The Regulation of Stomatal Aperture in Tobacco Leaf Epidermal Strips

Abstract

Stepwise decreases in the stomatal aperture of tobacco leaf epidermal strips followed stepwise increases in the concentration of KHCOa added to bathing solutions. Removal of KHCOa from the bathing solution resulted in a rapid increase in aperture. The reduction in aperture caused by KHCO., both in the light and dark, can be reversed by the addition of ATP or phosphoenol pyruvate to the bathing solution. The stomatal opening, supported by a NaCl bathing medium, is reduced by the addition of NaHCOa? From the results it is suggested that HCO;/C02t increases the permeability of guard cell membranes causing a net efflux of water or ions or both from the guard cells.