水稲の生殖生長期間の長短に及ぼす温度の履歴効果について

抄録

Memory effect (hysterisis) of temperature during the period of vegetative phase on the length of the period of reproductive phase of rice plants was examined under the precisely controled environmental conditions. 1. 9 leading rice cultivars grown in different rice zone in Japan from northern to southwestern districts were selected and 9 treatment plots (3 different levels of temperature during the period of vegetative phase and reproductive phase respectively) were adopted for the experiment. 2. Length of the period of vegetative phase, days from sowing to the stage of young panicle differentiation, was prolonged and marked varietal difference in prolongation was observed by low Temperature during the proper period. Delay of young panicle differentiation was more remarkable in cultivars grown in southwestern rice zone than that in northern district cultivars. Central and northeastern district cultivars lied between former 2 groups of cultivars. Varietal difference in the length of the period of vegetative phase was not remarkable in the moderate temperature plots. 3. The length of the period of reproductive phase was markedly affected by the temperature of the proper period. Heading was remarkably delayed by low temperature during the period of reproductive phase and considerable varietal difference was observed. 4. As far as the experiment concerned, cultivars examined was able to be classified into following 3 groups from the view point of the histerisis effect of temperature during the period of vegetative phase on the length of the period of reproductive phase ; (i) Length of the period of reproductive phase solely depends on temperature of the proper period and is irrelevant to the temperatue during the period of vegetative phase (typified by var. Sasanishiki). (ii) Low temperature during the period of vegetative phase lengthen the period of reproductive phase in case where the temperature during the period of reproductive phase, and when the temperature during the period of reproductive phase is low, hysterisis effect of vegetative phase temperature does not come out (typified by var. Sorachi). (iii) Temperature condition during the period of vegetative phase exerts a remarkable influence upon the length of the period of reproductive phase as the histerisis effect is shown irrespective of the temperature during the period of reproductive phase (typified by var. Harima).