Effect of potassium nutrition on antioxidative defense mechanisms of durum wheat under salt stress

The present study was conducted to investigate the effects of potassium nutrition on antioxidative defense mechanism of durum wheat under salt stress, plants were grown under controlled climate conditions and different potassium (75, 150 and 2010 μM) and NaCl (0 and 125 mM) doses. Shoot dry matter production significantly decreased with NaCl treatment. Due to salt application, both shoot and root Na concentrations increased as well. On the other hand, shoot and root Na concentrations decreased in the case of sufficient potassium treatment (2010 μM). Salt treatment decreased K and Ca concentrations, K/Na and Ca/Na ratios in both shoot and roots. Increased K nutrition resulted in augmented K/Na ratios in shoots and roots. Salt treatment increased lipid peroxidation under all K doses. Lipid peroxidation of both the control and 125 mM NaCl treatments were lower under sufficient K nutrition. SH-compound levels declined with salt stress and increased K nutrition also reduced SH-compound levels and ascorbic acid concentrations. Superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione reductase (GR), catalase (CAT) and guaiacol peroxidase (GuPX) activities were lower under low potassium doses than sufficient potassium. Under sufficient K treatment, 125 mM NaCl treatment distinctively enhanced SOD, GR, CAT and GuPX activities and such raises complied with the declines in lipid peroxidation with increased K-nutrition. Results revealed that, improved potassium nutrition is very important to prevent durum wheat against NaCl toxicity-induced oxidative stress.