Sucrose Breakdown and Synthesis in the Ripening Grape Berry

Abstract

Sucrose is the major translocated sugar in the grapevine (Swanson and EIShishiny 1958), but in the berry glucose and fructose together make up the bulk of the sugar content at all stages of development (Kliewer 1965a). The inversion of sucrose to glucose and fructose in ripening berries is suggested by the presence of invertase (Arnold 1965) and by the occurrence of approximately equal amounts of glucose and fructose (Kliewer 1965a). During the early stages of berry development, glucose and fructose concentrations are low, but at the onset of ripening there begins a phase of rapid glucose and fructose accumulation (Kliewer 1965a). Besides sugar, the other major soluble constituents of grapes are malate and tartrate. The concentrations of both substances increase rapidly in the immature berry, but when ripening commences sharp decreases occur, particularly in the concentration of malate (Kliewer 1965b). Some workers believe that malate and tartrate are translocated from the leaves (Amerine 1956; Peynaud and Maurie 1958) but there is evidence that some at least of the malate and tartrate is synthesized in the berry (Hale 1962). The mechanisms of the syntheses of malate and tartrate in the berry are not known.