Control of Lateral Bud Growth inPhaseolus vulgarisL. by Ethylene in the Apical Shoot

Elongation growth of the first trifoliate leaf axillary bud was induced by physical restriction of the apical growth or by treating the apical shoot with ethylene or ethephon. There is evidence to suggest that the promotion of axillary bud development by ethylene action on the apical shoot was associated with the availability of freely diffusible ethylene in the tissues of the treated shoot. Loss of apical dominance was not, apparently, directly dependent on either the internal ethylene concentration (i.e. concentration in the vacuum – extracted gases) or on the rate of ethylene emanation. The effects of aminoethoxyvinyl glycine (AVG) and silver nitrate on ethylene production were examined. Although treatment of the shoot with tri – iodobenzoic acid (TIBA) induced various morphological responses in the plant, including axillary bud outgrowth, which appeared similar to the responses to ethylene, the initial effect of TIBA is not thought to be ethylene – mediated.