Auxin promotes apical dominance. Ethylene promotes rapid internode/petiole elongation in deep water rice plants. It helps leaves/ upper parts of the shoot to remain above water. Ethylene is used to initiate flowering and for synchronising fruit-set in pineapples. It also induces flowering in mango. ABA inhibits seed germination. stimulates the closure of stomata and increases the tolerance of plants to various kinds of stresses. Therefore, it is also called the stress hormone. ABA plays an important role in seed development, maturation and dormancy.