Plant growth regulators (PGRs) are artificially synthesized chemical compounds that have the same physiological effects and similar chemical structures as endogenous plant hormones. Plant growth regulator belongs to the broad category of pesticides and is a class of pesticides that control plant growth and development, including synthetic compounds similar to natural plant hormones and hormones extracted directly from organisms.

Auxin is indole-3-acetic acid, with the molecular formula C10H9NO2. It is the earliest hormone discovered to promote plant growth. The English word comes from the Greek word auxein (to grow). The pure product of indole-3-acetic acid is white crystal and is insoluble in water. Easily soluble in organic solvents such as ethanol and ether. It is easily oxidized and turns into rose red under light, and its physiological activity is also reduced. Indole-3-acetic acid in plants may be in a free state or in a bound (bound) state.

Difference in activity: 24-epibrassinolide is 97% active, while 28-homobrassinolide is 87% active. This indicates that 24-epibrassinolide has higher activity among chemically synthesized brassinolides.

Prohexadione calcium is a highly active plant growth regulator that can be used to control the growth and development of many crops and is often used in agricultural production.