CARBOHYDRATE METABOLISM IN GA3-TREATED AND POLLINATED RABBITEYE BLUEBERRY FRUITS.

Abstract

Carbohydrate metabolizing enzymes and carbohydrate accumulation were examined in pollinated, non-pollinated and GA3-treated blueberry fruit. Our hypothesis was that GA3 induces fruit set in blueberry by increasing the carbohydrate metabolizing enzyme activity in the ovary with a subsequent increase in carbohydrate mobilization. FW of non-pollinated fruits increased little between 0-45 days, when abscission occurred. FW of GA3-treated and pollinated fruits increased from 20 mg at anthesis to 1 and 2 g, respectively, at ripening. Insoluble invertase activity decreased from 15 μmol gFW-1 h-1 at anthesis to 3 μmol gFW-1 h-1 at 45 DAA for GA3-treated and pollinated fruits, and 9 μmol gFW-1 h-1 in non-pollinated fruits. Soluble invertase was undetectable in any treatment from 0 to 45 days, but rose sharply, averaging 57 μmol gFW-1 h-1 at ripening for both GA3-treated and pollinated fruits. No consistent correlation was found between ovary carbohydrate concentration and fruit growth among treatments. Differences in fruit set and size among treatments were not due to differences in enzyme activity and subsequent differences in carbohydrate accumulation.