Metabolism of Sugars and Organic Acids in Immature Grape Berries

Abstract

Individual intact excised immature Sultana berries were supplied through the cut pedicel with C14-sugars and organic acids. When Cl4-hexoses were supplied malic and tartaric acids accounted for 25% and 10% of the total activity extracted after 24 hr., and sucrose was synthesized. It is proposed that the changes in the levels of organic acids during ripening are related to changes in the ability of the berry to synthesize them. Although administration of uniformly labeled sucrose resulted in the unequal labeling of glucose and fructose, the results indicate breakdown of sucrose by invertase. It is suggested that the route of entry of the pedicel-fed sugars into the berry may be different from the route taken by sugar translocated from the leaf.