Effects of coronatine on growth, gas exchange traits, chlorophyll content, antioxidant enzymes and lipid peroxidation in maize (Zea mays L.) seedlings under simulated drought stress

Coronatine is a phytotoxin that affects the accumulation of defence-related metabolites in plants but information on how its effects may be mediated by environmental stress is scanty. An experiment was carried out to determine the changes in growth, gas exchange, relative water content, chlorophyll (Chl) content, antioxidant enzymes and lipid peroxidation in maize (Zea mays L., var. 'Nongda 3138') seedlings treated with coronatine tinder simulated drought stress. Seedlings raised hydroponically in a growth chamber with simulated drought for 8d (long-period drought) or 3d (short-period drought) were treated with or without coronatine at the three-leaf stage. Under the drought condition, treated with coronatine significantly increased the fresh weight and relative water content in leaves of seedling leaves. The increase was accompanied by increased rates of photosynthesis and transpiration, and the maintenance of Chi pigments. Coronatine had no effects on catalase (CAT), guaiacol peroxidase (POD) and glutathione reductase (GR) under normal condition, but it significantly enhanced activities of CAT, POD and GR in stressed seedlings under the long-period drought treatment. Under the short-period drought treatment, the POD and GR activity in the seedlings treated with coronatine were much higher than in those not treated. Malondialdehyde (MDA) increased sharply under drought condition, but treatment with coronatine significantly reduced it by 15%. The total Chi content of leaves tinder the drought condition was markedly increased by the treatment with coronatine. Seedlings subjected to a short-period drought had reduced water content, but recovered fairly well by the treatment with coronatine with negligible effects on most physiological and biochemical processes. The application of coronatine alleviated the drought stress in maize seedlings and enhanced their tolerance of water stress through changes in physiological and anti-oxidant enzyme activities.