Important phytohormones (Indole-3-acetic acid = often abbreviated as IES) to regulate the growth of plants that like in the active growth zones of the plant motive and root tips are formed. Interacting with abscisic acid and cytokinins different processes are controlled. In low concentrations, auxins promote the elongation growth of the cotyledons, shoot axes and the root. Root and shoot growth are inhibited in high concentrations. They promote the breaking up of tree buds and the rapid growth of young ones shoots and control the leaf fall, Furthermore, the cell division rate in the cambium increased and thus stimulates the secondary thickness growth. Auxins can delay fruit ripening.
When planting young vines the cuttings are coated with the synthetically produced auxin indole butyric acid to promote root formation and growth. This is particularly the case with documents with crossing of the game species Vitis cinerea var. Helleri (Vitis berlandieri) and Vitis champinii necessary because of their cuttings generally poorly rooted. The auxins in the growing main shoot are the cause of that apical dominance, that is, they have an inhibiting effect on the expulsion of side shoots. This is why chemical substances related to auxins are used in the production of herbicides against weed used. All these substances belong to the group of Plant strengtheners, See also under Organic viticulture,