progressively up the stem to within one centimeter of the tip.
crease in polysaccharides was closely associated with an increase in disacchar-
ides, and both were almost uniformly greater in the less vegetative plants and
in the less vegetative portions of any given stem. This association of starch
content and condition of vegetation is clearly indicated in figure 18. Asso-
ciated with greater polysaccharide content was a greater thickening of the
walls of the xylem parenchyma cells, and in stems of equal age a far greater
proportion of xylem to cortex and especially to pith. This is made clear in
figure 14 and the diagrams of entire stems in figures 15 to 17. Starch was always
found in the starch sheath or endodermis, even in the most actively vegetative
stems, but was not found in any quantity in the pith cells. Frequently in the
very vegetative plants, there was no starch storage in the bases of the stems.
When nitrogen was limited, that is in those cases where the plants were less
vegetative, starch storage was first noticeable in the pith close to the xylem; as
more and more storage took place, all of the pith cells, the medullary rays and
the wood parenchyma became filled with starch grains.
Our experiments indicate that sucrose is not the first sugar formed by syn-
thesis but that it is present only in those instances where free-reducing sub-
stances are high and have been permitted to accumulate. The general situa-
tion seems to be a graded series from free-reducing substances through sucrose
to polysaccharides. Our observations, therefore, are apparently not in close
harmony with those of Parkin (35) onthe Snowdrop, for he has stated that in
that plant sucrose is the first sugar of synthesis.
The great fluctuation in the amount of free-reducing substances present in
the various types of stems may be due to a variation in the extent of their utili-
zation as well as their synthesis, dependent upon the presence of other sub-
stances in conjunction with which still other compounds are built from them.
If this were the case, it might be expected that the quantities present at any
given time or location would vary directly with the degree of such utilization.
At least two alternatives are conceivable, and although neither of them can be
proved from the work at hand nor from the various opinions as yet expressed by
various workers, still they may be suggested. In the first place, if the simpler
carbohydrates do serve as one of the building stones in the synthesis of amino-
acids and proteins, or if the synthesis of the latter is conditioned by the avail-
able supply of carbohydrates, as well as a suitable nitrogen supply, it might be
expected that the carbohydrates would be built over into these compounds
more or less rapidly according to the amount of such suitable available nitro-
gen, and the presence of the other necessary conditions, whatever they may be.
In the second place, if a suitable nitrogen supply were not available so that the
simple carbohydrates were not utilized in the formation of nitrogen-containing
compounds but accumulated as such, then there would be a possibility for their
being built into the more complex forms such as disaccharides, polysacchar-
ides, and the like. The tomato plant does not contain or store any consider-
able quantity of fat, hence estimations of it were not made in our experiments.
Because of the close relationship between carbohydrates and fat synthesis,
however, it would seem that there was at least a good possibility that similar
relations may exist in fat-storing plants.
76
Our own experiments give indications that the foregoing ideas on the carb)
hydrate transformations may be correct, for with an abundance of available
nitrates in the soil, the plants themselves are relatively high in total nitrogen
and nitrate nitrogen, and relatively less in carbohydrates; but when there is a
limitation-of the nitrates, the carbohydrates, first the simple and then the more
complex, accumulate rapidly, provided of course that other conditions for pho-
tosynthesis are not prevented. When available nitrogen is added to the soil
in which such nitrogen-low, carbohydrate-high plants are growing, however,
they very quickly increase in total nitrogen and nitrate-nitrogen content, and
become actively vegetative. Associated with such a change is a decrease in
the same complex carbohydrates. Microscopic examinations were made of the
plants in series O before transferring to a soil abundant in available nitrogen
and it was found that the cells of the pith, cortex, and medullary rays and even
those of the xylem parencyma were packed with starch grains. This was true
for sections taken up to within one centimeter of the tip. Within three days
following such transfer, the beginning of the disappearance of the starch grains
from the center pith cells and cortical cells at the tips of the plants was very
noticeable. Successive examinations as growth progressed showed an active
terminal elongation which contained no storage starch except in the starch
sheath, an active development of secondary xylem in the older portion of the
stem, and a very rapid, progressive, and finally complete disappearance of the
starch from the pith and xylem parenchyma and also the cortical cells even
down to the bases of the stems, where it was last to disappear. It may be
added that some stems which were thus packed with starch were not given ad-
ditional nitrates. They finally lost all their leaves except two or three at the
very tip about one or two centimeters long. These stems remained alive for
over seven months during which time there was a gradual disappearance of the
starch in some of them until only traces in the medullary rays and pith could
be demonstrated, while some of the others contained large starch reserves at
death. Even after this long period a few of these old, yellowed, leafless, ap-
parently dead stems put out new buds at a few of the nodes when calcium ni-
trate solution was applied to the sand in which they were growing. Every one
of the plants which sprouted still contained carbohydrate reserves.
While on this point, it is worth while to consider the behavior of the plants
in experiment VII. The results throw some light on the problem of regenera-
tion. When the plants which constituted series Q were collected, they were
vigorously vegetative, and the analyses showed that they were very low in the
more complex carbohydrates but high in total nitrogen. In taking the samples
the plants were generally cut off about one-half or three-fourths of an inch
above the surface of the soil. In most cases this left a bare stub of one to three
nodes, usually without sprouts but in several cases with sprouts from one-quar-
ter to one and one-half inches long. In every instance in which no sprouts
were left the stems rotted without any vegetative response whatsoever, where-
as when sprouts were present they usually grew rapidly. In several cases
sprouts one-half inch long withered and rotted also. Now the plants in series
O were collected in exactly the same way, and it will be remembered these were
77
WY
Vl)
YZ, . . “ZY
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Fig. 18.—Diagrammatic sections, base, middle, and tip, from plants of Serics O (S), Series P (K),
and Series Q (V) to show the range and location (in blue) of starch deposits, as indicated by the Iodine
test, and the comparative development of pith and secondary xylem. All drawn to the same scale.
78
non-vegetative, and very high in the more complex carbohydrates but relat ively
low in total nitrogen and almost without nitrate nitrogen. Not one had a
sprout at the base, but after cutting back, none of these stubs decayed. In-
stead, every one without exception produced from one to three new sprouts,
which grew vigorously for a short time but ceased before more than one-half
the volume of the top which had been cut away had been attained. Provided
no additional nitrate was applied to the sand, they again became filled with
starch. The rapidity with which these shoots began growth was truly aston-
ishing. What these sprouts did when appreciable quantities of nitrates were
added to the soil is clearly indicated in figures 9, 10, and 12.
As previously pointed out, the plants in these two lots differed greatly in
carbohydrate reserves, and in total nitrogen. Two suggestions present them-
‘selves; first, that without carbohydrate reserves or a means for their synthesis
regeneration does not result even though large amounts of nitrates are
available; and second, that with a carbohydrate reserve, even though ni-
trates are very much restricted, regeneration takes place very rapidly. It
must be remembered that the sand-culture plants of series O received traces of
nitrates or other nitrogen containing compounds in the water supply. The
very slow growth of the plants before cutting back and the early cessation of
the vegetative extension of the young shoots indicate that a certain amount of
nitrogen is required merely for maintenance, and that without additional quan-
tities vegetative extension cannot take place. What the result may be when
the supply of nitrates is increased is well shown in figure 8 and figure 10.
‘The plants shown in the former were grown as series O and later those which
were not cut back analyzed as series 8S. Two plants had been grown in each
pot of sand and fertilized with nitrate-free Knop’s solution. When the samples
were taken one plant only was collected. Many of these were then transferred,
without disturbance, to very rich soil. The plants shown in the latter were
treated the same as series O, but instead of being transferred to rich soil, cal-
cium nitrate was added tothe nutrient solution. The newsprouts had already
made considerable growth before the nitrate was added.
The first noticeable feature is, that the plants in the pots which had
received additional nitrates, when compared with the plants in those
which had not received them, made much greater growth, especially
those plants which had not been not cut back; the second, that the difference
in the growth of the new sprouts is very much less in the plants which
had been cut back; and the third that the unpruned plants made much more
growth than the’ pruned plants in the same pots when available soil nitrogen
was increased. In the latter the growth is apparently proportional to the car-
bohydrate reserve in the stems at the time of transplanting. Even though
there were much greater quantities of available nitrates in the nitrate-ferti-
lized pots than in the unfertilized, when the carbohydrate reserves had been
greatly limited through cutting back, the growth was not much greater for the
first few days. When greater quantities of carbohydrates were made available
through synthesis, however, growth was far more rapid in the fertilized pots.
In other words, this experiment indicates first, that the limitation of the
79
nitrates resulted in the suppression of growth and the accumulation of the more
complex carbohydrates; second, that the limitation of the carbohydrates, even
with large quantities of available nitrates in the soil, results in a suppression
of growth; third, that a rapid vegative extension results from an adjustment of
the carbohydrates and nitrates relative to one another so that both may be
utilized in the formation and expansion of such structures; and fourth, that
such a relationship can be secured either by increasing the nitrates without
decreasing the carbohydrates, or by decreasing the carbohydrates without in-
creasing the nitrates. While it is apparent that the amounts of these com-
pounds relative to one another would be the same in both the above cases, the
total amounts would be greater in the former and less in the latter, a condition
faithfully reflected in the amount of growth produced. These considerations
are very important in the problem of pruning and nitrate fertilization, pre-
viously discussed in this article.
One more point to be noted was the behavior of the severed stems of the
»lants in the foregoing experiment. Pieces of stems one to four inches long,
without leaves, and possessing both nodes and internodes were examined micro-
chemically to learn something of the nature of their content. They were then
placed on filter paper moistened with distilled water and placed under a bell
jar in the laboratory. These trials were repeated several times, always with
the same results. (1) Yellowish stems high in carbohydrates and low in total
nitrogen and nitrates pushed forth many roots, particularly along the inter-
nodes, to the length of one to four inches. One or two formed tiny yellowish
sprouts at the nodes. In ten days to two weeks the roots turned dark and be-
gan to decay. (2) Greenish stems containing starch and fairly high in total
nitrogen always produced roots along the internodes and sometimes small
green sprouts at the nodes. The root production was not so profuse as in the
foregoing. Decay began in about the same length of time. The succulent
tops of the same plants without starch reserves all decayed without root or
shoot production. (8) Green, succulent stems, without starch reserves and
very low in free-reducing substances but high in total nitrogen and nitrate ni-
trogen, all decayed without root or shoot production. These results are of in-
terest in connection with the vegetative propagation of many plants, for which
purpose the practical grower prefers the more “‘hardened”’ or mature portions.
From the general viewpoint expressed in this paper they are also interesting
in connection with some other experiments on tomatoes which will not be dis-
cussed here, except to state that a decided reduction in the development of the
root systems of the plants accompanied a continued removal of leaves from the
tops. According to microchemical tests, that practice also resulted in a
marked decrease in the carbohydrates in the stems, and a decided reduction in
vegetative extension and fruitfulness.
The accompanying diagrams, figures 19 to 22, show the relation between the
percentage of total nitrogen and the percentage of total carbohydrates (free-re-
ducing substances plus sucrose plus polysaccharides) expressed as dextrose.
It should be borne in mind that the free-reducing substances, sucrose, and poly-
saccharides are not absolute determinations, but that these terms are used with
80
0 L C P K B G R Q
Fig. 19. Diagram to show the comparative quantitative relationships of the total carbo-
hydrates (connected by broken line) and total nitrogen content x 7 (connected by solid line)
arranged on the basis of the descending values for carbohydrates, in the upper stems of the
several series.
the significance given under the methods of determination in an earlier part of
this paper. On the base line of the figure at equal distances apart are arranged
the series of plants and on the vertical lines are arranged the percentages of
total nitrogen multiplied by seven and of total carbohydrates, expressed on the
dry weight. On account of the wide differences in composition of different
parts of any plant grown under a given set of conditions, only similar portions
are compared. With but few exceptions increased amounts of total nitrogen
are associated with decreased amounts of total carbohydrates. This condition
holds fairly uniformly thorughout the plant with the exception of the lower
leaves.
This relation between total nitrogen and carbohydrate storage may be due
to any one or a combination of reasons, some of which are the following: (1) The
presence of the nitrogenous compounds or nitrates may retard assimilation or
the formation of the carbohydrates. (2) It may cause increased respiration
of the carbohydrates. (3) It may aid in the utilization of the carbohydrates for
the synthesis of organic nitrogenous substances. No definite, exact data on
any one of these points are available. It is not worth while, therefore, to at-
tempt conclusions concerning them, though a few suggestions may not be out
81
0 L P C B K G R Q
Fig. 20. Same as Fig. 19 except to show the relationships in the lower stems.
of place. The much greater leaf area developed by vegetative plants would
seem to indicate the reverse of the first proposal, nor does the presence of in-
creased amounts of carbohydrates in the non-vegetative plants of necessity in-
dicate that they are therefore likewise synthesized in greater quantities. Evi-
dence for or against the second point is not clear, but in keeping with the gen-
eral findings of increased respiration accompanying more active growth there
is a probability that more of the carbohydrates would be thus used in the vigor-
ously vegetative plants. The third possibility has been previously suggested.
The utilization of the carbohydrates in this manner as well as in the composi-
tion of portions of the walls of the new cells being formed and the thickening of
others, probably affords the main reason why they are found as storage sub-
stances in relatively smaller quantities in the more actively growing stems.
In general, there is a close correlation between the amount of nitrate nitro-
gen, total nitrogen, and moisture. Among others, the several factors which
follow might aid in accounting for this. (1) The nitrates may have a lyo-
tropic effect in increasing the water-holding capacity of the plant. (2) Car-
bohydrates and dry matter, substances which have a relatively lower water-
82
0 P L K R B C QO G
Fig, 21. Same as Fig, 19 except to show the relationships in the upper leaves.
0 P C B L G Q K R
Fig, 22, Same as Fig. 19 except to show the relationships in the lower leaves.
83
holding capacity, are greater where total nitrogen is less. (8) The nitrates
may prevent the lignification and thickening of cell walls which have a rela-
tively low water-holding capacity. (4) They may aid in rapid growth and
the formation of new cells which have relatively thinner walls and a greater
percentage of amphoteric substances whose water-holding capacity is relatively
large. Then, too, the vacuoles are generally more numerous and larger in the
decidedly vegetative tissues, and these may furnish more opportunity for the
retention of water.
In the absence of conclusive evidence which might show that the lyotropic
action of the nitrates is of significance, no definite conclusions can be drawn.
The plants which constituted series O were grown in sand and the nitrates of
the nutrient Knop’s solution were eliminated and partly substituted by caleium
chloride. Even with the presence of the chloride ion, which has a lyotropic
effect somewhat similar to the nitrate ion, the plants were very low in moisture.
Of course since no quantitative chlorine determinations were made there is no
way of comparing the quantities within the plant, and also the presence of the
calcium ion may overshadow the effect of the chloride ion. Microchemical
tests indicated an abundance of chloride in all types of plants. The second and
third points are self explanatory. There were, however, no specific experi-
ments on the influence of vacuoles on moisture -holding capacity, but the effect
of protein-like substances in this regard is fairly well established. Micro-
scopic examinations showed a lesser increase in cellular thickenings in the
vegetative stems.
From the investigations of others as well as our own, it has certainly been
shown that blooming, pollination, or even fertilization do not necessarily as-
sure actual fertility even in plants actually considered self-fertile, and it would
appear that at least some cases of self- or even inter-sterility are due, not so
much to astable hereditary character as to the condition of the nutrition of the
plant under investigation. Both heredity and nutrition must be taken into
consideration in a study of this problem, and while it is possible profoundly to
modify the expression of any particular plant dependent upon the conditions
imposed, it may well be argued that such modifications still remain within
hereditary limits. Just where such limits can be drawn certainly cannot, as
yet, be determined off-hand, and much more than the average or so-called
normal conditions must be investigated.
In general, the observed results and the analyses made in connection with
the foregoing experiments tend to support our proposed classification of vege-
tative and reproductive tendencies insofar as they may be based on a relation-
ship of the carbohydrate and nitrogenous compounds. Throughout the inves-
tigation, many questions naturally have suggested themselves; a few of them
have been indicated. We hope that further and more extended investigations
may be instituted and conducted not only to establish or deny the general
hypotheses proposed, but to furnish accurate and reliable data on which to
base interpretations of the more intimate processes and compounds concerned.
84
SUMMARY
1. Plants grown with an abundant supply of available nitrogen and the
opportunity for carbohydrate synthesis, are vigorously vegetative and un-
fruitful. Such plants are high in moisture, total nitrogen, nitrate nitrogen,
and low in total dry matter, free-reducing substances, sucrose, and poly-
saccharides.
2. Plants grown with an abundant supply of nitrogen and then transferred
and grown with a moderate supply of available nitrogen are less vegetative but
fruitful. Ascompared with the vegetative plants, they are lower in moisture,
total nitrogen, and nitrate nitrogen, and higher in total dry matter, free-reduc-
ing substances, sucrose, and polysaccharides.
3. Plants grown with an abundant supply of nitrogen and then transferred
and grown with a very low supply of available nitrogen are very weakly vegeta-
tive and unfruitful. As compared with the vegetative plants, they are very
much lower in moisture and total nitrogen and are lacking in nitrate nitrogen;
they are much higher in total dry matter, free-reducing substances, sucrose,
and polysaccharides.
4. When plants which have been grown with a large supply of available
nitrogen and moisture are subjected to a reduced moisture supply just about
the wilting point there is a decrease in vegetative activity. These plants com-
pared with those which are vigorously vegetative, are lower in total nitrogen
and nitrate nitrogen and higher in free reducing substances, sucrose, and poly-
saccharides.
5. Whatever the conditions under which a plant has been grown, consid-
ering the whole plant as a unit, increased total nitrogen and more particularly
increased nitrate nitrogen are associated with increased moisture and de-
creased free-reducing substances, sucrose, polysaccharides, and total dry
matter.
6. Fruitfulness is associated neither with highest nitrates nor highest
carbohydrates but with a condition of balance between them.
7. There is a correlation between moisture content and nitrate nitrogen.
This is probably due largely to the preponderance of non-carbohydrate ma-
terials to carbohydrates in the cases where nitrates are abundant.
8. In general, within the plant itself, in the stem from the top to bottom,
there is a descending gradient of total notrogen and moisture, and an ascending
gradient in total dry matter, polysaccharides and sucrose. The proportion of
free-reducing substances to other carbohydrates, total nitrogen, and nitrate
nitrogen is variable.
9. The great variations in the amount of carbohydrates in plants grown
under different nutrient conditions and in different parts of the same plant
indicate that in studying problems concerned with plant metabolism it is neces-
sary to know the specific environment of the plant as a whole and of its several
parts.
10. The conditions for the initiation of floral primordia and even blooming
are probably different from those accompanying fruit setting. The greatest
number of flowers are produced neither by conditions favoring highest vegeta-
tion nor by conditions markedly suppressing vegetation.
11. Lack of fruit development is not alone due to the lack of pollination or
fertilization. The flowers may fall soon after pollination (markedly vegeta-
tive plants) or remain attached for many days without development of the
fruit (markedly non-vegetative plants).
85
12. The tomato stem in cross section is made up of an epidermis from which
arise glandular hairs, several layers of cortical cells, endodermis, a more or less
interrupted layer of bast cells, the phloem with small patches of sieve cells,
primary and secondary xylem, small patches of internal phloem and internal
xylem separated from each other and the protoxylem of the outer bundles
by pith cells, and lastly the pith.
13. Vigorously vegetative stems are much greater in diameter than those
which are feebly vegetative. This is due to the greater number and size of the
pith cells in the former and is accompanied by a marked proportional reduction
in xylem. The collenchyma of the cortex is much less and the walls of the bast
and internal xylem much thicker in feebly vegetative stems than in those
which are vigorously vegetative.
14. Starch is present in the starch sheath of all stems. Starch storage in
the stems begins first in the pith cells near the primary vascular bundles, then
extends throughout the pith, xylem, and the cortical cells.
15. In vegetative stems there is a much greater number of chloroplasts.
These are present even in the central cells of the pith. In stems very feebly
vegetative there are no observable chloroplasts in the pith and their number
ne intensity of coloration is greatly reduced both in the cortex and in the
eaves.
16. Stems without storage starch at the base when cut off close to the sur-
face of the soil, fail to sprout but decay quickly, whereas those with large stor-
age produce new shoots. Accompanying such growth there is a total or com-
plete disappearance of the starch, depending upon the relative amount of
growth made and the available nitrogen supply. If the latter is abundant
vegetative extension is relatively great; if not, such extension soon ceases and
starch is again stored in the new growth.
17. The available corbohydrates or the possibility for their manufacture
or supply, constitute as much of a limiting factor in growth as the available
nitrogen and moisture supply. When the opportunity for carbohydrate manu-
facture within the plant itself is greatly reduced or eliminated even though
there is a relative abundance of moisture and available nitrogen, vegetation is
decreased. But when there is a carbohydrate reserve within the tissues under
the same conditions of nitrogen and moisture supply, growth is active. Very
large proportional reserves of carbohydrates to moisture and nitrate supply,
also accompany decreased vegetation.
18. Parts of the stems or cuttings of plants with a large amount of storage
carbohydrates and particularly those parts where such storage is localized,
when supplied with moisture or moist conditions, produce roots abundantly.
This would be of particular interest in vegetative propagation.
19. Microchemical tests indicate very little difference in potassium con -
tent of individual cells whatever the condition of the plant.
20. Withholding moisture from plants grown under conditions of relative
abundance of available nitrogen results in much the same condition of fruitful-
ness and carbohydrate storage as the limiting of the supply of available nitro-
gen itself.
21. Fertilizers containing available nitrogen or that which may be made
available, are mainly effective in producing vegetative response. They may
either increase or decrease fruitfulness, according to the relative available car-
bohydrate supply.
22. Irrigation or moisture supply is effective in increasing growth or fruit-
fulness only when accompanied by an available nitrogen supply and vice versa,
86
The effectiveness of the nitrogen value of leguminous cover crops is dependent
upon the accompanying moisture supply.
23. Cultivation is largely effective in conserving moisture and in promot-
ing the supply of available nitrogen. If in any given soil, moisture and avail-
able nitrogen are already present in quantities such that the plants growing
upon it are largely vegetative, a decrease in cultivation will tend towards
fruitfulness.
24. Non-leguminous companion crops or cover crops remove from the soil
both available nitrogen and moisture. In regulating vegetation and fruitful-
ness by this means the relations of the available moisture, nitrogen, and
carbohydrates largely determine the result.
25. Pruning is largely effective in promoting or retarding fruitfulness by
its effects in balancing the carbohydrate supply within the plant, or the means
for its manufacture, with the available moisture and nitrogen supply.
26. Girdling or ringing of the cortex or bark is effective through a modifica-
tion of the carbohydrate-nitrate relationship. In practice the entire range of
effects due to such a relationship may be expected from its application.
27. Fruit production is seemingly a specialized vegetative function usually
more or less closely associated with the function of gametic reproduction.
Parts concerned in reproduction range from but little-modified vegetative
parts to those highly modified portions classified as fruits. The degree in
which such modification is expressed, is dependent upon physiological changes
within any specific plant, and may vary widely within the same variety or
even the same individual.
28. At least some of the instances of sterility considered to be the result of
physiological incompatibility may be due to the state or condition of nutrition
of the plant itself.
29. Until more exact information is available, both environmental and
hereditary factors must be considered in any attempted explanation of the re-
productive or vegetative behavior of plants.
ACKNOWLEDGMENTS
The writers are indebted to the authorities of the Oregon Agricultural Col-
lege Experiment Station for permission to carry on the foregoing studies away
from the home Station. They desire especially to express their thanks and
appreciation to Doctor William Crocker of the Department of Botany of the
University of Chicago, for constant counsel and suggestions during the pro-
gress of their work, and to Doctor Sophia H. Eckerson of the same Department
for advice and direction, particularly on the microchemical studies.
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