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UNIVERSITY OF MISSOURI

A Study Of
Some Factors Influencing Fruitfulness
in Apples

CLEO CLAUDE WIGGANS, B.S. Agr., A.M.

SUBMITTED IN PARTIAL FULFILMENT OF THE
REQUIREMENT FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY

UNIVERSITY OF MISSOURI
COLUMBIA

1918

UNIVERSITY OF MISSOURI

A Study Of
Some Factors Influencing Fruittulness
in Apples

CLEO\CEAUDE WIGGANS, B.S. Agr., A.M.

SUBMITTED IN PARTIAL FULFILMENT OF THE
REQUIREMENT FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY

UNIVERSITY OF MISSOURI
COLUMBIA

1918

UNIVERSITY OF MISSOURI o>,

SP A
COLLEGE OF AGRICULTURE

Agricultural Experiment Station

BOARD OF CONTROL
THE CURATORS OF THE UNIVERSITY OF MISSOURI
EXECUTIVE BOARD OF THE UNIVERSITY
SAM SPARROW, Chairman, Cc. B. ROLLINS,
Kansas City Columbia
JOHN H. BRADLEY,
Kennett

ADVISORY COUNCIL
THE MISSOURI STATE BOARD OF AGRICULTURE

OFFICERS OF THE STATION
A. ROSS HILL, PH. D., LL. D.; PRESIDENT OF THE UNIVERSITY
F. B. MUMFORD, M. S., DIRECTOR

STATION STAFF

AGRICULTURAL CHEMISTRY FARM MANAGEMENT

C. R. Mouton, Ph. D. O. R. Jounson,? A. M.

e D. ope ah vhs R. M. Green, B. S. in Agr.

. S. PALMER, Sy Ds

W. S. RitcHiz, A. M. ees

S. B. Surrkry, B. S. in Agr. FrepertcK Duntap, F. E,

C. E. Mancets,! M. S. E. C. Pecc, M
T. H. Hopper, M. S. HORTICULTURE

V. F. Payne, A. B.
Mrs. Mary Cocurane Farris, B. S. in Agr. 9 Ge = De

Vv.
Tee SSS Ne
AGRICULTURAL ENGINEERING J. T. Rosa, Jr., M.S. H.
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es
‘3

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E. A. Trowsrince, B. S. A. . Kempster, B. S.
F. B. Mumrorp, M. . W. Hervey,’ B. S.

tt o gutiae. rat S. is SOILS

Toes VEAVER in Agr. j

B. J! Gmewot, Ax Epes he
BOTANY aE ti pAuBeecut, en 15

Grorce M. Reep, Ph. D. - L. DULEY, A.

Hrten Jouann, A. M. H. H. Krusexorr, A. M

Wa. DreYounc, B. S. in Agr.

ie) OSEAN VETERINARY SCIENCE

Mel Bl KLE SDB Sie
Mie come, APE J. W. Connoway, D. V. M., M. D.
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ENTOMOLOGY e°4) SEH. 1G, NEWMAN, BS ain. Agr,

J OTHER OFFICERS

Lronarp HaseMan, Ph. D. *;
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FARM CROPS e H. HucGurs, A. M., Asst. to Dean
W. C. Ernerrince, Ph. D. W. WEAVER, BoS:, "Agricultural Editor
E. M. McDonatp, B. S. cae REEDER, Director Weather Bureau
C. A. Herm, A. M. RACHEL Hotes, A. B., Seed Testing Lab-
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L. J. Stapter, A. M. J. F. Barnam, Photographer

1In U. S. Military Service.
2In service of U. S. Department of Agriculture.

(2)

nm, of D.
DEC 8 495

SOME FACTORS FAVORING OR OPPOSING
FRUITFPULNESS IN APPLES *

The Effect of Certain Conditions and Practices on the
Development and Performance of the
Individual Fruit Spur

C. C. WicGANS

INTRODUCTION

It is a generally observed fact that certain varieties of apples
tend to bear crops in alternate years, while others produce annual
yields. Some varieties are light bearers but others yield heavy crops.
In some cases the same variety, or even the same tree, shows great
variation in its performance from year to year. The principles un-
derlying these variations in behavior are of scientific interest as well
as of great importance to practical fruit growers. Horticultural lit-
erature contains numerous references to the biennial crops of the
Baldwin in the New England and New York fruit growing sections.
Among the varieties grown in Missouri, the Ben Davis, Gano, In-
gram, and York show marked alternation of crops, while the Jona-
than, Winesap, Grimes, and Missouri generally may be depended up-
on to give satisfactory crops each year.

The investigator in considering the factors influencing fruitful-
ness in apples, must, first of all, give his attention to a study of the
principles underlying fruit bud formation, for the flower must, of
course, precede the fruit. Many and varied have been the opinions
of investigators as to the factors causing flower production. The
argument has sometimes been advanced that the blooming power is
inherited, while some writers have maintained the view that flowers
are dependent upon the presence of a certain specific “blossom
building” substance. The latter view has been especially noticeable
among German investigators. Environmental factors such as light,
heat, accident, etc., have been considered the all important ones in
some cases, while in others, the effects of certain cultural practices
have been used as a basis for the explanation of the phenomenon.
Seemingly, the problem has been of as much interest to plant phys-
iologists and morphologists, as to the practical growers themselves.

*Also presented to the Graduate School of the University of Missouri, June, 1918, as
a thesis in partial fulfillment of the requirements for the degree of Doctor of Philosophy.
ACKNOWLEDGMENT. The writer wishes to acknowledge his indebtedness to the

following named men who assisted him to plan and carry out this investigation: Dr. J. C.
Whitten, Dr. G. M. Reed, Dr. P. F. Trowbridge, and Mr. H. G. Swartwout.

(3)

4 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32

It has long been recognized by those interested in plant life that
in every plant there are two seemingly antagonistic forces, one of
which is striving to preserve the individual plant, and the other, to
perpetuate the species. The first of these activities expresses itself
in the formation of purely vegetative parts, such as stems, roots and
leaves, thru which the life of the individual may be lengthened, while
the latter has to do with the formation and maturation of seeds in
greater or smaller numbers by which the species may be carried
over from one generation to the next. The former may be spoken
of as vegetative activity and the latter as reproductive activity, or, in
the case of fruit trees, as wood growth and fruit growth.

Vegetative activity always precedes reproductive development
and, so long as it proceeds with undiminished vigor, few or no blos-
soms will be formed. With our tree fruits the period of vegetative
activity may be several years in length while with certain annual
plants it may be a matter of only a few weeks. In any case, how-
ever, the maximum vegetative period passes before heavy reproduc-
tion begins. Maintaining the vigor of the wood growth serves very
materially to delay the formation of fruits, while, on the other hand,
a heavy fruit crop tends to decrease greatly the vegetative growth.
From these general observations, the cbvious conclusion has been
reached that it is impossible to have the greatest efficiency in both
wood and fruit growth simultaneously in a single individual. A
plant, then, cannot be of the highest degree of service to itself and
to its species at one and the same time.

Apple trees during the first few years of their life produce few
or no blossoms. ‘The energies of the plant are directed to the forma-
tion of a framework of branches upon which the later crops of fruit
are to be borne. Finally, however, the bearing age is reached but
this is found to differ very materially in the different varieties and
even in the same variety when grown under different cultural and
soil conditions. From this time until its death, the tree remains a
potential fruit bearing organization. The amount of fruit borne,
however, often shows a very striking variation, ranging from a very
light crop to a very heavy one. This phenomenon is sometimes
spoken of as alternation.

Alternation, referring primarily to the bearing of heavy and
light crops in alternate seasons, seems to be more or less a varietal
characteristic. With certain varieties regular crops are expected,
while with others a heavy crop is almost invariably followed by a
light one. This habit of alternation also seems to be much more

SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 5

characteristic of our later commercial varieties than of some of the
older sorts grown in the orchards of the early settlers. This may
have come about because of the emphasis that is now placed upon
high yields. In the earlier days, when markets were limited, regular
crops were more desirable than heavy crops.

In an investigation of the factors influencing fruitfulness in ap-
ples, so many avenues of research are open that it is folly to attempt
to take all of them into consideration in a single investigation which
must be more or less limited to certain lines. Previously, nearly all
investigators have been inclined to consider the problem from the
standpoint of the entire tree, or, of the entire orchard, in its rela-
tion to a specific treatment or factor. In this study, however, the
main idea centers around the factors and conditions influencing the
behavior of an individual fruit spur. Since the tree is composed of
numerous individual fruiting parts, the factors influencing the indi-
vidual spur must ultimately have a proportionate influence upon the
entire organization. Hence an attempt has been made to keep con-
stantly in mind the fruiting parts as individuals rather than in mass,
and the greater part of the work has been done with the individual
fruit spurs.

Moreover, for the purpose of this study, it is generally assumed
that a blossoming spur is also a fruiting spur. Under field condi-
tions, however, some flower clusters may fail to set fruit, but the
fact still remains that a spur developing a blossom is a potential
fruiting spur for the following year, and it is here so considered.

LITERATURE

A critical review of the literature bearing upon the factors favor-
ing or opposing fruitfulness in apples reveals the fact that many ex-
planations have been offered for the variations found in the fruiting
habit of an apple tree. It is quite noticeable that many of these ex-
planations are based upon general observations and conclusions
rather than upon actual scientific data, and especially is this true in
the older writings. Definitely planned experimental work is virtu-
ally confined to the last twenty-five years, and dates approximately
from the time the agricultural experiment stations became well estab-
lished in research work.

Not all writers have been interested directly in the production
of an increased number of blossoms for some have been concerned
with the reserve materials which are always found to be present in
woody plants. The amount and nature of these reserves vary accord-

6 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32

ing to the season and character of the part under consideration, and
these variations have sometimes been used as a basis to explain the
phenomena observed. Thus, are recorded not only the observations
of horticulturists but those of biologists and chemists as well.

The natural evolutionary development of the apple during the
centuries that it has been under cultivation, has very likely had con-
siderable influence upon the cultural practices of the succeeding
periods. Therefore, it seems but natural to suppose that the manage-
ment suitable for the apple as it was first known would be not at all
applicable to the modern commercial high yielding varieties. Also,
an increasing knowledge of plant structure and function, in all proba-
bility, has been productive of improved methods of fruit growing.
All recommendations, however, based upon either general observa-
tions or actual knowledge, have for their purpose an increase in the
yield or an improvement in the character of the fruits borne.

One point upon which the majority of writers are in perfect
accord is, that fruit bud formation is dependent upon a supply of re-
serve food material. With the better understanding of the sap flow
in plants, this idea has become more and more prominent. Even the
early writers seemed to appreciate that there is some connection be-
tween the food supply and the sap, and hence they devised methods
by which they thought they could modify the sap and thereby also
influence the food supply. Particular methods were evolved for the
various parts of the plant and changes in the character of the food
supply, etc., were also suggested.

Since many of the writers have considered the effects of several
methods or treatments upon fruitfulness, it seemed advisable to con-
sider the literature in chronological order rather than by topics. This
plan has been used in the following review:

One of the earliest records found of an interest being taken in
the factors influencing fruitfulness is the statement of Lonicerus
(1587) quoted by Zacharias®**. This early writer seems to have
reached the conclusion that an excess of nourishment leads to a
very marked extension of the vegetative branches, but that no fruit
will be borne under these conditions. This same doctrine, that great
vegetative growth is not compatible with great reproductive activity,
can be subscribed to today.

According to Noehden', Van Oosten, (1711) the Dutch botan-
‘ist, stated that a “moderate sap flow,” secured by frequent trans-
planting or by summer pruning, will result in fruit production. While

*See bibliography for this and subsequent number references thruout.

SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 7

he probably possessed very little knowledge concerning the sap flow,
yet this writer suggested two methods which will encourage fruitful-
ness and these methods are even now sometimes used for this pur-
. pose.

_ The beneficial effects of ringing were observed by De la Baisse
(1753), Bonnet (1754) and Duhamel (1758). These reports were
recorded by Mobius®®. Duhamel apparently seems also to have had
some knowledge of the effects of pruning.

Knight®® early in the nineteenth century published many papers
dealing with horticultural subjects. Among his observations, Knight
made note of the increased fruitfulness of horizontal branches as
compared with upright ones. He explained this by the assumption
that the decreased sap movement in the horizontal branches was the
direct cause of their greater fruitfulness. He suspected that the
heavy fruit crops borne immediately following a warm bright season
when only a few fruits were matured, was due to the fact that the
sap had not been expended in maturing an excessive crop. In some
of his earlier papers he leaned to the belief that the bearing age of a
tree is dependent to a large extent upon hereditary factors, but later,
ringing is mentioned as a way of increasing fruitfulness, this being
due to the accumulation of descending sap. Knight really had a
much better knowledge of plant physiology than his predecessors and
hence was enabled to give a more nearly correct interpretation of
his results. It is interesting to note the close agreement between some
of his ideas and those of the present day.

Forsyth** in a textbook on the general subject of fruit growing
published in 1802 made the following statement, “Never shorten the
young branches except they are very thin...... nor prune any of
the young shoots the second year, as many of the eyes, almost at the
end of the shoot, will, if it be strong, become fruit buds next year.”
Evidently, this writer had been making some very accurate observa-
tions upon the method of fruit spur formation.

_° That fruit bud formation may be stimulated by checking or di-
minishing the growth was the opinion of Noehden'’™ (1818). Ring-
ing was suggested as one means of accomplishing this end.

Prince™® (1830) believed that the amount of available moisture
had a marked effect upon the fruitfulness of grapes.

Philips? (1831) declared that, “Pruning is to be avoided as
much as possible as it creates useless branches and prevents the
fruiting.” Cole?® (1849) mentioned the following factors as being
conducive to fruitfulness and early bearing; root pruning, ringing,

8 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32

bending down the branches, transplanting, use of certain stocks, short-
ening-in, and change of soil or climate. He stated also that certain
varieties are regular bearers while others bear only in alternate years.
However, he did not agree with the opinions expressed by others
that this alternation is due to exhaustion and points out, in support
of his contention, that certain kinds produce annual crops. In his
opinion, the bearing year in alternating varieties may be changed by
removing all of the blossoms during the heavy bearing year.

Barry™ (1851), after observing that fruit buds originate as leaf
buds, the differentiation taking place during the latter part of the
growing season, finally stated that the immediate causes of fruit bud
formation are not satisfactorily understood. He quoted Dubreuil,
however, as being of the opinion that fruit buds are dependent upon
stored plant food and that their formation is brought about if the cir-
culation of sap is obstructed. This obstruction causes a slowing up
of the sap movement so that the sap is more thoroly elaborated, and
hence, becomes better adapted to fruit bud formation. Lindley®
(1852) believed that plants must attain a certain age before flowers
will be formed, and that this age may be influenced materially by
the nutrition of the tree. He further stated that fruit bud formation
is probably due to an accumulation of plant food.

Field*? (1859) recommended breaking, pinching, and twisting
the branches as methods of inducing fruitfulness in the pear. He
believed also that a large quantity of fibrous roots is essential for
fruit production and hence root pruning may be practiced. Down-
ing** (1864) agreed with Field that root pruning may be useful but he
assigned an entirely different reason for it. By lessening the root
system an overabundance of plant food is made available for the
branches and this material then forms fruit buds. In the opinion of
this writer, heavy crops exhaust the tree and thus cause alternation.
However, this habit may be overcome by thinning while the apples
are small. He also recommended that the soil be kept in “high
condition.”

Rivers'*? (1866) was a very strong advocate of root pruning,
especially for dwarf trees, as a remedy for barrenness. He supposed
that trees could be kept fruitful only by preventing the formation of
large roots since these go downward and imbibe crude sap which
causes great twig growth and few or no fruits.

Warder™* (1867) summed up his observations by stating that
fruit bud formation is due to the accumulation within the tree of
nutritive materials, and the exhaustion of the soil of wood-forming

SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 9

elements. From the time the tree reaches maturity, then, the bear-
ing habit is regulated by the balance between the materials which
produce wood and those that produce fruit. Young trees need sum-
mer pruning to check their vigor and cause laterals to develop while
older trees require dormant pruning to thin the fruit and to renew
the vigor. Thus, it is seen that in the young trees, vegetative vigor
must be restrained and fruit production encouraged, while in the
aged trees, the exact opposite is the case.

For twenty-five years following the publication of Warder’s
“American Pomology” very few papers appeared dealing with the
fruitfulness of apples. Seemingly, the writers of this period were
content to let the question stand without additional comment. How-
ever, about 1880 there began to appear frequent articles concerning
the chemical nature of the stored plant reserves. Halsted® (1890)
pointed out the importance of reserves to trees and also made some
descriptions of the various storage tissues. He found but little ap-

arent difference between leaf buds and fruit buds so far as sugar
storage was concerned. However, he pointed out that leaf buds store
up much more starch than the others on account of the fruit buds
having to supply the developing fruit with this material. In his
opinion flower buds are not terminal but rather simply overshadow
the terminal leaf bud which is down among the blossoms. Fischer**
(1891) also called attention to the importance of reserves, and of
their activities before any exterior growth takes place.
j Maynard®’ (1888) concluded from some girdling experiments
with crabapple trees that girdling will cause the production of an
abnormal number of blossom buds but that it is an unsafe stimulus
to use. Taftt®® (1891) gave root pruning as one cause of fruitful-
ness, but stated that this practice is not to be recommended. Quinn’?
(1892) said that summer pruning causes a change in the flow of sap
from the ends of the branches which results in fruit formation.
Gurney® (1894) assigned exhaustion as a cause of alternation but
said, “Bearing only in alternate years can in a large measure be
broken up by a careful system of feeding or fertilizing.”

Sorauer?®® (1895) has given this problem considerable attention,
mainly from the physiological point of view. He maintained that
under certain conditions, controllable to some extent by man, buds
may be changed from one form to another. He said in part:

“Plants will only develop flowering buds when the food material formed
in the leaves is copiously stored up in the stem and branches as reserve ma-
terial, and not when this material is immediately used up in the production of
new vegetative organs.

10 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32

“Of our apple trees it is a well known fact that in warm insular climates
they grow into magnificent foliage trees but remain unproductive of fruit.

“That a diminution of the supply of water accompanies the production of
flowers in nature may be gathered from the fact that most trees and shrubs
produce their flowers on short reduced branches or spurs. The comparison
of the anatomical structure of such a short shoot with that of a long leafy
shoot confirms our statement, too, that an increase in stored food material is
necessary for the production of flowers. The former shoots have by far
more storage tissue than the latter........

“The withholding of water in such a treatment prevents the use of
assimilated plant substance for the growth of new shoots and causes it to be
stored up near the buds.

“For the production of flowering buds it is essential to decrease the sup-
ply of water and of nitrogenous salts, to increase the phosphates supplied
to the plants and to increase the illumination.”

Sorauer also discussed to some extent the effects of pruning
upon fruitfulness and suggested that bending, twisting, notching,
ringing, and peeling may be used to make pruning even more effec-
tive.

Klebs*® (i890-1905) published several papers upon subjects re-
lating to the reproduction of plants. His earlier investigations were
carried out with algae and fungi because of their simplicity and
rapidity of development, and also because the external conditions
could be so easily and at the same time absolutely controlled. From
the lower forms, however, he progressed to the use of the higher
species and his later experiments were with phanerogams. This
writer, in particular, emphasized the fact that the environment of a
plant plays a most important role in the rate and kind of develop-
ment made by it and its various parts. He showed that a plant may
remain vegetative indefinitely if placed under the proper conditions.
On the other hand, when the vegetative growth is inhibited reproduc-
tion at once begins. These changes in the character of the growth
may be brought about entirely by a change in external conditions.

Work with the lower plants convinced Klebs that reproduction
is affected by the amount and intensity of light, heat, moisture, and
food supply, while the later experiments led him to believe that
higher plants reacted in precisely the same way. Plants pass from
the vegetative to the flowering state with changes in their external
conditions and, at the same time, interior changes resulting in greater
storage of plant food may also be taking place. Flowers, however,
are not the result of an absolute amount of nourishment but rather
of the relation between the decomposition and recomposition of these
substances. In support of this opinion, he pointed out the fact that

SOME FACTORS AFFECTING FRUITFULNESS IN APPLES tt

badly nourished plants always blossom early. Intense light and low
humidity are favorable to flower production and the intensity of
nutrition also has great significance in this connection. Lessening
the food supply results in flower production, provided the plant
possesses reserves. This is the condition brought about by ringing.
Whether external conditions are to exert a favorable or unfavorable
influence upon reproduction depends altogether upon the effect
which they have upon internal conditions.

Other investigators coming after Klebs and Sorauer have sub-
mitted additional proof that there is a definite relation between the
food supply and the character of plant development. External con-
ditions favoring flower growth always oppose extensive twig and
leaf development. External conditions favoring great availability of
plant food always result in vigorous vegetative growth. Climatic
conditions may have quite an influence in this respect. This was
very forcibly brought out by Balmer’? (1896) in describing the dif-
ference in the fruiting habits of the same variety when planted under
different conditions. In a region where rainfall is abundant, exces-
sive vegetative growth is noticed, while in a section where the rain-
fall is much less, even the young trees tend to overbear. This, of
course, means that much more attention must be given to pruning
and other orchard operations under those conditions.

During the more recent years a considerable literature has been
developed in connection with the effects of such orchard operations
as pruning, fertilization, cultivation, spraying, ringing, etc., and along
with this, some general observations with regard to the fruiting habit.

Schweitzer!2” (1898) commenting upon the results secured from
the ash analysis of twigs from apple trees said, “surely the much
larger absolute amount of lime, phosphoric acid and potash in the
bearing twigs must be either the cause or the condition of their bear-

ing.

Bailey’ (1898) enumerated several factors that may cause bar-
renness in apple trees but finally stated that in the nature of the
tree there is no reason why it should not fruit more or less continu-
ously. Later® (1911) this same author concluded that the side bud
on a bearing spur does not receive sufficient nourishment to develop
into a fruit bud and, even tho the blossoms may be removed, it still
may not produce a fruit bud for the following year. Waldron**?
(1899) mentioned an “inherited tendency” to produce flower shoots
as being a very potent cause of fruitfulness.

Gof f* ©? ®? (1899-1901) in making studies of blossom formation
in our common tree fruits showed that environmental factors have

12 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32

great influence upon the early development of the bud. He con-
cluded that fruit buds are due to nutrition rather than structure since
a spur may bloom at one, two, or three years of age, or it may
never bloom, and also because of the fact that a spur may bloom
and even fruit two years in succession. Alternation is not due to
exhaustion since a weakened or exhausted tree always produces a
large number of blossoms. Very favorable conditions for fruit bud
formation result in such great development of these buds during
that season that no spurs remain for the development of buds for
the succeeding crop. He*® also said (1916) “a water supply insuffi-
cient for rapid growth may suffice for abundant fruit bud forma-
tion,’ and then called attention to the fact that fruit buds are usually
formed during the drier part of the year.

Daniel®*? (1900) declared that from the physiological standpoint
there is little or no difference in the effects of girdling and grafting.

Experimental evidence submitted by Brown and Escombe??
(1902) indicates that the amount of carbon dioxide in the air has
a very marked effect upon flower formation.

Thomas*** (1902) called attention to the fact that some varieties
fruit more abundantly on the younger wood than do other sorts. He
also stated that summer pruning hastens the formation of fruit
spurs near the base of the pruned twig much more than dormant
pruning.

Speaking with reference to thinning, Beach?® (1903) said,
“thinning the fruit does not appear to cause any material change in
either the amount or regularity of the fruit production.”

Sablon’*? (1903) reported that the reserves in the twigs of a
pear grafted upon a quince root are greater than those of a tree
growing upon its own roots, thus tending to make it more fruitful.
Later® (1906) he made further studies upon the reserves of trees
and found that the great variation in the kind and amount of these
reserves was dependent upon the season and the part under considera-
tion.

Loew*®® (1905) combated the idea of earlier German writers that
there is a specific blossom building material when he stated that
blossoms are the result of a certain concentration of sugars. Fischer*
(1905) agreed with Loew that there is no special blossom forming
substance. He also stated that girdling, instead of causing starvation
of the parts above the girdle, results in an accumulation of plant re-
serves thereby causing greater blossom production.

SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 13

Flowers and flower bud formation require a relatively high
illumination according to Clark*’ (1905), a fact which is supported
by Paddock’s'*$ (1905) account of the greater and earlier fruitful-
ness of trees in the increased sunshine of high altitudes.

Chandler** (1905) presented the idea that alternation is due
more to the formation of the blossom than to the later development
of the fruit and for this reason thinning is not effective in overcom-
ing the alternating habit. He also stated that the bearing habit can
be controlled by pruning only in case the pruning dates from the
early development of the tree. MHerrick®’ (1910) reached the con-
clusion that systematic thinning should have some influence toward
annual cropping, thereby doing away with the “off years” of cer-
tain varieties.

According to Ikeda’! (1910) the Japanese fruit growers have
always felt that alternation is due to nature and can not be controlled
in any way. He then told of the pruning which is done by breaking
off the bearing twigs at the time the fruit is harvested.

Waugh"* (1910) reached the conclusion that if a tree is starved,
it will make no new growth, the spurs will deteriorate, and the crops
become scant, while too much wood growth will take place at the
expense of the spurs and fruit.

Manaresi and Tonegutti®®®* (1910) found that fruit-bearing
wood is much richer in nutrients than foliage-bearing parts, and also
that there are material differences in the size and shape of the leaves
on the bearing and non-bearing spurs.

Although Newell*®? (1910) stated that a single bud naturally
cannot produce two crops in succession, yet, according to this author,
the tree can be kept bearing annually. He expressed the opinion
that the fruit bud receives no sap until the needs of the end of the
branch have been fully satisfied.

Stewart? (1910) said, “the off year may be frequently largely
overcome by fertilization and other care,” and later'®* (1917), recom-
mended for maintaining high and uniform yields, first, the prevention
of large crops by thinning, second, an ample supply of food and
moisture, and third, the avoidance of injury to the roots thru culti-
vation, etc.

Pickett*?® (1911) reported that while fertilization had little or
no effect upon the number of fruit buds, cultivation with or with-
out a cover crop always showed an increase. A proper balance,
easily destroyed by too much pruning, or other treatment, between
the working area of the foliage and the food supply, is necessary to

14 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32

insure a full and regular supply of fruit buds in apple orchard™*
(1913).

Paddock and Whipple"® (1911) observed that varieties which
frequently form fruit buds upon the one year wood are more likely
to be annual bearers than varieties which fruit only on the older
parts. The alternation of individual spurs is, in their estimation, due
to a depletion of their energies by the fruit during the bearing year.

Dry weather at the time of fruit bud formation always makes a
good prospect for the next year’s crop, according to Macoun*’ (1912).

Batchelor’! (1913) thought that the spur needs a year to recover
its exhausted energies after fruiting, and hence, a light crop is borne
in alternate years. Newsham’ (1913) agreed with this statement
and then added that removing the blossoms or young fruit tends to
cause annual crops. This writer also stated that checking the growth,
while inducing fruitfulness, does not maintain it.

Magnien® (1913) recommended basic slag as a fertilizer for
apples because it leads to abundant fruit bud production. According
to Remy??° (1913), blossom formation is not affected by high
amounts of phosphorus, potash, or lime, but a certain amount of
nitrogen seems to be necessary.

Howe® (1914) said that ringing, while sometimes effective in
inducing or increasing fruitfulness, is an unsafe stimulus to apply
to fruit trees.

Gourley™’ (1914) reported that practically all methods of tillage
treatment resulted in yields superior to those secured from the sod
plots. In making a detailed study of the fruit spurs, this author*®
(1915) found that the spur having a fruit bud upon it possessed a
greater supply of starch than one without a fruit bud. The leaf area
of a spur is always greater during the non-bearing year. Thinning
experiments with the Baldwin did not give appreciable results so far
as the regular bearing of the tree was concerned.

Sears!’®§ (1914) agreed with Thomas’** (1914) that rank growth
is always opposed to fruitfulness since an abundance of plant food
is essential to blossom formation. He further stated that the effect
of summer pruning is not well understood—it depends upon the time,
nature, and extent of the treatment,—but Drinkard** (1915) and
Batchelor and Goodspeed?® (1915) recommended summer pruning as
a means of stimulating fruitfulness.

Alderman and Auchter?* (1916-17) in a series of experiments
in West Virginia came to the general conclusion that heavy dormant
pruning on young trees delays the bearing age while lighter pruning

SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 15

hastens it. In the case of old trees, however, vigorous pruning
stimulates fruit production. They found that corrective dormant
pruning was more effective in stimulating fruitfulness than summer
pruning. Auchter® (1917) states “thinning does not influence subse-
quent crops nor cause trees naturally biennial in bearing habit to bear
each year.”

From the work of Lewis®! (1915), Gardner*? (1915), Kraus”
(1915), Magness®® ®t (1916), Bradford’* (1915), and Yeager**? (1916)
of the Oregon agricultural experiment station, the following general
conclusions may be drawn: A large percentage of the spurs bear
only once in two years. Varieties fruiting on the newer parts are
more regular bearers than those which fruit on the older portions.
The condition of the tree as a whole determines whether a spur will
fruit two years in succession. There is a correlation between the size
of a spur and its productiveness but the floriferousness of a spur
lessens as the spur becomes older. Fruit bud formation is due to a
fair amount of adjacent leaf surface since the plant foods are stored
up near the point of synthesis, a state of affairs making each twig
more or less independent of the remainder of the tree. The greatest
effects of pruning are manifested near the pruning cut. Summer
pruning stimulates fruit bud formation near the base of the pruned
twig only, and not thruout the body of the tree where the fruit spurs
have already become well established.

Winklert#® (1916) concluded that under conditions favorable to
enzyme action, vegetative growth predominates, while conditions in-
hibiting enzyme activity are favorable to reproductive activity. An
accumulation of carbohydrates is given as one condition bringing
about the cessation of enzyme action.

According to Pickering’?® (1916) it is unproven that fruiting is
due to a gradual accumulation of the plant reserves which become
exhausted thru the production of a heavy crop. He concludes that
the great variation found in the size of crops borne over a series of
years is due to atmospheric conditions more than to any other factor
even tho there is a tendency to alternation in certain varieties.

Retardation of growth always results in an increase in the starch
proportion of the parts above ground,—at least, these are the results
reported by Hartwell®* (1916) after working with the potato.

Barker and Lees*® (1916) reported that different degrees of dor-
mant pruning result in practically an equal number of fruit buds be-
ing formed but that these buds are differently distributed on the tree.

Heinicke®® (1917) stated that a dry sunny season is favorable
for fruit bud production. He also found that bearing spurs are

16 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32

always heavier in weight than non-bearing spurs and that the great-
est leaf area is found on the spurs with the greatest amount of con-
necting tissue. The age of the spur from two to four or five years
apparently has little effect on its fruitfulness.

The established habit of the tree is far more influential upon the
fruitfulness than the kind or extent of the pruning, according to
Kains** (1917). Twig and small branch pruning, however, tend both
to thin the fruit and favor regular annual bearing.

Butler?? (1917) said that the theory that alternation is due to ex-
haustion has little or no foundation, but that it is a natural phe-
nomenon to be predicated from the mode of flowering. Flower bud
development, no matter on what kind of a branch, always occurs
where six to eight sessile leaves have developed in a single period of
vegetation. A slow, quick maturing, sessile growth, due to a scant
but sufficient moisture supply, coupled with a vigorous photosyn-
thetic activity is responsible for flower bud development. In his
opinion small yearly departures from the mean growth will result in
a more uniform production.

GENERAL STATEMENT OF THE PROBLEM

The apple yield of the entire United States shows a wide varia-
tion from year to year as the following table will indicate.

TaBLeE 1—ANNUAL PRODUCTION OF APPLES IN U. S.*

Year Yield Year Yield
Barrels Barrels

NOOO) rete ae te ee 48,707,000 MOUS hee Ae RU ee 48,470,000
STO itis sens rere tees Le Saw Eee 47,213,000 BO A ep cece Cen eae 84,400,000
UNC Ns CW ca aE ea eae nee 71,340,000 LOD Secs A ee 76,670,000
OT 2 ies ea Ue Ga ee 78,407,000 LOM Gee a eel ae 67,415,000

*Yearbook, U. S. D. A., 1916, p. 635.

The foregoing variation is probably to be expected when it is
considered that allowances must be made for the wide ranges of
both soil and climate over which the apple is grown in this country,
and also because of the increased plantings. Unfavorable conditions
in any one section are likely to be balanced by favorable ones in an-
other, and so, on the whole, the foregoing figures do not represent
the actual variation in yield which may be expected in any particular
section.

SOME FACTORS AFFECTING FRUITFULNESS IN APPLES L7

When the Missouri yield alone is considered even a greater
variation than that shown in Table 1 is found. This smaller area
represents more nearly uniform conditions and hence indicates the
degree of difference which is often found in apple yields.

Taste 2—ANNUAL PRODUCTION OF APPLES IN MISSOURI*

Year Yield Year Yield

Barrels Barrels
2,899,000 1G ee Rane ee aE RY ANE 2,067,000
2,420,000 110 (0). Eaae Ne Se ete as eoa ie See Te 3,233,000
3,220,000 UG 05.25 Sh eee ee 2,100,000
1,381,000 1 2) 0 oe ee ee eae ee 6,667,000
936,000 433,000
2,569,000 2,033,000
4,816,000 1.2 | 0,9 SE eee ene eS eters ae Se 3,323,000
3,780,000 2,533,000
3,599,000 3,867,000
784,000 6,400,000
2,165,000 2,633,000
2,767,000 WOT As ees ct ae ti, Bee ee 4,167,000
3,500,000 TOE Reet NT 4 1 Bas So see 6,287,000

3,900,000 1 Ot Hoye Salle ees ecr opr w ese Seeder 2,700,000**

*Missouri Bureau of Labor Statistics Report 37, 1915, p. 286.
te Vearbook Oa so. Wa As L916," ps635.

An examination of the foregoing table reveals the interesting
fact that, as a rule, the heavy yield occurred every third year. For
instance, the years 1915, 1912, 1909, and 1906, all showing heavy
yields, are invariably followed by a relatively light crop which in
turn is followed by a medium yield which, apparently, leads up to
the heavy production again. The same is shown to some extent for
the earlier years also, but here such regularity can hardly be ex-
pected since during the period 1889 to 1899 very extensive plantings
were being made and each year in that period showed a correspond-
ingly greater number of trees in bearing. Such a state of affairs
would naturally interfere with the regular sequence of bearing. How-
ever, the yields for the later years, which probably are more accurate
than the others, represent the production of a more uniform num-
ber of trees and consequently may be considered as more representa-
tive of the way in which trees normally bear.

From the foregoing it is evident that the question of fruitfulness
in apples is a very important one to the fruit grower who demands
regular annual crops in order that his business may be a stable one.

A search of the literature previous to the initiation of this pro-
ject revealed the fact that no particular attention had ever been

18 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32

given io a study of the individual fruit spurs. Previous investigators
have based their opinions with respect to spur behavior, largely upon
general observations and conclusions. Casual observations made by
fruit growers generally have indicated that there is probably a corre-
lation between the previous performance of a spur and its later fruit-
fulness, but data either confirming or contradicting this view have
not been recorded.

In the light of the above facts, when this investigation was be-
gun in 1913, it seemed advisable to center the attention upon the in-
dividual fruiting branches rather than to consider the performance
of the tree or orchard as a whole. It seemed only logical to look in
this direction for an answer to the question, Is the alternation of a
Gano tree due to the inability of the individual spur to blossom
and fruit two years in succession, or to some other factor, or factors?
The question also arises as to whether the regular bearing of the
Jonathan is caused by the fact that only a relatively small proportion
of the spurs blossom any one season. Here again an answer must be
sought by examining the fruit spurs and not by casual observation
of the entire tree.

While the general object of this investigation has been to de-
termine the effect of certain conditions and practices upon the de-
velopment and performance of the individual fruit spur or branch,
the following specific objects may be mentioned:

1. To determine whether an individual spur or branch blossoms
two or more years in succession, in alternate years, or only once in
its life history as a fruiting part.

2. To determine whether there is a correlation between the
concentration of plant sap and stored reserves in bearing and non-
bearing parts, and the observed bearing or non-bearing condition.

3. To correlate the leaf area of a spur with the fruiting habit
that it possesses.

4. To observe the exact effect of girdling upon the concentra-
tion of sap in various parts of the trees.

5. To determine the effect of fertilizers upon dwarf trees
planted in pots.

6. To record the osmotic strength of sap from different parts
of trees grown under different systems of tillage.

7. To note the effect of certain systems of pruning upon the
formation and development of the fruiting parts.

8. To note the effect of etherization upon the fruiting parts of
young trees.

SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 19

SPUR PERFORMANCE RECORDS

In order to determine accurately the exact behavior of the indi-
vidual spurs, it is essential to keep performance records of the spurs
over a series of years. Accordingly, in the fall of 1913 a suitable
label was attached to each spur that had produced a fruit that year.
(Fig. 1.) This labeling was carried out systematically upon one
tree each of the Jonathan, Gano and Rome varieties. These trees
were located on the Horticultural Grounds of the Missouri Experi-
ment Station. They were approximately eighteen years old and ap-
parently in full health and vigor.

In the spring of 1914, labels were attached to all of the blossom-
ing spurs on the same trees, these labels being so marked that they
could be distinguished from those attached the previous season. At
the end of the season still another distinguishing mark was made up-
on the labels attached to the fruiting spurs. These marks were so
made that by an examination of the label it was possible to determine
the exact behavior of that spur during the past year. The results
of the first year’s observations are:

Variety Gano Rome Jonathan
Number of spurs fruiting in 1913........... 598 223 228
Number of same spurs blooming in 1914.. 49 19 36
Paice tet rem ins defer sy Sire. Say nl nam 8.2 8.5 15.8

These data show distinctly that only a very small percentage of
the spurs which fruit one season will even blossom the next year.
However, there is shown a considerable difference in the behavior
of the spurs upon the different varieties. Thus, it will be seen in
the case of the Jonathan, the ability to blossom in the season imme-
diately following the one in which a fruit is matured, is shown in
nearly twice as great a proportion as in either the Rome or Gano.
(The greater number of fruits on the Gano tree was probably due,
at least to some degree, to the fact that it was a larger tree than
either of the others.)

From these observations as a starting point the work was con-
tinued during the seasons of 1915, 1916, and 1917, so that in all this
report covers a period of five years’ work. Labels were attached
to blossoming and fruiting spurs during these seasons so that at
the end of the period it was possible to tell exactly how each spur
had behaved each season since the observations were begun. The
variety list was also extended so as to include Winesap, Grimes, and
York, thus giving three varieties which are more or less regular

20) MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32

bearers and three that exhibit alternation under ordinary conditions.
Some later observations were also made upon fourteen-year-old trees
of various varieties growing in the famous loess soil along the Mis-
souri River.

Obviously, it would be almost impossible to record the perform-
ance of every spur upon every tree under observation. Hence, in
the following figures no attempt has been made to include all of
them. In each case, however, the number taken has been large
enough to preclude accidental variation, and since they were taken
from various parts of the tree so as to include all the different con-
ditions found on the tree, they may be taken as being representative
of the tree as a whole.

In Tables 3 to 13 inclusive, an attempt has been made to syste-
matize the blossoming records secured on the above trees. These
tables represent really the summary of still longer tables, and in order
to simplify them, no account has been taken of the spurs which both
blossom and fruit in distinction to those which blossom only. Since
only a limited number of combinations are possible for each spur’s
performance during the five-year period, the spurs showing the same
sequence of blooming and non-blooming have been grouped together.
New spurs are, of course, being added to the tree each year, so it
must be remembered that the following records represent the be-
havior of the present spur system of the tree and not the system
that was on the tree five years ago when the investigation began.
Many of the spurs which were fruiting at that time have now de-
veloped into larger branches upon which other fruit spurs are borne.

In the tables, the first five columns contain a record of the be-
havior of the spur during the past five years, while the right-hand
column indicates the number of spurs exhibiting that particular com-
bination. The letter “B” represents in each case a blossom cluster
for that particular season, while a blank indicates that no blooms
were shown. It might be noted that the record for the year 1913
indicates, in the main, only those spurs which fruited that season
altho an attempt was made to include all of those that blossomed.
However, since it was sometimes quite difficult to be sure upon this
point this explanation is given. The last line in each table represents
the percentage of blossoms, out of the total number, which blossomed
in the given years.

SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 21

TABLE 3.—PERFORMANCE ReEcorD OF INDI-
vipuAL Spurs From aA JONATHAN
Tree Grown 1n CxLay Loam Soii

No.of
1913 1914 1915 1916 1917 | Spurs
ae B 333
Bat B B 86
as B B B 41
B B B B 3
=e B B B 59
B a B B 2
ae Tie VB B 238
B B B 21
Be os B B 2
B eS B B 97
B B 66
B B B 1
B ae B 3
a B 137
io B B 47
s25 B Nees B 11
B ra B B 3 5
ee B B 101
B pas B 2
ae B
~e B B
165 tues Pee f B
ea ba Ned 23
9.0% ' 21.1% | 40.1% | 37.3% ° 70.7% | 1346

TABLE 5.—PERFORMANCE RECORD OF INDI-
vipUAL Spurs From A GRIMES TREE
Grown IN Cray Loam Soin

No.of
1913 1914 1917 | Spurs
B
B
=a B
B B
B B
= B
B as B
zs B B
B B B
B te B
= pte B
— B B
B B B
B B
Mee A 23 ei (ean ah | eka
2 B B
B kee B
B

Boe tiavesty si ebeaecil) Vay Atel!
8.3% | 4.4% ae 57.0%

TaBLeE 4.—PERFORMANCE ReEcorD oF INDI-
vipuaAL Spurs From A JONATHAN
Tree Grown 1N Loess Soin

, No.of

1913 1914 1915 1916 1917 | Spurs

134
92
20

bd
bd od bd
bd od td td td td |

bd td i
SMe MoM: eo B-se =
w

bd
bd od
bd td bd td td
_

58.7% | 557

20.4%

3.4% | 11.0%

TABLE 6.—PERFORMANCE Recorps oF INpI-
VIDUAL Spurs From A WINESAP TREE
In Cray Loam Sor.

No.of
1913 1914 1915 1916 1917 | Spurs

188
110
70
9
19
76

DOW:
lo= loo le~ Moe ilos loo iilosilesilc= leo ]e~)

od
bd

bd bd to bd |
w

a seer
B B ee Nee 2
B 3

3s a 3
56.1% | 82.4% | 661

— B
4.1% | 19.5%

MISSOURI AGR. EXP. STA.

TABLE 7.—PERFORMANCE RecorDs oF INDI-
vipuAL Spurs From A WINESAP TREE

GROWN
1913 | 1914 } 1915
mse
pees B
Mf B B
aay! B | B B
B tate B | B
B B
B B ae B
eabeaase B
Gains B
B an B
B as
B
see B B
abl B B B
B B B
Ze B oe B
B B ae B

6.0% | 16.1% | 28.8%

in Lorss Soin

(eoflooilo= ies Mleoiloc ico coos ocimley)

55.8% | 81.6%

TABLE 9.—PERFORMANCE RECORDS OF INDI-
vipuAL Spurs From A YorRK TREE

Grown IN Cray Loam Soin

1913 1914
B
fds B
B
B
B
6.3% | 2.1%

1915

1916

Li po!

No.of

RESEARCH BULLETIN 32

TABLE 8.—PERFORMANCE ReEcoRDS OF INDI-
vipUAL Spurs From A Rome TREE
Grown 1N Cray Loam Soin

No.of

1916 1917 | Spurs
abla ath

B zis B 1

1913 1914 1915

Bn hb dW
bo

itd td:
»

B a Al at 5

0.3% | 919

1.9% | 35.79% | 18.1% | 86.8%

TABLE 10.—PERFORMANCE ReEcoRDS oF IN-
DIVIDUAL Spurs FroM A YORK TREE

Grown 1N Loess SOIL
No.of
1913 | 1914 | 1915 | 1916 | 1917 | Spurs
B 47
B 5
B 4
B 1
paw B 1
aes B P 180
eats B B 31
s B B B 2
B B B B pues 1
ed, B B 22
B uA B B 4
B els B 5
(ae B 17
ext B B 1
B ee, B re: 1
B B i ee eu 1
2.790 | 3.9% | 25.7% | 76.7% 114.7% | 326

SOME FACTORS AFFECTING FRUITFULNESS IN APPLES

TasBLe 11.—PrrroRMANCE ReEcorps oF INn-
DIVIDUAL SpuRS From A GANO TREE
Grown 1N Cray Loam Sor.

1913

1914

Bh
hye
B

Oa
ssh ee
Fora ee
BoB
B

3.9% | 36.4%

1915

bd td bd!

1916

wid hd

1917

B
B

No.of
Spurs

3
37

87.19% |

0.5%

1864

TasLe 13.—PERFORMANCE Recorps oF IN-
DIVIDUAL Spurs From A GANOo TREE
(No. 2) Grown 1n Loess So1t*

1913 1914 | 1915
ue: B
B ee
seed B
B = B
B
ate B
B rae B
Rese B
B B
B ae
B
2.1% | 23.9% | 7.4%

bd td bd |

Bonn dw:

85.2%

1917

BwWonnwwdow |

No.of
Spurs

———

22
51
35

00
Bee eR Oe Ow Pp

*Blossoms practically all destroyed in

1916

spray solution.

for further explanation).

of blossoms one season and a comparatively low one the next.

(See page 24

Taste 12.—PERFORMANCE Recorps oF In-
DIVIDUAL Spurs From A GANO TREE

(No. 1) Grown 1N Loess Soin
No.of
1913 1914 1915 1916 1917 | Spurs
ara ana a [ice
pa B 2
ca B B 4
B B B 2
ae B 159
ree B B 1
B pat B B il
Mas B B 43
B B mad B 1
ee B B 1
B eae B 3
= B aoe é a 1
ne ree A
2.3% | 20.9% | 2.6% | 97.2%) 3.6%| 218

An examination of the preceding tables shows that the varieties
studied may be divided roughly into two classes, one of which pro-
duces a fair supply of blossoms each year but with no exceedingly
productive seasons, while the other exhibits a very high percentage

Jona-

24 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32

than, Winesap, and Grimes belong to the former, and Rome, York,
and Gano to the latter group. The varieties of the first group are
usually considered as annual bearers, while the others show rather
marked alternation.

The difference in the behavior of these two groups is brought
out more clearly in Table 14, which is a summary of the preceding
tables.

TABLE 14—PERCENTAGE OF FRUIT SPURS BIOSSOMING IN THE VARIOUS SEASONS.
(1913-1917)

(Summary of Tables 3 to 13.)

*Blossoms practically all destroyed in 1916 by spray solution.

It will be noted that the behavior in 1917 of the spurs on the
tree, Gano No. 2, is in apparent contradiction to that of Gano No. 1.
This may be explained by the fact that in 1916, at which time both
trees had a heavy bloom, the spraying operations were so delayed
that it was necessary to spray tree No. 2 when it was in full blos-
som. As a result, only a very small percentage of the blossoms set
fruit, hence the spurs were able to mature fruit buds for the fol-
lowing year. That they did so, is evidenced by the amount of blos-
som carried by the tree in 1917. It is thus seen, notwithstanding the
statements of some investigators to the contrary, that the bearing
year may be changed, and, to this extent, is subject to the control of
the horticulturist.

Attention is also called to the fact that the York tree growing
in loess soil, produces its blossoms in the season alternating with the
heavy fruit crop of the tree in the clay loam soil. Even in the
same orchard this same variation in behavior is sometimes found.
In each case, however, marked alternation is shown. It gives strength

SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 25

to the statement sometimes made that when alternation is once estab-
lished, there is a great likelihood that it will be continued thru the
following years, unless interrupted by accident or design.

Outside of the foregoing exceptions the varieties show very
great similarity in their behavior in the different soil types. This is
at least suggestive of the conclusion that after all the soil condi-
tions do not affect markedly the behavior of the individual spurs
with respect to their individual alternation.

With the idea of showing a little more clearly the behavior of
the individual spurs, Tables 15 and 16 have been prepared. The
first table indicates the percentage of the spurs now on the tree,
which have produced blossom buds in successive seasons, while the
second table shows the percentage of spurs which have blossomed in
alternate years.

TABLE 15—PERCENTAGE OF SPURS BLUSSOMING IN ALTERNATE SEASONS

Soil Total Total Per-
Variety Type No. Percentage Blooming in centage
Where of SS Showing
Grown Spurs | 1913-15 1914-16 1915-17 Alternation
ionelthiaty res ccretccers-wccse ne Clay Loam} 1346 0.6 7.6 26.6 34.8
omathiagi pees eas Loess 557 0.3 8.0 10.7 19.0
Grimes | Clay Loam 901 Ql. Les 21.8 25.8
Winesap | Clay Loam 661 0.4 yell! 10.9 16.4
Winesap | Loess 315 0.0 2.5 13.6 16.1
PRO TG ye cece ncpttee cee a2 | Clay Loam 919 1.4 34.2 0.1 ai Sei/
Clay Loam 190 0.0 0.0 37.9 37.9
Loess 326 0.0 1188) 1.5 3.0
Clay Loam} 1864 0.2 28.7 0.0 28.9
Loess 218 1.4 20.1 0.0 215
Loess 230 0.0 7.4 3.0 10.4

*Blossoms practically all destroyed in 1916 by spray solution.

TABLE 16—PERCENTAGE OF SPURS BLOSSOMING IN SUCCESSIVE SEASONS

Soil Total Total Per-
Variety Type No. Percentage Blooming in centage
Where |. of | Showing
Grown Spurs | 1914-15 1915-16 1916-17 Succession
[Rae le oe ah
Jonathan Clay Loam | 1346 0.3 4.6
Jonathan Loess 557 0.0 2.1 235) 25.6
Grimes Clay Loam 901 153 1.9 3.9 foil
Winesap Clay Loam 661 0.3 Zot 43.1 45.5
Winesap Loess 315 0.0 4.7 31.4 36.1
ROM eet rae ten Clay Loam 919 0.3 5.8 0.0 6.1
Clay Loam 190 0.0 2.1 Se 6.2
Loess 326 0.3 18.3 1.5 20.1
Clay Loam | 1864 0.0 0.8 0.0 0.8
Gano No. 1 Loess 218 ret 0.9 0.4 4.0
Gano No. 2* Loess 230 37.8 2.9 0.0 40.7

*Blossoms practically all destroyed in 1916 by spray solution.

26 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32

From Table 15 it will be noted that there are relatively slight
differences between the different varieties in regard to the percent-
the Jonathan tree, a regular bearer, has as great a percentage of
age of spurs which alternate in their blooming habit; in other words,
spurs which bloom only once in two years as the Gano, which is
notorious as an alternate cropper. When trees grown on similar
soils are compared, the difference is very slight, the only exception
occurring in the case of the Winesap. The Winesap is really one
of our most reliable regular annual bearers and an explanation for
this may rest in the fact that only a small percentage of the spurs
do alternate in their blooming habit. Gano No. 2 also shows a slight
variation from the average as do also the York and Jonathan grown
upon loess soil. This is perhaps to be expected since these trees as
yet have hardly attained a fully established bearing age.

Table 16 exhibits by no means such close agreement of varieties
as that noted for the preceding one but rather the varieties are again
divided into two general groups. With the apparent exception of
the Grimes, the varieties producing regular crops possess to a marked
degree the ability to produce a blossom on the same spur two years
in succession. This ability is exhibited to a higher degree in the
Winesap than in the Jonathan, a performance which might be ex-
pected because of the small percentage of Winesap spurs which show
alternation.

Examination of the performance records of the second group of
varieties shows that only a very small proportion of the spurs are
able to produce successive crops of blooms. The York grown in
loess soil is seemingly an exception, as is also Gano No. 2. The lat-
ter case, however, is fully explained by the fact that the 1916 crop
of blossoms was practically destroyed, and hence, the tree was able
to mature a larger number than normal in 1917. In the case of
the York, it may be said that local environmental conditions, as well
as the younger age of the tree, probably played a very important part.

The fact brought out just above, which is that spurs on varieties
which bear regularly are able to produce blossoms two years in suc-
cession in a high percentage of cases while alternate bearers are not,
suggests an explanation for the figures recorded in Table 14. The
regularity of the blossom in the case of the first group is conceiv-
ably due to the fact that a great many of the spurs are able to pro-
duce blossoms two years in succession. Also, the inability of the
second group of varieties to blossom two years in succession coupled
with their exceedingly heavy production of blossoms one year will

SOME FACTORS AFFECTING FRUITFULNESS IN APPLES

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28 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32

account for the small number of blooming spurs during the fol-
lowing season. Thus, the difference between alternating and non-
alternating varieties seems to be due to the ability of spurs on the
regular bearing sorts to blossom two years in succession.

While recording the performance record of the spurs, an attempt
was also made to approximate their age by counting the number of
scale scar rings upon the spur. In some instances the age given is
simply an estimate. This is especially the case with the old spurs
because after the age of six or seven is reached, it becomes difficult
to be absolutely positive as to just how old the spur may be. Table
17 will serve to show the relative ages of the blossoming spurs on
the various varieties.

It is of interest to observe that by far the greater part of the
blossoming spurs in every case are between three and seven years of
age. This holds true for both alternating and regular bearing sorts
and hence leads to the conclusion that the age at which the spur
begins to bear is of little significance in relation to the bearing
habit of the variety.

Because of the youthfulness of a large part of the spurs, it is
again noted that by far the greater part of the spurs present on the
trees when these observations were begun are spurs no_ longer.
They have developed into branches and many new spurs have been
formed. A spur seems to be at its highest state of efficiency when
from three to six or seven years of age.

THE FOOD RESERVES OF FRUIT SPURS

The amount of available plant food has long been considered as the
determining factor in fruit bud formation but there seems to be very
little evidence or actual data to support this view. It then has
seemed worth while to compare as far as possible the plant food re-
serves of fruiting and non-fruiting spurs and their various parts, that
is, their leaves and fruits.

There are two general methods by which the relative amounts
of stored food in plant tissue may be determined, the first, by de-
termining the concentration of the plant sap thru the use of the
freezing point method, and the second, by making an actual chemical
analysis of the parts under consideration. The former method was
used extensively by both Chandler?® and Winkler'* at this Station,
while the English investigators, Davis and Daisch®? employed the
latter in the determination of plant carbohydrates. In the first
method, it is not possible to calculate the absolute amount of materials

SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 29

present, only the relative proportions are indicated. Neither can the
amount of starch be determined by this method. Through the use
of the analytical method, however, both the identity and absolute
amounts of the substances present can be determined if suitable
methods are employed. Both methods have been used in this investi-
gation, but, in either case, only for the determination of the relative
amounts of the reserves rather than their absolute percentages.

1. Depression of the freezing point—The sap for the de-
termination of the freezing point depression was secured by grinding
up the parts under consideration by means of a food chopper and
then subjecting the ground material to considerable pressure. The
material was enclosed in muslin before being placed in the pressing
blocks. These blocks were of hardwood and so made that one of
them just fit into a cavity in the side of the other. A jackscrew
served as a means by which the pressure was applied. Figure 2
shows the various details of the press. The expressed sap was col-
lected into a test-tube thru a small funnel.

After being expressed the sap was kept in a cool place until its
freezing point could be determined. An ordinary Beckman ther-
mometer was used and the low temperature secured thru the use of a
salt and ice mixture. A small amount of sap was placed in a test
tube, the amount being just sufficient to cover the bulb of the ther-
mometer. The thermometer was then inserted and the tube plunged
into the salt and ice. It was usually found to be advisable not to
have this tube in direct contact with the ice because the cooling in
that case was too rapid. Best results were secured by first insert-
ing into the freezing mixture a tube slightly larger than the one con-
taining the sap, and then placing the latter inside the former. An
air jacket then surrounds the tube containing the sap and the ther-
mometer. This will slightly retard the cooling and thus insure a
more uniform cooling.

The depressions given in the following tables represent the dif-
ference between the freezing point of distilled water and the freez-
ing point of the particular sap. The plant saps, being of a“higher
concentration, freeze at a lower temperature.- The greater this con-
centration, the lower will be the freezing point, and hence, the greater
the depression. It is assumed that the saps with the greater depres-
sion possess the greater supply of plant food. No attempt has been
made to calculate the osmotic strength of the various saps but this
could be very easily done by reference to the osmotic strength tables
worked out by Harris and Gortner® ®,

30 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32

Table 18 indicates the depressions which were found in the
spur sap from spurs bearing or non-bearing in the years specified.
In every case, an attempt was made to get spurs representative of
these two conditions, the spurs being taken from the same branch
as far as possible. Only the short fruiting branches were used,
rarely were they more than three inches long. So far as outward
appearance was concerned, the only difference between the two sets
of spurs was that one group had fruited in the year specified and
the other had not. After the spur material was ground, the sap was
expressed as previously described.

TABLE 18.—DEpPRESSION OF JONATHAN FRuIT SpuR SAP

Bearing Non-bearing Bearing Non-bearing
Date previous previous same same
year year year year
Se
Degrees C. Degrees C. Degrees C. Degrees C.
Pebruarya Oslo) os a 2.450 2.300
February 27, 2.100 1.730
Marchal 9019115 % eee 2.120 1.990
2.370 2.170
2.130 2.000
Italy Wiel Mocs tseemecmeet eacceeneee en 1.200 1.340
UV Ena iped 5 eae NS pss hee ens te cone hose we nce ee econ ina ceaeeeetenenee rate
DGeU a peep Tbe Alsi Sa Nek A eS lI Oo ON UI Ve ce
AED py Ae TN Sp ee 1.355 1.340
Tisha BLS USES a I ee ee eet ae
ATIC TSE Ne aL OL Oe cere koe cess 1.265 1.210
JETS 8 | lye Reh one ee ee 1.285 1.215
September 15, 1916 1.080 1.040
October (4.4 1Od6:2 ees 1.290 0.910

*Spurs from trees grown in loess soil.

A study of the figures in Table 18 shows that during a consid-
erable portion of the year the sap from the bearing spurs and also
sap from spurs fruiting during the preceding season, has a greater
depression than sap from corresponding nonfruiting parts. This dif-
ference may not be large enough to be of special significance. It
gives no conclusive proof to the claim that in a non-fruiting year the
spur is accumulating reserves for the next year’s crop of buds.
However, it may be possible that the greater part of the reserves
are stored farther back from the end of the branch. Then, too,
these data do not include a measure of the reserves which are stored
up as starch.

The accompanying chart shows graphically the depressions re-
corded in Table 18. It is noticed that the sap of non-fruiting spurs
is slightly more concentrated than the sap of a spur holding a fruit

SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 31

at that particular time. On the other hand, sap from spurs bearing
the year previous to the determination shows consistently a greater
concentration than the sap from corresponding parts that did not
fruit during the preceding season. This difference gradually disap-
pears, however, and apparently both kinds of spurs reach a similar
degree of concentration about July 1.

\
2. 008
‘L00°%

Dearing previous

me 7? uty previous ee
'0,00°

;
7 of 2 oe S

Depression of Jonathan spur sap

Marked seasonal variations in the sap density are also observed.
The greatest change comes in late June and early July, at which time
there is a sudden drop in concentration. This is the season at which
the fruit buds for the next year’s crop are forming and this abrupt
drop may be either the cause or an effect of this fruit bud formation.
It is noticeable in both the bearing and non-bearing spurs.

Apparently there is little difference in the concentration of the
spur sap which can be attributed directly to soil conditions. Spurs
from trees grown in two widely varying soil types showed little
variation in the depression of the sap. Also, altho all of the above
determinations were made upon sap from a Jonathan tree, there
seems to be little varietal variation in this respect as the later de-
terminations show.

The observations noted above concerning the difference in sap
density in fruiting and non-fruiting parts at once opens up the ques-
tion as to whether this condition may not be due to a withdrawal of

32 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32

moisture from the spur by the ripening fruit or by the leaves—a de-
ficiency which may not be altogether overcome by the following
spring. Chandler?> has observed that toward the ripening period
water may be drawn from the fruit to the leaves. There may also
be a similar movement of moisture from the spur which would at
once have its effect upon the concentration of the sap of the spur.

The above determinations are perhaps too meager to warrant
any positive conclusions but they are given as being suggestive of
the idea that perhaps after all the food supply is not so important
as has been assumed by some writers.

Leaf sap taken from leaves on fruiting and non-fruiting spurs
did not show so consistent a difference as sap from the spurs them-
selves. The variations in these depressions, as shown in Table 19
are so great that it seems unwise to suggest any possible explanation,

TaBLE 19.—DeEpPRESSION OF LEAF SAp FRomM BEARING AND NON-BEARING

JoNATHAN FRuIT SPURS

Fruiting Condition
Date |

Bearing Non-bearing Bearing Non-bearing

1915 1915 1916 1916

Degrees C. Degrees C. Degrees C. . Degrees C.
June a2 TRA LO NG ihe eee ee 2.680 2.690 2.550 2.880
July 15, 1915 1.510 peak? 0 ieaiipeael eee oerereereemtererm aca Wesrrucen tk A AOS fo
July 22, 1916 1.970 1.980 2.035 2.015
August 1, 1916 1.605 1.890 1.510 2.100
AIS ASt ANT a) SONG eater eta ete 2.340 2.205 2.540 2.290
September 15, 1916 2.255 1.995 2.190 2.460
October palsy aL OVO eee 1.995 1.945 2.260 2.110

TABLE 20.—DEPRESSION OF SPUR SAP FROM SpuRS BEARING 3, 2, 1, OR NO FRUITS

Fruiting Condition
Date Variety
3 fruits 2 fruits | 1 fruit no fruit
|e
Degrees C. Degrees C. Degrees C. Degrees C.
Mineo, Ol oeeee Jonathan 1.905 1.860 1.865 1.855
June 21, 1916 .... | Woodmansee 2.060 2.040 2.000. eh pee eee
Jiatly, vb; 1916.22 Woodmansee 1.250 1.340 W160 ty itn | pecceceeeeees eee
Dilys els Se. onathan! Wrest) ere sot ae 1.130 1.200 1.330
Visthyeuliza edo hopes ae Jonathan 0.950 1.060 1.070
Vly Oo ees York* 1.200 1.130 1.300
aly 22. Ou tee W oodmansee 1.365 1.310 T2257 Me) Ir lease eee
Falys 3h; 196 Pionathan cn -4| Keane beura eel 0.920 1.010 1.100
August 1, 1916... | Woodmansee 1.270 1.295 1.510
July 17, 1916.2 Woodmansee 1.600 1.535 1.500
September 15, 1916 | Woodmansee 1.360 1.450 1.205

*Spurs from trees grown in loess soil.

el is

OU pS Tk. Mdina ee Oe

ype

Pei iy

Fig. 1—Gano apple tree on which some of the labeling work was done

Fig. 2—Press and blocks by means of which the plant saps were expressed

= = Ce. a>, ae

UISOI}IU FO S}IFFO
poyseut AIIA dy} 9I0N “YMOIS suosvas aUO Ja}ye soo1} o[dde Jrem—g¢ “sly

SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 33

Aliso figures on the depression of spur sap, leaf sap, and fruit
sap from spurs bearing three, two, and one fruits, are so inconsist-
ent as to be of no assistance in helping to explain fruitfulness or non-
fruitfulness. In general, it may be stated that it apparently makes
little or no difference upon the concentration of the sap as to how
many fruits a spur is maturing. The seasonal differences in the de-
pression of the fruit spur sap are again brought out by Table 20
which checks very well with Table 18 in this respect.

TABLE 21.—DEPRESSION OF LEAF SAP FROM SpuRS BEARING 3, 2, or 1 FRuitTs

Fruiting Condition
Date Variety

3 fruits 2 fruits 1 fruit

Degrees C. Degrees C. Degrees C.
IIe Wok DOU Gs eoen ce te Woodmansee 2.660 2.610 2.580
paly:n63,) DOUG Woodmansee 1.930 1.790 1.830
Fitaliys USE VOWS Ce ere ee Jionathan)— 2)))i)2e) eee 1.510 1.510
Jaalye Boe) MOUG ie oss cae So Woodmansee 1.940 1.830 2.035
PAI CNIS LOM By 47 ece eek eet n Woodmansee 1.895 1.870 2.135
PNG USE dit SLO LG) sk cts fcr W oodmansee 2.650 2.550 2.540
september 15, 1916 .~............... W oodmansee 2.640 2.045 2.190

TABLE 22.—DEPRESSION OF FRUIT SAP FROM SpuRS BEARING 3, 2, or 1 Fruits

Fruiting Condition
Date Variety

3 fruits 2 fruits | 1 fruit

Degrees C. Degrees C. Degrees C.
sab OYE? Nee a [A Ya RT ae ee Jonathan 1.000 -960 -950
(Ena, aA UO WG a ee Woodmansee 1.880 2.040 1.900
TENG) ALO (Se Woodmansee 1.180 1.040 1.040
ijivihyme aos WONG e es 2S oe 22 Woodmansee 1.325 1.345 1.290
August 1, 1916 Woodmansee 1.325 1.330 1.320
August 17, 1916 W oodmansee 1.395 1.440 1.320
September 15, - 1916) -2sccc.023.2 Woodmansee 1.415 1.435 1.355

2. Chemical Determinations.—In order to get at the problem
from a different angle and to compare especially the relative amounts
of sugars and starch in the spurs, it was decided to employ some
simple chemical methods. The method used in the sugar analysis
was adapted very largely from the work of Davis and Daish** and
the starch determination was made in accordance with the directions
in standard works on agricultural analysis. While these determina-
tions possibly may not be all that might be desired from the chemical
point of view, they are at least comparative and it is this connection
that they are of value here.

34 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32

Considerable difficulty was encountered in securing satisfactory
results, and, altho the work was begun early in 1917, several
months had passed before it was felt that results of any reliability
were obtained. The results given below were secured from spur ma-
terial only, since the buds alone or the leaves could not be used satis-

factorily.
The analyses were carried out according to the following plan:

1. Grind the material with a food chopper and then weigh out a 15-
eram sample.

2. Boil the sample for one hour in 500 cc. of 95 per cent alcohol to
which had been added 5 ce. of ammonium hydroxide.

3. Filter and wash the residue with alcohol. Preserve the filtrate for
the sugar determinations. Dry the residue for the starch determination.

4. Add 2 cc. of toluene to the filtrate and evaporate down to 40-50 cc.
at 70°C. Dilute to 250 cc. with water.

5. Precipitate the tannins in 200 cc. with basic lead acetate (sp. gr. 1.25),
adding a small excess of this material. Make up to 250 cc. and filter.

6. To 200 ce. of this filtrate, add enough solid sodium carbonate to re-
move the excess basic lead acetate. Again make up to 250 cc. and filter.

7. To 25 cc. of this filtrate add a small amount of Fehling’s Solution,
boil for two minutes and then filter. Dry and weigh the cuprous oxide precip-
itate. This gives a measure of the amount of reducing sugar present.

8. To another 25 cc. sample add enough sulphuric acid to make it faintly
acid to methyl orange. Then add 10 per cent by weight of citric acid crys-
tals. Boil for ten minutes and then neutralize to phenolphthalein with sodium
hydroxide. Add a sufficient quantity of Fehling’s Solution to precipitate the
total sugars as cuprous oxide... Filter, dry and weigh the precipitate.

9. Two and one-half grams of the residue from procedure No. 3 are
placed in a flask with 200 cc. of water and 20 cc. of hydrochloric acid (sp.
er. 1.125). It is then boiled in a reflux condenser for two and one-half
hours. One cc. of toluene is added after it cools.

10. Nearly neutralize with sodium hydroxide, using phenolphthalein as
an indicator. Dilute to 250 cc.

11. Add Fehling’s Solution to 25 cc., boil for two minutes, then dry and
weigh the cuprous oxide precipitate. This indicates the amount of starch
present. Pentoses and pentosans are also included.

The results secured are given in Table 23. No attempt has been
made to calculate the actual percentage of sugars or starch present.
The figures represent only the weight of cuprous oxide present in the
aliquots indicated. All determinations were made upon the spurs of
a Yellow Transparent tree. This variety was selected because of the

accuracy with which the past performance of the spurs could be
determined.

PU aia eas ap i ee

SOME FACTORS AFFECTING FRUITFULNESS IN APPLES =o

TABLE 23.—SUGAR AND STARCH CONTENT OF YELLOW TRANSPARENT FRUIT SPURS

Weight of Cuprous Oxide Representing

Date of Determination

Condition Reducing Total Starch
of Spur Sugar | Sugar

October 225 19179 | Bearing -0153 .0447 .1861
Non-bearing -0191 -0502 -1815

November. .3,°. £9175 2. | Bearing -0167 -0530 .1605
Non-bearing .0215 -0488 .1730

November 17,5, U9i7 2 oo. Bearing -0720* -0760 -1569
Non-bearing -0150 .0780 .1560

Mecempen Es VOU" 220s Bearing -0594 -0800 -1336
Non-bearing .0615 .0690 -0990

Decenther. 19S VLG) 2 ee. Bearing -0305 -0727 .1332
Non-bearing .0477 -0877 .1477

satiety Gon POLO Ry see te crete Bearing -0300 .0700 .1500
Non-bearing .0384 -0800 -1500

Jantaryy 24 0cl GUS) e122 soe. Bearing -0255 -0530 -1395
Non-bearing .0520 .0965 .0915

Bebriudacyrs lie OUsy eee ee Bearing -0335 -0780 .1145
Non-bearing -0325 -0750 1325

March? (G2 VOUS) oes Bearing -0320 -0855 .1685
Non-bearing -0400 -1000 .1585

March (205) 19. G22. ns Bearing .0225 -0740 SSIS
Non-bearing -0180 -0500 .0975

No rsltirSi pk Od Se a eos ee ee Bearing -0170 -0325 .1505
| Non-bearing .0275 .0540 -1505

*It is very probable that a portion of the non-reducing sugar is also included in this
determination.

The number of determinations is small and the series incom-
plete in that there are no figures available for the important summer
months preceding and during the time of fruit bud formation. Posi-
tive conclusions probably should not be formulated but the data are
at least suggestive. It will be noticed that in a majority of the cases
there seems to be a slightly greater amount of sugar, both reducing
and total, in the non-bearing spurs. The starch content of the non-
bearing spurs, however, does not average quite so high as in the
bearing spurs but there is considerable variation in these results. The
amount of starch apparently decreases somewhat, in both kinds of
spurs, as the growing season approaches, while the amount of sugars
increases.

Judging from these few determinations, some emphasis is given
to the theory that the non-bearing spurs are able to lay up a greater
amount of reserves than spurs which are maturing fruits. When
compared with the total amount of reserves, however, this excess is
very small. These results do not agree altogether with those secured
from the freezing point determinations. The latter, however, gave a

36 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32

measure of soluble materials only. If the conclusion reached by
Magness®*, that reserves are stored near the point of synthesis, is a
true one, then it would seem that the non-bearing spur accumulates
only a slightly greater reserve supply than the fruiting spur. This
difference, however, may be sufficient to account for the lack of
fruit bud formation on such a large percentage of bearing branches.

NUMBER OF LEAVES AND LEAF AREA OF FRUIT SPURS

General observation long ago led to the conclusion that spurs
maturing fruits had a smaller leaf area than adjacent spurs having
no fruit upon them. In order to secure some definite idea as to the
degree of this difference, some counts and measurements of the
leaves on fruit spurs have been taken.

Counts made in 1915 gave the following figures concerning the
number of leaves on the spurs. Several varieties were used, the
number of spurs taken being large enough to be representative of the
tree as a whole. In every case, as will be seen from Table 24, the
non-bearing spur has the greater number of leaves, when averages
are taken.

Taste 24—NUMBER OF LEAVES ON BEARING AND NON-BEARING FRUIT SPURS

Average Number of Leaves
Variety on Each Spur
Bearing | Non-bearing

Bett DD avis) aspect scanned ated tate senate sccenbge osdebenemeeateaee acento 8.70 8.66
Picormart hae rn ase ea is ae lh ee 7.98 9.14
EU pipers Cosco ocean ee nee ee 9.38 9.85

TANTS SSNS Se ae a ect nn bees eee 8.32 8.46

In the next two seasons further counts and also some measure-
ments were made, the leaf area being determined by the use of a
polar planimeter. A summary of these results is given in Table 25.
These data represent the figures secured from the measurements of
more than two hundred and fifty spurs and hence may be taken as
representative. It will be noted that from the average total leaf
surface of the spur and the average number of leaves, the average
size of the individual leaf has been calculated.

To give some idea of the range of variation found in both the
number of leaves on a single spur and their total area, the figures on
a few spurs taken at random from Jonathan and Woodmansee trees
are also given. (Tables 26 and 27.)

ee ee

|
|

SOME FACTORS AFFECTING FRUITFULNESS IN APPLES

Taste 25—AVERAGE NUMBER OF LEAVES AND AMOUNT OF LEAF SURFACE ON
BEARING AND NON-BEARING SPURS

Variety

No of Total Av. Leaf No of Total

Leaves area Size Leaves area
sq. in. sq. in. sq. in.

Woctor “22.4254. 6.10 13.72 2.25 7.40 20.80
Summer Colville 4.36 15.67 3.59 5.75 21.70
peta tesserae 6.16 9.86 ila sV¥/ 8.15 13.66
W oodmansee 4.38 6.83 1.55 6.16 13.67
Ben. Wavis 5.38 se AS) 2.08 6.66 15.39
Missouri 5.36 6.96 1.29 7.64 9.89
Jonathan 6.65 10.83 1.62 8.41 14.58

Bearing Spurs

Non-bearing Spurs

Av. Leaf
Size

TasLE 26—NUMBER AND Size or LEAVES ON BEARING AND NON-BEARING
JONATHAN FRruir Spurs

Bearing
No. of Total
Spur No. Leaves Leaf
Area
sq. in.
1 ARIe See aE Gi 15.76
2 7 9.69
3 10 17.53
4 9 12.48
5 5 8.45
6 6 13.19
Fi ee tee ah 12.72
ttt paeeecenr! 14 20.05
Ohy eh eeae 2 4.28
TOM see 6 12.78

Spur No.

Non-bearing

No. of
Leaves

ry
NF ODF UOUONDAAN

TaBLE 27—NUMBER AND SIzE OF LEAVES ON BEARING AND NON-BEARING WOoD-
MANSEE FRUIT SPURS

Bearing
No. of Total
Spur No. Leaves Leaf
Area
sq. in
Th i ten tebe 5 8.40
2) Re 4 5.41
a0 Gs ee 4 Eu?
4 3 3.82
5 4 6.56
6 3 5.05
fi 5 9.41
8 if 11.80
LS eR ae Sees 6 7.63
nO) albert 5 4.73

Non-bearing

No. of
Leaves

OUOWMDANFL UNA DH

38 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32

In every case it is shown that non-bearing spurs have a larger
number of leaves and a greater total leaf surface than non-fruiting
spurs. When the average size of the individual leaf is computed,
however, it is found that no very marked difference is present. It
seems, therefore, that so far as the size of the individual leaf is con-
cerned, it makes little difference whether it is upon a fruiting or
non-fruiting spur. The greater total leaf area of the non-bearing
part apparently comes almost wholly from the increased number of
leaves which it develops.

The relative sizes of the individual leaves, and also the total
leaf area, on bearing and non-bearing spurs is brought out clearly in
Table 28. To get the figures given in this table, it is necessary only
to divide the average individual leaf area of the non-bearing spur by
that of the bearing spur. A similar operation gives the proportion
between the total leaf area of non-bearing and bearing spurs.

Tapie 28—Proportions BerwrEN NON-BEARING AND BEARING SPURS IN RESPECT
To (1) Arka oF INDIVIDUAL LEAVES, AND (2) ToraL Lear AREA OF THE SPUR

Variety Individual Total Leaf
Leaf Area Area of Spur
AY copra eat aera ace eae a ah TL ea at kL Te 1.06 135
IMIESSO UIE ysis ee ORS LUN AL Sete NE le ga IE LIRR eae 1.00 1.42
ADy ayes chiens Sepia ee eee ev Ree lah Savane AMS RN ee GD 1.06 1.38
Sigmimeny Colvalle testes evo ae ty aE el ace Lea eon 1.05 1.38
WBA s oie B fe tad op oe ee RY Ss ad Be eM ae a ead Ce NOY ge ibgibil 1.36
LD Lovey ica lene seitp Ee nh ee Se ee Se ce ie aR CT RR UNA AU AYO 1.24 1.51
WYO O Grea Se ey IS 2a FEL LH NA aN AS alc 1.42 2.00

With the exception of Woodmansee and Doctor the varietal
agreement in Table 28 is exceptionally good. Ben Davis also shows
a slightly higher proportion between the sizes of individual leaves
from non-bearing and bearing spurs than the more regular cropping
varieties such as Missouri and Jonathan. There is just a suggestion
here that this higher proportion may be correlated with alternation,
for both the Ben Davis and Woodmansee are noted alternate bearers,
the Woodmansee alternating probably more even than the Ben
Davis. The other sorts have not fruited sufficiently long in this
section for their bearing habits to be well known.

From these measurements, it is made clear that potentially, the
non-{fruiting spur has the much larger leaf surface from which to
draw its supply of elaborated plant food. If this food is stored near
the point where elaborated, then the non-fruiting spur should have
the greater amount of such materials to draw upon in times of

La One at a ep ear oet « e ..

met

SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 39

emergency. Reasoning from this alone, it is not difficult to see why
fruit buds should form more often on non-fruiting than on fruiting
spurs.

EFFECTS OF GIRDLING UPGN THE CONCENTRATION
OF PLANT SAP

Girdling has often been recommended as a very effective means
of stimulating fruitfulness. With the purpose in view to determine
the actual effects of girdling as revealed by the changes brought
about in the plant sap concentration, some preliminary experiments
were begun in the spring of 1915. These first tests were conducted
with nursery trees three years old, since it was thought the results
obtained would be representative of what might occur on older trees.
The number of available trees was so small, however, that a com-
plete series of results could not be obtained at this time, so the work
was continued the following season.

The trees were girdled by removing a strip of bark approxi-
mately one inch in width from the trunk of the tree, the girdle usually
being quite close to the ground. Trees were girdled at regular inter-
vals thruout the spring and early summer and the subsequent effects of
the girdling noted by determining the depression of the freezing point of
the saps from time to time. These depressions were determined for
all parts of the tree, leaves, twigs, trunk, and roots. In the case of
woody tissues, the cortex only was ground up and pressed. The
sap was expressed and the freezing point determined as described
above in the case of the fruit spurs. The following tables present
the data secured.

TasLe 29.—Errect or GIRDLING UPON THE DEPRESSION OF TRUNK Sap
1—Bark from below girdle. 2—Bark from above girdle

Depression on Date Given, 1915
Date of Girdling a a a
June 1 af June 19| July 7 | July 28 | Aug. 18) Sept.10 | Oct. 23| Mov.20
(Grinds Ophea eee 0.920 0.995 0.870 0.890 0.870 1.070 1.360 | 1.320
TaN SNES 27 Mie saetont ano 1! 0.920 0.735 0.820 [6A] 0 am Mies eer nee ef cee eset [Wenn ge
Bah dles2Z0 1.160 1.370 LEB T Oa eS eee NS ete see eee
I Leh ai p22) ee ee ee 1 el hehe selene 0.765 0.920 0.920 Peles es 8s tie ota eet ate ee Eee
isl Rees aed 1.205 1.470 TH 2O ON ese e saer || Pees ee eee Nyse em i eee ee
Minaive nO Nee eats i ld ee ee oe 0.785 0.720 0.830 OL660% Hie eee
game 13025 i [, cd SOO, gh PePOGwn| deem On, feet ee eke ve
itelvare teh eae 1) I seere mee oral beeen | 0.800 0.780 0.520 OS630 eee
Aa) NEN Nee ola | Berea ee 1.030 | 1.080 1.250 T860) Wires
Uptalyig Woe TNS oh Lens ay ee eal) eee ae 0.820 0.650 0.850 0.930
PaO ap er toe | Na asda eee eee 0.910 1.090 1.310 1.420
Efitaliys Sie eee ee UU AOS SRS Vee an NUP acetate Sc eee a 0.810 0.910 0.750
Dh Vice PALS SIN Gh es AL A OL i THis ee 1.000 1.220 1.450
AIG Es lor eee eece Ulin PANE A nem Atae se ARC acinel NIV Ene Ol eed DM Acti aima MA reed 0.930 0.830
Di FRE IRN Accu NENTS HP ca ea | Sea eo HS SS SE 1.130 1.550
September 8 .......... STR ENS AOS URED NAN AN aU Hak He LR YP ae 0.930
PW I SRR YE) ees Te EE Aap lz al NEO oe ae os aeamenee res 1.380

a oe ee

40 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32

TABLE 30.—EFFECT OF GIRDLING UPON THE DEPRESSION OF Twic SAP

ne eee

Depression on Date Given, 1915 i
Date of Girdlin eee
avis : June 3 } June 21 | June 24 July 7 | July 28 | Aug. 18 ?
1.240 1.200 1.090 0.870 1.020
V4 5 Olan iS SOR ust essen eee 1.370 1.050. 3) 2
a cores Lee 1.450 1.300 Lise a a ee
Sy as 1.410 1.250 1.090 0.870
we ggb sa Bea cebes |e: gtece cea cel |e emeuees eee ee 1.170 1.170 1.210
Bere Dee mens Potent oeetesy (ent lee eal ka a! 1.110 1.230
Secon ene ate WUC Speier ey exes ee anne |ceg an ae ST teh 1.150

TasLE 31.—Errect oF GIRDLING UPoN THE DEPRESSION OF LEAF SAP

Depression on Date Given, 1915 ~
Date of Girdling =

|
|
|
|

June 3 June 21 | July 7 July 28 Aug. 18 Sept. 10 | Oct. 23
1.630 2.010 2.570
Apriliea7 fee 2360 eyj| | eeae eee a1 ee
May 29 _..... BAO IA) sees eee) i ¥
June: 9) eh | ne PI 222700 2270) WV 2 O20) aa SI S258 nal) Ce ee ee -
July 2) eke: 2 L380) i) eee
July, oS gree 1.970 2.800
july, 3 1820) Wh ORs a
August 18 2.000 2.740
September 78.2 i}i sees oe Be LS | cee oe ene a 2.770

TaBLE 32—ErFrrect oF GIRDLING Uprpon THE DEPRESSION OF Root Sap

Depression on Date Given, 1915
Date of Girdling

June 21 July 7 July 28 { Aug. 19 Sept. 10 | Nov. 5 Nov. 22
Check) 222: 0.830 0.740 0.750 0.900 0.960 1.120 1.310
SAI ga serene 0.640 0.720 OLS OO! or] See eee eee
May 129 ee. 0.680 | 0.570 Oi61.0 yh eee ee Oa ae
une, Oh eee e «| 10269022 20-550 a 02680 Parle OLS OO wkm peer se
Vitaly: alte ee 0.620
JittlyzweLo ee 0.975
Maly esileeree 0.730
August 18...... 0.780

September 8....

A study of the preceding tables shows rather distinctly the fol-
lowing features. In the case of sap from the trunk of the tree, the
girdled trees had the highest concentration above the girdle and the
lowest below, with the check tree intermediate. These differences
were discernible almost immediately after the girdle was made, and
remained consistent. However, there is evidence pointing to the con-
clusion that these differences grow less as the season advances. When
it is considered that in many cases the girdled area had been partly

SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 41

or almost entirely healed over by cambium development, this evidence
is not surprising.

Twig sap from girdled trees is slightly more concentrated than
that from normal trees but the difference is hardly so great as those
noted above for trunk sap. Leaf sap shows more variation than
either the twig or trunk sap but in a majority of the determinations
the leaf sap from the girdled tree possessed the greater supply of
plant food as evidenced by its lower freezing point.

Root sap differs from the other portions of the tree by having a
sap of the lower concentration in the case of girdled trees.

From the foregoing it is readily seen that the sap of all parts
above the girdle has an increased sap density, and that of all parts
below, a decreased sap density, when compared with sap from cor-
responding parts of similar ungirdled trees.

Nursery trees were also used for the 1916 work, but these were
four or five years old,—in fact, they were sufficiently old that some
had begun to produce a small amount of fruit. The scope was
broadened so that in addition to the root and trunk sap, leaf sap was
secured from new growth, both above and below the girdle, and from
the one-year-old spurs, potential fruiting wood, which the trees had
developed. The twig sap determinations were made upon sap from
the new growth both above and below the girdle and also from the
one-year-old twigs.

Examinations of the trees had revealed that several specimens
had been either totally or partly girdled by rabbits the previous win-
ter (1915-16). It was decided to include these along with the newly
girdled trees, to see just what effect such injury might have upon
the plant sap.

The trees were girdled in a manner similar to that employed
upon the earlier ones and the determinations made as noted above.
The results follow:

TABLE 33.—EFFECT OF GIRDLING UPON THE FREEZING POINT
Depression of trunk sap above the girdle

Depression on Date Given, 1916

Date of Girdling

June 26 ; July 12 July 24 |

Checks iy ee eee 1.220 1.510 | 1.085 1.255 2.145 2.695
Partly girdled by rabbits

POSING = S17! ced itis eee 3S 1.430 1.340 1.280 2.025 2.255 1.715
Entirely girdled by rabbits

TAYE (test 7 Aner eee pea 1.000 1.660 1.395 1.765 2.250 1.925
ari) Oy Ae eee ae Nd Reh e mn g 1.460 1.110 1.760 2.195 2.720
U5 oA Choo ae ee cee Maeaereanh IONOT | WRPLRRESERESR BLO f(a eee 1.020 1.245 1.675 2.070
ye Wis Pa ily BS RE Nee pea NE | arr wae Ge (ees ty Ueno Roe At ee eer 1.250 1.665 2.605
ED ces PEPSI RT Le Pl] eee heen tt ee ae a (MERU Stee (ee eee as 2.100 2.240

MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32

TABLE 34.—-EFFECT OF GIRDLING UPON THE FREEZING POINT

Date of Girdling

Depression of twig sap

Depression on Date Given

June 12 June 26 , July 12 July 24 | Aug. 7 Aug. 24
SB AAI RA Nt EDN “a ee

Check—not girdled........ 1 1.930 1.260 PISO O1e085 1.720 1.495
2 2.590 1.510 1.605 1.480 1.780 1.900
3 2.000 | 1.800 1.640 2.200 2.210 2.665

Partly girdled by rabbits |
winter of 1916-17...... 1 | 1.560 1.440 1.030 1.585 1.445 1.405
Andie D00, 1.650 1.475 1.945 | 1.890 1.745
3 2.540 2.030 12375 2.260: 2.330 2355

Entirely girdled by rabbits
winter of 1916-17...... 1 1.150 1.210 O29 OO) aiietee ee ss 1.450 Unc muna

2 2.270 2.110 1.425 ZiSoNw Wher ee bes: 1.745
%) 2.100 1.410 1.540 TePAlSy Hl 2a ANO) 2.370
Pave 12) en sean el rig Peete 1.060 0.735 1.425 1.810 1.920
2) \\e ee SNe 2.230 1.240 1.515 1.965 1.985
GJ Rao 2.760 ZALES 2.845 3.430
Mitta] | P26) eee et ne SAI ose ell pesos een cere gM NINO he IME ER Re ac 1.395 1.185
Di eae es on a A SSI es itech 1.470
jh epeesenie ete al Neto ee ne 1.620 2.035 1.520
yet ate Git See Ne ee een ee DG \reeet ee | 1.010 1.790 1.405
2 | ates ee UNG EN CCE Heel 655 2.170 1.610

2—New growth above the girdle. 3—One

NOTE: 1—New growth below the girdle.
year old twigs or spurs.

These tables may be very briefly summed up by repeating the
general conclusions reached from the earlier work, which are that
the parts above the girdle show a greater density, and the parts below,
a lesser concentration of plant sap, than is found to be the case
with check trees. The trees girdled by rabbits exhibit a behavior
very similar to the other girdled trees except that the sap from the
partly girdled tree is more variable. This is probably to be expected
since varying amounts of the cambium had been removed from these
trees. Sap from corresponding parts above and below the girdle on
the same tree shows the higher concentration, with few exceptions,
in the parts above the girdle. As a rule, the sap of one-year-old
twigs has a greater density than sap from twigs representing the
current year’s growth. Leaf sap from these parts stands in the
same relation as the twig sap.

That girdling does lead to increased fruitfulness is a matter of
common knowledge. The foregoing data furnish one definite reason

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SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 43

TABLE 35.—EFFect oF GIRDLING UPON THE FREEZING POINT
Depression of leaf sap

Depression on Date Given
Date of Girdling a
June 12 June 26 | July 12 July 24 | Aug. 7

Check—not girdled ...... 1 2.940 1.710 1.915 2.265 2.240
2 2.730 1.910 2.360 PSS 2.615
3 2.530 2.750 2.275 2.435 2.430
Partly girdley by rabbits
winter of 1916-17...... 1 2.230 2.160 1.780 2.310 22325
2 2.580 2.140 2.035 2.675 2.790
3 2.870 2.070 2.005 2.505 2.460
Partly girdled by rabbits |
winter of 1916-17...... 1 | 2.020 ECHR all h Bee tee theses 2.065
2 2.760 2.390 2.825 2.970
3 2.610 2.215 3.015 2.925
Eptrpe tii) Portis. tees nk ee 1 | TAGHOS. Vek Se Ra 1.970 2.545
2 | 2.880 | 2.300 2.725 2.995
3 2.810 2.290 2.800 2.915
ANT eC) EA Ores ere kee TU Rake ses Reet Uy aoe t feats | |e teats] WA cing Pane 2.130
7S (SS SRLS V9! NR Para 2.545 2.530 2.855
3 | Recents ha San Neate sae Dees 2.550 2.445 2.880
itchy gel te ee eS eS DE fh She eRe eo tl es ae 1.975 2.145
Fe aaeteoe es MAES al GE eee Seem ee a eee 2.555 3.015
3
EVA) ZA? yeaa eee ee 1
2
3
VAIS TIG EU pete see cla ch es ok 1
2
3

NOTE: 1—From new growth below the girdle. 2—From new growth above the
girdle. 3—From one year old branches or spurs.

TABLE 36.—EFFEcT OF GIRDLING UPON THE FREEZING POINT
Depression of root sap

Depression on Date Given

Date of Girdling

June 12 June 26 July 12 July 24 | Aug. 7 | Aug. 24
ae a ee
Pee eats Hees a : 1.240 1.210 1.420 1.455 2.085
Partly girdled by rabbits
TIN Neer IY sie eters nea 0.920 1.010 1.150 1.685 1.500 1.540
Entirely girdled by rabbits
1916-17 1.073 1.085. 1.410 1.610
June 12 0.825 1.390 1.180 2.355
June 26 1.075 1.080 1.250 1.810
pas ETE TE eS CO ae eS oes CI ee me ae | | ome | FY ee ie 1.245 1.675 1.940
Bienlivicgt Ae temerec et eae enc NER eel Metered. fy Ihe PERIZ Nee oe See ee es 1.375 135
SSE (TE Sas Meh ies ek oe SR nea nU RO) Myer Sete MMAR Se NR EBRD N aee ee ee ar Re pe SREP | Nap ae i 1.530

why this phenomenon occurs, since it is very evident that girdling
does cause an increased supply of food materials to accumulate in
the parts above the girdle. It is conceivable that such an accumula-

44 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32

tion of reserves should result in the formation of a greater number
of fruit buds. The data also indicate that girdling in early summer
is likely to be most efficacious in promoting fruit bud formation
since the greatest differences in concentration are evident if the
girdling is done at that time.

This conclusion does not agree altogether with the data secured
from the fruit spur studies in which it was found that the differ-
ences in the amount of food reserves present in bearing and non-
bearing parts were very slight. However, it will be noted that girdl-
ing, severe as it is, did not cause a marked difference in the con-
centration of the sap of the outermost parts of the tree. The great-
est effect is to be observed on the trunk sap but this difference les-
sens as the distance from the girdle increases. The leaves and twigs
at the periphery of the tree where the fruit buds are formed do not
show such great variation. This may furnish an explanation for
the slight difference found in the case of the bearing and non-bearing
spurs. It is entirely possible that the reserves which are responsible
for fruit bud formation are brought from some point beyond the
spur itself, and hence, data based upon spur sap alone may not indi-
cate the difference which actually exists in the food supply.

THE EFFECT OF FERTILIZERS UPON FRUITFULNESS

The following experiment, begun at the Missouri Experiment
Station in 1914, was designed to show the specific effects of chemi-
cal fertilizers, applied either singly or in combination, upon the
fruitfulness of apples. The results are as yet incomplete, since the trees
are just beginning to show some of the effects of the fertilizers. It
is the plan to continue the work for several seasons, but a part of
the data are of interest in connection with this investigation and for
that reason are included here.

The plants used for this work were one-year-old Rome Beauty
apple trees, budded upon Paradise stock. The trees were very uni-
form in size and appearance at the time of planting. They were set
in wooden boxes 18x18 inches at the top, 16x16 inches at the bottom,
and 16 inches in depth. One-half the number of boxes were filled
with Missouri River sand and the other half with loess soil. The
amount of sand used in each case was 75 kilograms, and of soil, 90
kilograms. Suitable samples showed that the soil contained 13.27
per cent of moisture while the sand held only 3.42 per cent.

It was thought that by planting the trees in the boxes, the effect
of the fertilizers could be more readily distinguished, since there

ee +

:
§
4
.
Ed

SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 45

would not be so many outside factors to be taken into consideration.
For similar reasons, it was thought advisable to use sand, a medium
practically free of plant food, on one medium and loess soil, a soil
type well suited to fruit trees generally, for the other. Both mechani-
cal and chemical analyses were made of the sand and of the soil.
These analyses in tabular form follow:

TaBLeE 37.—CHEMICAL ANALYSES OF Loress Sol AND Muissourt RIvER SAND*

Material

Per Cent in
Sand

Per Cent in
Loess Soil

Nuh lays Cee eee aR Sune R Ls LORE pe Sar pa hcn Uva eUilices ie

BING Pan INID PROG Cid ep catego a a Se .005
Total Phosphorus -056
FD OTANI OLASSIUh ys tens ee ee Le eee ee 1.599

*Analyses furnished by Agricultural Chemistry Department of Missouri Experiment
Station.
**In air-dry material.

TABLE 38.—MECHANICAL ANALYSES OF Loess SomL AND MissourI RIVER SAND

Soil Particles Per Cent in Per Cent in
Loess Soil Sand

Deviate gael Un meen ee SPS eR Oe ANE be eR peeraih OO 0.00 6.59
(CraThre. Aire (oh PE AUS Bi Ae eee ee Le ee eee oe 0.00 19.05
0.93 Sisee)

45.79 35.31

Very fine sand 33.81 0.13
Silt 11.07 0.00
Clay 8.42 3.47

The fertilizers used have been sodium nitrate, acid phosphate,
and potassium sulphate, in their common commercial forms. They
were applied singly and in all possible combinations. Each plot con-
tained eight trees, four in loess soil and four in sand. A check plot
received no treatment at all. All fertilizer applications were made in
the spring just as growth was beginning. The amounts used per
tree were, sodium nitrate, 15 grams; acid phosphate, 30 grams; and
potassium sulphate, 30 grams.

The trees have remained exposed to outside conditions from the
time of planting, except that during the winter the roots have been
protected somewhat from the cold by filling the spaces between the
boxes with sawdust and also covering the boxes with boards. When-
ever necessary, water has been supplied during summer drouths.
Figure 3 shows the trees in the second seasons’s growth.

Data have been kept upon a great many different points, but the
only phases of any particular interest here are (1) the number of

46 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32

potential fruiting parts developed and (2) the actual number of
fruit buds formed. The number of fruiting parts was determined
by counting the number of short branches, two inches or less in
length, that had developed on the various trees, and the number of
fruit buds by counting the number of blossom clusters that opened.
These figures are given in Tables 39 and 40.

TABLE 39-—AVERAGE NUMBER OF POTENTIAL FRUITING PARTS DEVELOPED ON
TREES IN FERTILIZER EXPERIMENT

nay ; Year
Fertilizer Medium : ane for
DN eecesencnnccceccecceeceereceneenneesceeceecnsesensnnnensnansnsnennescneaneseceserasence Soil 53 64
Sand 8 28
TR ee Ne ee NN ea Mi Calter caaaen ioe qaaenempeencasncnana=soghnaaazae Soil 9 21
Sand 12 iV)
Fee ee ee ek ae Ua ecto Soil 8 19
Sand 4 18
Fe ee eae eee ee ee ee eee Ar pee ee ere er tener ores Soil 31 62
Sand 9 33
ND oaeeeeenecennncneneeeeeceeteceeceeeneneecesesesrensaenenenenenesnscenentaaemenntes Soil 49 52
Sand 2 35
PRR ete eevee Er aan a a eres ee Soil 8 15
Sand 5 15
NKP -.u.ensesennnencnceneneseeneceneeseeeenoneeneenennsnecaenenceneneneececneneenene Soil 45 69
Sand 6 22
(OPES) ee er ee Soil 8 20
Sand 6 30

NOTE: N—Sodium Nitrate. K—Potassium Sulphate. P—Acid Phosphate.

TasL_e 40.—ToraL NuMBER oF BLossom Bups PropUCED ON TREES IN FERTI-
LIZER EXPERIMENT

Blossom Buds in

Fertilizer Medium No. Trees
1916 1917
Tas ego ee Re aoe eam ane Va 2 Alles 45 22
4 0 0 83
TR ay ene Ear bee ais te eee 3 0 0 0
4 0 0 0
Sp Be cee RUN ROI De 3 0 0 0
4 0 0 0
INI eS se hee ee Jala 4 11 29 287
4 2 8 241
TAL dig yaa Se Nae Nueva Ns) tea 4 8 8 hie
4 1 27 139
RSP 2 cee See SN ee SA RE BE 3 0 0 0
3 0 0 0
UNI ee a oe a Lae OD wa 4 37 124 306
4 2 1 107
Check 220 ee ee 4 0 0 2
4 0 0 6

NOTE: N—Sodium Nitrate. K—Potassium Sulphate. P—Acid Phosphate.
*One tree in this lot had become girdled with a label wire and it alone produced 24
clusters in 1915,

SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 47

From these two tables, it is very evident that the application of
nitrogen has been a very decisive factor in both the formation of
fruiting parts and the development of bloom buds. Apparently the
mediums used needed little or no potassium or phosphorous in this
connection, for these elements gave really no increase over the check
when applied either singly or in combination. It is only where the
nitrogen was added that any effect is noted, this effect being nearly
as great in the loess soil plots as in the sand plots.

EFFECT OF THE TILLAGE SYSTEM UPON THE CON-
CENTRATION OF SAP IN YOUNG APPLE TREES

That the method of handling the soil and the kinds of plants
used for intercropping a young orchard have considerable effect upon
the subsequent bearing and behavior of apple trees is the conclusion
that must be reached if weight is given the opinions of many grow-
ers. This phase of orchard management is now receiving consider-
able attention at the Missouri Experiment Station. Quite an exten-
sive experiment was begun in 1911. Many of the trees, however,
were not set until a year or two later. From time to time, it has
also been necessary to replant because certain trees died. The
present planting, therefore, consists of trees of different ages.

fhe problem, primarily, has been to make observations relative
to the effect of various kinds of intercrops and cover crops and
methods of soil treatment upon the vigor, size, earliness of bearing,
and amount of fruit produced upon apple trees set in the loess soil
on the University Fruit Farm. The planting consisted of several
commercial varieties but it was so arranged that several trees of
each variety were included in each of the tillage plots.

In arranging the cropping systems, an attempt was made to
provide various degrees of cultivation ranging from clean cultiva-
tion with a leguminous cover crop, to a permanent timothy and blue-
grass sod. In one plot, the ground was kept in a high state of cul-
tivation up until June each year when a crop of cowpeas or soy-
beans was planted. A second plot has grown successive crops of
corn, a third has been planted to red clover in alternate years, a fourth
has produced successive crops of alfalfa and another has been seeded
to permanent timothy sod. Thus, it will be observed that two plots are
cultivated each year, one is plowed in alternate years and the others
(one planted with a legume and one with a grass) receive no culti-
vation. (As a matter of fact, it has been necessary to plow. and

48 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32

then reseed the alfalfa plot two or three times on account of blue-
grass. )

This project has by no means been carried to its conclusion, for
the older trees are just now beginning to come into bearing. How-
ever, the following data concerning the freezing point depression of
twig and leaf sap are-of interest in connection with the present prob-
lem and for that reason are presented here.

TaBLE 41.—ErFEcT OF THE TILLAGE MetTHop Uron DeEpRESSION OF Twic Sap
oF APPLE TREES

Depressions in the Various Plots

Date Variety (a ,,
Beers ee eC en aE i Timothy Alfalfa | Clover Corn Cowpeas
Mar. 11, 1916 -.....-.... Jonathan 2.325 2.435 2.275 2.230 2.195

Benoni 2.350 2.395 1.985 1.980 2.220
Delicious 1.510 1.675 1.655 Pes25 1.675
Apres iO aL O17 eesce eae Jonathan 1.760 1.695 1.655 1.765 1.685
Niovisi6, el Ollie ees: King David 1.822 1.973 1.931 1.716 1.755
Ben Davis 1.543 1.687 1.604 1.454 1.398
Mar22)) 101g * 5S. King David 1.439 Ba k7A 1.482 1.339 1.215
Rome 1.407 1.453 1.426 1.349 1.361

*These determinations were made by A. J. Winkler.

TABLE 42—EFFECT OF THE TILLAGE METHOD UPON THE DEPRESSION OF LEAF
Sap oF APPLE TREES

Depressions in the Various Plots

Date Variety sO
Timothy | Alfalfa | Clover | Corn Cowpeas

Faclgor, O16 eL spe Jonathan 3.40 s(t een eee 2.790 3.540 3.640
Benoni BOO} hethieere eee 2.790 2.960 2.290

Delicious 3.400 2.830 3.460 3.500 2.490

Yutly POA OG cee Jonathan 2.725 3.070 2.553 2.290 2.195
Delicious 2.065 2.265 2.140 2.280 1.995

Ben Davis 2.770 2.305 2.030 2.310 2.115

King David 2.470 2.755 2.925 2.530 2.405

arg mas OL Ge ee Jonathan 2.285 2.520 . 2.200 2.465 2.570
Delicious 2.180 2.245 2.485 2.310 2.305

Ben Davis 2.260 2.505 2.385 2.220 2.180

King David 2.430 2.455 2.565 2.500 2.875

Aries ial G yd O16 a ee Jonathan 2.255 2.190 2.305 2.330 2.230
Delicious 1.935 2.040 2.125 1.975 1.875

Ben Davis 1.830: 2.010 1.960 1.905 1.890

King David 2.210 2.440 2.615 2.500 2.140

Table 41 shows very conclusively that the tillage method does
materially affect the sap density of the twigs of apple trees. Con-
trary to what might have been expected, trees from the alfalfa plot
show a greater depression of twig sap than trees from the timothy
plot. As a general thing, there is not much difference between trees

i Ske ig a eg ee

YIMOIS Suoseas
‘JuowtIodxe sutunid oy} Ut posn S901} a[dde snoitjaq—yp “sy

JSIf ot IDV
es > mae ae CS a “ee ce oe ok n ke ie. aes mikey E BS Scares
: : i “a S ~ oe ie :

Fig. 5.—Jonathan apple tree showing effects of severe pruning. Note the
large amount of watersprout growth. (Compare with Figure 6)

Fig 6—Jonathan apple tree showing development of a large number of
fruiting parts. (Compare with Figure 5, a tree of the same age but
pruned more severely)

SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 49

growing in clover sod and those intercropped with corn. These
stand next to timothy in density and first above the trees in the
cowpea plot. In the latter case, the concentration is least of all.

From these data, it would seem logical to conclude that the trees
growing in timothy or alfalfa should be the ones to come into bearing
earliest, a conclusion also supported by general observations. How-
ever, it must be stated that the trees in the more intensively culti-
vated areas are considerably larger at the present time and hence, in
this way may be able to overcome the advantage that the other trees
may now possess.

The figures representing the depression of leaf sap from trees
growing in the various plots present such a wide range of variation
that no safe conclusion can be drawn.

EFFECT OF THE PRUNING SYSTEM UPON THE
FORMATION OF FRUITING PARTS

That pruning does have « very marked influence upon the
fruiting habit of the tree has long been a matter of common obser-
vation. Dormant pruning in most instances has tended to promote
wood growth and to decrease fruitfulness. Even different amounts
of pruning done at the same time show considerable variation in
their effects.

That the system of pruning may likewise be influential in caus-
ing the formation of fruit spurs is also nicely shown by the follow-
ing figures compiled from data collected under another project. A
pruning experiment was begun in 1914 upon 64 one-year-old Delicious
apple trees with the object of determining the relative influence of
different pruning systems (particularly high heads vs. low heads)
upon the size, the character of growth, and the fruiting age of ap-
ple trees. The experiment is incomplete, yet the following table is
interesting 1n connection with the present problem.

The trees were very uniform in size and were treated in ex-
actly the same manner except one series was forced to form the
head at a height of about two feet and the other at five to six feet.
The accompanying photograph (Fig. 4) indicates the appearance of
the trees after their first season’s growth.

From the beginning it has been very noticeable that the low-
headed trees make by far the greater amount of twig length growth
and at the same time form a much larger number of branches. Dur-
ing the season of 1917, it was observed that the low-headed trees
were forming a great many very short branches which made only a

50 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32

limited growth, usually two inches or less, and then formed a termi-
nal bud. Since this is the usual history of the formation of fruit-
ing parts, it has been assumed that these were potential fruit spurs.
While a large number of such branches probably would never develop
into fruit spurs under normal conditions, yet it is likely that the
relative number in the two sets of trees would be maintained. A
record of the number of these short branches as well as the number
of longer twigs was taken in the fall of 1917. The figures are
given in Table 43.

TABLE 43—AVERAGE NUMBER OF TWIGS AND FRuIT Spurs oN HIcGH- AND Low-
Herapep APPLE TREES

| No. of Twigs | No. of Spurs
Eli oh healde Guy eee ee BRU eis Sa a EN Ot A 35.5 | 14.9
LBTo fol Kore Ko Kora bis APES INE ALPINE AM ta tag ioe OSA pe SAUNAS ALA ee eM NPC A Pathe 62.8 34.1

From the foregoing it may be clearly seen that the system of
pruning used has a very marked influence upon the number of poten-
tial fruiting parts formed in the early life of the tree, the low headed
trees forming more than double the number of short branches or
spurs found on the high-headed trees.

EFFECT OF ETHERIZATION UPON THE SAP DENSITY
OF APPLE TREE FRUIT SPURS AND LEAVES

Etherization has proven to be a very effective stimulant upon
the enzyme activity of detached parts of woody tissues. Howard*
has made extensive experiments along this lme. Since this treat-
ment does have a marked effect upon the availability of the food
supply, the thought has come that perhaps etherization of the entire
tree at various seasons of the year might have some effect upon the
amount of available food and thus influence the number of fruit
buds formed for the following season. For the above reason the
following experiment has been designed and carried out.

The effect upon the food supply was measured by the concen-
tration of the sap from the treated as compared with the untreated
trees. While they plainly do not justify any definite conclusions,
yet the results are submitted below.

A number of Jonathan apple trees were available for this work.
They were five or six years old, just at the point where fruitfulness
normally begins. They were growing in the clay loam soil of the
Experiment Station grounds.

SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 51

Twelve trees were selected for etherization and a different one
was etherized each month, beginning December, 1914, and continuing
until November, 1915. For this exposure the trees were enclosed
in a galvanized iron can and all joints tightly sealed. Ether was then
introduced in sufficient quantity to have 0.5 cc. per liter of air
space. A little injury to the leaves and new growth resulted from
the May and june treatments. It was undoubtedly due to exces-
sive temperatures inside the can at that time. Even tho an at-
tempt was made to keep the temperature down by shading the can,
yet it sometimes reached a fairly high point during the summer
months. It is interesting to note that the trees treated in October
began to show bud growth, especially near the ends of the main
branches, early in November.

From time to time sap samples were secured from spurs and
leaves on both etherized and unetherized trees. The results secured
are given in Tables 44 and 45.

TABLE 44—DEPRESSION OF SPUR SAP FROM ETHERIZED AND UNETHERIZED TREES

Depression
Date Pantin Gears Tae CARTS aA
Treated | Untreated

Jeb eg Voie LS US US Se RE cea aR Pee een re aNd 1.630 1.580
MIME NIA POMS yee eee ee ae i A 1.305 1.345

TABLE 45.—DeEpPrESSION OF LEAF SAP FROM ETHERIZED AND UNETHERIZED TREES

Depression on Date Given

Date of Etherization oe ——ooOoOO eee
| July 16, 1915 June 17, 1916 | June 30,1916} July 17, 1916
December Lavi Oi4t ea. | 1.580 2.790 1.760 1.710
Faniany miles nh POtSe eee | 1.530 2.280 1.750 1.750
February 20, 1915 | 1.560 2.280 1.750 1.750
March 12, 1915 1.600 2.040 2.210 1.910
Dagareth Wigs W225 hia Ron ai AEA eae 1.630 1.840 2.180 1.810
TLE sh oN aieg oi Es) ae ea wee 1.590 1.730 2.030 2.030
PUNE VUAS LOO es Sele eens 1.610 2.200 1.680 1.640
Aiea TsyaanipdeSis SLI Ease a oe aie a 1.660 2.430 1.680 1.730
PATISTIStY BLOM MOG stow Laue SL IE tay) ete ee 2.000 1.590 1.690
Sepremiberyestaue LOU Gece etp het been ora 1.760 1.720 1.740
Octobe, hae wl Ou sree shallows OY hy) Peete 1.970 1.760 2.060
November rls yp LOU 5 nce ole lh eet 2.280 1.730 1.910
Checker weitere he 1.430 2.480 1.620 1.950

The small supply of leaves and spurs on the trees prevented a
large number of determinations and then, too, the work had to be
discontinued after the first series. The results probably do not

52 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32

justify conclusions. It does seem, however, that ether has little effect
upon the sap concentration of fruit spurs. The sap of the leaves ap-
parently was affected by such treatment, but, as is seen by the later
determinations, this effect does not carry over to the next year. The
effect seems to be immediate. With the higher concentration of the
leaf sap which comes in July because of etherization, the hypothesis
might be advanced, that with a greater amount of food available a
larger number of fruit buds might be formed. No supporting data,
however, are furnished.

SUMMARY AND CONCLUSIONS

Missouri apple yields tend to rotate in three-year cycles, the
sizes of the crops produced showing the following order: heavy,
light, medium, heavy, etc.

A five-year study of the behavior of individual apple fruit
spurs of six commercial varieties, as contrasted with previous opin-
ions based upon casual observation of the entire tree or entire
orchard, leads to the following conclusions:

Jonathan, Grimes and Winesap are able to develop a fairly high
percentage of blooms each year, while Rome, York and Gano, pro-
duce an exceedingly high percentage of blooms one season and a
very low one the next.

The varieties used show remarkable uniformity with respect to
the percentage of the individual fruit spurs which alternate, that is,
bloom only once in two years.

Jonathan and Winesap are able to develop blossoms in succes-
sive seasons on the same spur in a much greater proportion than the
other varieties observed.

The soil in which a tree is growing has little effect, apparently,
upon the performance of the individual spurs, with respect to alter-
nation.

The fruitful year of certain alternating sorts may be changed
by a removal of the blossoms thru either accident or design.

The age of the spur systems of the various varieties is practically
the same, ranging usually from two to eight years, three to six or
seven years being apparently the most effective fruiting age.

Sap from bearing spurs has a slightly higher concentration
(lower freezing point) during a considerable portion of the year than
sap from non-bearing spurs. The depression of the freezing point,
however, gives no indication of the amount of starch which may be
present.

SOME FACTORS AFFECTING FRUITFULNESS IN APPLES 33

A marked decrease in the sap concentration of both bearing and
non-bearing spurs occurs in late June or early July.

Leaf sap from bearing and non-bearing spurs shows considerable
variation in concentration.

The number of fruits on a spur affects the concentration of
neither spur nor leaf sap.

Sugar and starch are present in slightly greater amounts in the
bearing spur than in the non-bearing one. (Determinations made by
chemical methods.)

Bearing spurs have a smaller total leaf area than non-bearing
spurs, the difference being due to the number of leaves developed
rather than the size of the individual leaves.

Experiments in girdling nursery apple trees gave the following
results:

Girdling, regardless of the season, caused an increased concen-
tration of sap in the parts above the girdle and a decreased concen-
tration in the parts below. (Determinations made by freezing-point
method. )

Girdling produced its most marked effect in the parts nearest
the girdle, the effect being lessened as the distance from the girdle
increased.

Fertilizer experiments with dwarf Rome apple trees planted in
boxes of sand or soil showed that effects upon (1) the size of the
tree, (2) the development of its fruiting wood, and (3) the produc-
tion of blossoms, could be attributed only to the use of nitrogen.
Potash and phosphorus applied either singly or in combinations had
no apparent effects.

Tillage experiments showed that trees growing in a permanent
sod of either a grass or a legume had a higher concentration of twig
sap than trees growing in plots planted with either annual or biennial
cultivated crops.

Trees headed at five or six feet did not produce so many short
branches—potential fruiting wood—during the first three years in the
orchard, as trees headed at two feet.

Etherization of young Jonathan apple trees had little effect
upon the concentration of either twig or leaf sap, and the small
differences observed seemed to be only temporary.

54 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 32

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BIOGRAPHY

I, Cleo Claude Wiggans, was born on a farm near Princeton, Mercer
County, Missouri, on October 20, 1889. I attended various country schools
and then entered Princeton High School in 1904, graduating therefrom four
years later. Entering the College of Agriculture in September, 1908, I was
able to complete the requirements for the degree, Bachelor of Science in Agri-
culture, in three and one-half years. I held the position of Student Assistant
in Horticulture in 1910-1911 and in 1911-1912. I entered the Graduate School
of the University of Missouri in February, 1912. During the following
school year I held a Research Fellowship in Horticulture at the same institu-
tion, and was granted the Master of Arts in June, 1913.

I was then appointed Assistant in Horticulture in the University of Mis-
souri, which position I held for one year. I was then advanced in rank to
Instructor in Horticulture, a position which I am holding at the present time.

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