Protective effects of exogenous ABA on oxidative damage in maize seedlings under drought stress

Pot experiments were conducted to study the effects of different concentrations of abscisic acid (ABA) on the growth of maize seedlings under moderate drought stress (15% Polyethylene glycol). The experimental results showed that drought stress considerably inhibited the growth of maize seedlings compared with the control. The activities of catlase (CAT), superoxide dismutase (SOD) and peroxidase (POD) decreased by 65.56%, 51.27%, and 39.05%, respectively, Malondialdehyde (MDA) content increased by 85.06%, and soluble sugar, soluble protein and chlorophyll contents decreased by 55.91%, 54.80%, and 43.08%, respectively. Appropriate concentrations of exogenous ABA effectively alleviated drought stress on maize seedling growth, inhibited an increase of MDA content in maize seedlings caused by drought stress, increased the activity rates of SOD, POD and CAT, inhibited the decrease of chlorophyll, and prevented a decrease of soluble sugar and soluble protein contents in the drought-stressed maize seedlings. The results showed that these effects of ABA have an obvious dosage effect. A 15 μmol·L^–1 ABA treatment can alleviate the inhibitory effect of drought stress on maize seedlings. Compared with the drought stress, the activities of CAT, SOD and POD in maize seedlings increased by 73.91%, 69.79% and 50.69%, respectively; MDA content decreased by 40.63%, while soluble sugar, soluble protein and chlorophyll contents increased by 79.75%, 57.81% and 44.24%, respectively. Therefore, the exogenous ABA treatment of 15 μmol·L^–1 can improve the activity of protective enzymes and drought tolerance of maize seedlings.