EFFECT OF FUSICOCCIN ON PHOTOSYNTHETIC INDUCTION IN SOYBEAN LEAVES

The time-course of photosynthetic induction was studied upon irradiati on of control and fusicoccin-treated soybean (Glycine max L.) leaves. Control leaves showed a rapid phase in which the net rate of carbon as similation, P(N), increased to a plateau within about 8 min of irradia tion, followed by a slower phase (8-25 min) in which P(N) increased fu rther. Application of fusicoccin stimulated stomatal opening and speed ed up the second phase considerably, but had no noticeable effect on t he first phase. The results suggest that the second phase of photosynt hetic induction of control leaves is stomatally determined.