Analysis of the ripening mechanism of rice under low temperatures

[摘要] The present study was carried out to investigate the mechanism of ripening in the rice plant under a low temperature (at 15°C) using as material several varieties of the plant of different resistance to irrigation with cold water. The experimental plants were defoliated artificially after degrees of their heading. The results obtained are as follows ; (1) As for the weight of individual grains ripened under the low temperature for 45 days, no relation was recognized between the ripening power under low temperatures and the degree of resistance to irrigation with cold water at the vegetative stage. (2) When the grains were subjected to a low temperature, the less the individual grainweight was, the more the ripening process under the low temperature was retarded. Moreover, it may be said that one of the reasons which induced ripening retardation more remarkably on Fukei-No.29 than on the other varieties, was a high ratio of the number of inferior spikelets to the whole spikelets. (3) Comparing with Fukei-No.29, Hakkoda showed a more rapid decrease of starch contents in the culm and a more rapid increase of it in the panicle under the low temperature as well as under the out-door temperature. (4) Under out-door temperatures, the total amounts of fertility in both Towada and Fukei-No.29 were found chiefly conditioned by the function of leaf -blades from 10 days after heading to harvest. In the varieties Hakkoda and Akita-No.1, however, there were found no such relations. (5) When the factors which influence the ripening power from 10 days after heading onwards under low temperatures are classified as (A) Contribution to the grain-production of the leaf-blade. (B) Contribution to the grain-production of the organs other than the leaf -blade, then, the effects of both A and B in Hakkoda and in Akita-No.1, respectively, would be considered remarkably larger than those in Fukei-No.29. On the other hand, in Towada variety although the effect of B was not found always fairly large, A proved itself of high role value through the whole life of the plant.

[学科分类] 农业科学（综合）