Apical dominance cytokinins

Auxin, cytokinin, and other unknown substances are thought to regulate apical dominance.482 Application of cytokinin or overexpression of the 1PTgene shows a phenotype with a reduction in apical dominance.404 483 484 Arabidopsis mutants with increased levels of cytokinin also show reduced apical dominance 485-487 These results suggest that cytokinins play a role in the promotion of bud outgrowth. 

A root-derived suppressor negatively regulating the formation of roots has been hypothesized.497 This proposed mechanism, termed root apical dominance, is analogous to the means for apical dominance in shoots. The cytokinin, tZR, in root xylem sap is hypothesized to play the role of the main suppressor, and tZR transported from roots to shoots via the transpiration stream negatively regulates the formation of adventitious roots.365... 

It is generally known that the equilibrium between auxin and cytokinin concentrations is determinative for the type of organ regenerated from callus tissue in vitro. High cytokinin to auxin ratio leads to the shoot Ibrmation, whereas the change in the ratio on behalf of auxin eventuates mostly in root proliferation [253]. Concerning apical dominance and... 

Other processes involve an antagonistic action of auxin vs. cytokinin as well. For example, studies with transgenic plants containing genes for enhanced synthesis of either auxin or cytokinin has shown that both apical dominance and xylem development depend on the relative amounts of these hormones [32]. Enhanced auxin increases apical dominance and xylem formation, while enhanced endogenous cytokinin promotes the outgrowth of lateral buds, leading to a more branched plant, and decreased xylem development. 

BAP riboside, a synthetic cytokinin, supplied via the root system induced some effects in the shoot which are characteristic of the leaf curl syndrome, especially release of lateral buds from apical dominance and hyponasty. 

Cytokinins are a group of mobile phytohormones that play a critical role in plant growth and development by regulating leaf senescence, apical dominance, root... 

Wooley DJ, Wareing PF (1972) The interaction between growth promotors in apical dominance. I. Hormonal interaction, movement and metabolism of a cytokinin in rootless cuttings. New Phytol 71. 781-793... 

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