Effect of salt stress on antioxidative enzymes and lipid peroxidation in leaves and roots of salt-tolerant and salt-sensitive maize genotypes

Abstract

The effects of salt stress on the activity of antioxidative enzymes and lipid peroxidation were studied in leaves and roots of two maize genotypes, BR5033 (salt-tolerant) and BR5011 (salt-sensitive), grown under control (nutrient solution) or salt stress (nutrient solution containing 100 mM NaCl) conditions. Leaves and roots of control and salt-stressed plants were harvested at various times starting 1 day prior to initiating the salt treatment. In leaves of salt-stressed plants, superoxide dismutase (SOD), ascorbate peroxidase (APX), guaiacol peroxidase (GPX) and glutathione reductase (GR) activities increased with time when compared to the controls. The increase in enzyme activities was more pronounced in the salt-tolerant than in the salt-sensitive genotype. Salt stress had no significant effect on catalase (CAT) activity in the salt-tolerant, but it was reduced significantly in the salt-sensitive genotype. In salt-stressed roots of the salt-tolerant genotype, SOD and CAT activities decreased and APX, GPX and GR activities remained unchanged in comparison with the control. In roots of the salt-sensitive genotype, salinity reduced the activity of all studied enzymes. The data show that CAT and GPX enzymes had the greatest H 2O 2 scavenger activity in both leaves and roots. Moreover, CAT, APX and GPX activities in conjunction with SOD seem to play an essential protective role in the scavenging processes. Lipid peroxidation was enhanced only in salt-stressed leaves of the salt-sensitive genotype. These results indicate that oxidative stress may play an important role in salt-stressed maize plants and that the greater protection of BR5033 leaves and roots from salt-induced oxidative damage results, at least in part, through the maintenance and/or increase of the activity of antioxidant enzymes.