Plant growth regulator is the product of organic synthesis, microanalysis, plant physiology and biochemistry, modern agriculture, forestry, horticulture and cultivation and other scientific and technological comprehensive development. From 1920s to 1930s, it was found that trace amounts of natural plant hormones, such as ethylene, 3-indoleacetic acid and gibberellin, could control the growth and development of plants. In the 1940s, the study of synthetic analoges-2, 4-D, aminoester (DA-6), clopramide, sodium nitrophenol, -naphthoacetic acid, and yutan were developed and gradually used to form a category of pesticides. Over the past 30 years, more and more plant growth regulators have been synthesized. However, due to the complexity of application technology, the development of plant growth regulators is not as rapid as insecticides, fungicides and herbicides, and their application scale is also small. But from the point of view of agricultural modernization, plant growth regulator has great development potential, in the 1980s has accelerated the trend of development. China began to produce and apply plant growth regulators in the 1950s.
For the target plants, plant growth regulators are exogenous non-nutritive chemicals, which can usually be transmitted to the action sites in the plant body. At a very low concentration, they can promote or inhibit some links of the life process, making it develop to meet the needs of human beings. Each plant growth regulator has a specific purpose and its application is technically demanding. Only under specific application conditions (including external factors) can it produce specific effects on the target plant. Changing the concentration often results in the opposite effect, such as promoting effect at low concentration and inhibiting effect at high concentration. Plant growth regulators have many USES, depending on the species and target plant. For example: controlling germination and dormancy; Promoting rooting; Promote cell elongation and division; Control of lateral buds or tillers; Control plant type (short and strong anti-lodging); Control flowering or sex, induce seedless fruit; Sparse flower and sparse fruit, control fruit dropping; To control the shape or ripeness of the fruit; Enhance stress resistance (disease resistance, drought resistance, salt resistance, freeze resistance); Enhancing the ability to absorb fertilizers; Increase sugar or change acidity; Improve flavor and color; Promote the secretion of latex or resin; Defoliation or urging (for mechanical harvesting); Preservation, etc. Some plant growth regulators are herbicides when used in high concentrations, and some herbicides have growth regulation effects at low concentrations.
