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

        Image source: onlinesciencenotes

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.

Image source: creativeproteomics

 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.

References:

i) https://untamedscience.com/biology/plants/plant-growth-hormones/

ii) https://nph.onlinelibrary.wiley.com/doi/10.1046/j.0028-646X.2001.00281.x

Plant hormones ( Phytohormones )