Effect of Cycocel and Abscisic Acid on Bud Growth of Redblush Grapefruit1

‘Redblush’ grapefruit seedlings, with and without leaves, were sprayed 1 to 5 times with 100 to 1000 ppm abscisic acid or 500 to 3000 ppm cycocel. Plants were subsequently exposed to several day/night temperature regimes which included 70°/50°, 90°/70°, and 95°/95°F. Both abscisic acid and cycocel delayed bud growth of leafy and defoliated seedlings. Abscisic acid was more effective than cycocel, and both compounds were most effective in delaying bud growth at lower temperatures, higher concentrations, and with more than one application. Abscisic acid was more toxic than cycocel, and both compounds were more toxic to defoliated plants than to leafy plants. Gibberellic acid overcame a correlative bud inhibition by the leaves, and abscisic acid decreased the effect of gibberellic acid.