Abstract
Possible roles of leaves and growing points in varietal differences of flowering time were examined by means of mutual grafting of 6 soybean varieties ranging from early to late. They were grown under either natural day length or various photoperiods. Recording of flowering time of the defoliated scions showed that production of fiowering stimulus (or stimuli) in leaves were mainly responsible for the varietal difEerences of flowering time. Although the varietal dif-ferences in the sensitivity of the growing points to the flowering stimulus were also significant, their role in determining fiowering time was not so much as in the production of the flowering stimulus.
