Annals of Botany 36: 525-532, 1972
© 1972 Annals of Botany Company
RESEARCH-ARTICLE |
Light and Hormone Interaction in Apical Dominance in Phaseolus vulgaris L.
Lincoln College Canterbury, New Zealand
Received: 11 August 1971
Gibberellic acid (GA2), kinetin, and indole-3yl-acetic acid (IAA) each at four concentrations (0, 0.5, 5, and 50 µM) were applied alone and in all possible combinations to roots of Phaseolus vulgaris L. grown under four different light regimes (7000, 14 000, 21 000, and 28 000 lx). GA3 increased growth of main stem and laterals but reduced apical dominance, especially in the absence of, or at low kinetin concentrations. A high level of kinetin lowered GA3 induced growth of main stems and, to a lesser extent, laterals. Kinetin greatly reduced apical dominance, especially in the absence of, or at low GA3 concentrations. IAA slightly reduced growth of main stems and laterals and slightly increased apical dominance. Generally the magnitude of the IAA effects were less than those of GA3 or kinetin and there were less interaction between IAA and other factors than between GA3 or kinetin and other factors. Light affected growth of both main stem and laterals but the effect was dependent on GA3 and kinetin levels and the interactions were complex. Generally a hormone balance seems to be operative with gibberellin-promoting growth of main stem and laterals and cytokinins and possibly auxins preventing excessive elongation. Differential responses between main stem and lateral may be due to different local hormone concentrations and over-all responses may be tempered by light intensity.