Numerous Hormonal Interactions Influence Plant Growth and Development

Auxin

Stimulates cell elongation; involved in phototropism, gravitropism, apical dominance and vascular differentiation; stimulates ethylene synthesis and induces adventitious roots in cuttings

Cytokinin

Stimulates cell division, reverses apical dominance, involved in shoot growth, delays leaf senescence

Gibberellin

Stimulates cell elongation, bolting and flowering in biennials; regulates production of hydrolytic enzymes in grains

Abscisic acid

Inhibits growth; stimulates stomatal closure; maintains dormancy

Ethylene

Stimulates fruit ripening, leaf and flower senescence, and abscission

Brassinosteroids

1. Stem elongation

2. Pollen tube growth

3. Grass leaf bending at sheath

4. Xylem differentiation

5. Enhanced ethylene production

Jasmonic acid

1. Inhibits seed/ pollen germination

2. Retards root growth

3. Promotes curling of tendrils

4. Induces fruit ripening and abscission of flowers

5. Involved in insect and pathogen resistance

Ethylene

Tissues of ripening fruits, nodes of stem, senescent leaves and flowers

Abscisic acid

Leaves, stems, green fruit

Gibberellin

Meristems of apical buds and roots, young leaves, seed embryo

Cytokinin

Synthesized in roots and transported to other organs

Auxin

Meristems of apical buds, embryo of seed, young leaves