Flowering and fruit set of 'fortune' hybrid mandarin. Effect of girdling and growth regulators

Young orchards of 'Fortune' mandarin usually have a low productivity due to insufficient fruit set. The trees flower profusely, and most of the flowers are borne on leafless inflorescences. Leafy inflorescences are formed in a very low proportion and vegetative sprouts are nearly absent. This sprouting pattern results in a very low leaf/flower ratio. The carbohydrate reserves of the trees are lower than reported for other citrus cultivars, and are depleted shortly after anthesis. Therefore, the growth of the developing fruitlets depends mostly on current photosyntate formation. Most of the ovaries abscise shortly after flowering, having made very little growth. There is a main peak of abscission from early May until the end of June. Late fruitlet abscission lasts until late July. A GA3 spray at flowering retarded the abscission of reproductive organs, but failed to increase the final fruit set. On the other hand girdling did not affect the main wave of drop, but reduced late abscission, which resulted in an increase in set and final yield. Girdling did not increase the level of carbohydrates in the leaves, which indicates that carbohydrate use is determined by availability and fruit set may be limited by photosynthate supply. info:eu-repo/semantics/publishedVersion