Effect of Abscisic Acid on Bud Break and Shoot Elongation in Rosa and Syringa1

Abstract Abscisic acid 4 (ABA), when applied as an immersion application at 200 and 400 ppm during cold storage or as a spray application at 100 and 200 ppm at 2 stages of growth, was evaluated as an inhibitor of bud break and shoot elongation in dormant plants of Rosa cv. Helen Traubel and Syringa cv. Monge. ABA applied on 2 consecutive days at 100 and 200 ppm inhibited bud break in Rosa , but did not inhibit shoot elongation. ABA did not inhibit terminal and lateral bud break or shoot elongation in Syringa . Immersion applications at several dates during cold storage inhibited bud break and shoot elongation in Rosa and inhibited terminal and lateral bud break in Syringa . The most effective concentration in inhibiting bud break was 400 ppm. Time of application significantly affected bud break in Rosa and lateral bud break in Syringa , but did not alter shoot elongation in either plant.