Plant Growth Regulators: Meaning of Plant Growth Regulators: Phytohormones (For CBSE, ICSE, IAS, NET, NRA 2022)

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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

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.