Indole-3-acetic acid is a broad-spectrum plant growth regulator with indole auxin activity

Indole-3-acetic acid is used as plant growth stimulant and analytical reagent. Indole-3-acetic acid, 3-indoleacetaldehyde, 3-indoleacetonitrile, ascorbic acid and other auxin substances exist naturally in nature. The precursor of Indole-3-acetic acid  biosynthesis in plants is tryptophan. Indoleacetic acid is broad-spectrum and versatile. In the early stage, it is used to induce Parthenocarpy and fruit setting of tomato. At the full flowering stage, the flowers are soaked in 3000mg / L solution to form seedless tomato fruit and improve the fruit setting rate; Soaking the base of cuttings with 100 ~ 1000mg / L solution can promote the formation of adventitious roots of tea, gum, oak, metasequoia, pepper and other crops and accelerate the speed of nutritional reproduction. 1 ~ 10mg / L indole-3-acetic acid and 10mg / L oxamyl were mixed to promote the rooting of rice seedlings. Spraying chrysanthemum with 25 ~ 400mg / L solution once (under 9-hour time cycle) can inhibit the emergence of flower buds and delay flowering. When crabapple growing in long sunshine is sprayed once at the concentration of 10-5mol / L, the female flowers can be increased. Treatment of Sugarbeet Seeds can promote germination, increase root tuber yield and sugar content. Indoleacetic acid is synthesized in expanded young leaves and apical meristem, and accumulates from top to bottom to base through long-distance transportation of phloem. Roots can also produce auxin and transport it from bottom to top. Auxin has many physiological effects, which is related to its concentration. Low concentration can promote growth, while high concentration will inhibit growth and even kill plants. This inhibition is related to whether it can induce the formation of ethylene. The physiological effects of auxin are manifested in two levels. At the cellular level, auxin can stimulate the division of cambial cells; Stimulate the cell elongation of branches and inhibit the growth of root cells; Promote the differentiation of xylem and phloem cells, promote the rooting of cuttings and regulate the morphogenesis of callus. At the organ and whole plant levels, auxin plays a role from seedling to fruit maturation. Auxin controlled the reversible red light inhibition of hypocotyl elongation in seedlings; When indoleacetic acid  was transferred to the lower side of the branch, the geotropism of the branch was produced; When indoleacetic acid is transferred to the backlight side of the branch, the phototropism of the branch is produced; Indoleacetic acid caused apical dominance; Delaying leaf senescence; Auxin applied to the leaves inhibited abscission, while auxin applied to the proximal end of the abscission layer promoted abscission; Auxin promotes flowering, induces the development of unisexual fruit and delays fruit ripening. The complex of indoleacetic acid and receptor has two effects: first, it acts on membrane proteins and affects medium acidification, ion pump transport and tension change, which belongs to fast reaction; Second, it acts on nucleic acid, causing cell wall changes and protein synthesis, which belongs to slow reaction. Indoleacetic acid can activate ATPase on the plasma membrane, stimulate hydrogen ions to flow out of the cell and reduce the pH value of the medium. Therefore, relevant enzymes are activated to hydrolyze the polysaccharide of the cell wall, soften the cell wall and expand the cell. Administration of indoleacetic acid  resulted in the emergence of specific messenger RNA (mRNA) sequences, which changed protein synthesis. Indoleacetic acid  treatment also changed the elasticity of cell wall and enabled cell growth.