THE RESPONSE OF THE BARLEY GENOTYPE TO NIGHT TEMPERATURE Flies-is for f: a Degree of M. Sc. PIIZCHEGAN SMTE ENWERSETY Kufidip Singh Bains 1956 THE RESPONSE OF THE BARLEY GENOTYPE TO NIGHT TEMPERATURE BY KULDIP SINGH EAINS AN ABSTRACT SUBMITTED TO THE SCHOOL OF GRADUATE STUDIES OF MICHIGAN STATE UNIVERSITY OF AGRICULTURE AND APPLIED SCIENCE IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE Department of Farm Crops 1956 Approved Kuldip Singh Bains THE RESPONSE OF THE BARLEY GENOTYPE TO NIGHT TEMPERATURE The performance of a genotype is determined by its response to environment. A study was initiated with four barley varieties to observe their response to three night temperatures and to determine the association of certain physical characteristics of barley to night temperature. The characters observed were plant height, date of heading, green and dry weight of -bu1m, weight of main head, and number of seeds set. A significant variety night temperature interaction was observed for plant height, date of heading, green and dry weight of ~eulm, number of seeds set, and green and dry weight of the main head. The interaction variances seem to indicate differential behavior of genotypes at different night temperatures. A linear relationship was observed between respiration and temperature in the dark. The Q10 recorded for respiration was much greater than 2 which strongly indicated that an enzyme system is involved. This would appear to have great bearing on the adaptation of genotypes. Broadly Speaking, high night temperature has been found to decrease the number of days to heading, decrease the number of seeds on the Iain head, and increase rate of respiration. Significant negative correlation between temperature and date of heading and number of seeds set on the main head was observed. Kuldip Singh Bains Respiration was found to be closely associated with night temperature with an r value of {0.9999- The data suggest that the adverse effects of increased earliness, decreased seed set and increased respiration rates may be responsible for low yields of barley. THE RESPONSE OF THE BARLEY GENOTYPE TO NIGHT TEMPERATURE By KULDIP SINGH BAINS A THESIS SUBMITTED TO THE SCHOOL OF GRADUATE STUDIES OF MICHIGAN STATE UNIVERSITY OF AGRICULTURE AND APPLIED SCIENCE IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE Department of Farm Crops 1956 -.-_._...p.. 5- a..fl ACKNOWLEDGEMENT The author expresses his sincere appreciation to Dr. John E. Grafius for the valuable advice and guidance during the course of this study and in the preparation of this manuscript. Acknowledgement is also given to Dr. Donald H. Dewey; Associate Professor of Horticulture for his cooperation and guidance in the respiration study. Thanks are extended to Professor Hubert M. Brown for his advice in statistical analysis. I also express a special note of gratitude to my parents and younger brother, Onkar Singh Bains, whose unfailing encouragement in the face of adverse family circumstances made it possible for me to pursue higher studies over here. TABLE OF CENTENTS II‘ETRODUCTICI‘I 0.000.000.000000.0000.00000000000... RE‘IIEEKJ C.F LEER‘AXTITRE .000.0.00....00....000.00.0. U1 [\J l-‘C'Q I'LEXTERIA.LS (EXI‘TD 1.:THODS 00.0.0000...0.000.000.0000. EXPERIEENTA RESULTS I. Effect of night temperature on plant grovzth .000000.00.00.000.0.0.00.0...0... (I) II. Effect of temperature on night time respiration ............................ CD [0 III. The influence of respiration rate on plant tempera ure ...................... 20 IV. The r’eneral effect of night temperature 6.» o . on barlel'r plant .00. .0. 00 0 0 0 00.000 0 00... 21 DISCUSSION 0000.00.00.00.000000Cocooooooooooooooo 23 SLTIE.T.ARY ELIE mI‘ICLLTSICI‘TS 0.0.000000000000000000000 26 LITERIFLTLTRE (:ng 00.000.000.000.0.000000000000000 28 INTRODU CT I ON Temperature has been observed to be one of the most _important factors of the climatic complex affecting plant growth. The influence of temperature upon plant growth has been the object of intensive study particularly in vegetable crops. These studies have brought out the fact that regardless of how favorable the other environmental factors such as light and soil moisture may be, a certain optimal temperature is required not only for different species but also for the different stages in the growth cycle of the same species for successful crop production. The importance of the genotype x night temperature inter- action has been stressed (9T*in analysing the yield of barley and oat nursery data and a mathematical basis has been developed to measure it, to a limited extent, in the field. The object of the present study was to determine the response of certain physical characteristics of barley genotype to night temperature. The eXperimental work was conducted under controlled conditions in the green house. * Numbers in parentheses refer to the "literature cited" REVIEW OF LITERATURE Sachs (18) studied the role of temperature as it in- fluenced plant growth and development and visualized periods of optimum, maximum and minimum temperature ranges associated with specific stages of plant growth for particular species. He concluded that an increase or decrease of temperature from the optimal temperature affected the plant adversely. Thompson and Knott (20) working with lettuce observed that _ii at 70° to 80° F no heads were formed regardless of the photo- period, whereas at 60° to 70° F head formation was most satisfactory. They concluded that high temperature is an important factor involved in premature seeding of lettuce. In a study of the responses of some ornamental plants to temperature, Post (13) noted striking differences in their behavior as to growth and flower formation. He observed that Trachyme and Clarkia produced vegetative growth below 60° F but produced flowers at higher temperatures whereas Cytisus and Mathiola's behavior was the reverse. In an analysis of the physiological factors affecting blossom drop in tomatoes, Radspinner (l4) concluded that high temperatures and low humidities favored abscission of tomato blossoms. Went (22) (23) found an optimal temperature of 18°C for stem elongation of tomato plants when the whole plant was raised at this temperature, but noted that the growing zones, when exposed to 26°C, elongated much faster. Went and Cosper (24) found a controlling effect due to temperature on fruit set in tomatoes which was also confirmed by‘Wittwer and Schmidt (26). 3 Binkley (3) concluded that the blossoming period of garden beans is very sensitive to variations in environmental con- ditions, i.e., high air temperatures, sudden fluctuations in air temperature and inadequate moisture supplies, causing reduced seed set. Boswell (4) (5) in his papers analysing certain factors affecting the yield and quality of peas emphasized the im— portance of temperature. He observed that the higher the mean temperature above the Optimal temperature, the lower the yield. He advocated the theory of a fairly constant amount of effective heat required by a strain of peas to attain blossoming stage and maturity. Cordner (7) found that pod yields of lima beans are closely correlated with bearing area and temperature, and as the temperature increased above the optimal, the fruit setting decreased. Andrews (1) (2) found that lowered maximum tempera- tures and high humidities were accompanied by increased yields of lima beans. During conditions of high temperature and medium to low humidities, the blossoms of Fordhook lima beans become dehydrated. Consequently, the enclosed pollen did not germinate while the pistil was receptive and flower abscission resulted. Lambeth (ll) eXplored the problem of seed set and yield of lima beans and found that reSponses to constant air temperatures of 62°, 72° and 86°F were a varietal characteristic. It was noted that Fordhook 242 set 91 percent of its blossoms while Fordhook set only 37 percent at 62°F whereas at 72°F both varieties yielded similarly. He found that tube growth at pollen germina- tion was greater for the Fordhook 242 than Fordhook at 62°F which corresponded with their seed set behavior. Decker (8) studied the effects of temperature on photo- synthesis and respiration in red pine and found lower P/R ratio at higher temperatures. Murneek (12) attributed con~ tinuous vegetative growth or premature bud initiation to certain environmental factors, especially temperature and light. Roberts and Struckmeyer (15) (16) observed the inhibitory effect of cool and long days on flowering on cosmos and soya- beans. They found that the temperature factor is not only essential for bud initiation but also to the actual process of fertilization and subsequent fruit development as well. Roberts (17) showed that warm nights and cool days caused reduction in setting of Alaska peas and alfalfa while cool nights and warm days increased fruiting. Thayer (19) noted that the growth of barley crop is markedly influenced by seasonal environment. Harlan, Martini and Stevens (10) found that during long continued heat the pollen ripened at earlier and earlier stages in the development of the barley spike, resulting in a reduction in percent seed set and a reduction in the size of kernels obtained. It was found that temperature had a significant negative correlation with the seed set five days before emasculation. Wiggans (2S) advocated a heat unit accumulation theory to mature a crop. It was noted that the accumulation of temperature over 40°F required to mature a given Variety of oats was about the same for the plant- ings made in April to early May. Minor variations were recorded from year to year for a specific variety. Walster (21) working on barley under controlled conditions found less carbohydrates at higher night temperature 20°C than at 15°C. MATERIALS AND IETHODS The study included four barley varieties, Moore, Montcalm, Kindred and Plains. They were grown under controlled conditions in the green house with six replications at three constant night temperatures 75°, 70° and 63°F with a range of £20r. It was not possible to control temperature during day- time and it represented the weather conditions prevailing at the time of the eXperiment. Planting in the first experiment was done on October 20, 1955 in 8" size earthen pots filled withloam soil and sand in the ratio of 2:1. Four seeds were seeded in each pot and allowed to germinate at a constant night temperature of 60°F maintained in the experimental room. On germination three seed- lings were left in each pot for experimental use. Night temperature control was exercised on the completion of germination. The pots were arranged in circles under the infrared bulbs of 250 watts each which were hung on the top of growing seedlings for radiating artificial heat at night. The first circle under the infrared bulbs comprised the temperature 75°F, second circle the night temperature 70°F, and the third temperature comprising pots at 63°F. However, some uncontrol— lable fluctuations in the temperature range of 62°F did occur during the course of the eXperiments. The heat bulbs were raised as the plants grew and artificial heat at night was radiated from 6 P.M. to 6 A.M. Watering was done daily or on alternate days and the plants were fed with standard nutrient solution at an interval of about 10 days. 6 Data were taken on the height of main shoot, date of heading of main shoot, green and dry weight of Culm, green and dry weight of main ear and tillers, and number of seeds set on main head. One plant from each pot was harvested 78 days after seeding. In the meantime, mice caused damage to most of the heads of the standing plants and rendered the results of these plants unus able. The second eXperiment was planted on March 3, 1956. The material and procedure was the same except that the infrared bulbs were now adjusted parallel to the growing plants instead of at the top to expose the entire plant length to as uniform an artificial heat as possible. Accordingly the pots were arranged in a semicircle opposite to infrared bulbs. On account of warm and open weather the plants made rapid growth and the three plants of each pot were harvested individually 56, 63, and 70 days after seeding. Data were taken as for the first experiment. Rate of respiration determinations were made in a controlled temperature room at 65°, 70° and 75°F in the dark for a ten hour period for a barley introduction from Iran C I No 6658. Three tin cans containing growing plants were placed in the respiration jar. Before placing the plants in the respiration Jar, the earth surface in these pots around the growing plants was sealed with melted paraffin. The colorimetric method for 002 determination in respira- tion studies as described by Claypool (6) was followed. Briefly, the procedure consisted in passing a known volume of compressed air with constant per cent C02 through the respiration jar 7 containing plants and then equilibrating the outcoming air sample with a dilute solution of sodium bicarbonate containing phenol red indicator. The test tube containing this solution through which the out coming air from the respiration Jar was passed was then placed in a colorimeter and the percent trans- mission determined. A 565 filter with transmission limits 550 and 585 was used. The test tube was made air tight with a rubber stopper immediately on changing the flow to the second test tube containing the solution with indicator. The test tubes were used in turn and the readings were recorded at an interval of 10 minutes. The solution in the test tubes was changed after recording 6-8 readings. The rate of air flow was regulated by flowmeters. The internal temperature of the stem and the air inside the jar in the reSpiration experiment at the three temperatures was recorded by introducing separate thermocouples and reading millivolts resistance with a potentiometer. The data was subjected to analysis of variance and cor- relations between night temperature and date of heading, number of seeds set on main head and rate of respiration were worked out. EXPERIMENTAL RESULTS 1. EFFECT OF NIGHT TVHPERATURE 0N PLANT GROWTH Several aspects of plant growth under the different night temperatures were observed. In general the results were as expected. Significant differences due to different night temp- eratures were observed for date of heading, dry matter in the main culm, plant height, seed number and ear weight. These data together with analysis of varience are presented in tables 1 to 9. The real purpose of these experiments was to observe relative rather than absolute differences. It was hoped that a significant variety-temperature interaction could be found as this would indicate some varieties to be better adapted to high night temperatures than others. Such a case was observed for plant height, date of heading, green and dry weight of culm, number of seeds set on main head and green and dry weight of main head. This would seem to indicate that the genotypes behave differently at one night temperature in comparison to another night temperature thus affecting the performance of barley genotypes at different night temperatures. Table 1 indicates that plants grown at relatively low night temperatures attained greater final height. It can be seen from table 2 that relatively low temperatures lengthened the period of growth and delayed the date of heading of barley varieties. Significant differences were observed between night temperatures for these characters. 9 There seemed to be a general trend in the accumulation of more green as well as dry weight of the culm, as illustrated Iingtable 3 at comparatively low temperatures, although, some -. '1’: ,f: ‘ '5 : A fluctuations have been recorded. Significant differences were recorded between night temperatures for green and dry weights of culm in experiment 1 in the plants harvested after 85 days (table 4). In general, the number of seeds set increased with a decrease in night temperature as shown in table 5. However, the differences are not significant. A significant interaction was recorded between varieties and night temp- eratures as illustrated in table 6. This indicated differential behavior of genotypes at different night temperatures. Average green as well as dry weights of all tiller heads per plant are given in table 7. It can be seen that per cent dry matter at all temperatures was very low as compared to that recorded for the main head, table 8, indicating an immature stage of heads at harvest. The green and dry weight of the main head, table 8, was considerably depressed at high temp- erature 75°F as compared to 70° or 63°F. Significant differences were obtained for green weight between night temperatures and a significant interaction between varieties and night temperature is shown in table 9. 10 TABLE I THE EFFECT OF NIGHT TEMPERATURE ON THE GROWTH OF BARLEY GENOTYPES Height of main shoot at harvest ExptE I 2 ‘ Expt.AII Variety 63°F "'70 r 75UF 63“?“ 70°F 73°r'“' (inchesT(inches)(inches) (inches)(inches)(inches) Moore 24.3 22.9 22.8 27.2 28.5 26.6 Montcalm 23.6 23.6 18.6 26.9 28.7 26.0 Kindred 23.4 25.3 20.3 27.7 30.5 30.1” Plains 18.4 18.3 16.9 23.0 21.4 20.5 Analysis of variance for Height of main shoot Source of 2 Expt. I L“. EXpt. II variance D.F. H.S. F. M.S. F. Total 71 — — - _ Blocks 5 7.723 - 5.051 - Varieties 3 90.024 3.31 194.402 29.73** Night Temp. 2 59.416 2.19 15.947 2.44 Var.xN. Temp. 6 27.193 7.9¢H' 8.168 1.28 Error 55 3.425 - 6.361 - Pooled Error 61 - — 6.538 — * F value exceeds 5% level of significance. ** F value exceeds 1% level of significance. THE RESPONSE OF DATE OF HEADING TABLE II OF BARLEY GENOTYPES AT DIFFERENT NIGHT TEHPERATURES 11 Days seeding to heading Variety EEUF ETUEF I 75°F 63°F——EETU°FII_’750F_ Moore 52.3 49.3 45.2 35.5 32.9 31-5 Montcalm 52.2 49.4 46.9 35.6 34.5 31.1 Kindred 50.3 46.5 42.2 34.7 32.3 29.3 Plains 42.8 41.1 38.3 30.6 29.6 26.0 Analysis of variance for date of heading Source of ____ Expt. I _§§p§&_l1 variance D.F H.S F MLS F Total 71 - — — _ Blocks 5 2.299 - .458 - Varieties 3 303.503 73.24** 92.598 22.68** Temp. Treatments 2 252.382 60.95** 128.741 31.54** Var. x Temp. Tr. 6 4.141 2.85* 1.917 0.47 Error 55 1.453 - 4.318 - Pooled Error 61 - - 4.082 - * F value exceeds 5% level of significance. ** F value exceeds 1% level of significance. 12 DRY HATTER BY HARVEST DATES IN CUTE TABLE III CF BARLEY GEI‘IOTYPES GROWN AT DIFFEIEITT NIGHT TE’E‘ERAT RE Experiment I a. igr‘ Average weight :2331 per plant in grams and % :gg. dry dotter'by dlys seeding to harvest mL/ Variety E: 78 j? 858 /9 92 % G.w D.w D.M G.w D.w D.H G.w D.w _gpgg 63 4.515 .973 21.55 4.375 .975 22.29 3.015 .781 25.90 Moore 70 4.097 .855 20.87 3.675 .780 21.22 3.573 .830 23.23 75 3.557 .727 20.44 3.939 .838 21.27 4.726 1.006 21.29 63 2.907 .628 21.60 2.843 .632 22.23 2.751 .637 23.16 Montcalm 70 2.869 .647 22.55 2.963 .615 20.76 2.763 .646 23.38 75 2.418 .527 21.80 2.032 .487 23.97 2.207 .532 24.11 63 2.620 .525 20.04 2.996 .624 20.83 2.792 .719 25.75 Kindred 70 2.456 .493 20.07 3.061 .616 20.12 2.344 .534 22.78 75 2.510 .497 19.80 1.926 .443 23.00 2.187 .523 23.91 63 2.659 .607 22.83 2.836 .697 24.58 2.647 .749 28.30 Plains 70 2.586 .563 21.77 2.580 .619 23.99 2.112 .566 26.80 75 2.608 .577 22.12 2.411 .580 24.06 2.078 .571 27.48 TABLE III (Continued) 13 Experiment 11 Average weight vufhn per plant in grams and % dry.matter by days seeding to harvest 56 63 0 70 Z G.W D.w D.M 0.w D.w D-M G.w D.W’ 0.r 3.394 .702 20.68 3.028 .653 21.57 2.321 .647 27.88 3.099 .621 20.00 3.050 .640 20.98 2.583 .682 26.40 3.757 .765 20.36 4.297 .826 19.22 3.463 .789 22.78 3.102 .599 19.31 3.000 .599 19.97 2.930 .713 24.33 .3.824 .767 20.06 2.770 .610 21.97 2.832 .665 23.48 3.862 .735 19.03 2.996 .612 20.61 3.136 .734 23.41 3.553 .706 19.87 2.926 .620 21.19 2.581 .597 23.13 3.010 .633 21.03 2.275 .522 22.95 2.193 .583 26.59 3.236 .619 19.13 2.913 .643 22.07 2.089 .697 22.56 2.987 .646 21.63 2.914 .680 23.34 2.748 .681 24.87 2.643 .592 22.40 3.015 .670 22.22 2.634 .661 25.10 2.811 .622 22.13 2.762 .666 24.11 2.060 .504 24.47 l4 .oonooflmanmfim no Ho>oH RH mooooxo cramp m ** .ooCmofiwflcme no Ho>oH mm mooooxo odao» m r 1 mmo. 1 mmo. 1 emo. 1 1 1 1 1 1 Ho aoaam ooaoon 1 HNO. 1 omo. 1 mmo. 1 oeo. 1 omo. 1 mmo. on aoaam Hm.a omo.. oo.o oao. om.H omo. 1 ooo. 1 oHo. 1 omo. o .aa room a .ao> o . moo. ee.a omo. om. moo. mo. Heo. .mm.e sma. eo.a moo. m mocoapooaa poem so.a meo. oo.m omo. oo.a omo. *oe.s mam. .roo.HH 4mm. 11ms.ma nos. m noapoaaes 1 mmo. 1 moo. 1 omo. 1 oao. 1 Hoo. 1 oHo. m aaooam 1 1 1 1 1 1 1 1 1 1 1 1 as Hopoa HmoH :_wmo 1 mom. 1 Hoo.o 1 som.o 1 1 1 1 1 1 Ho aoaam ooHoon 1 one. 1 moo.o 1 mom.o . oms. 1 own. 1 mmo. mm aoaam oo.m omH.H om.H eoo.o ano.H omo.o .eo.m ooo.m 1 moo. 1 wow. o .aa poem x .ao> mm.a omo. oo.a oom.a mmo.o ooe.o mo. emo. .mo.m moo.m mm.H moo.a m assessooaa seem mm.H mom. mn.m moo.H .me.m oHo.m eo.m mem.o .aoH.oH Hee.o *amm.aa omm.o m ooaeoaaoa 1 ooo.H 1 moH.H 1 mnH.H 1 mom. 1 oso.m 1 Hmm. m meooam 1 1 1 1 1 1 1 u 1 1 1 1 as Hence amona :ammo mocmfinw> a m.a a m.a a m.a a m.a a m.a a m.a m.a no I condom mon 0&1 mama mm WNmQ mm mama mm mme1Mm, mama mu HH pqoafipoaxm H pcoefiaomxm mmmbaémmmzma BmUHz HammmhmHD ad 230mm mmawm Hmm>m¢m Mm mmmwaozmo wmgmdm EQDU mo BmemB wmn Qz< Bmemg zmmmw mom moz¢Hm¢> mo mHmNA¢z< >H mqmda TABLE V AVERAGE* NLTTBER OF SEEDS SET ON ETAIN HEAD BY HARVEST DAlES FOR BARLEY VARIETIES GROWN AT DIFFERENT NIGHT TENPERATURE Expt. Ij< he Expt. II Night Temp. 78 Days 56 Days 63 Days 70 Days Variety (OF) No seeds No seeds No Seeds No seeds 63 2.3 17.0 17.2 17.0 Moore 70 7.8 15.0 16.2 19.0 75 11.5 13.5 12.5 10.0 63 7.0 8.3 10.8 15.3 Hontcalm 70 3.2 10.8 10.8 12.7 75 2.5 7.0 9.2 6.8 63 8.2 16.0 15.2 14.7 Kindred 70 15.0 16.5 14.8 16.7 75 8.2 14.5 13.3 14.0 63 .2 2.7 1.8 2.8 Plains 70 - 2.8 3.2 3.2 75 2.2 2.5 2.2 2.8 * Average of six replications 16 .oonooHMacmHm mo Hoaofi ma mooooxo oSHop h ** .ooCoofiMHQMHm mo Hobofi Rm mooooxo oSHm> m * 1 oom.oa 1 oo¢.om 1 mos.sa 1 omm.om mm aoaam .mm.m ome.om 1 oom.o 1 Hme.n saom.m moo.on o .naoa names a .ao> mm.m mom.ooa om.H Hoo.om ee.H mom.mm um. noa.om m oasaeaoaaoa prose .amo.oa ome.mao 11o4.om mma.mmo raoo.om oom.sso on.e so¢.nom m moapoaao> 1 1 1 1 1 1 1 m.oe m mxooam 1 1 1 1 1 1 1 1 as Hopoa a are a We a was a : oocoaaos IIMNmQ on 1mNmn mo Ilmwom om mammIMNIIII mo condom HH 9:658me .1.,11--11.1.1.1-:-..411 H Hofianomxm mmfipedmmmfima HEUHZ dammmmHn ad afiomcmmflwaozmw mammwm mOh Hmfi>m¢m ho mmadn fl>memmcomm H4 Qdmm ZH mo mHmwgdz« H> wands 17 m.nm omo. omH. o.om Nae. Nee. m.om eoo. mam. o.He odd. ome. on e.om on. mom. o.mm owe. onm. o.om moo. mum. m.oe ooa. omm. on oaaoan o.oe Hoe. woe. o.om oma. oHe. o.nm Hmo. oomw o.om moo. omm. mo o.mm one. mam. H.em mma. ewe. m.nm ooo. omm. o.me Hmm. oem. mu 1 1 1 1 1 1 1 1 1 o.Hm moo. on. on ooaocam H.om mea. mum. m.mm ooo. mom. o.mm ooo. eem. e.me oeH. omm. mo m.sm mom. mum. m.em moa. mom. m.om omm. men. m.om moo. omm. on o.mm moo. oom. o.om mHH. eee. H.Hm «no. mem. m.se eoH. omm. on aaoopaoa o.mm one. mom. s.om omo. oeH. 1 1 1 A.He mso. owe. mo o.mm Hmm. «on. o.Hm meo. eHm. H.om ooo. mam. m.nm mma. omm. on o.om omo. omm. o.mm ooo. owm. .mm eoo. mom. m.em eoo. ohm. on oaooa 1 1 1 w.em moo. oam. - 1 1 H.5m eom. omo. mo _ II 2.9 :89 3.6 2.9 3.9 gnu .249 3.9 3.0 2.9 3.9 3.6 Muofinmb gm N\ ‘dme; QHBIN mmMDawmmmEmH HmcHz 9299999H9 H¢ zaomo mmmeDZMb qumdm mo mmaadfi.wm9 momazmomwa 92¢ mmdm mZHHHHH 90% Wde0 ZH Hm¢99 mam HmUHmm Mm9 92¢ zmwmo mo¢mm>¢ HH> 999¢B 18 mo4oo oe. eoa. o .oo oofl. om.oo moo. om.oo oeo. oaéo Hoo. oo.oo oom. mo.Ho ooo. oH.om emu. oo.oo Nee. Ho.oo mom oe.oo emu. 2.9 3.9. B.w _lelnmgmanw ooe. mom. 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HH.mo mam. omo.a oe.ee mao. eom.H oo.om omm. moo. mo 26. to a; a. oMaVIIJI. 2.6 )oum 8.3.2; amllmwmmmm mulmaoo [mlumwmmm ”fiwmw HH pcoafimo K9 111th\\ HHH> 999¢H 9¢mm ZH¢E ho EOH mutt mmmbaammmswe BmmHz HzmmmhmH9 B< anomo mmma180340 MHdem mom 999949 M99 90¢9290999 92¢ 9949 9mm>mez Wm memo 2H madmm>4 .wocoofiwacwfim mo Hmpofi EH mommoxm m59m> m .mommoamfinwfim 90 Hw>mH mm mwmwoxm msaw> m ** * a u n mmo.o n mmo.o n 1 Ho ponom ochoo Hmo.o . omo.o . umo.o . flao. mo .. poppm **Hm. o moa. o I uHo.o . ooo.o .mo.m omo. o .pa oommo x .no> an. m mom. o om.m ooo.o ¢o.o Hmo.o mo. ooo. m mucospmmna .oEma *om. m mmm. 0 **mol om Nmo.H **©m.am mwm.o **uH.NH mom. m wmfipwfipw> a ooo. o moo.o u Hoo. . mmo. m mxooam : I n u n .1 Ho Hopes Hmong mmn . u . mmH.o a ooo.o . Hoo. Ho “chum omHoom omo.o s ¢HH.o . moa.o n Hoo. mm gonna **mm.m oMH.o . oom. o . mmo.o - moo. o .pa .oama x ”poo mm. m oo¢.o **mo.ma moo.H *mm. m mom.o Ho.o omo. m mpcmEpmopa .pEma *mo. o ooH.H **oo.mm mam. m **o¢. om ooo.m **oo.oH Ho.H m mmfioofipm> . moo.o . ooo. o . HmH.o . ma. m axooam : u n n u n n u an Hmooe amona.zmmmo m m.z m m.: m m.: m m.: m.m wocofipo> mo mopdom nwmp om, whomMmo wwwmxom mMmQ‘mN HH .poxm . H .poxm mummy omoume Boo Hz Bong EH9 Ho zsomo mu mwaormo mqmom mo mmeoo 90 Emma Pka >C9 92d 39 Hmo mom moron db mo mHm>9<-¢ NH 99949. Hmmbmdm >m 94m? ZHdL 20 II. EFFECT OF TENPERATURE ON NIGHT TINE RESPIRATICN It would seem logical to assumethat variations in night temperature would affect respiration rates. The rate of increase of respiration of immature barley plants in the dough stage is shown in table 10. TABLE 10 Rate of respiration in a dark room of C. I. No. 6658 barley at three temperatures. Data in milligrams of 002 per hour per kilogram of green weight. 65- 63.501“ 70 - 70.57? 77- 757.5% Hours after start of filant Plant Plant expt. Material Mg002 Material MgCOg Material HgCOZ ' (grams)41g/HR (grams) ig/HR (grams) lngR 4 96.3 737.8 82.0 1098.4 75.0 1464.2 5 96.3 731.9 82.0 1104.5 75.0 1448.4 7 96.3 709.8 82.0 1108.5 75.0 1438.4 9 9603 712.4 82.0 ' 7500 - 10 96.3 712.4 82.0 1103.5 75.0 1412.3 It will be noted in table 10 that the relationship between respiration and temperature is linear. It is of interest to note that the Q101 is much greater than 2 indicating that an enzyme system is involved. Temperature responses of this magnitude would appear to be of great importance in theaflapta- tion of a species. III. THE INFLUENCE OF RESPIRATION RATE ON PLANT TENPERATURE Highly significant differences were obtained between the internal plant temperature in the culms versus the air temperature by means of thermocouples. These differences are l. The Q 0 of any process - physical chemical or physio- logical is defined as the number of times that the rate of the process increases with a 10°C. rise in temperature. 21 extremely small and the experiment should be repeated for this reason. The smallness of the differences indicates a rapid dis- sipation of heat into the atmosphere. Kore suitable means of checking this point through the use of insulation on the culm could most certainly be devised. TABLE 11 The difference in average air temperature vs. internal temperature of culm as an indication of respiration rate. No. of Average air Average tem- Difference Rate of observations temperature perature in— Stem - Air respiration inside Jar side plant MgCOz/Kg/HB stem (or) (CF) (0F) 24 65.1046 65.1214 /0.0l68 707.0 24 70.1909 70.2500 /0.0S91** 1101.2 28 75.4565 75.4913 #0.0348** 1443.6 ** Differences significant at 1% level IV. THE GENERAL EFFECT OF NIGHT TEIPEIATURE ON THE BARLEY PLANT As a general statement high night temperature has been found to decrease the number of days to heading, de- crease the number of seeds on the main head and to increase respiration rate. These relationships are given in table 12. TABLE 12 Correlation coefficients between night temperature and certain physical characteristics of barley Comparison d.f r 1. Temperature vs date of heading 10 - 0.669* of main shoot. 2. Temperature vs number of seeds 70 - O.295* set on main head. 3. Temperature vs rate of respiration.l6 # O.999** * Differences significant at 5% level. ** Differences significant at 1% level. 23 DISCUSSION The experimental evidence indicates that night tempera- ture is an important environmental factor in determining the performance of barley varieties. It is of interest to note that in the early stage of the growth cycle for the barley varieties under study, stem elongation was more rapid at the higher temperatures. However, plants at the lower temperature, continued to grow for a longer period and attained a greater final height. The number of days from planting to heading in each variety decreased as the temperature increased. In the first experi- ment plants grown at lower night temperatures yielded more green and dry weights of culms but this was not confirmed in the second experiment. This may be due to cloudy weather in the first experiment whiph considerably increased the period of growth. “tifi‘\“l 7" Night temperature produced no significant effect on seed set when averaged over all varieties. However, the variety temperature interaction was significant. This indicated a dif- ferential response of genotypes to seed set at different night temperatures, and may explain, to some extent, the erratic behavior of barley varieties in different localities. Studies on the process of photosynthesis (8') have revealed that at the normal range of temperature for plant growth for a particular species, the net photosynthate was not materially affected by temperature. In the study being reported there was not an appreciable difference in the growth of plants 24 raised at different night temperatures whereas there was a conspicuous decrease in the weight of the main head at the night temperature 75°F as compared to 700 and 63oF. The bulk weight of heads is mainly contributed by the grain which is essentially a form of stored carbohydrate. A deficiency of carbohydrate was shown at the higher night temperature 75°F in comparison to lower temperatures 700 and 63oF when the yields of main head at different dates of harvest were compared. Significant differences were obtained for the 56 and 63 day period in the second experiment for green weights of the main heads. A highly significant interaction was observed between varieties and night temperature treatments for both green and dry weights of the main head, which further substantiates the differential reaponse of the genotypes at different night temperatures. An increase in respiration without an accompanying in- crease in photosynthesis will decrease the carbohydrates available for storage and thus reduce yield. A straight line relationship between respiration rate and the temperature at 65°, 700 and 75°F was found for the first five hours of the eXperiment. After the lapse of 10 hours of respiration in the dark the rate of respiration was found to have decreased more at the higher temperature, 75°F than at 65° or 70°F. This indicates a more rapid exhaustion of carbohydrate material at the high night temperature. This agreed with the work of Walster (21) who found less soluble and hydrolyzable carbo- hydrates in barley at a higher temperature 20°C than lower one 15°C. This may also eXplain, in part, the low weights of 25 heads obtained at 75°F in comparison to 700 or 63°F. However, the main decrease in weight is probably due to increased sterility at the higher temperatures. The difference between the internal temperature of the stem and of the air in the respiration jar in the dark was small but statistically significant. It was hoped that the release of energy in respiration could be used as a measure of respiration rates. However, the size of the differences obtained indicates a very rapid dissipation of heat into the atmosphere. Obviously, some other procedure, such as insulat- ing the culm, must be used to either prove or diSprove the assumption. The r values recorded between night temperature and certain physical characteristics of the barley genotype under study explain why low yields are obtained at high night temperatures. The night temperature showed a significantly negative cor- relation with date of heading and number of seeds set. The dry weight of main head has also shown negative correlation with night temperature (r I - 0.191) but the r value is not significant. The rate of respiration is closely associated with temperature with an r value of [ 0.9999. The data in- dicate that the main causes of decreased yield are: 1) close positive association of night temperature and rate of respiration, 2) shortening of the crop cycle as shown by the negative association of date of heading and, 3) significant negative correlation with seed set. Genotype night temp- erature interaction was indicated by the data which may explain, to some extent, the differential behavior of barley varieties at different night temperatures. l. 2. 3. 4. 5. 26 SUMHARY AND CONCLUSIONS Four genotypes were grown in the green house to study the response of certain physical characteristics of barley to night temperature at 75°, 70° and 63°F with a range of f 2°F. The night temperature was controlled by radiating artificial heat from infrared bulbs. The plants were harvested at the progressive dates of maturity of the main head. The height of main shoot was affected by night temperature. The higher the night temperature the quicker was the rate of elongation of the main shoot in the early stage of deve10pment of the plants but the order was reversed in the advanced stage of growth. At harvest the plants raised at low temperature were tall as compared to the plants raised at high temperature. Date of heading was found to have significant negative correlation with night temperature. Average night temperature seven days after date of head- ing showed a significant negative correlation with seed set. No significant difference in the green or in dry weight of culm was recorded between different night temperatures except in the plants harvested after 85 days in experiment I. No significant difference was recorded in the dry weight of the main head between different night temperatures. A highly significant variety x night temperature inter— action for dry weight of main head was recorded in 7. 9. 27 experiment I and for the plants harvested after 70 days in experiment II indicating differential response of barley genotypes to night temperature. Respiration in the dark in the above ground parts of the plant increased with temperature and was found to be closely correlated with temperature with an r value of % 0.9999. The decrease in the rate of respiration at 75°F after 10 hours of respiration in the dark was more than the decrease at low temperatures 650 and 70°F which indicated exhaustion of oxidizable carbohydrates at high temperature. The internal temperature of the stem was higher than that of the air in the respiration jar at different temperatures. This difference, though small, was significant. The data obtained in this study revealed a significant negative correlation of night temperature with date of heading and seed set accompanied by increased rate of respiration which caused a defficiency of carbohydrate at high temperature. Presumably this, could account for lower yields obtained at higher night temperatures in barley varieties. 3. 4. 10. 11. l2. l3. LITERATURE CITED Andrews, F. 3. Physiological factors associated with the fruiting habits of the bush lima bean. Proc. Am. Soc. Hort. 801. 33: 473"760 19350 . Factors influencing the yield of the Fordhook lima bean. S. Car. Exp. Sta. Ann. Bept. p 101. 1933. Binkley, A. M. The amount of blossom and pod drop in six varieties of garden beans. Proc. Am. Soc. Hort. Sci. 29: 489-93. 1932. Boswell, V. R. The influence of temperature upon the growth and yield of garden peas. Proc. Am. Soc. Hort. 8C1. 162-68. 1926. . Factors influencing yield and quality of peas. Biophysical and Biochemical studies. Univ. of Maryland. 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