Sircar —125 — In the Tropics 



of drying and exposing vernalized seeds of mustard to high temperature were 

 found to be different from those of wheat (M. Lojkin, 1936) and winter 

 rye (F. G. Gregory and O. N. Purvis, 1938) where such treatment re- 

 sults in devernalization. According to B. Sen and S. C. Chakravarty 

 (1942) the different effects of heat treatment are not due to the types of 

 embryo concerned but to the stages of the development of the seed during 

 the period of low temperature treatment. F. G. Gregory and O. N. Purvis 

 (1938) have reported that devernalization takes place when vernalized win- 

 ter rye seeds are exposed to high temperature, but there is no devernaliza- 

 tion when the embryo developing in the ear is chilled. The effects of drying 

 on the vernalized embryo at the preceding and succeeding stages of dor- 

 mancy are thus different. The stage of the development of the mustard 

 embryo lying within the elastic limit of the seed coat at the time of low tem- 

 perature exposure was compared with that of the developing embryo of win- 

 ter rye chilled in the ear. Although low temperature does have a quan- 

 titative effect on vernalization of mustard, yet low temperature is not ob- 

 ligatory for flowering, because in sowings in summer the time to flower- 

 ing is very much reduced without pre-sowing low temperature treatment 

 (B. Sen and S. C. Chakravarty, 1942). In their experiments on photo- 

 periodic response they have observed that mustard type 27 is neither a 

 short day nor a long day plant since it flowers under photoperiods of 10 

 hours as well as of 16 hours. But it is not indifferent to photoperiods, as 

 flowering can also be induced earlier by subjecting the seedlings to increased 

 photoperiods without chilling. They have indicated the importance of pre- 

 vailing temperature during photoperiodic exposure ; with higher temperature 

 range the same photoperiod causes a greater shortening of the vegetative 

 phase. 



J. C. Sengupta and N. K. Sen (1944c) in their studies on the effect of 

 the time of sowing of mustard have made contradictory statements, i.e., that 

 the vegetative period shortens with low temperature ; further they mention 

 that the same variety shows a lengthening of vegetative period with the 

 shortening of the light period and a greater shortening of vegetative period 

 is observed with increased temperature range. These statements have been 

 criticised by B. Sen and S. C. Chakravarty (1944) as they have found, 

 under otherwise similar cultural conditions, that lower temperature in- 

 variably lengthens the vegetative period. J. C. Sengupta and N. K. Sen 

 (1944c) failed to show acceleration of flowering by low temperature treat- 

 ment of two varieties of mustard. This may be a case of varietal difference 

 and according to B. Sen and S. C. Chakravarty (1944) the period of low 

 temperature of 30 days in their experiments is too short a period to induce 

 vernalization. 



Miscellaneous Crops: — Gram (Cicer arietinum L.) — Vernalization 

 response in gram was noted by B. P. Pal and G. S. Murty (1941) and K. 

 P. Pillay (1944) although I. M. Vasiliev (1939) classed gram among 

 those plants which did not respond to vernalization treatment. The impor- 

 tance of low temperature in the phasic development of this crop has been 

 suggested by B. P. Pal and G. S. Murty (1941) from complete failure of 

 unvernalized plants to form even flower buds under natural days in summer. 

 Varieties with long life periods respond more than those with shorter 



