Flowering and Podding Responses to Cool Temperature Treatment Imposed During the Flowering Period of Soybeans

Abstract

Flowering and podding under cool temperature treatment were investigated using three determinate soybean varieties, Enrei, Okushirome and Suzuyutaka.Plants were treated at 15°C/13°C(day/night)in a growth chamber for 2 weeks starting 4 days after the beginning of flowering.Open flowers in both treated and nontreated plants were tagged every day.Pods were counted at maturity and related to the time of flowering.Suzuyutaka was not affected by the cooling treatment.For Okushirome, the number of flowers decreased when treatment was started but the podding ratio was unaffected for the first 10 days.For Enrei, in addition to a decrease in the number of flowers, flowers produced both 2 days before and after the start of treatment did not produce pods.Also for Enrei, a considerable increase in the podding ratio was observed during the latter half of the cooling treatment.Thus, Enrei showed higher sensitivity to cool temperatures as compared to Okusirome and Suzuyutaka, especially at the stage of early flowering.