Selenium mitigates salt-induced oxidative stress in durum wheat ( Desf.) seedlings by modulating chlorophyll fluorescence, osmolyte accumulation, and antioxidant system.

Hydroponic experiments were conducted to investigate the effects of different concentrations of sodium selenate (NaSeO) and sodium selenite (NaSeO) on durum wheat seed germination and seedling growth under salt stress. The treatments used were 0 and 50 mM NaCl solutions, each supplemented with NaSeO or NaSeO at 0, 0.1, 1, 2, 4, 8, or 10 μM. Salt alone significantly inhibited seed germination and reduced seedling growth. Addition of low concentrations (0.1-4 μM) of NaSeO or NaSeO mitigated the adverse effects of salt stress on seed germination, biomass accumulation, and other physiological attributes. Among them, 1 μM NaSeO was most effective at restoring seed germination rate, germination energy, and germination index, significantly increasing these parameters by about 12.35, 24.17, and 11.42%, respectively, compared to salt-stress conditions. Adding low concentrations of NaSeO or NaSeO to the salt solution also had positive effects on chlorophyll fluorescence indices, decreased the concentrations of free proline and malondialdehyde, as well as electrolyte leakage, and increased catalase, superoxide dismutase, and peroxidase activities in roots and shoots. However, high concentrations (8-10 μM) of NaSeO or NaSeO disrupted seed germination and seedling growth, with damage caused by NaSeO being more severe than that by NaSeO. It is thus clear that exogenous selenium can improve the adaptability of processing wheat to salt stress and maintain higher photosynthetic rate by decreasing the accumulation of reactive oxygen species and alleviating the degree of membrane lipid peroxidation. NaSeO was more effective than NaSeO at all given concentrations.