CHANGES IN CARBOHYDRATE IN BRANCHES AND ITS RELATION TO FLOWERING IN AVERRHOA CARAMBOLA

Seasonal changes in carbohydrate concentration in different branches of 8-year-old Averrhoa carambola ‘B10’ were studied. The results showed that at the first flowering stage, the proportion of branches flowering (flowering branch rate) and the number of flowers in one panicle on thick branches (2±0.2cm in diameter) tended to be more than those in thin ones (1±0.1cm in diameter). Two peaks of total soluble sugar, sucrose and fructose concentrations were found at the two stages of flower bud emergence, and two minima were found at the two later fruit development stages. Sucrose concentration in xylem was higher than that in phloem in thick branches. Glucose concentration in thin branches was higher than that in thick ones. Starch concentration in phloem of thick branches was higher than that in xylem of both thick and thin branches. Starch concentration in phloem in thin branches was low and changed little over the course of the study. Two minima in starch concentration in thick branches and in the xylem of thin branches were found at the two stages of flower bud emergence, and two peaks in these tissues were found at two stages of later fruit development. These trends were generally opposite to those of soluble sugar concentration. The results suggested that a high starch concentration in branches before flower formation and a high soluble sugar concentration during flower bud formation might be beneficial to flower bud formation in star fruit.