Photoperiodism in rice

Summary

The influence of 10 hour short-day photoperiod (8–00 a.m. to 6–00 p.m.) has been studied on four late-winter varieties of rice, C. No. 3 (a selection from Kajal Champa of Cuttack District), S.R. 26 B (a selection from Kalambank of Puri District), F.R. 13 A and F.R. 43 B (both flood-resistant varieties) of Orissa. Out of these four varieties, C. No. 3, S.R. 26 B and F.R. 13 A react to short-day photoperiod likewise and the other variety F.R. 43 B behaves differently. Short days for 3 weeks during the seed-bed stage bring about a delaying effect in ear emergence in the above stated three varieties. As the duration of short-day treatment increases to 4, 5, and 6 weeks in the seed bed, there is more and more delay in the time of ear emergence. The interesting point is that when the short-day phctoperiod has been given to the seedlings for 6 weeks and then continued after transplantation till ear emergence, a reverse effect, namely, a marked earliness in ear emergence is noted. Variety F.R. 43 B has behaved a little differently. In the prolonged short-day treatment set, 85% of the plants have shown an average earliness of 35 days in ear emergence, while the rest 15% have shown an earliness of 68 days in ear emergence.