Whyte — 31 — Research in Vernalization 



Seeds which sprout as well as those which remain unsplit during the period 

 of chilling are vernalized, but, for the same dose of chilling, plants from 

 sprouted chilled seeds are earlier. The vernalization effect is not transmitted 

 to the progeny. When growth of the embryo is successfully confined within 

 the elastic limits of the seed coat, the unsplit chilled seeds can be dried and 

 stored for long periods (at least 863 days) without any resultant dever- 

 nalization. 



It was found that the mustard Type 27 used in these experiments has 

 no obligatory low-temperature requirement for the thermo-phase, plants 

 from untreated seeds flowering even when the minimum night temperature is 

 20° C. or more. Partial natural vernalization can, however, be induced in 

 Type 27 when the embryo develops under a low temperature, and artificial 

 vernalization has its maximal effect in 6 weeks. Once the thermo-phase 

 has been completed, mustard appears to develop towards maturity best in a 

 photoperiod of 13 hours, with an optimal associated temperature of 30° C. 



Following these experiments, other Indian workers at the Botany Dept., 

 Presidency College, Calcutta (Sen Gupta and Sen, 1944) made observa- 

 tions on the effects of time of sowing, photoperiods and vernalization on 

 the growth and development of the two varieties of mustard. Tori No. 7 

 and Rai No. 5. Finding no response to vernalization, it was stated that 

 their results did not confirm those of Sen and Chakravarti. The latters' 

 reply (1944) was to the effect that their own results applied only to the 

 five strains tested. They considered that no definite conclusions by Sen 

 Gupta and Sen are warranted because the maximum period of chilling 

 they used was only 30 days. The fact that unsprouted soaked seeds were 

 chilled at 2 to 4°C. for different periods does not in itself ensure that they 

 were properly vernalized ; the technique or the conditions following chilling 

 have not been described, and the conclusions are based on data obtained 

 from a single sowing of Rai No. 5 and Tori No. 7. 



Other crops dealt with by physiologists in India include gram {Cicer 

 arietinum), rice and wheat. Low temperature applied to gram at the time 

 of germination accelerates subsequent inception of the reproductive phase, 

 while high temperature definitely retards it. The degree of response in 

 both cases is a varietal character (Pal and Murty, 1941 ). Pillay (1944) 

 has reported a preliminary experiment to determine whether pre-sowing 

 treatment with low temperature would induce earlier flowering and high 

 yield in gram under the conditions of Orissa. Seeds of uniform size of the 

 variety, Sabour Type 4, were soaked in water for 22 hours at room tempera- 

 ture. The smaller seeds were then placed in a Kelvinator at to 2° C, one 

 lot for 7 days and another for 14 days. The latter seeds produced plants 

 which flowered only 3 days earlier than the controls, and there was no sig- 

 nificant difference in dry weight of pods or of stems. 



Much work has been done in the United States of America, Japan, India 

 and other countries on the developmental physiology of rice, more par- 

 ticularly with regard to photoperiods. In addition, Indian and Russian 

 workers write about the vernalization of rice by short day or temperature. 

 Using the former treatment in Bengal, Sircar and Parija (1945) obtained 

 results of agricultural importance with a winter variety of rice, "Rupsail." 

 The time to flowering of this variety has been reduced from 133 to 47 days 



