Hormones

Ethylene is a plant hormone responsible for regulating fruit ripening and stress responses.
1. Fruit Ripening: Ethylene accelerates ripening in climacteric fruits like bananas, mangoes, and tomatoes.
2. Leaf Abscission: Causes leaf and flower drop by weakening cell walls at the base of petioles.
3. Stem Thickening: Promotes lateral expansion, resulting in shorter, thicker stems.
4. Root Growth: Enhances root initiation and adventitious root formation.
5. Applications of Ethylene in Agriculture:
(i) Used in artificial fruit ripening in commercial agriculture.
(ii) Promotes flowering in pineapples.
(iii) Induces synchronized fruit maturation in crops.

Indole-3-Acetic Acid (IAA) is the primary and most prevalent naturally occurring hormone from the auxin family, playing a crucial role in regulating plant growth and development.
Functions of IAA:
(i) Cell Elongation: Facilitates cell elongation, especially in shoot growth.
(ii) Apical Dominance: Maintains the supremacy of the primary shoot over the side branches.
(iii) Root Growth & Development: Aids in the initiation and development of roots.
(iv) Tropisms: Critical for phototropism (reaction to light) and gravitropism (reaction to gravity).
(v) Fruit Development: Encourages fruit development and helps prevent the early dropping of fruit. Produced primarily in the shoot apical meristem and young leaves, IAA is transported downwards through the plant by means of polar transport.