EFFECTS OF ABA IN ISOLATED GUARD-CELLS OF COMMELINA-COMMUNIS L

The effects of 2 .times. 10-5 M ABA [abscisic acid] on ion fluxes in isolated guard cells of C. communis L. were studied, using 86RbCl and K82Br, in epidermal strips in which all cells other than guard cells were 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.