Effect of Hormone Antagonist on the Rooting of Shoot Cuttings

Abstract

Antagonists of plant growth regulators offer the possibility of observing the physiological effects of a lowering of the natural growth regulator status of tissues, and the present results were obtained while exploring such possibilities. Regeneration on shoot cuttings was chosen for observation because exogenous auxin (15), gibberellin (2), and cytokinin (6) were known to affect root formation on them, but little was known about the contributions of endogenous regulators to the observed effects. The results are relevant also to the increases in root numbers on shoot cuttings produced by plant extracts (3, 5, 8). The regulators and antagonists employed were the auxins, IAA and 2 4-D, the auxin antagonist, PCPIB,' the gibberellin, GA, and the gibberellin antagonist, EL 531.