Interaction between Hormones, Light, and Nutrition on Extension of Lateral Buds in Phaseolus vulgaris L.

Abstract

Gibberellic acid (GA3), kinetin, and indol-3yl-acetic acid (IAA) contained in lanolin were applied in various combinations and concentrations to decapitated stems and petioles and to buds of Phaseolus vulgaris L. GA3 applied alone usually promoted growth of main stems and laterals but this was by no means consistent and occasionally it acted in the opposite way. IAA applied alone reduced lateral bud extension slightly, but not consistently; however, when applied with GA3 or GA3 plus kinetin, it often markedly inhibited the promotion caused by these compounds. On occasions, however, GA3 and IAA acted synergistically to promote and sometimes to inhibit lateral shoot growth. Kinetin alone showed few significant effects on lateral shoot growth but applied with GA3 it often dramatically increased GA3-induced growth of main stems and laterals. The diversity of these results, which parallels that found in the literature, was shown to be partly dependent on the point of hormone application and age of the plant or bud, on concentration of hormone and on light intensity or nutrition. However, no meaningful relationships were found and it is concluded that growth of laterals and main stems is dependent on a hormone balance which can be critically modified by a wide range of internal and external factors the nature of which is still to be determined.