A STRUCTURAL AND FUNCTIONAL STUDY OF THE COORDINATED REACTIONS OF INDIVIDUAL COMMELINA COMMUNIS L. STOMATA (COMMELINACEAE)

Opening and closure movements of individual stomata were analyzed by light microscopy, scanning electron microscopy, and time-lapse photomicrography. Turgor-pressure-induced changes in pore shape of Commelina communis L. stomata were observed in vivo and in fixed material. The ventral wall of the guard cells undergoes three-dimensional alterations during opening and closing. Stomatal aperture increases with increase in light intensity and with decrease in CO₂ concentration as previously described, while reactions to relative humidity and anaerobiosis are somewhat divergent from common experience. Low humidity induces opening rather than closure of stomata in well watered greenhouse plants, and lack of oxygen induces consecutive opening and closure movements. Individual stomata characteristically open by three distinct steps: (1) rapid opening; (2) immobility or slow closure; (3) relatively rapid opening. Since the timing of the second step varies for individual stomata, it is obscured by methods that integrate the responses of several stomata. The movements of individual stomata are well synchronized, but active communication between stomata in different areas can not be confirmed.