Ecological Study on the Rice Varieties : V. Effects of the sowing time to the agronomical characters, or yielding capacity, time of young-ear differentiation, and elongation of internodes, in rice.

Abstract

1). It carried out the ecological study on the main agronomical characters; e. g., yielding capacity, time of young ear differentiation, and elongation of upper stem internode, in rice plants taken by the movement of sowing time, for a research material to the planning of rice culture. 2). The numbers of elongated internodes in rice culm increase by the late croping, but in case of over-late croping these numbers decrease because of temperature in early fall. 3). The critical air-temperature of young ear differentiation in rice plant was 18°C., such as usual mentioned. However, in case of very short time exposure, the differentiation are not occurence even under this temperature. On the other hand, the elongation of internodes in a culm were possible in spite of very short time exposure, under available lowest temperature. 4). The elongation of terminal internode was clearly affected by low temperature, but the effect of low temperature to the internodes of stem lower part which being started elongation seems to be a little. 5). In the choice of rice variety forhigh yield, it should be thought the sum-temperature of them from seeding to heading; e. g., 2, 300°C in early croping, 2, 100°C in standard croping, and 1, 800°C in late croping. This problem, varietal responces to temperature, is very importance to the planning culture of rice, and to increase of effective yielding capacity in each varieties.