Intercellular pH of Peach and Apricot Mesocarp

Abstract

Intercellular pH of developing peach (Prunus persica (L.) Batsch) and apricot (Prunus armeniaca L.) mesocarp was estimated from the pH of small volumes of water in contact with washed cut surfaces. In both fruits, the pH changed from neutral to acidic as the rate of growth changed from slow and declining to rapid. In peaches, the changes in intercellular pH and growth rate occurred gradually over a 4-week period, while in apricots these changes were more rapid. Studies on the mechanism of the pH change showed the measured pH values to be a reasonable and adequate estimate of intercellular pH in vivo. We propose that intercellular acidity influences mesocarp development in at least two ways. It allows high rates of assimilate utilisation by inducing activity in existing intercellular invertase, and it predisposes the tissue to ripening.