The distribution of sugars (sucrose, glucose, and fructose) and related enzymes between the stem and the blossom halves of `Valencia' oranges [Citrus sinensis (L.) Osbeck] was determined at three stages of fruit development. The blossom half contained significantly higher concentrations of sugars during later stages of development and maturation (12% and 20%, respectively). Neither the enzyme marker for sucrose synthesis [sucrose-phosphate synthase (SPS)] nor enzymes of CO2 fixation (NADP-malic enzyme, PEP carboxylase, and PEP carboxykinase) were significantly different between the halves. Sucrose synthase (SS), the enzymatic marker for sink strength, had significantly higher activity in the blossom half during later stages of fruit development when rapid sugar accumulation takes place. These data suggest that differential distribution of sugars between the stem and the blossom halves of citrus fruit is, in part, the result of differential sink strength.
Changes in Antioxidant Activity during Fruit Development in Citrus Fruit
