抄録
We have investigated by using the same materials as these of previous report the relation between day length temperature and heading time of those rice varieties that are principal in every towns and villages sampled in 1951. Aaccording to many studies, we may explain the result of this research as follows. Generally, when basic vegetative grown is completed, rice plant turned into ear differentiating stage. But this differentiation is to be contorolled by day-length and temperature ; differentiation is inhibited under certain degree of long day-length or low temperature in this stage, and range of inhibiting day-length and temperature differs with varities. In practical culture, we expect rice plant not only to sprout ear, but also to bring good harvest. Therefor the suitable variety and season are choosen against contorol of long day and low temperature. When we calculated the length of the shortest intervals between transplanting and heading, all varieties, from the earliest one-Norin 20 to the latest one Zuiho, show 50∼75 days. We consider the minimum quantity of growth for normal yield may be achieved within these days
