Growth regulators, also known as plant growth regulators (PGRs) or phytohormones, are chemical substances that influence the growth and development of plants. They play a crucial role in various physiological processes, including cell division, elongation, differentiation, flowering, fruit development, and responses to environmental stimuli. PGRs can be naturally occurring within the plant or synthetically produced for agricultural and horticultural applications. The major classes of plant growth regulators are:



  1. Auxins:

    • Function: Promote cell elongation, root initiation, and differentiation.
    • Examples: Indole-3-acetic acid (IAA), Indole-3-butyric acid (IBA), Naphthaleneacetic acid (NAA).
    • Applications: Used to promote rooting in cuttings, control fruit drop, and enhance growth.

  2. Cytokinins:

    • Function: Promote cell division, delay leaf senescence, and influence nutrient mobilization.
    • Examples: Kinetin, Benzyladenine (BA), Zeatin.
    • Applications: Used to promote shoot formation, delay aging in leaves, and improve crop yields.

  3. Gibberellins (GAs):

    • Function: Promote stem elongation, seed germination, and flowering.
    • Examples: Gibberellic acid (GA3), GA1, GA4.
    • Applications: Used to increase fruit size, break seed dormancy, and promote flowering in some plants.

  4. Abscisic Acid (ABA):

    • Function: Inhibits growth, promotes stomatal closure during water stress, and induces seed dormancy.
    • Examples: Abscisic acid.
    • Applications: Used to manage stress responses in plants and improve seed storage.

  5. Ethylene:

    • Function: Promotes fruit ripening, leaf abscission, and flower senescence.
    • Examples: Ethylene gas.
    • Applications: Used to ripen fruits like bananas and tomatoes, and to induce flowering in certain plants.

  6. Brassinosteroids:

    • Function: Promote cell expansion and elongation, vascular differentiation, and stress resistance.
    • Examples: Brassinolide, Castasterone.
    • Applications: Used to improve plant growth and resilience to environmental stresses.

  7. Jasmonates:

    • Function: Regulate plant responses to stress and wounding, and play a role in reproductive development.
    • Examples: Jasmonic acid.
    • Applications: Used to enhance plant defense mechanisms against pests and diseases.

  8. Salicylic Acid:

    • Function: Involved in plant defense responses and systemic acquired resistance.
    • Examples: Salicylic acid.
    • Applications: Used to induce resistance against pathogens and improve plant health.

These growth regulators can be used in various ways to manipulate plant growth and development for agricultural, horticultural, and research purposes.