Plant growth regulators are a group of chemicals for controlling and enhancing the natural plant growth processes to better meet the requirements of food supply in general,
Plant hormones are produced naturally by plants and are essential for regulating their own growth. They act by controlling or modifying plant growth processes, such as formation of leaves and flowers, elongation of stems, development and ripening of fruit.
In modern agriculture, people have established the benefits of extending the use of plant hormones to regulate growth of other plants. When natural or synthetic substances used in this manner, they are called Plant Growth Regulators.
At the present time, plant growth regulators(PGRs) are one of the most powerful tools available for manipulating the vegetative and reproductive growth of crop plants. For a wide variety of annual, biennial and perennial crops, plant growh regulators have been used to solve production problems. For example, plant growth regulators have been used successfully as foliar sprays to increase flowering, synchronize bloom, or change the time of flowering to avoid adverse climatic conditions or to shift harvest to a time when the market is more economically favorable. Foliar-applied plant growth regulators are routinely used to improve fruit set, reduce June drop or to prevent pre-harvest drop to increase yield. Plant growth regulators sprays are applied to increase fruit size directly by stimulating cell division. Application of a Plant Growth regulators that reduces the number of flowers formed or promotes flower or fruit abscission increases fruit size indirectly by decreasing fruit number. Plant growth regulators have been used as both pre- and post-harvest treatments to hasten or slow the ripening process, color development, and maturation of specific tissues to improve the quality of the product sold in the market. An emerging use of plant growth regulators is for overcoming the adverse effects of abiotic stresses. Surprisingly, these successes have been achieved with a modest number of commercial PGRs that are members of or impact the synthesis of one of five classic groups: auxins, cytokinins, gibberellins, abscisic acid and ethylene.
From the regulatory control perspective, plant growth regulators are classified under “ pesticides ”. The same classification applies both internationally.