EFFECT OF UGHT AND TEMPERANRE APPLIED T0 ONEON SULBS 1N STORAGE 0N THEE SUBSEQUENT VEGETATEVE AND REPRODUCTWE'DEVELOPMENT finesis for the Degree of M. 5. meme: STATE UNIVERSITY . PHELDON BRENT 999:1.qu 1974 MM. [7 , P771" V/xji‘ 3"? 103 "D L"- . "‘ . ), 41-1.; 5‘, J gig”. Y r 1‘ s <"'“‘ 1?: ~Zd“ ABSTRACT EFFECT OF LIGHT AND TEMPERATURE APPLIED TO ONION BULBS IN STORAGE ON THEIR SUBSEQUENT VEGETATIVE AND REPRODUCTIVE DEVELOPMENT By Phildon Brent DeMille EXperiments were conducted to ascertain the vegetative and reproductive development of onion bulbs (Allium 2223 L.) after receiving light and temperature treatments while in storage. The Open pollinated onion variety 'Trapp's Downing Yellow Globe' was used. Bulbs were exposed simultaneously to fluorescent and incandescent light in three different storage temperature regimes (7 C. 7 and 2 C, and 2 and 7 C). Each temperature regime included the following light treatments: continuous light, a 12-hour photoperiod, and continuous dark. In addition, at one temperature regime some bulbs were trans- ferred after half the storage period from continuous light to continuous dark and vice versa. Bulbs were planted in the spring and the following data were recorded at the time each bulb flowered: days to flower- ing from planting, number of leaves. number of seed-stalks, and seed-stalk height. At maturity the seed was harvested and the seed yield was determined. Light was shown to be effective in reducing the number of days to flowering in all treatments where bulbs were eXposed to some light during the storage period. In general, continuous light was more effective in reducing days to flower- ing than a 12-hour photoperiod. Light applied to onion bulbs during the first half of the storage period tended to reduce the number of days to flower- ing to a greater extent than light applied only during the second half of the storage period. Subjecting the bulbs to a temperature of 2 C during the first half of the storage period delayed flowering and reduced the number of leaves more than did the 2 C temperature during the last half of storage or a continuous temperature of 7 C. Exposing onion bulbs to light in storage had no effect on the number of leaves, the number of seed-stalks, or seed yield. Storage temperature did influence seed yield and the highest seed yields occured when bulbs were stored at 7 C for the first half of the storage period. Increases in yields were the result of more and larger seed being produced per bulb. EFFECT OF LIGHT AND TEMPERATURE APPLIED TO ONION BULBS IN STORAGE ON THEIR SUBSEQUENT VEGETATIVE AND REPRODUCTIVE DEVELOPMENT BY Phildon Brent DeMille Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Horticulture l97h :3 <9 I". "I . hi..- i f .. dc“ ACKNOWLEDGMENTS The author expresses appreciation to Dr. H. Grant Vest for the suggestion of the problem, and his guidance during the course of this study. Appreciation is due also to Drs. M. L. Lacy and R. C. Herner who served as guidance committee and assisted in the preparation of the manuscript. TABLE OF CONTENTS LIST OF TABLES....................................... LIST OF FIGURES...................................... INTRODUCTION......................................... LITERATURE REVIEW.................................... MATERIALS AND MTHODSOOOOOOOOOOOOOOOOOO00.00.000.000. RESULTSOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO00.00.000.000. Days to Flowering............................... Continuous Storage 7 C..................... First Half 7 C - 2nd Half 2 C (Dark)....... lst Half 2 C (Dark)-2nd Half 7 C........... Storage Temperatures....................... Number of Leaves................................ Number of Seed-stalks........................... Seed-stalk Height............................... Seed Yield...................................... Weight per Seed............................ Number of Seed per Bulb.................... Number of Seed per Umbel................... DIEECIUSSIOFJOOO.00......0.0.0....OOOOOOOOOOOOOOOOOOOOOO BIBIJI~3GRAPHY0.0...0.000.0.00.0...OOOOOOOOOOOOOOOOOOOO iii Page iv 11 11 11 13 15 18 18 20 20 2b 2a 28 LIST OF TABLES TABLE Page 1. Light and temperature treatments used on onion bu1bs in stomgeOOOOOOOOCOOOOOOCOOOOOOIOOOO... 9 2. Summary of days to flowering as affected by different light treatments and storage temper- atureSOOOOOOOOOOOOOOOOOO0.00.00...OOOOOOOIOOOO l7 3. Summary of the number of leaves for bulbs ex- posed to light treatments in three storage tempemtureSOOOOOIOOOOO0.0.0.0....0000000000... 19 4. Summary of the number of seed-stalks for bulbs eXposed to light treatments in three storage tempemturESOOOOOOOOOOOOOOOOOOOCCCOOOOOOOOO... 21 5. Summary of seed-stalk height (in centimeters) for bulbs eXposed to light treatments in three storage temperatures.......................... 22 6. Summary of the seed yield (in grams) per bulb for bulbs exposed to light treatments in three storage temperatures.......................... 23 7. Summary of the weight (in milligrams) of each seed from bulbs exposed to light treatments in three storage temperatures................. 25 8. Summary of the number of seed per bulb for bulbs eXposed to light treatments in three storage temperatures.......................... 26 9. Summary of the number of seed per umbel for bulbs eXposed to light treatments in three storage temperatures.......................... 27 iv FIGURE 1. LIST OF FIGURES Number of days to flowering for bulbs ex- posed to light treatments while stored at 7 00.000.00.000.a...OOOOIOOOOOOOOOOOOOOOOOIO Number of days to flowering of bulbs stored at 7 C during lst half and at 2 C during 2nd half of the storage period.................. Number of days to flowering of bulbs stored at 2 C during lst half and at 7 C during 2nd half of the storage period.................. Page 12 14 16 INTRODUCTION Temperature and light are among the environmental factors that have a pronounced influence on the growth and development of the onion plant. Temperature and light (4, 5, 13, l#, l6, 17, 18’ both influence bulb development, and temperature at which the bulbs are stored has been reported (3, 5, 8, 9, 17) to influence bolting. The demand for high quality and productivity of onions has increased in recent years. Research efforts are being made to develop superior high yielding and disease resistant varieties of onions, and to ascertain environmental effects on seed production. Information that can be gathered from this research will be useful for the grower and seedsman. Onion bulbs are commonly stored for various lengths of time during the winter before being planted in the spring for seed production. 'Low onion seed yields have caused concern for continued supply, and research is underway to investigate the factors responsible. There is no information available to date on the effect light on onion bulbs in storage may have on seed production of these bulbs when they are planted. The object of this research was to determine what influ- ence light and storage temperature have not only on seed yields, but on time to flowering, on the number of leaves and seed-stalks produced, and on seed-stalk height. 1 LITERATURE REVIEW The onion plant is sensitive to its environmental sur- roundings and responds in a number of ways to external stimuli such as temperature and light. Early work on the response of onion plants to light was reported by Gardner and Allard (h). Onion sets of the 'Sil- verskin' variety grown under different.day-lengths showed that plants exposed to a 10-hour day-length failed to form bulbs and remained vegetative while normal bulb formation occured under longer day-lengths. It was concluded that with this variety bulb formation was a result of the long days of summer while short days favored vegetative growth. McClelland (1h) reported onions to be not only sensitive to varied light exposures, but that varieties also differed in their sensitivity, and what was a sufficient exposure for one variety may be inadequate for another. Magruder and Allard (13) studied the effects of different day-lengths on bulb formation in eighteen varieties commonly grown in the United States and eight other varieties commonly grown in Europe. Controlled day-lengths ranged from 10 to 18 hours while the check treatment (normal day-length) varied from 12.h to 14.9 hours. It was found that the variety ’Yellow Bermuda' was the only one to bulb in the lO-hour day- length. Most of the other American varieties bulbed in day- lengths from 12 to 14 hours, while the varieties from EurOpe 2 3 required a day-length of about 16 hours. The combined effects of light and temperature were studied by Thompson and Smith (17), and Heath and Holdsworth (5). Thompson and Smith planted sets in the greenhouse on October 29 and kept them at two different temperature ranges. In December the bulbs were placed into either long-day or normal-day length at one of three temperature ranges: 10.0 to 15.6 C, 15.6 to 21.1 C, and 21.1 to 26.7 C. Plants given a long-day and kept at 21.1 to 26.7 C formed bulbs and matured. At 15.6 to 21.1 c bulbs were formed and the tops had fallen over, but were still green, but plants in the 10.0 to 15.6 C range were still green and showed no signs of bulbing. Plants in the normal day-length showed almost no bulbing at any of the three temperature ranges. Heath and Holdsworth (5) also used onion sets to deter- mine day-length and temperature effects on bulb formation. The plants were grown throughout the summer at an 11 1/2 hour daily illumination at two different temperature ranges (means 18 and 26 C respectively). In October half of the bulbs from each temperature range were transferred to a 16 1/2 hour day of supplemental light while the other half remained in the short day illumination. They found that bulbing began after five weeks at the high temperature range (mean 24 C) and there was no bolting. At the low temperature range (mean 14 C) only 7% of the plants produced bulbs after 10 weeks, and at 16 weeks only 40% had formed bulbs. Of the plants remaining in the short-day length in the high or low temperature, only 3% formed bulbs. a When fluorescent lighting began to replace incandescent lighting in greenhouses, other responses of plants were noted. Borthwick and Parker (2) reported that with sugar beets grown for seed 2? of a total of 29 plants developed seed-stalks when they received incandescent light while only 2 of 31 plants had seed-stalks under the white fluorescent, and no seed-stalks had developed in the daylight fluorescent. The bulbing response in onions was also reported (18) to be affected differently by fluorescent and incandescent lights. Three onion varieties were grown in the greenhouse under 16 hours incandescent or fluorescent light, and under 15 hours of incandescent or fluorescent light followed by one hour of the opposite light. The greatest bulb diameter occured in bulbs grown under 16 hours of incandescent light, the second largest occured under 15 hours of incandescent followed by 1 hour of fluorescent. Plants grown under fluorescent light for 16 hours or 15 hours followed by one hour of incandescent showed little or no bulbing. A later study (16) was done to determine the influence of a B (blue), R (red), and FR (far-red) light on bulbing in onion plants. Onion plants in the 3 to 4 leaf stage received 8 hours of sunlight followed by 16 hours of mixed R + FR, B + FR, and R + B. It was found that mixed light of R + FR caused an in- crease in bulb diameter with an increase of FR intensity, and decreased with greater R intensity, but R light promoted bulb formation when its intensity was less than that of FR. Bulb diameter increased in a B + R where there was an increase of B but decreased with an increase of intensity of R light. 5 When bulbs were irradiated with B + FR the bulb diameter in- creased with the intensities of B and FR light. No reference has been made in any of the above citations as to the effect light has on stored onion bulbs. However, the effect of temperature on stored onion bulbs and sets has been studied by many investigators (3, 8, 9, 17). Boswell (3) studied the effect of storage temperature on bulbs in storage and their subsequent vegetative and reproductive development. He reported that when bulbs were stored at 0, 4.4, and 10.0 C the flower primordial formation was almost totally inhibited at 0 C, and that an exposure to 0 C for six months inhibited floral development less than an exposure of eight months. Thompson and Smith (17) stored sets of 'Ebenezer’,'Yellow Globe Danvers', 'Southport Yellow Globe', and 'Red Iethershield' in temperatures of -l.l, 0, 4.4, 10.0, and 10.0 to 15.6, and 15.6 to 21.1 C. The storage period ran from October to April. The highest percent of seed-stalk development came from sets stored at 4.4 and 10.0 C. The lowest percent of seed-stalk development came from sets stored at 15.6 to 21.1 C. The per- centage of seed-stalks increased when sets were transferred the last month of storage from -l.l, and O C to 4.4 or 10.0 C. Jones (8) studied temperature and its effect on seed pro- duction in the 'Ebenezer' onion. Mother bulbs were stored in California from August 4 until they were planted on December 6. The storage temperatures were 3.5, 7.5.11 to 12, 16 to 22(cellar storage), 30 C, and common storage which was about the same as the outside temperature. Bulbs stored at 7.5 and 11 to 12 C produced their seed-stalks earliest and were the first to flower. There was also a greater number of seed-stalks and higher seed yield at these temperatures. Jones and Emsweller (9) stored bulbs at temperatures of 3.3, 7.8, 11.7, 30.0 C, and in a cellar storage at 16.1 to 21.7 C from late July or early August before planting them in the field in early December. The earliest flowering oc- cured from bulbs stored at 7.8 and 11.7 C. The greatest number of seed-stalks occured at 11.7 and the least at 30.0 C. MATERIALS AND METHODS During 1971 and 1972 bulbs of Allium cepa L., variety 'Trapp's Downing Yellow Globe', were grown at the Michigan State University Muck Farm, harvested after each growing season, and cured for approximately four weeks following harvest. Bulbs were then selected for uniform size and randomly assigned to light treatments before being placed into controlled storage chambers. The storage period ran throughout the winter both years. In the first year, the storage period began October 25, 1971 and ended April 21, 1972. The total storage time was 179 days. Midway through the storage some bulbs were changed from one light treatment to another. The midway point was a predeter- mined date set to equal approximately half the storage period. The predetermined midway point the first year occured after 88 days of storage or on January 21, 1972. The storage period the second year began October 27, 1972 and continued to April 19, 1973 for a total of 174 days. The predetermined midway point occured on January 24, 1973 or 89 days. One cold storage chamber was used for the 1971 experiment, and two chambers were used for the 1972 experiment. These cham- bers were kept at 7 C {45 F). Each storage chamber was parti- tioned into three light proof sectidns in order to accommodate each of the following light treatments: 1) Continuous light; 7 8 2) 12-hour photoperiod: 3) Continuous dark. The three sections in each chamber were constructed so that air could circulate freely from section to section throughout the entire chamber in order to maintain a constant temperature. Light in all treatments was provided by two 40 watt cool white fluorescent tubes and one 40 watt incandescent lamp sus- pended at approximately 50 cm above the bulbs. The light intensity was measured to be approximately 150 foot candles of light. Bulbs in each treatment were arranged upright one layer high on a flat surface to assure maximum exposure to the light source. Thermometers were kept in each section and temperatures were checked regularly and recorded on a recording thermograph. Maximum and minimum thermometers were used when the thermo- graph broke down during the 1972-73 storage period. There were no detectable differences in the temperatures of the different compartments at bulb level or at approximately 30 cm just below the level of the lights. At the midway point in the storage period, a previously selected random sample of bulbs was removed from the continuous light and continuous dark treatments and interchanged. In addi- tion, random samples of bulbs from each light treatment were removed and placed in a dark cold storage at approximately 2 C (35 F). Other bulbs already in this storage were then placed in each of the three light treatments for the remainder of the storage period (Table 1). At the completion of the storage period the bulbs from each treatment were randomly planted and enclosed within two 9 Table 1. Light and temperature treatments used on onion bulbs in storage. TEMPERATURE C 1. Continuous Light 2. 12-hour Photoperiod 3. Continuous Dark 4. lst Half Light - 2nd Half Dark 5. lst Half Dark - 2nd Half Light TEMPERATURE lst HALF Z,C - 2nd HALF 2 C (Dark) 6. Continuous Light - Dark 7. 12-hour Photoperiod - Dark 8.. Continuous Dark - Dark TEMPERATURE lst RALF 2 Cg(Dark) - 2nd HALF Z C 9. Dark - Continuous Light 10. Dark - lZ-hour Photoperiod 11. Dark - Continuous Dark 10 3.6 x 7.3 m lumite mesh cages. Prior to flowering, bees were placed into the cages to provide for pollination as the flowers opened. In 1971, each treatment consisted of 20 bulbs and was re- plicated two times (40 bulbs). In 1972 forty bulbs per treat- ment were used, but the bulbs were divided into two subsamples of five bulbs in each of four replications. Several bulbs per treatment were used in order to minimize the variation found in the open pollinated onion variety used. The number of days until flowering was determined from the date of planting to the date the first floret opened on the primary seed-stalk. The number of leaves (1972 only), the number of seed-stalks, and seed-stalk height were recorded for each bulb at the time the first floret opened on the primary seed-stalk. Mature umbels were harvested and dryed at 35 C. The seed was threshed by hand and cleaned by removing trash and light, non-viable seeds. ’ Seed yield was expressed as the average weight of seed per bulb. Seed of each treatment was combined and five samples of 1000 seeds each were taken from each treatment to find the weight per seed. An analysis of variance of seed per bulb and seed pmm~umbel was performed from only first year data because the second year the weight of seed of the individual bulbs was not obtained. RESULTS DAYS TO FLOWERING Continuous Storage 7 C Data obtained in the two experiments (1971-72 and 1972-73) showed that light was effective in reducing the number of days to flowering when bulbs were exposed to light while stored at 7 C (Figure 1). In the first experiment.bulbs kept in continuous light flowered earlier than bulbs from all other treatments. In the second experiment.bulbs kept in con- tinuous light flowered later than bulbs from the other light treatments, but this was attributed to extreme genetic differ— ences in dormancy noted for 3 individual bulbs inthe contin- uous light treatment. I A The bulbs that flowered last in both experiments were those that received no light during the storage period. In the first eXperiment,bulbs kept in continuous dark flowered 2.8 days later than bulbs kept in continuous light. Likewise, the data obtained in the second eXperiment showed that there was a difference of 1.7 days between the number of days to flower- ing for bulbs kept in continuous light and bulbs kept in con— tinuous dark. In order to expose bulbs to one half the light received by the bulbs in continuous light a 12-hour photoperiod was used, as well as interchanging bulbs half way through the 11 12 Figure 1. Number of days to flowering for bulbs ex- , posed to light treatments while stored at 7C. lst Year 2nd Year I lst Year lst Year 2nd Year 74 III 2nd Year I 3 - 73 82 a: 2 2 ,w .5. I “ 72 81 III g - a g I *’ H III m a. 71 80 III E; O P III a 2, I - 0 0 "‘ 3 I I I 8 7O 7 I I I I 5 9 I I I I :3 I I I I it: I I - I '63 I I I I 78 I I - - I I I - I I - I I I - I l Light l2-hr Dark Light Dark Dark Light l/'Bulbs were transferred after half the storage period from continuous light to continuous dark and vice versa. 2/'Continuous light treatment used as standard for deter- mining differences in days to flowering. 13 storage period from light to dark and vice versa. Results from these treatments showed that bulbs receiving a 12-hour photo- period flowered later than those bulbs receiving continuous light, but interchanged from light to dark and dark to light half way through the storage period. Bulbs kept in the 12-hour photoperiod always flowered earlier than bulbs kept in contin- uous dark. Bulbs eXposed to light during the first half of the storage flowered before those that were exposed to light during the last half of the storage period. lst Half 7 C - 2nd Half 2 C (Dark) I Results also showed that light was effective in reducing the number of days to flowering when bulbs were eXposed to light treatments at 7 C and then placed in dark storage at 2 C for the last half of the storage period (Figure 2.). In both experiments bulbs eXposed to continuous light flowered before those bulbs receiving the 12-hour photoperiod and those kept in continuous dark. These data are similar to those already reported for the continuous 7 C storage tempera- ture. However, there were significant differences in the second experiment between the number of days to flowering for bulbs stored in continuous light and those in the continuous dark. The light effect which the bulbs received at this particu- lar temperature regime was retained by the bulbs even after they were removed from the light and placed into the dark at a colder temperature. This result was the same as that obtained when bulbs were kept at 7 C and interchanged after half the storage time from light to dark_and vice versa» it: Figure 2. Number of days to flowering of bulbs stored at Days to Flowering, 7 C during lst half and at 2 C during 2nd half of the storage period. . ‘43-: “g, \‘ a m m a «4 e m m o >: >4 >: >4 :1 +’ '6 +3 'u .a m c m c u r-ON' HN g 83 let Year ,3 = 3 "3 b 2nd Year A 3 +’ III III m III 5’ 78 - a I 2 .5 III g 78 = : ab :1 - I 1 a: I I 1 I I I I 7 8' I I aZ/ I I o I - - 0 III III III 7 7. III III III III III III I I I I I I Light 12-hr Dark l/'Continuous light treatment used as standard for deter- mining differences in days to flowering. ;/ Means followed by the same letter are not significantly different at the 5% level (Duncan's new multiple range test. 15 let Half 2 0 (Dirk) - 2nd Half 7 C When bulbs were removed from dark storage at 2 C and placed in the light treatments at 7 C for the second half of their storage period, results again showed the effect that light had on reducing the number of days to flowering (Figure 3). Bulbs placed into continuous light flowered earlier than bulbs placed into either the lZ-hour photoperiod, or those kept in continuous dark. These data were similar to the results reported in the previous two storage regimes. Data obtained in the second eXperiment showed that bulbs placed in continuous light and in the lZ-hour photoperiod flowered significantly earlier than bulbs placed in continuous dark. Differences in the number of days to flowering between bulbs in continuous light and continuous dark treatments were greater in this storage regime than in the other two regimes. In the first experiment, there were 3.2 days difference in flowering between bulbs kept in continuous light and bulbs kept in continuous dark. In the second experiment, there were 4.4 days difference in the number of days to flowering between these same two light treatments. Storage Tempgratureg The results from the three storage temperatures are sum- marized in Table 2. The mean of each storage temperature showed that temperature also had an effect on the number of days to flowering. Bulbs stored at 7 C flowered significantly earlier than bulbs stored the first half at 2 C and the second half of the storage time at 7 C. Significant differences were not is Figure 3. Number of days to flowering of bulbs stored at 2 C during lst half and at 7 C during 2nd half of the storage period. lst Year 2nd Year lst Year 2nd Year 5 8 b - 4 III III “ I I h lst Year - 3 § - I «a I I 3 g - 2nd Year I 3 .0 III fi~ .5 I 2 3 g I m o II. 2 i: a = 2 3 7 8 I 1 '2 g I g S I l 3 a - a 7 I ..-: I - o a I - - I o I - 72 8: III III I - I - I - Light 12-hr Dark 1/ Continuous light treatment used as standard for determin- ing differences in days to flowering. ;/ Means followed by the same letter are not significantly different at the 5% level (Duncan' 8 new multiple range test 17 Table 2. Summary of days to flowering as affected by dif- ferent light treatments and storage temperatures. l9Zl-22 Light lst Half 7C lst Half 2C Treatment 70 2nd Half 20 2nd Half 70 Mean . ’ .1./ Contlnuous Light 70.6 71.7 72.8 71.7a Continuous Dark 73.4 73.8 76.0 74.4b Mean 72.2 73.0 74.3 1972-23 Light lst Half 7C lst Half 2C Treatment 70 2nd Half 20 2nd Half 7C Mean Continuous Light 79.6 79.5a 80.5a 79.9a 12-Hour Photoperiod 79.4 80.8ab 81.0a 80.4a Continuous Dark 81.3 82.4b 84.9b 82.9b Mean 80.la 80.9ab 82.1b 1/ Means followed by the same letter in each year are not significantly different at the 5% level (Duncan's new multiple range test). 18 obtained in the first year, but the trends were the same as those of the second year. Cold temperature (2 C) during the first half of the storage period had a greater effect in delaying the flower dates than did cold during the last half of storage or a con- tinuous temperature of 7 C. Significant differences in the days to flowering were found when averaged across the three storage temperatures. Data showed that bulbs in continuous light flowered signifi- cantly earlier than bulbs in continuous dark. The largest differences in the flowering dates for both eXperiments occured between bulbs stored in continuous light at 7 C and bulbs kept in continuous dark at the storage tem- perature of 2 C the first half and 7 C the second half of the storage time. This difference was about 5 days. NUMBER OF LEAVES The light treatments did not influence the number of leaves that were produced by bulbs stored in any of the three storage temperature regimes. However, storage temperatures had a marked effect on the number of leaves that were produced (Table 3). Bulbs that were kept at 2 C the first half of the storage time and 7 C the second half produced significantly fewer leaves than bulbs kept in the other two storage temperatures. NUMBER OF SEED-STALKS There were no appreciable differences in the number of seed-stalks for bulbs receiving the three light treatments. Storage temperature effects were evident only from bulbs in 19 Table 3. Summary of the number of leaves for bulbs exposed to light treatments in three storage temperatures. 1972-73 Light lst Half 70 lst Half 20 Treatment 70 2nd Half 20 2nd Half 70 Mean Continuous Light 25.9 24.4 21.9 v24.l 12-hour Photoperiod 24.1 25.5. 20.4 23.3 Continuous Dark 24.2 24.5 20.7 23.1 Mean 24.7al/fl 24.8a 21.0b 1/ Means followed by the same letter are not significantly different at the 5% level (Duncan's new multiple range test . 20 the second eXperiment (Table 4). Bulbs stored at 7 C produced significantly more seed- stalks than bulbs stored at 2 C the first half and at 7 C the second half of the storage period. These results are similar to those obtained from the effects of storage temperature on the number of leaves. Correlation studies indicated that the number of leaves increased with the increase in the number of seed-stalks. SEED-STALK HEIGHT There were no significant differences in seed-stalk height associated with light treatments: however, storage temperatures produced significant differences in seed-stalk height in both eXperiments (Table 5). Bulbs stored at 7 C had significantly shorter seed-stalks than those kept in the other temperature treatments. The highest seed-stalks were produced from bulbs stored in 7 C the first half and 2 C the second half of the storage time. SEED YIELD The light treatments did not cause appreciable differ- ences in seed yield: however, analysis of the data from storage temperatures showed significant differences for seed yield associated with temperature (Table 6). The highest seed yields were obtained from bulbs stored at 7 C the first half and 2 C the second half of the storage time. In the first experiment, the lowest yields were obtained from bulbs stored in the 7 C storage temperature. In the second eXperiment the lowest seed yields were obtained from 21 Table 4. Summary of the number of seed-stalks for bulbs exposed to light treatments in three storage temperatures. 1971-72 Light lst Half 70 lst Half 2C Treatment 70 2nd Half 20 2nd Half 70 Mean Continuous Light 3.5 3.6 3.2 3.4 lZ-hour Photoperiod 3.2 3.5 3.5 3.4 Continuous Dark 3.2 3.2 3.1 3.2 Mean 3-3 3.4 3-3 1972-73 Light lst Half 70 lst Half 20 Treatment 70 2nd Half 2C 2nd Half 7C Mean Continuous Light 4.5 3.7 3.5 3.9 12-hour Photoperiod 4.2 4.0 3.4 3.9 Continuous Dark 3.8 3.7 3.1 3.5 Mean 4.2al/fii 3.8ab 3.3b 1/ Means followed by the same letter are not significantly different at the 5% level (Duncan's new multiple range test . 22 Table 5. Summary of seed—stalk height (in centimeters) for bulbs exposed to light treatments in three storage temperatures. 1971-72 Light lst Half 70 let Half 2C Treatment 70 2nd Half 2C 2nd Half 7C Mean Continuous Light 86.9 96.0 96.8 93.2 lZ-hour Photoperiod 89.7 100,1' 98.3 96.0 Continuous Dark 90.9 99.3 96.8 95.7 Mean 89.2ai/1 98.5b 97.3b 1972-73 Light lst Half 70 lst Half 20 Treatment 7C 2nd Half 2C 2nd Half 70 Mean Continuous Light 97.0 101.3 96.8 98.4 12-hour Photoperiod 94.0 103.6 97.8 98.5 Continuous Dark 97,8 104.1 99.1 100.3 Mean 96.3a 103.0b 97.9b 1/ Means followed by the same letter in both years are not significantly different at the 5% level (Duncan's new multiple range test). 23 Table 6. Summary of the seed yield (in grams) per bulb for bulbs exposed to light treatments in three storage temperatures. . 1971-72 Light lst Half 70 lst Half 2C Treatment 7C 2nd Half 2C 2nd Half 70 Mean Continuous Light 11.0 11.7 12.4 11.7 12-hour Photoperiod 9.7 14.1 12.6 12.1 Continuous Dark 10.3 13.5 11.2 11.7 Mean 10.3al/8 13.1c 12.1b 1972-73 Light lst Half 7C lst Half 2C Treatment 70 2nd Half ZC 2nd Half 70 Mean Continuous Light 11.4 11.9 10.1 11.1 12-hour Photoperiod 11.5 12.3 9.8 11.2 Continuous Dark 10.5 12.1 10.3 11.0 Mean ll.la 12.1a 10.1b 1/ Means followed by the same letter in both years are not significantly different at the 5% level (Duncan's new multiple range test). 24 bulbs stored in the storage temperature of 2 C the first half and 7 C the second half of the storage period. Weight per Seed Analysis of variance showed that there were significant differences among weights of onion seed associated with the storage treatment means (Table 7). However, there were no appreciable differences in the weights of individual seeds as affected by the light treatments. The smallest seeds in both experiments were produced from bulbs in the continuous 7 C storage temperature. Number of Seedgper Bulb Analysis showed that light had no effect on the number of seeds produced per bulb (Table 8). However, in both ex- periments bulbs stored at 7 C the first half of the storage period and 2 C the second half produced more seed than bulbs receiving the other two temperature treatments. Number of Seed per Umbel The highest number of seeds produced per umbel in both eXperiments was from bulbs stored at 7 C the first half and 2 C the second half of the storage period. The smallest amount of seed produced per umbel in both experiments was from bulbs stored in the continuous 7 C storage temperature (Table 9). 25 Table 7. Summary of the weight (in milligrams) of each seed from bulbs eXposed to light treatments in three storage temperatures. 1971-72 Light lst Half 76 lst Half ZC Treatment 70 2nd Half 20 2nd Half 7C Mean . 1/ Continuous Light 3.84g 4.03 cd 4.15a 4.01 12-hour Photoperiod 3.97ef 4.08 b 4.18a 4.08 Continuous Dark 4.00de 4.17a 4.07bc 4.08 Mean I3.93 4.09 . 4.13 1972-73 Light Qt Half 7c I 1:1: Half 20 8 Treatment 70 2nd Half 20 2nd Half 7C Mean Continuous Light 3.83f 4.06a 3.93bc 3.94 12-hour Photoperiod 3.87cdef 3.9lbcde 4.02a 3.93 Continuous Dark 3.859f 3.94b 3.92bcd 3.90 Mean 3.85 3.97 3.96 1/ Means followed by the same letter in each year are not significantly different at the 5% level (Duncan's new multiple range test). 26 Table 8. Summary of the number of seed per bulb for bulbs exposed to light treatments in three storage temperatures. 1971-72 Light lst Half 70 lst Half 2c Treatment 7C 2nd Half 20 2nd Half 70 Mean Continuous Light 2827.0 2969.4 3080.3 2958.9 l2-hour Photoperiod 2505.4 3538.4 3105.8 .3049.9 Continuous Dark 2613.6 3323.7 2833.2 2923.5 Mean 2648.7a£/I3277.208f1 8V3006.4