Apical dominance is suppression of lateral bud outgrowth by the growing tip of a shoot. Removing that tip can allow previously inhibited buds to grow into branches, explaining why pinching a growing plant can make it bushier. The effect concerns the growth of existing buds, not simply whether they were formed.
It is tempting to attribute the response to one inhibitory substance. Time-resolved experiments in pea instead found that buds began growing after tip removal before local stem auxin content had declined. Sugar redistribution and sucrose feeding implicated resource supply in this early response. The result does not eliminate later hormonal regulation; it shows why measuring the order of events distinguishes a trigger from a correlated consequence.[ref]
Sugar demand, not auxin, is the initial regulator of apical dominance by Michael G. Mason and others. 2014, abstract and Results: bud release, auxin timing and sucrose supply
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