Effects of Light/Dark on Cation Fluxes in Guard Cells ofCommelina communisL.

The effects of light/dark on cation fluxes in isolated guard cells of Commelina communis L. have been studied, using 86RbCl and 22NaCl. Transfer to the dark has no effect on 86Rb influx, but produces a marked transient stimulation of 86Rb efflux, similar to that seen previously on adding ABA. The 86Rb efflux falls on return to light only during the period of stimulated flux; after the transient, return to light has no effect on efflux. The ability to produce this transient stimulation on transfer to the dark is recovered in a subsequent light period. In general, in Na-loaded cells, the stimulated efflux is not seen. and the cells do not close in the dark. The results are not consistent with a simple permeability or potential change, but suggest a specific ion excretion activated by the transfer to the dark.