AGRICULTURE LIBRARY OF THE UNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN no. - 355 Cap. 2, NOTICE: Return or renew all Library Materials! The Minimum Fee for each Lost Book is $50.00. The person charging this material is responsible for its return to the library from which it was withdrawn on or before the Latest Date stamped below. Theft, mutilation, and underlining of books are reasons for discipli- nary action and may result in dismissal from the University. To renew call Telephone Center, 333-8400 UNIVERSITY OF ILLINOIS LIBRARY AT URBANA-CHAMPAIGN flue 05 1999 L161— O-1096 UNIVERSITY OF ILLINOIS Agricultural Experiment Station BULLETIN No. 341 A COMPARISON OF THE TRANSPIRATION RATES OF TWENTY-ONE DECIDUOUS FRUIT SPECIES BY VICTOR W. KELLEY URBANA, ILLINOIS, FEBRUARY, 1930 CONTENTS PAGE REVIEW OF LITERATURE 95 Drouth Resistance 95 Transpiration and Growth 96 Transpiration and Water Content of Foliage 97 Transpiration and Number and Size of Stomata 97 METHODS OF EXPERIMENTATION 99 Plant Materials. 99 Measurement of Transpiration ^ 100 Environmental Conditions 101 EXPERIMENTAL DATA 101 Different Series Compared 108 DISCUSSION Ill CONCLUSIONS 114 LITERATURE CITED 115 A COMPARISON OF THE TRANSPIRATION RATES OF TWENTY-ONE DECIDUOUS FRUIT SPECIES BY VICTOR W. KELLEY, Associate in Pomology* The loss of water thru transpiration has long been a question of great interest to plant scientists. There are perhaps few physiological problems which have been investigated so much, yet about which so little really is known. Most writers regard transpiration as a func- tion of plants, but less than two decades ago a prominent botany text3* called it a "menace to plant growth," an "unavoidable danger." The object of this experiment was not to investigate the mechanics of transpiration, or to determine whether it is a plant function or a plant hazard, but rather to find out how much difference exists in the rates of transpiration in some of the economic deciduous fruit species and to determine whether such knowledge might be useful in explain- ing some of the differences in adaptability and response to cultural conditions. REVIEW OF LITERATURE There is much divergence of opinion as to what differences in rate of transpiration really signify, or to what factors differences in rate may be attributed. Those opinions which are related to the problem under investigation are here presented briefly. Drouth Resistance Some investigators have concluded that transpiration is a measure of water economy ; that a plant which transpires relatively small quan- tities of water may be considered as drouth resistant. Others think that transpiration is not a measure of drouth resistance. Iljin17* reported that it was not yet possible from a study of transpiration rate alone to ascertain the degree of protection enjoyed by types biologically different. In 1916 this same author, as a result of his study of the relation of transpiration to assimilation in steppe plants, concluded that we may expect to find in drouth-resistant plants an economical evaporation of water. Dosdall9* employed transpiration as the basis for classifying Equisitum fluviatile as a hydrophyte in relation to mesophytes and xerophytes with which it was compared. Gavarra and Espino11* con- 'Grateful acknowledgment is made to Dr. W. A. Ruth, Chief in Porno- logical Physiology, for assistance in planning the experiment and designing the apparatus. 95 96 BULLETIN No. 341 [February, eluded that transpiring power, determined experimentally, and drouth resistance are correlated with varieties of abaca (Musa textiles). Koketsu24* concluded that with Coleus blumei, Triticum vidgare, and Glycine soja the index of foliar transpiring power and the soil moisture residue at time of wilting may be applied as the measure of comparative xerophytism of plants. On the other hand, Maximow,30* working with the sunflower, buckwheat, and other plants, stated that the rate of transpiration under conditions of normal water absorption from the soil cannot be used for judging the drouth resistance of a plant; he considered xerophytism to be the ability to resist prolonged wilting. Pool,35* using the cobalt chlorid method, which, however, he did not regard as satisfactory, found little correlation between habitat xerophytism, leaf anatomy, and transpiring power among about forty species which were included in his experiments. Miller and Coffman31* found the rate of transpiration per unit area of leaf surface lower for corn than for sorghums. Kiesselbach,21* as a result of his studies with many varieties of corn and sorghums, concluded that drouth-resistant qualities must lie elsewhere than in a low water requirement per pound of dry matter. Haines12' 13* regarded actual or relative transpiration as not neces- sarily an index of drouth resistance. He has evolved a method for determining "drouth resistivity" which consists of finding the rela- tionship between transpiration rate, "pressure deficit," and evapora- tion as measured by an atmometer, according to a somewhat compli- cated formula. Transpiration and Growth As in the case of drouth resistance, considerable difference of opinion exists among investigators in regard to the relation of transpi- ration to growth. Livingston25* regarded transpiration to be as good a criterion for comparing the relative growth of wheat as the weight of the plants. Cole and Matthews,2* working with spring wheat, found a high cor- relation between the total amount of water consumed by the crop and the yield. Dastur8* found that in different leaves of the same plant a high rate of assimilation accompanied a low water content of foliage ; and a low rate of assimilation a high water content. Bews and Aitken,1* working with Bidens pilosa, found the actual amounts of water lost by transpiration to be more or less proportional to the weights of the plants. On the other hand, Dachnowoski5* found no direct relation between growth, green and dry weight, and transpiration. Cullinan4* con- cluded that neither relative nor total transpiration was a reliable index to growth activity in the apple. 1930] TRANSPIRATION RATES OP SOME DECIDUOUS FRUIT SPECIES 97 Transpiration and Water Content of Foliage More unanimity of opinion is found in the literature dealing with the relation of transpiration to water content of foliage. Knight22* stated that the water content of the leaf played an im- portant part in the control of transpiration. Livingston and Brown26* recognized that the water content of leaves under conditions of rapid evaporation varied at different times in the day, and that such a re- duction acted as a check upon transpiration. Lloyd28* found that with ocotillo the rates of intake and outgo of water were not a constant, but that the outgo during the day was greater than the intake, the reverse being true at night. Because the decrease in water content occurred during the opening of the stomata, Lloyd concluded that these organs were not closely regulatory of the loss of water by transpiration. Knight23* found the diurnal change in leaf water content of plants in southeastern England to be less than 2 percent. He also found that wilting really commenced and could be predicted from a flaccid con- dition of the foliage before it was possible to determine experimentally a definite decrease in water content. As much as 2 percent variation in the water content of leaves similar in external appearance was noted in several species. Maximow30* corroborated much of Knight's work. While studying the relation of wilting to drouth resistance, he found that xerophytic types at wilting had a much greater water deficit than did mesophytic types. In fact, with shade mesophytes, visible loss of turgidity ap- peared when the decrease in water content was so insignificant that it could be ascertained analytically only with difficulty; while under conditions of prolonged wilting, xerophytic plants were capable of losing one-half of their water without apparent harm. He concluded that one of the principal features of drouth-resisting plants is their capacity for enduring a considerable loss of water without permanent injury. Inamdar19* made a study of the hourly variations in water content of leaves of jasmine under conditions of rapid transpiration, and found that the water content varied in an inverse direction to the amount of the transpiration. Bews and Aitken1* found that leaves of the com- mon natal weed transpired in proportion to their water content, those leaves having the highest percentage transpiring most rapidly. Transpiration and Number and Size of Stomata Investigators are agreed that stomata exert an influence on the regulation of transpiration, but to what extent they control water loss is still in dispute. 98 BULLETIN No. 341 [February, Yost38* and Palladin34* both stated that the transpiration rate is in proportion to the number of stomata. Lloyd27* was perhaps the first to question the completeness of stomatal control of transpiration. Eckerson10* determined the number and size of stomata for 37 differ- ent plants. She found marked variations occurring in number and size of stomata, not only in different varieties, but in the same varie- ties grown under different external conditions. The variation seemed greater in number than in size. In general, she reported an inverse proportion between number and size of stomata. Muencher32* found no correlation between either the length of the pore or the number of stomata per unit area of leaf surface and tran- spiration. He concluded that the amount of transpiration is probably not governed by the number and size of the stomata but by a complex of several factors. Kiesselbach21* found no apparent relation between stomatal number and transpiration in corn and sorghums. Wilson37* found that the so-called xerophytic plants of Australia were provided with a high average number of stomata, and concluded that this enabled these plants to regulate the transpiration rate under rapid variations in temperature and water supply. Coulter, Barnes, and Cowles3* quoted the results of a transpira- tion test for ten species of plants varying in rate from 2.81 to 16.4 grams per 100 square centimeters for 24 hours. Eckerson,10* who counted the number of stomata on eight of these species, found a range of 49 to 500 stomata per square millimeter of leaf surface. By using the data from these two sources, it was possible to make a study of the relation of stomatal number to rate of transpiration. This comparison showed that there was no correlation between the number of stomata per unit of leaf area and -the transpiration rate. With such a wide range in stomatal number, as well as transpiration rate, it would seem that if there were a correlation between these two factors, it would be evident in these species where the extremes are so great. Briefly summarized, the literature shows that investigators are perhaps about equally divided on the relation between transpiration and drouth resistance and transpiration and growth. This would in- dicate either that these relationships vary with different species or that we must wait for further research for a definite answer as to the nature or extent of this relationship. Workers in this field agree that the water content of foliage fluctuates daily under different environ- mental conditions, and that this variation influences the transpiration rate. The results to date show that stomata are to some degree regu- latory of the water loss thru transpiration. The older idea, perhaps largely theoretical, that the rate of transpiration is in proportion to the number of stomata, is being replaced gradually by later research, which is almost unanimous in concluding that there is no correlation between transpiration rate and stomatal number. 1930} 99 METHODS OF EXPERIMENTATION Plant Materials Twenty-one species of deciduous fruits available on the horticul- tural grounds of the University of Illinois were used in the experi- ments. They included the common fruit trees, a num- ber of nut species, and several small fruits. In some cases several varieties of a species were used. The fruit species included in this study differ widely in many characteristics. In form and size they vary from the recumbent straw- berry, thru the bush fruits and brambles, to trees of different sizes and shapes. Each species has a wood structure peculiar to itself. Leaf characters vary from simple to compound, from long, narrow leaves to those broader in proportion to length. In some species the leaf surface is glabrous, in others varying amounts of pubescence occur. The depth and extent of the root system of each is peculiar to itself. While the native home of many of these species is in dispute, we may be sure that they have come from several FIG. 1. — POTOMETER USED IN EXPERIMENTS A is an ordinary burette; B is a glass cylinder (specimen jar) fitted with a three-hole rubber stopper; C is a glass tube, the purpose of which is to equalize the atmospheric pressure. The cutting is sealed air-tight with plastoline. The differ- ence between two successive readings is the amount of water taken up by the cutting. continents and from regions widely different in soil and climate. In resistance to cold, drouth, and heat, and general tolerance or intolerance to unfavorable conditions great differences exist. In selecting the material for study from so many different types, only cuttings of the current season's growth were employed. Care was exercised to choose terminal shoots of average vigor which were com- parable in rate of growth, age, size of leaf, and as free from disease and insect injury as possible. In the fruits, the trees from which the wane: urine -mmrmirr 'ISfB '• *'.""• ::. •BHIL 'MBXK: :: • : -- •'•-- L:<: I.. .:-•;• ^•~ -- - •*•-•- • .--^ rat. 2r-— IlBBBt V ::: . v " . -ilir T'li* : - > • -: - . - • .-- • i -: •'•>-" -.-. _ : I.: ••-•: • v - L' I -- - - - : .. --- n -.- - ,-. ,-- • : - - - :_ : .::. • •• - .„ -.'-.!' i_ ./ - hpnie.mil> w3B mil i BB i n 1 T':H • - IS TTT— - :n Xo. 341 [ February y i -j = = §£:=• -?*1 f : s * «= = *; 5 5 5 - 5 E — — — ~ — -^ = == *= "S«=.J = = ^ ~s . r : 5 r ^ ^ — *• ? 5 s -= £- "i = s X BOB «r Saemm DBOBCVCS FBOT when it was dear and hot. dear weather fe flruriailf by relatively low Immiility^ which favors rapod transpiration. A temperature also farinfair* water loss from the leaves. The condi- tions,, therefore, at the time this series was nm were faronhle for a rapid rate of transpiration. A study of these data shows that on the bask off tn rate these plants may be grouped into three classes. The peach, tarinc, and plum, all belonging to the genus Prunusy have a very low rate; the apple,, pear, and M««lli«».j form a group with the fcg^Mt. rate; and the sour cherry,, sweet cherry,, and apricot, also from the genus Prannsr are in an intermediate group. The most iiliilmf, differ- ence is that of the peach,, plum, and nectarine, which have am aver- age rate in this series of leas than 2D pf" ffffft- of that off the apple. The night rate in every m**m*+ fe lover than the day rate, bat there IB considerable variation in this relationship with the diMSaent species. Climatic conditions at night generally favor a draitiaae in transpiration in comparison to the day rate because of a lower tem- perature and Irijgpier relative humidity- The maximum •.fc^tj"|» of *fc* stomata at night, however,, is p***r» the gicatefti factor in the re- duction of water Ions during liaiiurnnii The very low night rate re- corded for the pear in this series is not usual for tins .qn-nfj^ as wffl be seen by comparing subsequent series. Series 3. Even a wider range off •Mlifidnaliij is encountered among the plants in this group « Table 2) than was found in Series 1. Eleven species representing seven genera are compared, the group comprising three tree fruits, four nut species,, and four small fruits. On the basis of their relative rates of transpiration, this series may likewise be divided into three groups. The blackberry, currant, filbert, raspberry r and qrance. in the order named, have a high tn tion rate; the gooseberry and sour cherry,, a P"~J™" rate; and the peach, almond, black walnut,, and pecan,, a very low rate. The nor cherry and the peach are the only species included in both Series 1 and 3; hence these may be used to compare the relative rates off the species in the two series. On tkb basis the high transpiration group in Series 3 is somewhat higher in rate than that group in Series 1. all of the species ranking higher than the apple,, which ranked first in Series 1. The Taylor blackberry seems to have a higher rate than the unknown variety included in Series 1. As was true in Series 1, the most striking difference is in the low transpiration group, h being in general less than one-half that of the sour chary and only about one-fifth as great as the group with a high transpiration rate. The effect of cbmatic differences on transpiration is shown by a comparison of Series 1 and 3. The lecmda indiralr that the tempera- ture was somewhat lower, with perhaps not much JMfaente in the relative humidity. The average transpiration rates for the peach and . ^—- *-x. =ff^5 ^ - -' _~ -T - r - .-:-:- - — . — r — - - - — — - •— — r*~ . - ^=^^^= ~.^. - ~^£ 5 ^-? ~ '•MMBMM* &CTK v&mt&KaimtntBaanz&msmc JOS ".if? mir mKKKif -.'imnujiL 11 3«rtL aESJeafe. ancEt lenwesr JL ; 3 t&BL in. 3wii» 1. TfflKrmin 11 ^tg^ rmtt -a BET rme lywar ri«HL in Sera* E. TEn* i* ine ;mmafflrr ^ "he OHSE: ^uar ..- ...:;. --:. ____ ; ..;..- ;; r. ...- .. •-:"-: ena& -tie TiriF remzn. 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SBSIBR "ins- -SESTES- 411 'rt±- Jt swjfL mimrruiiii v/. "nun HER ~fa.e t^T~ 'imr ;imnr .TIEES- viiii. 3.e2E23Hn*s ~Q TTiuic -JL. ^^TTJT Titniiiii- ""^SHHI m ITHH "33 iav^ ^aitt. r aitrws- "insr "liesEt *mui \nin :UIIL Jii^ir rates- in 3nte >n: "iiet :acr ~trar "tie niiie -gTmimr Hhe ^rrtezr8* iiat 3nnwn -faaar ~ti«t JE5: TTHTTRF TifflnTTT '2USH1 J37. tins- ~o :ie TIB 'viiiL asa'fgatl Tnes2.es- ir ?mmi=- oAn. "imr "tiis- nittmHmm ig. me ~cr -^JIH»MJH inuBs -H2tnT* -- . ,r "Hie peac*i -50Eans- "u rBEnics lis- "ilsilL ~tlC 'Itilffi? ^resSES "rr "iris- ^Egress. JHJ mgnr is- TJIHWIL jy- -nee iiazc "iiar. im jaL "tte -^g ram ^r^ Jigrmr -faasi. iie The ^esnicriniL JL iie TansniaranL if sntnn^ ~Lme it ~her ^eCTsraaiun- "rnrnr utra n "he ^Ttnimr iieaiesi: *3aTio in: •iiiatfl cfiwr orifee TJI ms; cam'' The- race am die ^eearat ^iasy is nriiTr ^swr^tnmg JF r\m j^ an. tire rrrsr iav^ JL ^rret of a. liwear 3aaa±ret iimnmiiy: T""nsF is nie ~u ~iie : :u-T~ nur in. tilT' dinmi^i^-c i^* rxsmaaon. JOHL "ins "VCCOICL air nrairr 106 BULLETIN No. 341 [February I I J i < -I bC S3 1 a fe *a IZ M "* ^ g oj S HB ^s y r^ Q ^> r, J o ^ ° a § "** 02 O fe ^ w « Cb Q ® 0 § & ^ o S ^ r^i cu Q*— ' 4S & >H o -^-j i I 32 -S-g >C C^ CM co I-H o ro •* c