Plant Growth Regulators: Meaning of Plant Growth Regulators: Phytohormones

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Meaning of Plant Growth Regulators

  • Those chemical substances, which govern all the factors of development and growth within plants.

  • Phytohormones and plant growth hormones are the other names for Plant Growth Regulators.

  • Plants need light, water, oxygen, and nutrition to grow and develop.

Phytohormones

  • These chemical messengers coordinate cellular activities.

  • They control and modify the physiological processes such as the growth, development, and movement of plants.

Characteristics of Plant Growth Regulators

  • Ripening of fruits.

  • Seed dormancy.

  • Formation of leaves flowers and stems.

  • Elongation and differentiation of cells.

  • They can accelerate as well as retard the rate of growth in plants.

Types of Plant Hormones

  • Auxin

  • Gibberellins (GAs)

  • Cytokinins

  • Abscisic acid (ABA)

  • Ethylene

Types of Plant Growth Regulators

Types of Plant Growth Regulators

Types of Plant Growth Regulators

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Plant Growth Regulators

Auxins

  • Charles Darwin discovered phytohormone as the first Auxin.

  • Auxins play an important role in producing fruit without prior fertilization.

  • They are also used by gardeners to keep lawns free from weeds.

  • They are produced by the apex of root and shoot.

  • They are also used in the process of plant propagation.

Gibberellins

  • They are plant hormones that regulate various developmental processes.

  • This includes stem elongation, germination, dormancy, flowering, flower development, and leaf and fruit senescence.

  • They are one of the longest-known classes of plant hormone.

  • They are involved in leaf expansion.

  • They are acidic in nature.

  • They are used in the brewing industry to accelerate the malting process.

Cytokinins

  • They are a class of plant growth substances (phytohormones).

  • They promote cell division, or cytokinesis, in plant roots and shoots.

  • They are involved primarily in cell growth and differentiation.

  • They promote nutrient mobilization.

  • They keep flowers fresh for a longer duration.

Plant Growth Inhibitors

Abscisic Acid

  • It is a plant hormone.

  • It functions in many plant developmental processes, including seed and bud dormancy.

  • It is also involved in control of organ size and stomatal closure.

  • It further inhibits plant metabolism and seed germination.

  • It is also used a spraying agent on trees.

Ethylene

  • It is a hydrocarbon which has the formula or .

  • In pure state, it is a colorless flammable gas with a faint “sweet and musky” odour.

  • It is used as both plant growth promoters and plant growth regulators.

  • It enhances respiration rate during ripening of fruits.