The effects of syntheticdl-dormin (Abscisin II) on the growth of the oat mesocotyl

Abstract

The growth-inhibitory properties of syntheticdl-dormin (Abscisin II) and itstrans, trans isomer were assayed using the oat mesocotyl section. Growth of this tissue was promoted by IAA and GA; dormin inhibited the elongation caused by both compounds and also the small amount of growth that occurred in blank buffer. A given concentration of dormin inhibited growth to about the same proportion in all these cases. IAA and GA mixtures stimulated growth in the presence of 2.0 mg/l dormin slightly more than the sum of growth with IAA+2.0 mg/l and GA+2.0 mg/l dormin. At lower concentrations of dormin (0.02 mg/l and below) the relationship was reversed. Dormin inhibited growth slightly at 0.02 mg/l but below that concentration it had no observable effect. Kinetin did not affect mesocotyl elongation, nor did it interact with the inhibition of IAA- or GA-stimulated growth. Thetrans, trans isomer had 1/30th the activity of the natural 2-cis-4-trans compount; when they were assayed together in mixtures of different proportions the inhibitions were additive. Most experiments were carried out with GA₃ but dormin also inhibited the action of gibberellins 1, 4, 5, 6, 7 and 9. The action of dormin was not competitive with that of IAA or GA. The effect of dormin as an inhibitor of plant growth is discussed.