Moderate salinity enhances the antioxidative response in the halophyte Hordeum maritimum L. under potassium deficiency

Abstract: Changes in the leaf antioxidant metabolism upon exposure to salinity and potassium deficiency were investigated in the annual halophyte Hordeum maritimum L. Plants were hydroponically grown either with a complete nutrient solution containing 3mM K+ without (+K/−NaCl) or with 100mM NaCl (+K/+NaCl), or in K+-free medium containing 100mM NaCl (−K/+NaCl). Malondialdehyde (MDA), carbonyl group (Cydrogen peroxide (H2O2) contents as well as antioxidant enzyme activities [superoxide dismutase (SOD; EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), guaiacol peroxidase (GPX, EC 1.11.1.7), ascorbate peroxidase (APX, EC 1.11.1.11), monodehydroascorbate reductase (MDHAR, EC 1.6.5.4), dehydroascorbate reductase (DHAR, EC 1.8.5.1), and glutathione reductase (GR, EC 1.6.4.2)] and non-enzymatic antioxidant contents (ascorbate and glutathione) were determined. Plants exposed to salinity, either alone or in combination with K+ deprivation, showed enhanced lipid peroxidation along with higher antioxidative response. This tendency was generally more marked in −K/+NaCl plants as compared to +K/+NaCl plants. H2O2 concentration was negatively correlated with the plant antioxidative capacity, either enzymatic or non-enzymatic. As a whole, these data suggest that the enhancement of the antioxidative response is of crucial significance for H. maritimum plants growing under salinity and potassium deficiency. [Copyright &y& Elsevier]