POTASSIUM FLUXES IN MESOCARP TISSUE SLICES OF RIPENING PEACH FRUITS

Mesocarp slices of peach (Prunus persica L. Batsch) were analyzed for Rb+ uptake and K+ leakage at three stages of fruit development, and ATPase activity of an isolated microsomal fraction was characterized.
Rb+ uptake over a 0–60 min period was not linear, with higher rates during the first 15 min, strongly decreasing from 15 to 60 min.
K+ content varied with development reaching maximum level (25.4±0.01 μmol/gfw) at the second stage.
K+ leaked at higher rate during the first 15 min, and at sharply lower rates in the subsequent period.
Mannitol at concentrations close to tissue osmolarity reduced K+ leakage at all the three stages of development, whereas Rb+ uptake was enhanced at the first and second stage and inhibited at the third stage. (Mg,K) ATPase specific activity of microsomes increased as fruit developed.
K+ stimulation and enzyme inhibitors showed that most of the activity was associated with plasma membrane vesicles.
Optimum pH shifted from 7.0 to 6.0 and, at the third stage, a second peak of activity appeared at pH 7.0.

This evolution of membrane components and properties has to be considered when the biochemical bases of solute transport and allocation into peach fruit are studied.

II International Peach Symposium

R. Pinton, G. Vizzotto, Z. Varanini, G. Costa, A. Ramina, A. Maggioni

https://doi.org/10.17660/ActaHortic.1989.254.59