‘4: iNFLUEfiCE G23 EQA’LENG'W Aw.) TEEMQERATURE as“ m m ' qua‘agac -grva ngt.fl-a;'a,c. Til-:1 «Luge mam-a «it \ wag: Ms”: 23.13383. ~. “I’SZ‘WGM‘er ":m*m.mr:rr.¢ ‘1' I . o.’_ ' '9 or t ' .mmss 1m" may Dagmar an; :51. S. ...fi_ ‘*(4 ° 3319173-2 5.1;. 'f'xq m .k"~.£ui“.i\a:§‘§\ a, ‘10. . a «Q-gagfiz: gzfi’i ‘5 “:1; 13'1“. :Lfi THESIS A 69 This is to certilg that the thesis CDllthtl presented bg has been accepted towards fulfillment of the requirements for degree in Mainr prnlesseu‘ Date _ —- - '0' "H' -— ‘ I THE INFLUENCE OF DAYLENGTH AND TEMPERATURE ON THE GROWTH AND FLOWERING 0F CALLISTEPHUS CHINENSIS NEES. By Lok-chien Lin “—g—n—nu. A THESIS Submitted to the School of Graduate Studies of Michigan State College of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of Master of Science Department of Horticulture 1949 Acknowledgments The author expresses here his thanks to the following for guidance, help in gathering reference material, reading and editing of manuscript: Dr. D. P. Watson, Dr. R. E. Marshall, Dr. L. M. Turk, Prof. C. E. Wilden, and Prof. H. W. Lautner. Introduction During the late winter and early spring months the China aster (Callistephus chinensis Egggg) is frequently grown in the greenhouse as a cut flower crep. It has pre- viously been shown by Post (14) in 1935 that the growth of this plant is influenced by the length of the light period and the temperature at which it is grown. The commercial grower is usually interested in timing the flowering date to coincide with the greatest demand for his crap. Consequently it is important to him to be able to take advantage of these factors, both so that he can produce his crOp when he wishes and also in as short a period as is practical. Table I shows that the days at East Lansing from August 13 to April 29 are too short for China asters to form flower buds when axis elongation occurs. This experiment is a study of the influence of daylength and temperature on the growth and flowering of Callistephus chinensis figggg' Plants were grown with and without artificial light in Michigan State College greenhouses, East Lansing, Michigan, during the period.from October 1948 to April 1949. 7 Lu. 2 Table I. Daylength throughout the Year from Sunrise tc Sunset, as Compiled at East Lansing, Michigan Presented in Hours and Minutes (U. S. Department of Commerce) Month Day of Month Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. 1 9' 7" 9'59" 11'12" 12'45" 14' 5" 15' 6" 15'17" 14'50" 15'11" 11'45" 10'20" 9'18" 2 9' 7"’ 10' 2" 11'15" 12'46" 14' 7" 15' 8" 15'16" 14'27" 15' 9" 11'42" 10'17" 9'16" 5 9' 8" 10' 4" 11'19" 12'49" 14' 9" 15' 9" 15'16" 14'25" 15' 6" 11'59" 10'15" 9'15" 4 9' 9" 10' 6" 11'21" 12'55" 14'12" 15'10" 15'14" 14'22" 15' 5" 11'57" 10'15" 9'14" 5 9'19" 10' 9" 11'24" 12'55" 14'14" 15'11" 15'15" 14'20" 15' 0" 11'54" lO'll" 9'15" 6 9'12" 10'12" 11'27" 12'58" 14'16" 15'11" 15'15" 14'17" 13'58" 11'50" 10' 7" 9'10" 7 9'15" 10'14" 11'29" 15' 1" 14'19" 15'15" 15'11" 14'15" 12'55" 11'27" 10' 5" 9'10" 8 9'14" 10'17" 11'55" 15' 5" 14'22" 15'14" 15'10" 14'13" 12'51" 11'35" 10' 5" 9' 9" 9 9'15" 10'19" 11'56" 15' 6" 14'24" 15'15" 15'10" 14'10" 12'48" 11'22" lO' 1" 9' 8" 10 9'16" 10'21" 11'59" 15' 9" 14'26" 15'15" 15' 8" 14' 8" 12'46" 11'19" 9'58" 9' 7" 11 9'18" 10'24" 11'41" 15'11" 14'28" 15'17" 15' 7" 14' 5" 13'43" 11'17" 9'56" 9' 6" 12 9'19" 10'27" 11'45" 15'15" 14'51" 15'17" 15' 5" 14' 3" 13'40" 11'13" 9'54" 9' 5" 15 9'20" 10'29" 11'48" 15'18" 14'55" 15'17" 15' 4" 14' 1" 12'37" ll'lO" 9'51" 9' 5" 14 9'22" 10'51" 11'50" 15'20" 14'55" 15'18" 15' 5" 15'58" 13'34" 11' 8" 9'49" 9' 4" 15 9'24" 10'55" 11'55" 15'25" 14'57" 15'19" 15' 1" 15'56" 12'32" 11' 5" 9'4?" 9' 4" 16 9'26" 10'56" 11'56" 15'25" 14'59" 15'19" 15' 0" 13'53" 13'29" 11' 2" 9'45" 9' 5" 17 9'27" 10'59" 12' 0" 15'28" 14'41" 15'19" 14'58" 13'51" 12'25" 11' O" 9'45" 9' 5" 18 gtggtt lol43tt 12! 3t! 13t31tt 14'43" 15.20" 14t58tt 13.47" 12128" 10.54" 9|4Ott 9t 3t! 19 9'50" 10'45" 12' 5" 15'52" 14'45" 15'20" 14'54" 13'45" 13'19" 10'56" 9'38" 9' 2" 20 9'55" 10'48" 12' 8" 15'56" 14'47" 15'20" 14'54" 13'42" 12'17" 10'51" 9'37" 9' 2" 21 9'55" 10'50" 12'11" 13'59" 14'49" 15'20" 14'52" 13'40" 12'14" 10'49" 9'34" 9' 2" 22 9'56" 10'55" 12'14" 15'42" 14'51" 15'20" 14'50" 13'37" 12'11" 10'46" 9'32" 9' 2" 25 9'59" 10'56" 12'17" 15'44" 14'52" 15'20" 14'48" 13'35" 13' 8" 10'44" 9'51" 9' 2" 24 9'41" 10'59" 12'20" 15'47" 14'54" 15'20" 14'46" 13'32" 12' 5" 10'40" 9'29" 9' 5" 25 9'45" 11' 1" 12'25" 15'49" 14'56" 15'19" 14'44" 13130" 12' 3" 10'58" 9'27" 9' 5" 26 9'46" 11' 4" 12'26" 15'52" 14'58" 15'19" 14'42" 13'35" 13' on 10'35" 9'25" 9' 5" 27 9'48" 11' 7" 12'29" 13'54" 14'59" 15'19" 14'40" 13'34" 11'57" 10'33" 9'23" 9' 3" 28 9'49" ll'lO" 12'51" 15'56" 15' 1" 15'18" '14'59" 13'32" 11'53" 10'31" 9'22" 9' 5" 29 9'51" 11'12" 12'55" 15'59" 15' 5" 15'18" 14'56" 13'19" 11'50" 10'27" 9'20" 9' 4" 50 9'54" 12'58" 14' 2" 15' 4" 15'17" 14'54" 15'17" 11'48" 10'25" 9'19" 9' 5" 51 9'56" 12'41" 15' 5" 14'51" 13:14" 10'33" 9' 6" Review of Literature The first record of the effect of light upon plants was made by John Hay in 1686 (Laurie and Poesch 12), who found in Historia Plantarum differences due to light variation. It was fully two centuries later before any comprehensive research along this line was undertaken. The earliest horticulturist in this country who brought to the A public the study of the influence of electric lamp upon greenhouse plants was L. H. Bailey (1). He used radishes, peas, lettuce, tulips, verbenas, and petunias as material and found that "the electric light promotes assimilation; it often hastens growth and maturity; it is capable of producing natural flowers and colors in fruits; it often intensifies colors of flowers and sometimes increases the production of flowers. The experiments show that periods of darkness are not necessary to the growth and deve10pment of plants." Stone (20) found that light has an important in- fluence on the configuration of plants. Since most of the plant energy is derived from the air through sunlight, the optimum light conditions were important, and there was a marked difference in the light requirements of carnations, roses,lettuce, cucumbers and tomatoes. In 1920, Garner and Allard (5) published the results of tests on the effects of the relative length of day and night and other factors of 4 the environment on growth of asters, soybeans, tobacco, climbing beans, violets, and other vegetables. Duration of the flowerless condition of some plants in response to shortened days may continue for years. . Garner and Allard (6) found further that relatively short alternating cycles of light and darkness tend to produce effects similar to those of a long day or of continuous light in that they favor flowering in long day plants but not in short day plants. A suggestion by Kellerman (10) is that the plant could belong to the long or short day group. since 90mg varieties bloom when the light periods are less than 12 hours if the equational length of day of 12 hours is regarded as a standard. Poesch and Laurie (15) classify China aster (variety Sunshine) as a long day plant. While it blooms after August 15 when the days in the north of the hemisphere are rapidly becoming shorter, its flowers are probably initiated earlier in the season. Their results are based on the affects of additional light during the winter, which was found to reduce the time necessary for flowering. Greene, lithrow and Richman (7) have shown that the short day months increase the time required for flowering. They found that artificial light supplementing daylight made possible the production of an early spring crOp of asters of excellent quality. 5 lithrow and Benedict (22) found that under condi- tions used in these experiments the light from a 15-watt lamp placed 4 feet above the bench and applied for 10 hours each night is nearly as effective in the winter forcing of good quality flowers (China aster variety iHeart of France") as a SOC-watt lamp producing approximately 75 times the visible light and.applied under the same conditions. lithrow (25) showed that favorable results were obtained by using high intensity lights for a few weeks to hasten flowering. Low intensity lights produced extremely variable results. Short stems developed at high temperatures in short days for Biebel (3). He was able to produce the normal habit only with long days. A temperature of 70° F. affected not only the time of flowering in China aster and the inflores- cence produced but sometimes caused flowering despite unfavorable length of days (Biebel 4). Post (15) found that additional light in the early stages of growth made the plants start to flower from 12 to 23 days earlier than in the checks, depending upon the time of propagation. Higher temperature with the additional light further hastened the time of bloom of light-treated plants. The production and.quality were further reduced by the higher temperature under long days. . With regard to the responses of Callistephgg chinensis 322;; Post (16) showed that the use of artificial 6 light during the short days from September to May prevented resetting and caused elongation of the plant stems followed by flower-bud formation.) The reduction of the day length, which can hasten the results, caused short stems and small flowers. Temperatures above 65° F. caused slight stem elongation so that even during short days buds might form and develop into flowers. Post (14) concluded that the additional day length in the early period of growth followed by reduced day length during summer after buds had developed produced earlier flowers of normal size on late types than other treatments. Post (18) maintains further that from the tempera- ture standpoint there were three groups of plants: (a) those requiring low temperature for bud formation and producing vegetative growth at high temperatures, (b) those requiring high temperature for flower bud formation and producing vegetative growth at low temperature, and (0) those requiring high temperature for growth and flowering. Honeywell (9) demonstrated that artificial lighting on aster seedlings immediately after germination resulted in flowering as much as two weeks earlier under field condi- tions. Artificial light supplementing daylight during early October, five hours at night using 25-watt lamps, made possible the production of a mid—winter crop of greenhouse asters of excellent quality. In 1948 Withrow (21) published an article on artificial lighting for forcing greenhouse 7 creps. He recommended that the period for lighting for winter forcing of asters begin at six weeks or more after seeding and continue until buds set and stems reach desired length. Certain conditions of the environment, specifically a long day and definite temperature, are necessary for most rapid seed germination, growth, and flowering of these plants (3, 12, 14). Optimum temperature for seed germina- tion is between 60° and 65° F. (9). Flower buds do not initiate when the temperature is below 50° F. or when the light period is less than 15 hours (18). Taking advantage of this information, this study was undertaken to attempt to learn: (a) the number of days required to produce flowers on plants which are being grown at high and low temperatures and with long and short days, and (b) the variations in growth habit caused by different temperatures and day lengths. From these data it would seem likely that more accurate recommendations could be made to growers who desire to closely limit the time of flowering or to alter the stem length or overall form of their plants. Materials and Methods China aster (variety Sensation) was grown in the greenhouse. Seeds were sown in sandy soil in a greenhouse maintained at 65° F. on October 50, 1948. After 57 days (December 6, 1948), 120 seedlings were transplanted into 2%-inch clay pets and then divided into two groups to be grown.at 50° F. (low temperature) and.65° F. (high tempera- ture), respectively. One hundred and six days later (March 22, 1949) they were repetted into 5-inch clay pets. As seen as the plants were transplanted, artificial light was used on 50 low temperature seedlings and on 50 high temperature seedlings. This artificial light was pro- duced from a 60-watt, lZO-velt incandescent lamp suspended 2% inches above the plants. From December 6, 1948 to March 51, 1949, this light was used five hours after sunset every day. This made a total of four groups of plants: (a) low temperature long day, (b) low temperature short day, (0) high temperature long day, and (d) high temperature short day. Thus the day length treatment with this additional light is termed "long day" and without it, "short day". Records were kept of (a) diameter and.height of plants every 15 days between the 68th day and 158th day after seeding (Tables IV and V and Fig. I, A and B) and (b) the time of appearance of first buds and first full bloom on each plant until there was a total of approximately 50 buds or flowers for each group of 20 plants. 9 Collections were made at 15-day intervals (between the 68th day and 158th day after seeding) of: (a) leaves produced under each growing condition (Fig. II, A), and (b) whorl of young leaves at center of growing axis where flower initiation was likely to be present (Fig. II, B). All plant material was preserved in formalin- aeete—alcohel (50% ethyl alcohol 90 cc., glacial acetic acid 50c., formalin 5 cc.). The material was then dehydrated in the usual manner for paraffin imbedding. It was cut on a rotary microtome ten micra in thickness and stained with saffranin and Heindenhain's haematexylin. Permanent sections were mounted in Canada balsam. Three hundred and sixty permanent slides were made for the whole study. . . ., .. .. thithcpwtzscswl . . I .. . .vloo .. . .56... 0.7... i. . 3.0 . v.4... . a... is it.” 1.. .I" a‘n‘ Q‘e....oe.o -. .ne. . METHOD OF MEASUREMENT METHOD OF COLLECTION 11 Presentation of Data Table II and Figure III indicate that on the "high temperature, long day" plants, buds were visible on the 150th day after seed sowing. They formed 49 buds between then and the 165rd day. On the "high temperature, short day" plants, buds were visible on the 165th day after seed sowing. They formed 47 buds between then and the 187th day. On the "low temperature, long day" plants, buds were visible on the lSlst day after seed sewing. They formed 47 buds between then and the 168th day. On the "low temperature, short day" plants buds were visible on the 176th day after seed sewing. They formed 49 buds between then and the 199th day. Table III and Figure IV indicate that on the "high temperature, long day" plants flowers were visible on the 165th day after sowing. They formed 45 flowers between then and the 180th day. On the "high temperature, short day" plants flowers were visible on the 179th day after seed sowing. They formed 50 flowers between the 179th and 202nd day. On the "low temperature, long day" plants, flowers were visible on the same date as on the "high temperature, long day" plants. But the "low temperature, long day" plants did not develop fully open flowers until 4 days later than the "high temperature, long day" plants. 0n the "low temperature, short day" plants a flower was visible on the 192nd day after the seed sewing. They formed 46 flowers between then and the 215th day. 12 Table IV and Figure V show that on the 68th day after sowing (January 6, 1949), the average diameter of the "high temperature, long day" plants was 7.11 cm.; the average diameter of the "high temperature, short day" plants, 5.95 cm.; the average diameter of the "low temperature, long day" plants, 6.52 cm.; and of the "low temperature, short day" plants, 4.82 cm. Measurements were taken at 15-day intervals. On the 158th day after the seed sowing (April e, 1949), the average diameter of "high temperature, long day" plants was 15.28 cm.; the average diameter of the "high temperature, short day" plants, 12.86 cm.; the average diameter of the "low temperature, long day" plants, 15.84 cm.; and.the average diameter of the "low temperature, short day" plants, 11.50 cm. Briefly, the greatest plant diameter was obtained where plants were subjected to a long day light period and high temperature (Fig. VII and VIII). From Table V and Fig. VI it is observed that on the 98th day after seed sowing (February 5, 1949), the average height of the "high temperature, long day" plants was 7.68 cm.; the average height of the "high temperature, short day" plants was 2.20 cm.; the average height of the "low temperature, long day" plants was 5.15 cm.; and the average height of the "low temperature, short day" plants was 2.45 cm. Measurements were taken every 15 days. On the 158th day after seed sowing (April 6, 1949), the average height of the "high temperature, long day" plants was 15 15.12 cm.; the average height of the "high temperature, short day" plants was 6.71 cm.; the average height of the "low temperature, long day" plants was 8.69 cm.; and the average of the "low temperature, short day" plants was 5.65 cm. "Long day, high temperature" environment resulted in greater length growth (Fig. VII and VIII). Table IV shows that the average diameter of plants at high temperature was 1.91 cm. more than without additional light, and at low temperature the diameter was 2.20 cm. more than without additional light. Table V shows that the average height of plants at high temperature was 6.18 cm. more than without additional light and at low temperature was 2.51 cm. more than without additional light. 14 Table II. Influence of Temperature and Daylength on Accumulative Bud Development. (data in number of buds) Days after High tegperature Low temperature seeding —Long day Short day Long day Short day 150 7 151 10 3 152 10 4 155 11 4 154 14 7 155 20 10 156 25 15 157 29 16 158 34 20 159 59 21 160 40 22 161 44 24 162 ' 45 37 163 49 30 164 51 165 3 33 166 3 38 167 4 39 168 5 45 169 7 47 170 8 171 8 Days after seeding 172 .175 174 175 176 177 178 179 180 181 182 185 184 185 186 187 188 189 190 191 192 195 194 15 Table II. Continued High temperature Long day Short day 12 15 15 16 19 22 22 24 27 29 30 33 38 45 47 Low temperature Long day Short day ~e -Q o: 14 12 13 15 16 19 19 23 25 30 32 32 34 37 4O Days after seeding 195 196 197 198 199 Table II. Continued High temperature Long day Short day _, Low temperature ‘Long day Short day 45 45 45 45 49 16 17 Table III. Influence of Temperature and Daylength on Flower Development. (data in number of flowers) Days after Highgtemperatuggl Low temperature_ seeding Long day Short day Leng day *Short day 165 7 4 166 10 5 167 14 5 168 14 7 169 19 9 170 21 10 171 24 12 172 25 15 175 28 16 174 50 19 175 52 25 176 ‘ 52 24 177 59 25 178 41 25 179 42 1 28 180 45 4 51 181 7 54 182 9 58 185 9 41 184 ll 48 185 14 186 15 187 19 188 25 189 26 18 Table III. (Continued) Days after High temperature Low temperature seeding Long day Short day Long day Short day 190 28 191 29 1 192 55 1 195 55 l 194 55 5 195 59 6 196 41 9 197 41 10 198 45 16 199 45 16 200 45 16 201 47 18 202 50 ' 25 205 25 204 25 205 29 206 55 207 56 208 56 209 57 210 40 211 45 212 45 215 . 45 214 , 45 215 45 arson ’0 MM“ gh‘l‘Ub 84 55858535552881!!! sauna E g I. ‘h Ulbk¢xrah t0...- ushggur ’04 his: 3. we a; etc usage 8 328.5...1! Table IV. Influence of Temperature and Daylength on Average Diameter Development of Plants (Produced from Table VI, data in cm.) Days after High temperature Low temperature seeding Long day Short day ‘Leng day Short day 68 7.11 5.95 6.52 4.82 85 8.56 7.44 7.90 5.82 98 10.56 8.74 9.95 7.26 115 11.88 9.72 10.84 8.18 128 15.20 10.85 12.05 10.21 145 14.08 11.55 15.00 11.08 158 15.28 12.86 15.84 11.50 Table V. Influence of Temperature and Daylength on Average Height Development of Plants (Produced from Table VII, data in em.) Days after High temperature .__Low temperature seeding ‘Leng day Short day Long day Short day 98 7.68 2.20 5.15 2.45 115 8.84 5.41 4.77 2.99 128 10.15 4.25 6.41 5.69 145 12.58 4.88 7.45 4.45 158 15.12 6.71 8.69 5.55 I. «will: at... r . _ flame-ventured“; Ti.- in days after seeding . 20 Table VI. Influence of Temperature and Daylength en Diameter Development of Plants (data in cm.) Days after ‘ seeding 68th 85;; Temperature _High Low High Low Daylength Long *Short Long Short Long Short Ieng Short Data of 7.0 7.5 7.1 5.0 9.7 8.7‘ 9.2 5.6 diameter on plants 7.5 6.7 7.5 6.1 7.8 08.0 8.0 6.5 ' 6.9 7.5 7.0 5.2 7.5 8.5 9.1 5.5 7.0 5.2 4.1 5.2 8.5 7.7 6.0 5.5 8.8 6.5 6.0 4.0 9.4 7.8 7.0 6.5 6.4 5.8 5.2 5.0 7.0 7.2 8.0 5.0 6.8 4.2 6.0 5.0 10.5 6.6 10.0 6.0 6.4 6.1 6.2 4.5 K 9.4 7.6 7.0 8.0 6.0 5.1 6.0 5.2 7.6 7.6 10.8 6.0 5.0 6.0 5.0 5.2 4.5 7.2 5.5 5.0 6.0 6.8 9.0 5.0 7.4 7.0 10.9 7.0 6.9 5.2 5.4 6.1 9.7 7.9 9.5 6.6 8.9 6.0 8.5 5.1 9.8 6.8 10.0 5.6 8.0 5.0 9.0 4.2 9.4 6.6 11.0 5.2 7.0 6.5 7.0 6.1 9.4 7.0 9.5 7.0 7.5 6.5 6.1 5.7 9.1 6.5 5.5 6.0 8.2 5.0 7.0 2.5 9.2 6.8 9.0 3.0 8.5 5.5 5.2 4.0 10.0 8.0 7.0 5.4 6.6 5.8 6.1 5.0 8.0 7.0 6.5 4.8 7.2 5.5 6.4 4.5 7.8 8.5 6.5 6.2 Average 7.11 5.95 6.52_ 4.82 8.59 7.44 7.9 5.82 21 Table VI. (Continued) H 98th L H 113th L 128th igh ow igh ow High EEng Short Long Short Dong Short ‘IEng Short Long Short 11.5 9.0 10.2 6.5 14.0 9.6 10.8 7.5 15.0 10.0 10.5 10.0 9.1 8.0 11.5 10.7 10.3 8.5 13.1 10.8 9.0 9.0 12.0 7.0 11.0 9.2 12.6 8.2 13.1 10.6 9.6 8.0 7.5 7.1 13.0 8.5 9.0 8.4 14.4 9.5 10.5 9.0 12.5 7.0 11.2 11.2 13.2 8.0 12.8 12.8 9.1 8.5 9.4 6.3 12.6 9.3 -10.1 7.3 13.6 10.0 11.2 7.0 13.0 8.0 13.6 8.2 13.8 9.0 14.0 9.6 9.8 8.5 8.5 9.2 11.5 9.5 9.1 9.5 12.7 10.3 9.4 9.5_ 11.4 8.2 12.2 10.2 12.0 8.8 11.0 11.6 6.6 8.6 7.0 6.4 8.0 ‘9.5 8.2 7.0 10.0 9.8 8.0 8.5 11.5 8.0 9.6 8.2 12.4 8.2 11.9 9.0 12.6 9.2 10.5 7.9 14.0 10.7 11.5 8.3 15.2 11.4 11.6 8.0 11.5 6.4 12.2 8.4 12.5 7.6 13.5 9.3 ' 10.4 9.5 12.3 6.0 11.5 9.9 12.8 7.3 12.8 10.7 10.0 8.1 . 10.0 8.1 11.2 8.7 10.6 8.5 14.0 11.3 11.0 8.0 8.2 8.9 11.2 10.2 9.8 7.5 12.0 11.6 12.0 9.0 11.0 5.0 12.8 10.5 12.0 7.2 13.2 12.0 12.0 9.5 8.5 8.0 13.6 10.3 9944 8.9 14.2 12.5 13.0 10.0 7.5 6.0 14.0 11.2 8.3 6.8 15.3 12.8 22.2.40... 15.93.159.195 8.5 11.215.111.49. 10.36 8.74 9.95 7.26 11.88 9.72 10.84 8.18 13.20 10.83 Table VI. (Continued) 128th 143rd 158th Law ’High Low Sfligh Bow Long Short Long Short Long Short Dong Short W 11.6 10.6 16.0 10.8 12.6 11.0 18.2 11.6 13.5 12.0 11.2 11.0 14.0 11.5 12.5 11.8 16.2 12.6 13.5 12.6 13.2 10.0 14.0 11.2 14.4 11.0 15.3 12.0 15.0 12.2 11.2 10.3 15.8 10.4 12.0 11.2 16.3 11.5 13.0 12.3 14.6 10.0 13.0 12.0 15.6 11.0 14.0 12.9 16.1 11.9 11.6 9.0 14.7 11.6 12.8 10.0 15.5 12.6 13.6 11.0 14.6 11.1 15.0 10.5 15.2 11.9 16.0 11.6 16.1 12.5 11.0 11.8 13.0 11.2 11.9 12.6 14.0 12.4 12.6 13.0 13.2 10.5 12.3 12.4 14.4 11.3 13.4 13.5 15.0 11.8 9.3 8.0 12.0 11.0 1015 9.0 13.0 12.0 11.5 10.0 13.5 9.5 11.8 10.1 14.5 10.2 12.6 12.2 15.2 11.0 12.5 10.0 16.0 12.0 13.6 11.0 17.6 12.6 15.3 11.8 13.7 8.4 14.0 11.5 14.5 9.3 15.0 12.0 15.0 10.2 13.4 8.2 13.4 11.2 13.8 9.0 14.8 12.6 14.6 10.0 11.2 9.8 14.8 12.4 12.2 10.6 15.9 13.7 13.2 11.2 10.2 8.8 13.0 12.4 11.4 9.5 13.6 14.0 12.0 10.3 13.0 8.5 13.8 12.9 13.5 9.0 14.6 13.8 14.7 9.7 10.2 9.7 15.0 13.3 11.5 10.7 16.2 14.8 12.4 11.5 9.4 7.0 16.1 13.0 10.4 8.0 18.4 14.5 12.0 9.0 9.5 12.0 14.0 12.7 11.5 12.5 15.3 13.5 -12.5 13.0 12.05 10.21 14.08 11.55 13.00 11.08 15.28 12.86 13.84 11.30 23 Table VII. Influence of Temperature and Daylength on Height Development of Plants (data in cm.) Days after . seeding 98th 113th Temperature High Low 'High Low Daylength Long Short Long Short Long Short Dong Short Data of 7.5 2.5 3.5 2.0 9.0 3.0 6.0 2.5 height on plants 9.5 2.0 3.0 2.2 10.0 2.9 4.2 3.0 4.0 2.5 2.5 2.6 6.5 3.0 5.4 3.0 6.0 2.4 2.5 2.6 7.2 3.2 5.0 2.8 7.5 2.6 2.6 2.0 8.5 3.6 5.2 2.6 10.5- 3.2 3.2 2.0 12.4 3.4 5.6 2.5 8.4 2.7 3.7 2.0 9.5 3.5 '4.6 2.4 7.2 3.0 3.0 2.0 8.5 4.0 6.4 2.5 8.0 2.5 3.5 3.5 9.0 3.0 4.5 4.8 4.8 2.6 3.5 2.5 6.5 4.2 5.0 3.0 6.5 1.6 3.6 3.5 7.0 3.2 4.3 3.8 10.5 2.8 3.5 2.5 11.5 3.5 4.6 3.2 7.4 2.4 2.6 2.3 8.4 2.4 3.2 2.8 7.8 3.0 2.8 2.6 9.5 3.5 3.8 3.0 6.0 2.2 2.4 2.8 6.5 3.1 3.6 3.5 8.0 3.0 4.5 2.5 9.5 3.5 5.0 3.0 7.5 2.3 3.2 1.5 8.0 2.9 3.7 1.8 10.0 3.5 3.0 3.6 10.8 4.0) 15.5 4.0 8.0 3.3 3.3 2.3 9.0 3.8 5.8 3.2 8.6 4.0 3.5 2.0 9.6 4.5 4.0 2.5 Average 7.68 2.20 3.15 2.45 8.84 3.41 4.77 2.99 Table VII. (Continued) 128th ' l43rd ‘High How 'High Lew Long Short Long Short ‘Eang Short Long Short 10.0 4.0 9.0 3.2 12.2 4.5 10.5 4.0 11.5 4.0 7.0 3.5 14.5 4.5 8.2 4.4 8.0 4.5 7.0 3.5 8.5 5.2 8.4 4.5 11.5 4.0 7.5 3.4 12.8 4.0 9.6 4.6 9.6 4.4 7.5 3.6 10.6 5.6 8.0 4.0 13.2 4.2 7.2 2.8 14.6 4.8 8.0 3.5 10.3 4.5 5.3 3.0 12.0 5.0 6.8 3.8 9.5 4.6 7.0 3.0 11.5 5.6 9.6 3.0 9.8 4.0 5.5 5.6 10.8 4.8 ,6.5 6.4 7.4 4.8 7.0 3.6 8.4 5.0 8.0 4.0 8.0 4.0 5.5 4.6 9.0 5.6 6.5 5.2 13.0 4.0 7.0 4.2 18.0 5.5 7.8 4.7 9.6 3.8 5.2 4.0 10.6 4.4 6.0 4.8 10.8 4.2 4.8 3.7 11.8 4.6 5.6 4.2 8.2 3.5 5.8 4.2 9.4 4.0 6.2 4.8. 10.5 4.4 7.5 3.8 11.5 4.8 8.0 4.2 9.5 3.6 4.9 2.5 10.6 4.0 5.5 3.0 11.6 4.6 6.0 4.6 12.8 5.0 6.5 5.0 10.2 4.3 6.4 4.0 ,11.4 4.8 7.0 4.4 10.4 5.2 5.2 3.0 10.5 5.6 6.3 3.6 10.13 4.23 6.41 3.69 12.58 4.88 7.45 4.45 Table VII. (Continued) 158th High Low Long Short Long Short 13.8 6.2 12.5 4.5 15.5 5.4 10.0 8.0 11.5 7.6 9.6 6.2 13.5 5.3 10.0 5.0 11.6 6.2 9.8 5.0 16.3 5.8 10.0 4.0 13.4 6.3 7.4 5.2 12.5 8.4 10.6 4.3 12.0 7.8 7.8 7.4 9.6 9.4 9.2 5.5 10.0 7.8 7.5 6.2 20.2 6.2 9.0 6.0 11.8 5.8 8.4 6.0 13.4 6.0 6.5 5.5 10.6 6.2 6.8 5.5 13.5 7.2 9.4 5.6 11.4 6.8 6.0 4.2 13.3 7.6 8.0 5.8 12.6 5.8 7.8 5.6 16.0 6.4 7.5 7.1 13.12 6.71 8.69 5.63 Flower Initiation and Development Figure IX B to D shows the early stages of flower bud deveIOpment: B, bud beginning to differentiate as a specialized form; C, bud beginning to deve10p into three parts; D, a bud differentiated into its component parts; A, a cross section of deveIOpment of buds and their locations. Miscroscopic observations of the sections of the tips of 68-day old plants (Fig. IX B) showed the ini— tiation of flower buds had taken place in "long day“ plants but not in "short day' plants. Apparently additional periods of light had speeded up initiation of flower buds so that they were visible within 68 days after seeding. Under ”short day" conditions, flower buds differentiated between 68 and 83 days at the "high temperature" and between 68 and 98 days at the ”low temperature". Therefore, while temper— ature effect had little influence on the initiating time under long days, high temperature speeded up the initiation under short days at least 15 days. It is not correct, however, to assume that temperature can be used by itself to grow successful flowers because of the day length response to vegetative growth. From the data compiled in Table VIII we might con— clude that plants with additional light were budding 15 days earlier at "high temperature long day" than the "high temperature short day", 25 days earlier at "low temperature long day" than ”low temperature short day", and were flowering 14 days earlier at 27 "high temperature long day” than the “high temperature short day", 27 days earlier at "low temperature long day“than at 'low temperature short day”. Relation between bud initiation, budding, and flowering can be seen on Table VIII. Plants with additional light at high or low temperatures took about 82 days to show buds after bud initiation, and.about 15 more days to form flowers. Plants without additional light required.about 82 days from initiation to budding in a high temperature but only 78 days in a low temperature. This was probably the result of the increased length of time required to initiate the buds at the low temperature. From budding time to flowering showed very slight differences under any treatment. 8.x; .8 .2353 45.38 88 .588 see 28 .5 no emerald; .mE £29.. I 0.: aim... 30.. \. >