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