Influence of Exogenous Application of Silicon on Physiological Response of Salt-stressed Maize (Zea mays L.)

The influence of silicon (Si, 3 mM), sodium chloride (NaCl, 135 mM), and Si, 3 mM + NaCl, 135 mM supply on chlorophyll content, photosynthetic activity (CO2 -fixation), the concentration of malondialdehyde (MDA) and H2O2, activities of superoxide dismutase (SOD), catalase (CAT) enzymes, free proline and protein contents were studied in maize seedlings leaves after two month of treatments. The results indicated that silicon partially offset the negative impacts and increased tolerance of maize to NaCl stress by enhancing SOD and CAT activities, chlorophyll content and photosynthetic activity. Salt stress although decreased SOD, CAT activities and total soluble protein content, addition of silicon (3 mM) to the nutrient solution enhanced SOD and CAT activities and total protein. In contrast, salt stress considerably increased H2O2, free proline level and MDA concentration and Si addition significantly reduced H2O2, free proline level and MDA concentration in stressed maize leaves. Enhanced activities of SOD and CAT by Si addition may protect the plant tissues from salt induced oxidative damage, thus mitigating salt toxicity and improving the maize growth. These results suggest that the scavenging system forms the primary defense line in protecting oxidative damage under salt stress in crop plants.