Introduction

Plant growth regulators may be defined as any organic compounds, which are active at low concentrations (1-10 ng / nl) in promoting, inhibiting or modifying growth and development. The naturally occurring (endogenous) growth substances are commonly known as plant hormones, while the synthetic ones are called growth regulator.

Plant hormone is an organic compound synthesised in one part of the plant and translocated to another part, where in very low concentrations it causes a physiological response. The plant hormones are identified as promoters (auxins, gibberellin and cytokinin), inhibitors (abscissic acid and ethylene) and other hypothetical growth substance (florigen, flowering hormone, etc.,)

Classification

1. Auxins
2. Gibberellins
3. Cytokinenins
4. Etylene
5. Dormins  {Abscissic Acid (ABA), Phaseic Acid}
6. Flowering Hormones {Florigin, Anthesin, Vernalin}
7. Phenolic Substances {Coumarin}
8. Miscellaneous Natural Substances {Vitamins, Phytochrome Tranmatic Substances}
9. Synthetic Growth Retardants {Ccc, Amo, 1618, Phosphin - D, Morphacting, Malformis}
10. Miscellaneous Synthetic Substances {Synthetic Auxins, Synthetic Cytokinins}

(Source: http://www.ikisan.com/links/ap_regulators.shtml  )