The Effects of the Photoperiod and Temperature on the Time of Flower Primordia Formation and Flowering and the Expansion of Leaves on the Main Stem of the Late Soybean Variety (Oshoku-Aki)

Abstract

Experimental results obtained may be summarized as follows : 1) There is a critical photoperiod between 15 and 16 hours for the flowering of Oshoku-Aki soybean. (Fig. 2, 3). 2) The time of flower primordia formation of Oshoku-Aki soybean plant is not determined only by the gradual change of photoperiod such as the succession of seasons. (Fig. 2). 3) The time of expansion of leaves on the main stem is not affected by the photoperiod within the limits of 10-16 hours. (Fig. 3). 4) The time of flower primordia formation and flowering and the expansion of leaves on the main stem is more hastened by high temperatures (26°-30°C) than by low temperatures (14°-26°C). But, these are hastened no longer by temperature higher than 30°C. (Fig. 4, 5, 6, 7). 5) The rate of hastening time of flower primordia formation and flowering caused by high temperature is nearly equal to that of expansion of leaves on the main stem. (Fig. 4, 5, 7).