Changes in Concentration of Glucose, Fructose, and Total Soluble Solids in Flowers and Berries of Vitis Vlnifera

Abstract

Concentrations of glucose, fructose, and soluble solids in the flowers and berries of eight varieties of Vitis vinifera were determined every 7 to 11 days over an entire growing season (April 20 to October 20, 1964). Concentration of glucose and fructose in the inflorescence reached a maximum at the beginning of the bloom period. Concentrations of these sugars decreased during the latter part of bloom and remained at a relatively low level until véraison. Concentrations of glucose and fructose in the berries of all varieties investigated increased from less than 1% to over 10% in 40 to 50 days following véraison. The relative concentrations of glucose and fructose were approximately the same during prebloom, bloom, ripening, and ripe stages of flower and berry development. Per cent glucose exceeded that of fructose during the green berry stage, while fructose constituted the major sugar in overripe grapes. Overripeness was associated with a sharp decrease in tne concentration of glucose in the fruit and a corresponding increase in the level of fructose.