Plant Growth Hormones
Plant growth and development are maintained by hormones/regulators are variously described as plant hormones or phytohormones.
This is one of the common topic in competitive exams like the Kerala PSC Exam,SSC, Railways
Major Phytohormones
Auxin
Chemical Name – Indole 3 Acetic acid (IAA)
It is also known as Natural Auxin
Synthetic Auxin: Naphthalene Acetic acid (NAA) and 2,4-Dichloro Phenoxy Acetic acid(2,4-D)
Functions of Auxin
- Auxin is responsible for Cell elongation and longitudinal growth
- It promotes root growth and root initiation
- Induces Parthenocarpy (ie; formation of seedless fruits without fertilization)
Gibberelins
- It was discovered by Kurosawa in 1926
- GA3 is the most important gibberelic acid
Functions of Gibberellins
It helps the Elongation of Stem
Gibberelin helps in Breaking of dormancy
Control growth and development of fruits.
Cytokinins
It was invented by Miller in 1955
Naturally occurring cytokinin : Zeatin
Functions of Cytokinins
- It acts on cell division but have little or no effect on growth
- It stimulates the growth of lateral buds and thus suppress apical dominance
- Increase shelf life of marketed vegetables
Ethylene
it was invented by Burg in 1962
It is a simple gaseous plant hormone
It is also known as ripening hormone
Functions of Ethylene
- Inhibits Growth
- Helps in fruit growth and ripening
- Flowering in pineapple ,mango and various other plants is induced by the application of ethylene
Abscisic acid
It was discovered by Adicote and Corsin in 1965.
it functions as growth inhibitor
Functions of Ethylene
- Inhibits growth and metabolism
- Seed development and germination
- Maintains dormancy in many seeds
