Plant Growth and Development

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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


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)


  • 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.


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


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

Next Topic : Branches of Biology


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