Compartments and Permeability for Potassium in Developing Fruits of Tomato (Lycopersicon esculentumMill.)

Abstract

Permeabilities of plasmalemma and tonoplast, and the distribution of potassium between free space, cytoplasm, and vacuole, were estimated from the kinetics of the efflux of potassium from slices of tomato pericarp. The permeabilities of plasmalemma and tonoplast did not change during development, but the proportion of potassium in the cytoplasm increased during ripening. It is suggested that the effects of ethylene, and the changes taking place during ripening are not caused by changing permeabilities of membranes. Increasing activities of ions in the cytoplasm, rather than increasing membrane permeabilities, may explain previous observations that the efflux of solutes from fruit tissues increases during ripening.