Change of Flux of Orthophosphate Between Cellular Compartments in Ripening Tomato Fruits in Relation to Climacteric Rise in Respiration

Abstract

Slices cut from the pericarp of mature-green tomato fruit and incubated at 18°C in isotonic mannltol (0.25 M) containing 25 µM CaSO₄ undergo changes in rate of respiration and in colour similar to whole ripening fruits. When fluxes of orthophosphate were analysed using washout techniques, the fluxes from vacuole to cytoplasm and from free space to cytoplasm increased markedly as the rate of respiration of the fruits from which they were cut increased. This is consistent with stimulation of the enzyme phosphofructokinase (previously identified as the point of regulation of respiration) by increasing concentration of orthophosphate at the enzyme site.