Question

Briefly describe the roles and interactions of hormones in determining axillary bud growth versus dormancy

Answer 1

Hormones Auxin and cytokinin coordinate the dormancy and outgrowth of axillary bud.

Phytohormone measurement and pharmacological experiments have firmly proved that high auxin accumulation inhibits the outgrowth of axillary bud.

In contrast, suppression of auxin activity by high level of cytokinin promotes the outgrowth of axillary bud.

Various studies have revealed the antagonistic roles of the plant hormones auxin and cytokinin during shoot architecture formation.

According to the lasting model, auxin is produced in the shoot apical and transported basipetally along the shoot which is important for the establishment of competition between branches. Auxin transport in the main stem blocked auxin export from the axillary buds, leading to bud dormancy

Contrarily, cytokinin can be transported into the buds to promote bud release. Recent evidences have proposed that cytokinin might regulate bud outgrowth through the control of auxin transport.

Decapitation, NPA or cytokinin treatment is able to remove the inhibition of auxin export in the axillary buds, resulting in the release of dormant buds.

Therefore, Auxin and cytokinin play antagonistic roles in the regulation of axillary bud dormancy or outgrowth.

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