Regulation of antioxidant activity in maize (Zea mays L.) by exogenous application of sulfur under saline conditions

Abstract

One of the major effects of salt stress is high production of reactive oxygen species that adversely affect essential cellular metabolic pathways. To limit the elevated production of reactive oxygen species, plants stimulate various types of antioxidants. In this study, sulfur was used to induce tolerance against oxidative stress through modulation of the activities of various antioxidants. Two maize genotypes (Agatti 2003 and Pak Afgoi 2003) were subjected to different salinity (25 and 75 mM) and sulfur (40 and 80 mM) treatments and a control treatment. Various antioxidants and oxidative stress determinants in maize organs (leaf, shoot, and root) were studied. It was found that salt stress decreased ascorbic acid and tocopherol, but stimulated the production of total phenolics, carotenoids, lycopene, superoxide dismutase, peroxidase, catalase, malondialdehyde, and hydrogen peroxide. Exogenously applied sulfur decreased carotenoids, malondialdehyde, and hydrogen peroxide and increased ascorbic acid, tocopherol, total phenolics, lycopene, superoxide dismutase, peroxidase, and catalase. Agatti 2003 showed higher antioxidant activity than Pak Afgoi 2003. In conclusion, sulfur application at the 40 mM level balanced antioxidants and oxidative stress determinants to induce salt tolerance in maize plants.