Abstract: To explore the mechanism underlying the saline-alkali tolerance of maize and promote the breeding of saline-alkali tolerant cultivars, the seedlings of maize cultivars “Zhengdan 958” and “ZN451” were subjected to saline-alkali stress with 25 mmol·L^-1  Na₂CO₃ and 100 mmol·L^-1 NaCl. We investigated the effects of saline-alkali stress on the growth and physiological characteristics of maize seedlings. The results showed that plant height, aboveground dry weight and total dry weight per individual of “Zhengdan 958” under saline-alkali stress were significantly lower than those in control. The root-shoot ratio under saline-alkali stress was higher than that of control group, but the difference was not statistically significant. The proline content in treatment group was significantly higher than that of control, while soluble protein was lower but the reduction was not significant. The MDA content and the SOD activity in treatment group were significantly higher than the control. POD activity and SPAD readings were significantly lower than those of the control. G_s, C_i, P_n, F_v/F_m, and PI values were all significantly lower than those in the control. The contents of ABA and JA were significantly higher than those in the control. Plant height and aboveground dry weight of “ZN451” in the treatment group were significantly lower than those in the control. The dry weight of individual plant was higher than that of control group, but the difference was not significant. The root-shoot ratio was significantly higher than that of control group. The contents of proline and soluble protein were significantly higher than those of the control group. The MDA content was higher than that in the control, but the increase was not significant. SOD and POD activities in the treated group were significantly higher than that in the control. The SPAD, P_n, F_v/F_m, and PI values were all slightly lower than those in the control. The G_s and C_i values were significantly lower than those in the control. The contents of ABA and JA were significantly higher than those in the control. Our results suggest that cultivar “ZN451” may have a strong regulatory mechanism for biomass allocation under saline-alkali stress. The high activity of antioxidant enzyme system of “ZN451” ensures the integrity of cell membrane, improves the cellular ability of osmoregulation, and thus provides better protection for antioxidant enzyme activity and photosynthetic system. Although the stomatal conductance of “ZN451” is reduced under saline-alkali stress, the structure and function of the relevant systems are not damaged. Therefore, cultivar “ZN451” has high salt-alkali resistance.

Key words: maize seedling, mixed saline-alkali stress, growth index, physiological index.