Plant growth regulators are the product of the integrated development of various scientific technologies, including organic synthesis, microanalysis, plant physiology and biochemistry, and modern agriculture, forestry, and horticulture. In the 1920s and 30s, trace amounts of natural plant hormones such as ethylene, 3-indoleacetic acid, and gibberellins were discovered in plants, playing a role in controlling growth and development. By the 1940s, research into the artificial synthesis of analogs began, leading to the development of 2,4-D, DA-6, chlorpyrifos, sodium nitrophenolate, α-naphthaleneacetic acid, and thiophanate-methyl, which were gradually promoted and used, forming a category of pesticides. Over the past 30 years, the number of artificially synthesized plant growth regulators has increased significantly, but due to the complexity of their application technology, their development has not been as rapid as that of insecticides, fungicides, and herbicides, and their application scale is also smaller. However, from the perspective of the needs of agricultural modernization, plant growth regulators have great development potential, and their development accelerated in the 1980s. China began producing and applying plant growth regulators in the 1950s.
For target plants, plant growth regulators are exogenous, non-nutritive chemical substances that can typically be translocated within the plant to their sites of action. Even at very low concentrations, they can promote or inhibit certain aspects of the plant's life processes, guiding them towards processes that meet human needs. Each plant growth regulator has a specific purpose, and its application requires strict adherence to technical specifications. It only produces specific effects on the target plant under specific application conditions (including external factors). Often, changing the concentration will yield the opposite result; for example, a low concentration may promote growth, while a high concentration may inhibit it. Plant growth regulators have many uses, varying depending on the variety and the target plant. For example: controlling budding and dormancy; promoting rooting; promoting cell elongation and division; controlling lateral buds or tillers; controlling plant shape (short and sturdy to prevent lodging); controlling flowering or sex, inducing seedless fruit; thinning flowers and fruits, controlling fruit drop; controlling fruit shape or ripening time; enhancing stress resistance (disease resistance, drought resistance, salt resistance, frost resistance); enhancing fertilizer absorption capacity; increasing sugar content or changing acidity; improving aroma and color; promoting latex or resin secretion; defoliation or expedited ripening (facilitating mechanical harvesting); preservation, etc. Some plant growth regulators become herbicides when used at high concentrations, while some herbicides also have growth-regulating effects at low concentrations.
