One is natural plant hormone or called plant endogenous hormone; The other is a synthetic plant growth regulator, also known as exogenous hormone.

(2) Classification by chemical structure.

It can be divided into indole compounds (indoleacetic acid), naphthalene compounds (naphthylacetic acid), phenoxyacetic acid (2,4-d, 2- methyl -4- chlorine), terpenoids (gibberellin), quaternary ammonium salts (chlormequat chloride), chlormequat salts (pyridine, chlormequat chloride), substituted ureas (diphenylurea) and lactones.

(3) According to the physiological functions of plant hormones.

Promotion: including cell elongation and division, rooting, flowering, fruiting, breaking dormancy and germination; Suppression: including weeding, defoliation, bud suppression, flower thinning and fruit thinning; There are two functions: most plant hormones have both promoting and inhibiting effects, which can not only promote germination, but also inhibit germination, and can also keep fresh and achene. Most plant hormones have two functions, on the one hand, it depends on the concentration of hormones, on the other hand, it depends on the cells and organs of plants themselves.

(4) Classification according to the use of plant hormones.

Control dormancy and germination; For example, treating potatoes, onions and garlic with fresh elements before harvest can reduce the germination rate and prolong the storage period; Prevent organs from falling off; By applying plant hormones, the flowers, fruits and leaves of vegetables such as solanaceous fruits, melons and beans can be prevented. Sex control or castration; Adjust plant growth, such as promoting growth, cutting and rooting, inhibiting rooting, preventing overgrowth and dwarfing plant types; Controlling bolting and flowering; Sparse flowers and fruits; Promote fruit development and ripening; Postharvest preservation.