A discovered only in the 1950s Phytohormon (Abbreviation ABA, outdated Dormin), which interacts with plants auxins. cytokinins and gibberellins has a growth-regulating effect. This substance abolishes the effect of the growth-promoting hormones and causes, among other things, in already woody, perennial plants, the bud rest. With vines it is at leaf fall, Shoot dehydration, growth inhibition and during grape ripening involved. During the expulsion the concentration in the buds drops drastically. Conversely, the ABA level in the newly formed winter buds increases in parallel with seed and fruit formation, in order to bring about the wintry bud dormancy. When so-called water stress the proportion in the leaf tissue increases enormously, because ABA controls the movement of the stomata (Guard cells, leaf pores) through which the plant water gives off (transpiration) and carbon dioxide receives.