Investigation of the physiological and biochemical effects of ascorbic acid applications in corn (Zea mays L.) plant under salt stress

In this study, the effect of foliar ascorbic acid (100 ppm) application on maize genotype (Zea mays L. Ada 9510) under salt stress (50, 75 and 100 mM NaCl) was investigated through some physiological and biochemical parameters. All salt concentrations used in this study decreased superoxide dismutase, ascorbate peroxidase, glutathione reductase, guaiacol peroxidase activity and reduced ascorbic acid content in the leaves of maize plants as compared to respective controls. Lower superoxide dismutase activity showed that salt stress increased superoxide radical accumulation in the leaves of maize. Similarly, decreased level of ascorbate peroxidase and glutathione reductase activity and reduced ascorbic acid content may indicate lower efficiency of ascorbate-glutathione cycle which is responsible for the degradation of H 2 O 2 . In consistent with these results, higher level of H 2 O 2 was detected in the leaves of maize seedlings under salt stress (75 and 100 mM) and therefore the degree of lipid peroxidation was found to increase, as indicated by higher MDA content at the same salt concentrations. Photosynthetic pigment (chlorophyll a, chlorophyll b, total chlorophyll and total carotenoid) content was also lower in the salt-stressed maize leaves as compared to controls, probably due to lower antioxidant activity, higher H 2 O 2 accumulation and lipid peroxidation. Foliar ascorbic acid application, on the other hand, increased superoxide dismutase, ascorbate peroxidase and glutathione reductase activity and reduced ascorbic acid content in the leaves of maize under salt stress (75 and 100 mM). These results confirmed that foliar ascorbic acid application decreased superoxide radical accumulation and induced ascorbate-glutathione cycle enzymes in the leaves of maize genotype under salt stress. Therefore, higher activity of antioxidant enzymes led to the lower H 2 O 2 and MDA content, and higher photosynthetic pigment content. According to these results, it may be concluded that, foliar ascorbic acid application ameliorates the negative effects of salt stress in maize leaves by increasing antioxidant capacity and photosynthetic pigment content and by decreasing H 2 O 2 accumulation and membrane damage.