Plant hormones ( Phytohormones )

  • Organic compounds produced within the plants body.
  • Regulates growth and development in plants.
  • Move from the site of production to the site of action.
  • Mainly produced in apical bud, young leaves, root tip, embryo, etc.

Important characters

  • Produced at the apices of roots, stems and leaves.
  • Transported to other parts of the plants through phloem.
  • Promote growth in very low concentration.
  • All are organic in nature.
  • Used in extremely small amount.

Types of phytohormones:

  1. Auxins: indol-3-acetic acid(IAA), naphthalene acetic acid (NAA), indole butyric acid (IBA), etc.
  2. Gibberellins: gibberellic acid (GA3),GA4, GA5, GA7, etc.
  3. Cytokinins: kinetin, zeatin, adenine, etc
  4. Ethylene
  5. Abscissic acid

Plant hormones (types and functions) - Online Science Notes

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Roles and applications of auxins

  • Cell elongation.
  • Apical dominance.
  • Controlling abscission.
  • Root initiation and callus production in tissue culture.
  • Cell division in vascular cambium.
  • Weed control.
  • Flower initiation.
  • Parthenocarpy (development of fruit without fertilization)
  • Thinning of crops.
  • Inhibition of stem sprouting.
  • Prevent pre-harvest fruit drop.

Plant Hormone Analysis Service - Creative Proteomics

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 Roles and applications of gibberellins

  • Stem elongation and genetic dwarfism.
  • Parthenocarpy.
  • Bolting (rapid elongation in the inter-nodal length of rosette plants).
  • Seed germination.
  • Sex expression.
  • Flowering.
  • Breaking dormancy.
  • Enzyme formation.

Roles and applications of cytokinins

  • Cell division.
  • Cell enlargement.
  • Promote organ differentiation in callus.
  • Dormancy.
  • Counteraction of apical dominance.
  • Protein synthesis.
  • Delay of senescence (yellowing and falling older leaves from the plant).

     Roles and applications of ethylene

  • Fruit ripening.
  • Flowering.
  • Sex expression.
  • Root initiation.
  • Dormancy.
  • Senescence.

Roles and applications of abscissic acid

  • Abscission of leaves and fruits.
  • Dormancy of seeds.
  • Antitranspirant.
  • Flower initiation.
  • Adaptation.




Plant hormones ( Phytohormones )