Ethylene is used in the artificial ripening of climacteric fruits (eg, apple, banana, mango). It is gaseous hormone. It also promotes fruit growth.
Abscisic acid is common stress hormone. It causes inhibition of a-amylase synthesis in barley seeds, dormancy of seeds and buds and also plays a role in stomatal closure.
Gibberellic acid was extracted from a fungus Gibberella fujikuroi (Fusarium moniliforme). It causes bolting enzyme formation and breaking of dormancy.
IAA (auxin) is natural auxin. Its main roles are apical dominance, root differentiation and parthenocarpy.