Plant Nutrition :: Plant Growth Regulators


Growth retardants

  • The term growth retarding or growth retardant is that the chemical slows cell division and cell elongation of shoot tissue and regulate plant height physiologically without formative effects.          
  •   Eg. AMO 1618, phosphon-D, CCC, MC and Alar. These do not occur naturally in plants and acts in retardation of stem elongation, preventing cell division.


Suppress the growth of plants. There are phenolic inhibitors and synthetic inhibitors and Abscissic acid (ABA). Benzoic acid, Salicylic acid, Coumarin and Chlorogenic acid are examples for phenolic inhibitors, while malichydrazide (MH) and Triiodo benzoic acid (TIBA) are examples of synthetic inhibitors. Inhibitor from young leaves of Betula spp. prevents the growth of apical buds eg. ABA and Dormin.

Abscisic Acid (ABA)

  • To stop elongation
  • Induce dormancy
  • Delay germination
  • Inhibit growth process

Role of inhibitors

  • Accumulation leads to induce dormancy
  • Regulation of flowering, senescence and tuber formation
  • Induction of cold hardiness
  • Cause abscission and dehiscence of fruits
  • ABA application increase GA (Gibberellic acid) levels and may cause increase in growth
  • Suppress the formation of a amylase in the barley endosperm
  • Interfere with DNA and RNA synthesis
  • Modify the nucleic acid and protein synthesis systems.
  • Phenolic compounds inhibit stem and root growth
  • Phenolics affect almost all the metabolic system
  • Control Gibberellin -  stimulated growth

Methods of application

  • Spraying method
  • Injection of solution into internal tissues
  • Root feeding method
  • Application of powder mixtures to the bases of cuttings
  • Dipping of the cutting in PGR solution
  • Soaking in dilute aqueous solution


Dr. P.Jeyakemar, Associate Professor (Crop Physiology), Dept. of Fruit Crops, TNAU, Coimbatore

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