Plant growth regulator is the product of organic synthesis, microanalysis, plant physiology, biochemistry and modern agriculture, forestry and horticulture. In the 1920s and 1930s, it was found that there were trace amounts of natural plant hormones such as ethylene, 3-indole acetic acid and gibberellin plants, which had the effect of controlling growth and development. By the 1940s, studies on artificial synthesis of analogues were carried out, and 2, 4-d, amine fresh ester (DA-6), chloropylurea, denitrophenol sodium, naphthalene acetic acid, and granulator were developed and applied gradually, forming a category of pesticides (see table). Over the past 30 years, more and more artificial plant growth regulators have been synthesized, but due to the complexity of application technology, their development is not as rapid as that of pesticides, fungicides and herbicides, and their application scale is also small. However, in view of the need of agricultural modernization, plant growth regulators have great potential for development, and there has been a trend of accelerated development in the 1980s. China began to produce and apply plant growth regulators in the 1950s.
For target plants, plant growth regulators are exogenous, non-nutritive chemicals that can normally be transmitted to the site of action in plants. At a very low concentration, they can promote or inhibit certain processes of their life and make them develop in accordance with human needs. Each plant growth regulator has a specific purpose, and the application technology is quite strict, only under certain application conditions (including external factors) can the target plant have a specific effect. Often changing the concentration results in opposite results, such as promoting at low concentration and inhibiting at high concentration. Plant growth regulators have many USES, depending on the species and target plants. For example: controlling germination and dormancy; Promote rooting; Promote cell elongation and division; Controlling lateral buds or tillering; Control plant type (short strong anti-lodging); Control flowering or gender, and induce fruitless fruit; Sparing flowers and fruits, controlling fruit drop; Control the shape or maturity of the fruit; Enhance resistance to disease, drought, salt and cold; Enhance the ability to absorb fertilizer; Increasing sugar or changing acidity; Improve flavor and color; Promote the secretion of latex or resin; Defoliation or estimation (for mechanical harvesting); Preservation, etc. Some plant growth regulators become herbicides when used at high concentrations, and some herbicides also have growth regulation effects at low concentrations.