Osmolytes and metal ions accumulation, oxidative stress and antioxidant enzymes activity as determinants of salinity stress tolerance in maize genotypes

Abstract

Effect of soil salinity was studied in two maize (Zea mays L.) genotypes, DTP-w-c 9 (comparatively tolerant) and Prabhat (susceptible) under control and three levels of salinity at vegetative and anthesis stages during summer–rainy season. Salinity stress decreased relative water content (RWC), chlorophyll (Chl) and carotenoid (Car) contents, membrane stability index (MSI), potassium (K+) and calcium (Ca2+) contents, and increased the rate of superoxide radical (O 2 ·− ) production, contents of hydrogen peroxide (H2O2), thiobarbituric acid reactive substances (TBARS) (measure of lipid peroxidation), proline, glycine-betaine, total soluble sugars, sodium (Na+), and Na+/K+ and Na+/Ca2+ ratios in both the genotypes. Activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT) and glutathione reductase (GR) increased up to S2 salinity level in both the genotypes, and up to highest salinity level (S3) in DTP-w-c 9 at the two stages. Salinity-induced decrease in RWC, Chl, Car, MSI, K+ and Ca2+ was significantly greater in Prabhat, which also recorded higher Na+ content and Na+/K+ and Na+/Ca2+ ratios than DTP-w-c 9. DTP-w-c 9 recorded higher contents of proline, glycine-betaine, total soluble sugars, K+, Ca2+, activity of SOD, APX, CAT, GR, and comparatively lower O 2 ·− , H2O2 and TBARS contents compared to Prabhat. Results show that salinity tolerance of DTP-w-c 9, as manifested by less decrease in RWC, Chl, Car and MSI, is associated with maintenance of adequate levels of K+ and Ca2+, greater contents of osmolytes, higher antioxidant enzymes activity, and lower O 2 ·− , H2O2, TBARS and Na+ contents than Prabhat.