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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]

John Doebley studies the genetics of changes in plant form, especially the domestication of maize from teosinte. His own research profile describes quantitative genetics as a principal approach.^[ref]

In 1997, Doebley and colleagues identified teosinte branched1 as a regulator associated with the stronger apical dominance of maize. Higher expression in maize connected altered gene regulation to reduced lateral branching. This work made a major crop difference experimentally approachable as a change in a developmental programme rather than an inexplicable difference between two plant forms.^[ref]

A PNAS biographical profile includes a labelled photograph taken in 2003.

Maize is the domesticated grass Zea mays, grown for its grain. A maize kernel is a caryopsis: a fruit in which the enclosing wall is closely attached to the seed. The male flowers form the tassel, while female flowers occur in ears; wind carries pollen between them. Having both kinds of flowers on one plant is different from having separate male and female plants.

Its domestication from teosinte provides a concrete example of how changes in developmental regulation alter a crop. Research on apical dominance identified the teosinte branched1 gene as a major contributor to the suppression of side branches in maize. Comparing gene activity and mutant plants connected a conspicuous architectural difference to regulation of axillary growth.^[ref]

Michael G. Mason is a plant researcher credited as first author of a 2014 study of sugar supply and apical dominance. The paper lists an affiliation with the School of Biological Sciences at the University of Queensland and credits Mason with research design, experiments, analysis and writing.

The team measured the timing of pea bud growth after removal of the shoot tip, alongside changes in stem auxin and sugar supply. Buds began to grow before the measured local decline in auxin; supplying sucrose also promoted release from inhibition. The result challenged a simple account in which depletion of apically supplied auxin must be the immediate trigger. Its strength is the combination of time-resolved observations and a direct resource manipulation, rather than correlation between branching and sugar abundance alone.^[ref]

Teosinte branched1, conventionally written tb1 for the gene, encodes a transcription factor that suppresses outgrowth of lateral buds in maize. It is a major component of the difference in apical dominance between cultivated maize and its wild teosinte relatives.

John Doebley and colleagues connected tb1 expression and mutant morphology to suppression of axillary growth. Cultivated maize showed increased tb1 expression in the relevant comparison, linking altered regulation of a developmental gene to a conspicuous domestication trait.^[ref]

This illustrates why regulatory change matters: a large difference in branching need not require inventing an entirely new protein. Changing where or how strongly an existing regulator acts can reshape the plant.