Roles of plant hormones

Roles of auxin

Control cell elongation; prevent leaf abscission; maintain apical dominance; gravitropism; phototropism; stimulate ethene release; involved in fruit ripening.

Roles of gibberellin

Stem elongation; trigger mobilisation of food stores in a seed at germination

Roles of ethene

Causes fruit ripening; promotes abscission in deciduous trees.

Roles of ABA (abscisic acid)

Maintains dormancy of seeds and buds; stimulates cold protective responses (antifreeze production); stimulates stomatal closing.