Response of maize genotypes to salinity stress in relation to osmolytes and metal-ions contents, oxidative stress and antioxidant enzymes activity

Effect of long term soil salinity (control-S-0 and three levels S-1 to S-3) was studied in two maize (Zea mays L.) genotypes, PEHM 3 (comparatively tolerant) and Navjot (susceptible) 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 and calcium contents, and increased the contents of superoxide radical (O-2 (center dot-)), hydrogen peroxide (H2O2), thiobarbituric acid reactive substances (TBARS), proline, glycinebetaine, total soluble sugars, and sodium, and Na+/K+ and Na+/Ca2+ ratios in both the genotypes. Contents of zinc, copper, manganese and iron increased up to S-2. Though under S-0 PEHM 3 had higher content of all the metals, Navjot recorded higher content of Zn at all salinity levels and contents of all metal ions at S-2 and S-3. Activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT) and glutathione reductase (GR) increased upto S-2 in both the genotypes, and upto S-3 in PEHM 3 at the two stages. Salinity induced decrease in RWC, Chl, Car, MSI, K+ and Ca2+ was significantly greater in Navjot, which also recorded higher Na+ content and Na+/K+ and Na+/Ca2+ ratios than PEHM-3. PEHM-3 recorded higher contents of proline, glycine-betaine, total soluble sugars, K+, Ca2+, activity of SOD, APX, CAT, GR, and comparatively lower O-2 (center dot-), H2O2 and TBARS contents compared to Navjot.