Exogenous selenium application enhances the photosynthetic pigment and antioxidant defense of mash bean (Vigna mungo) to confer tolerance to salt stress

Mash bean is an important crop enriched with proteins and highly praised in Pakistan due to its nutritional values. However, due to abiotic stresses like salinity, its production is decreased. This study was conducted to investigate the effect of selenium on mash bean to produce salt tolerance. Mash bean seeds were sown in plastic pots filled with sand. Three levels of NaCl (0 mM, 100 mM, 200 mM) and five levels of selenium (0 ppm, 20 ppm, 40 ppm, 80 ppm, 120 ppm) were applied with Hoagland solution. Salinity reduced plant height (28%), leaf area (33%), chlorophyll a (14%), chlorophyll b (9%), carotenoids (20%), potassium ions, calcium ions, superoxide dismutase, peroxidases, catalase, salt tolerance index and increased sodium ions (21%), H2O2 content as well as secondary metabolites. However, selenium application in low concentration enhanced plant height (31%), leaf area, chlorophyll a (17%), chlorophyll b (12%), carotenoids (40%), potassium, calcium, superoxide dismutase, peroxidases, catalase, salt tolerance index, proline, flavonoids, total phenol, while decreased sodium ions (25%) and hydrogen peroxide content under salt stress. Findings showed important function of selenium in improving physical characteristics, absorption of ions, photosynthetic pigments, and antioxidant defense in plants under salinity. Applying selenium at 40 ppm concentrations showed greatest efficacy in alleviating negative impacts of salt stress (100 mM) on plant growth and biochemical attributes. Maximum positive results of selenium application (40 ppm) were obtained at 0 mM of salinity.