Auxin is a class of endogenous hormones containing an unsaturated aromatic ring and an acetic acid side chain, abbreviated as IAA in English, and its chemical essence is indoleacetic acid. In addition, 4-chloro-IAA, 5-hydroxy-IAA, naphthalene acetic acid (NAA), indole butyric acid and the like are auxins.
Auxin was the first plant hormone to be discovered. The most important chemical in auxin is 3-indoleacetic acid. Auxin has the functions of regulating the growth rate of stems, inhibiting lateral buds, and promoting rooting. It is used in agriculture to promote rooting of cuttings, and the effect is remarkable.
Auxin is indole acetic acid, and its molecular formula is C10H9NO2. It is the first hormone discovered to promote plant growth. English comes from the Greek auxein (to grow). [1] The pure product of indoleacetic acid is a white crystal and is hardly soluble in water. Soluble in organic solvents such as ethanol and ether. It is easily oxidized under light and becomes rose red, and its physiological activity is also reduced. Indole acetic acid in plants is either in a free state or in a bound (bound) state. The latter are mostly ester or peptide complexes. The content of free indoleacetic acid in plants is very low, about 1-100 micrograms per kilogram of fresh weight.
There are 5 pathways starting from tryptophan. Auxins are found in zucchini, in some cruciferous plants, and in tomatoes. The degradation of auxin, most notably, is easily destroyed by photo-oxidation in the presence of light. Tang Yuwei and J. Bonner in 1947 found that some oxidase in plant tissue can degrade indoleacetic acid, called indoleacetic acid oxidase.
