Effect of different temperatures given to the culm-base of rice plant on the emergence and elongation of its tiller under controlled environment.

The emergence and elongation of the tiller buds of rice plants are greatly affected by the environmental temperature, especially by the temperature around the culm-bases where the tillers differentiate. Temperature switching from low to high and vice versa was carried out and varieties used were Norin 1 and Zosan 1. The experiments were conducted in growth cabinets at 25°C (light) and 18°C (dark). The results : (1) Compared with those given no temperature treatment, tillers increased in number in low temperature treatment (15°C) . On the contrary, emergence was inhibited in the high temperature treatment (33°C). (2) In Zosan 1, the emergence of secondary tillers ceased completely, while in Norin 1, there were six secondary tillers in the high temperature treatment. (3) In the temperature switching treatments in the 8th leaf stage of the main stems, the tillers which were inhibited in growth during the supply of high temperature water emerged after switching in the former treatment, and, synchronous regularity was disturbed in this case. In the inhibited in growth after switching to high temperature. The inhibition of emergence by high temperature was more conspicuous in Zosan 1 of the heavy panicle type.