Investigation on the effect of alternate bearing and 2,4-D application on changes in reserved starch and activity of abscission enzymes in Satsuma mandarin

The effect of seasonal changes pattern of internal carbohydrates of trees on flowering, fruit set, and fruit development is an important subject for orchard management and physiology of fruit production. With the aim of alternate bearing control, a research was performed based on RCBD design under dry farming condition at Ramsar on 24 years old of Satsuma mandarin trees. Main purposes of this research were to investigate the partitioning of soluble and insoluble carbohydrates of trees during on and off years, evaluating the relation between carbohydrate reserves, flowering and fruit set, effect of 2,4-D foliar application on carbohydrate partitioning, abscission enzymes activity, control of alternate bearing and crop quantity and fruit quality. Results showed that bearing level had a meaningful effect on carbohydrate partitioning and its seasonal fluctuations. Activity of abscission enzymes were affected by crop load as well as exogenous 2,4-D application. Results also showed that 2,4-D could regulate alternate bearing of Satsuma mandarin trees and improve fruit weight. Based on obtained information, the leaf starch content at the end of June-drop is a reliable biochemical index for predicting of final individual fruit weight at the same year as well as the flower density in the next year.