Effects of Fusicoccin in ‘Isolated’ Guard Cells ofCommelina communisL

Abstract

The effects of 3 × 10⁻² mol m⁻³ FC on rubidium fluxes and contents in isolated guard cells of Commelina communis L. have been studied using ⁸⁶RbCl. Fusicoccin causes a marked stimulation of influx and an immediate, apparently irreversible, decrease in efflux of ⁸⁶Rb. The effect on influx is usually more important in determining the new net flux of Rb. Observed fluxes differ markedly from those predicted by the Goldman-Hodgkin-Katz equation, suggesting that FC does not act solely via an effect upon the plasmalemma potential. Fusicoccin appears to have a more direct effect upon the ion movements associated with changes in stomatal aperture than either ABA or transfer to the dark. Observed changes in Rb content cannot account fully for the osmotic changes associated with aperture increase.