DEVELOPMENT IN CITRUS FRUIT OF A NONRESPONSIVENESS TO ABSCISSION- INDUCING CHEMICALS BY GROWTH REGULATORS

Three-year-old Citrus sinensis (L.) Osbeck (cv. Valencia) orange trees with 10 to 20 fruit on C. limon (L.) Burm. f. (cv. rough lemon) rootstock growing in growth chambers (26°/21° day /night, 12-hr day with 1300 microeinsteins m^-2sec^-1) were treated with 25ug GA₃, 25ug 2,4-D, or 50ug IAA in lanolin paste. In one set, 1 g of lanolin was applied to the leaf subtending the fruit, in the other set 1 g was applied to the upper hemisphere of the fruit. After another 6 weeks, the fruit were clipped with pedicels attached and treated with 20 ppm 'Acti-Aid' [(3-[2-(3,5-dimethyl-2-oxocyclohexy 1-2-hy= droxyethyl]-glutarimide)] or H₂O containing 0.1% Triton X-100. Ethylene (1), cellulase (2) and the fruit removal force (FRF) (2) were measured in 3- and 5-day samples.