Vernalization and Photoperiodism — 126 — A Symposium 



duration. Long photoperiods are also found to bring about earlier flowering 

 and short photoperiods tend to retard flowering. Combination of low tem- 

 perature and long days still further accelerates flowering. Like mustard, 

 vernalized seeds of gram undergo no devernalizing effect when such seeds 

 are stored for more than 3 months or subjected to high temperature (B. P. 

 Pal and S. Ramanujam, 1944) . But exposure of seeds to low temperature 

 and high temperature alternately does not produce vernalization. It has 

 further been shown that seeds could also be vernalized during the time of 

 ripening on the plant by low temperature treatment. 



Jute (Corchorus capsularis L. and C. olitorius L.). — For the production 

 of fibre from jute, acceleration of flowering is of no practical importance, 

 but formation of early seeds has obvious advantages for breeding more gen- 

 erations in one year and this has been claimed by J. C. Sengupta and N. K. 

 Sen (1944&), and B. K. Kar (1944) in their studies on photoperiodic 

 effect on jute. Short day exposure reduced the fruiting days from 135 to 36 

 days with a possibility of growing more generations in the same season 

 (J. C. Sengupta and N. K. Sen, 1944b). On the other hand long photo- 

 periods were found to delay flowering. 



Cotton {Gossypium spp.) — Pre-sowing temperature treatments on cot- 

 ton seeds have little effect but short days produce early flowering (B. Sen, 

 .1944-45). 



Sugarcane (Saccharum officinarum L.). — By varying day length the 

 flowering of sugarcane varieties has been controlled by N. D. Yusuff and 

 N. L. DuTT (1945). It is interesting to note that short days of 2 hours 

 induce flowering in wild forms (Saccharum spontaneum L.) which do not 

 normally flower at Coimbatore (Lat. 11.0° N.). Long days are found to de- 

 lay flowering in the cultivated varieties. By controlling light periods flow- 

 ering of late and early strains of cultivated and wild Saccharum spp. has 

 been so adjusted that a wide crossing is possible. 



Soy bean {Glycine hispida Maxim.) — No appreciable effects of differ- 

 ent temperatures on the flowering of Soy bean were found by B. P. Pal 

 and G. S. Murty (1941). However, a remarkable effect of diminished 

 photoperiod of 9.5 hours on the acceleration of flowering with improved 

 quality of beans has been recorded by B. Sen (1944-45). 



Biochemical Changes in Relation to Vernalization and Photoper- 

 iodism in the Tropics : — Comparing the enzyme contents of vernalized and 

 unvernalized seeds B. Sen (1943-44, 1944-45) found that diastase and phos- 

 phatase in wheat ; lipase, catalase and phosphatase in mustard and diastase 

 in barley are higher in the vernalized seeds. In order to understand fully 

 the effects of photoperiods on the acceleration of flowering and growth rate 

 of rice culminating in increased grain yield, investigations on the assimila- 

 tion changes of the plants subjected to different treatments were carried out 

 by S. M. Sircar and his students, the approach to the problems being dif- 

 ferent from that of previous workers in this field. Photoperiods necessary 

 for the acceleration of flowering of winter rice were applied in the seed bed, 

 and after transplantation the chemical composition of the plants was deter- 

 mined at frequent intervals, with a view to ascertaining the differences in 

 metabolites caused by the photoperiodic induction. The work on carbo- 

 hydrate metabolism (S. M. Sircar and P. M. Samantaray, 1942) showed 



