Stomatal responses to light and CO2 are dependent on KCI concentration

Abstract. The responses of stomata on detached epidermis of Commelina communis to light and CO₂ have been shown to be strongly dependent on the concentration of KCI in the incubation medium. There was a high sensitivity to the two stimuli in 50 mM KCI, but there were much reduced responses at lower and higher concentrations. It is considered that an appropriate choice of medium is essential if useful physiological studies of stomata are to be made using epidermal strips. At lower KCI concentrations, the ability of the stomata to open is thought to be limited by the availability of K⁺ ions, and at higher concentrations their ability to close may be affected because of an inhibition of the net efflux of K⁺. The production of malate was related to KCI concentration, and was largest in the medium containing zero KCI which supported poor stomatal responses to light and CO₂It is concluded that malate metabolism is unlikely to play a central part in the changes in guard cell turgor that are brought about by light and CO₂.