Effects of Auxin, Auxin-Transport Inhibitors and Mineral Nutrients on Apical Dominance in Pharbitis nil

Abstract

Summary An analysis and comparison was carried out in Pharbitis nil on the effects of treatments with nutrients (N, P and K), auxin and the auxin transport inhibitors, triiodobenzioc acid (TIBA) and 2-(1-pyrenol) benzoic acid (PBA), on lateral bud outgrowth in decapitated/intact upright plants and/or in plants with inverted shoots. Although it could not be unequivocally determined whether or not the initiation of bud outgrowth was dependent on a nutrient signal, it was clearly demonstrated that the continued outgrowth of the lateral bud was dependent upon an continuous supply of nitrogen and phosphorous via the root system. There was also evidence, though not conclusive, for a significant role of auxin in the control of apical dominance. IAA treatment of decapitated shoots delayed but outgrowth. Stem treatment with the auxin transport inhibitors TIBA and PBA promoted lateral bud outgrowth. The shoot-inversion approach as employed here allowed for the analysis of interaction between the shoot apex and lateral bud both before and after the release of apical dominance.