Growth regulating substances can be divided into six categories: auxin and its related compounds, cytokinins and its related compounds, gibberellins and its related compounds, ethylene and its related compounds, growth inhibitors and Growth retardants, others.
(1) Auxin and its related compounds.
Auxin is the earliest discovered plant hormone. Its precursor is tryptophan, which is the decomposition product of storage proteins under the action of enzymes. The naturally occurring ones are mainly indole acetic acid (IAA) and indole. Indole acetaldehyde (IAAD), indole acetonitrile (INA), etc. The synthetic ones include indolepropionic acid (IPA), indolebutyric acid (IBA), indoleethylamine (IAD), etc. The most commonly used compounds on fruit trees are indolebutyric acid, naphthyl acetic acid (NAA), naphthol compounds, pyrrolic acid, etc. (2) Cytokinins and related compounds.
Cytokinin, also known as cytokinin, was isolated from denatured deoxyribonucleic acid (DNA) in 1955 and is a degradation product of DNA. In 1963, Letham discovered the first natural cytokinin, zeatin. Naturally occurring cytokinins are all derivatives of isopentenyl adenine. The main cytokinins can be divided into three categories according to their side chain R1: zeatin, dihydrozeatin, isopentenyladenine, and more than 10 types. Artificially synthesized compounds with cytokinin activity include kinetin, benzyladenine (BA), tetrahydropyranylbenzyladenine (PBA), etc. Allowed to be used are BA (benzyladenine, 6-benzyladenine, etc.). (3) Gibberellins and related compounds.
Gibberellin (GA) was isolated from rice bakanae disease in Japan in 1938. It was introduced to Europe and the United States in the 1950s and attracted widespread attention. By 1981 there were 62 known gibberellins. Gibberellins GA3 and GA4+7 are commonly used on fruit trees. (4) Ethylene and related compounds.
The regulation of plant growth and development by ethylene (Eylene) was discovered very early. It was initially only found in mature fruits. With the application of gas chromatography, ethylene was commonly found in plants and was confirmed in the 1960s. An endogenous hormone. Ethylene is a gas at normal temperature, so it is difficult to use it as a regulator. In the late 1960s, an ethylene generator was invented and is now widely used. Drugs that can promote the production of ethylene include: ethephon (CEPA), ACC, etc. The only one allowed is ethephon. (5) Growth inhibitory substances.
Compounds that inhibit the elongation of roots and stems, bud germination and seed germination of plants are called growth inhibitory substances and can be divided into growth inhibitors and growth retardants. Growth inhibitors include abscisic acid (Abscisicacid, referred to as ABA), methacrycin (MH), plasticine, triiodobenzoic acid (TIBA), etc. Growth retardants include bijiu (B9), chlormequat (CCC), paclobutrazol (PP333), shuijianan (chiosin, mesoquat, and gosmequat), etc. Chlormequat is allowed. (6) Other types of growth regulators.
Most of the five growth regulators introduced above work by affecting the control system of natural hormones in plants. These control systems themselves must also exert their influence on developmental processes through enzymes as mediators. There are currently some new growth regulators, which can affect the reaction rate of certain enzymes that play a key role, and some may more directly control certain important physiological processes, such as photosynthesis and nitrogen reduction. To increase crop yields, such as brassin, triacontanol, etc.