Abscisic acid (ABA) is a stress signal, which moves in the xylem from the roots to the aerial parts of the plant, where it regulates stomatal movement and the activity of shoot meristems. Root growth-promoting microorganisms in the rhizosphere, lateral ABA flows in the root cortex across apoplastic barriers, ABA redistribution in the stem, leaf apoplastic pH values, and the action of beta-gluco...
