Vernalization and Photoperiodism — 128 — A Symposium 



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Postscript: — Vernalization by high temperature has practical difficulties. Radicles and plumules 

 emerge from the seed coat during treatment involving difficulties of transportation and broadcast 

 sowing. This has been overcome in two varieties of summer rice by limiting the moisture content of 

 seeds to 25 to 30 percent of fresh weight. Seeds at this moisture content germinated without radicles 

 and plumules penetrating the seed coat and gave vernalization response when exposed to high tem- 

 perature, 35° C, for 10 and 20 days (S. M. Sircar and B. N. Ghosh, Nature 159: 605, 1947). 



Further work by S. M. Sircar and S. K. Mukherjee (in press) on nitrogen metabolism of a 

 winter rice variety, Rupsail, has shown that the total-N, protein-N, soluble non-protein-N, amide-N, 

 amino-N and ammonical-N were higher in both leaves and stems of 8-hour day plants than in the 

 controls. These nitrogenous substances increased in the leaves up to three weeks of photoperiod 

 while an abrupt fall in total-N and protein-N was noted at the end of the fourth week. On the 

 other hand, in the stems total-N and protein-N decreased and soluble non protein-N, amide-N, amino- 

 N, and ammonia-N increased after successive weeks of photoperiod. These results in conformity 

 with the work of S. M. Sircar and B. N. De (1947) indicate that greater depletion of total nitro- 

 gen in the leaves after the plants had considerably gained in dry matter in the first three weeks with 

 a corresponding increase in all soluble nitrogen fractions in the stem is due to translocation of nitro- 

 genous substances to growing points inducing a considerable earliness in this variety where flowering 

 takes place within 6 weeks of 8 hours photoperiod. 



