The effect of abscisic acid on root and shoot growth of cauliflower plants

Addition of abscisic acid (ABA) to the nutrient solution increased the root to shoot ratio of hydroponically-grown cauliflower plants by reducing the dry weight of the shoot and increasing that of the root. At concentrations higher than 10^–7 M, ABA increased root branching and root hair formation. Root extension was inhibited in plants kept continuously in solutions containing high ABA concentrations but following removal from the ABA solution root elongation was increased in comparison with plants given no ABA treatment. This elongation was greatest in plants with increased root branching caused by higher ABA concentrations.