Stomatal Opening and Photosynthesis in Greening Leaves of Vicia faba L

The development of the ability of stomata to open in greening leaves of broad bean (V. faba L.), and the onset of photosynthetic activity in chloroplasts isolated from these leaves, were examined in parallel. The stomata showed biphasic kinetics of opening. They began to open after 4 h of illumination, which correlated with the beginning of cyclic phosphorylation. The extent of the stomatal aperture remained small (2 �m) until 8 h after the onset of illumination, at which time wider apertures were observed (6-8 �m). This wider opening was concurrent with the detection of carbon dioxide fixation seen in isolated whole chloroplasts from the greening leaves.