Effects of ABA in ‘Isolated’ Guard Cells ofCommelina communis L.

Abstract

The effects of 2 x 10⁻³ M ABA on ion fluxes in isolated guard cells of Commelina communis L. have been studied, using ⁸⁶RbCl and K⁸²Br, in epidermal strips in which all cells other than guard cells have been killed by treatment at low pH. The effect of ABA on influx is small, if present, and the major effect is a marked transient stimulation of the efflux of both ⁸⁶Rb and ⁸²Br at the plasmalemma; there is also an increase in the flux of ⁸²Br from vacuole to cytoplasm. The stimulation is transient, and the cells do not simply become more leaky. The results are not consistent with previous speculations on the mechanism by which ABA reduces aperture.