ABSTRACT
In this study, 15% PEG, 100 mmol·L-1 NaCl and PEG-NaCl mixed solution were employed to respectively simulate the drought (D), salinity (S) and the combined stress (D+S), and effects of these three stresses on the seed germination and the physiological characteristics of seedlings were investigated. The results showed that seed germination, seedling growth and biomass accumulation were significantly inhibited by these three stresses, and the impact of stress ranked as D>D+S>S. The content of reactive oxygen species like H2O2 and O-·2, as well as malondialdehyde (MDA) and membrane permeability were increased under these stresses, meanwhile, proline (Pro), soluble sugar and soluble proteins contents were significantly improved, which were higher in seedlings than in roots with a rank of D>D+S>S. The activities of antioxidant enzymes such as superoxide dismutase (SOD), peroxide (POD), catalase (CAT) and ascorbate peroxide (APX) were also obviously increased. In addition, SOD and APX induced by PEG-NaCl mixed solution were ranked in the middle compared to those induced by their single stress, but POD and CAT were more induced by PEG-NaCl mixed solution than their single stress. It was demonstrated that effect of drought-salinity combined adverse condition on maize seed germination and seedlings physiological characteristics were not simply additive of their single stress, compared with their single stress, drought-salinity combined adverse condition could reduce the effects of drought stress on maize seeding to a certain extent.
