DEVELOPMENT OF RADIOIMMUNOASSAYS FOR MEASUREMENT OF ABSCISIC ACID AND GIBBERELLINS DURING FLORAL INDUCTIVE TREATMENTS IN (CITRUS LATIFOLIA TAN.)

The hormonal control of citrus flowering was investigated by utilizing several approaches. Water stress for as little as 2 weeks induced flowering in container grown 'Tahiti' lime (Citrus latifolia Tan.) trees. Low temperature (18(DEGREES)C day/10(DEGREES)C night) induced a time dependent flowering response like that of moderate water stress. Low leaf xylem pressure potentials, as compared to controls, were found only under water stress treatment, suggesting that a common stress-linked event, separate from low plant water potential, is involved in floral induction. Leafless, immature cuttings were induced to flower by water stress treatment, suggesting that leaves are not essential for a floral inductive response.; Total abscisic acid (ABA) levels in leaves and buds increased as the duration of floral inductive stress increased and were higher under water than low temperature stress conditions as measured by radioimmunoassay (RIA). Total ABA levels decreased when water stress was alleviated by rewatering. Free ABA in leaves changed in a similar pattern to that noted for total ABA in trees grown under the above stress conditions. Levels of free ABA were less after water or low temperature than before stress and fell sharply after alleviating water stress in trees. Levels of free ABA were 4- to 35-fold lower than total ABA.; Antisera against gibberellins (GA) were produced by immunizing rabbits with a GA(,4)-adipic acid-bovine serum albumin immunogen. The antisera significantly cross reacted with GA(,1), GA(,7), and GA(,9). Gibberellin levels in leaves and buds collected from trees grown under water stress were dissimilar to those levels measured in low temperature stressed tissues as measured by GA RIA. Gibberellin levels decreased in leaves and increased in buds when water stress was alleviated by rewatering. The increased GA levels in buds corresponded to the alleviation of water stress. Gibberellins and ABA may play a role in water stress-induced bud dormancy and budbreak. Water and low temperature stress treatments induce flowering in 'Tahiti' lime, but the levels of ABA and GA do not change in a similar manner as a result of stress treatment.