Stomatal opening in isolated epidermis of Commelina benghalensis L. heterophasic response to KCl concentration

The pattern of stomatal opening in epidermal strips detached from leaves of Commelina benghalensis was examined. Two different phases could be distinguished in the stomatal response to KCl, one at low concentrations of KCl (up to 60 mM) and the other at high KCl concentrations (above 100 mM). The stomatal opening at low KCl concentrations was stimulated remarkably by light or fusicoccin and was suppressed by abscisic acid. At higher KCl concentrations, the stimulation by light or FC as well as the inhibition by ABA was limited. Both phases of stomatal response to KCl were sensitive to carbonyl cyanide-m-chlorophenyl hydrazone. The results suggest that illumination or FC favours selectively stomatal opening only at low KCl concentrations. The ionic participation in the stomatal opening is similar to the heterophasic uptake of ions by plant cells/roots.