Light-dependent Influx and Efflux of Potassium of Guard Cells during Stomatal Opening and Closing

Abstract
Stomata in epidermal strips of Vicia faba opened in light and closed in darkness when floated on dilute K+ solutions. Opening and closing, respectively, paralleled the fluxes of labeled K+ into and out of the strips. The gain and loss of K+ by the strips were shown by colbaltinitrite stain to be centered at guard cells. Intact epidermal cells, however, appeared to take up K+, complicating interpretation of the data.