EFFECTS OF ABSCISIC-ACID INJECTION ON SUGAR AND ORGANIC-ACID CONTENTS OF CITRUS-FRUIT

The effect of exogenous abscisic acid (ABA) injections into citrus fruits in autumn on fruit drop, ABA catabolism, and sugar and organic acid contents were evaluated. Fruit drop increased after ABA injection proportional to the ABA concentration. Ninety-two percent of citrus fruits were retained 16 days after injection with 0.2 mu mol ABA per fruit. Injection of C-14-ABA revealed that exogenously applied ABA was catabolized to a level of about 10% in the fruits within four days. Injection of ABA caused an increase in the glucose and fructose concentrations, but had no effect on the organic acid in the juice. ABA appears to play a role in increasing Sugar content of fruit juice.