Silicon and Selenium supplementations modulate antioxidant systems and mineral nutrition to mitigate salinity-alkalinity stresses in cucumber (Cucumis Sativus L.) plants under hydroponic conditions

Experiments were conducted to investigate the role of silicon (Si, 75, 100 mg. L-1 sodium silicate) and selenium (Se, 4, 6 mg. L-1 sodium selenate) in ameliorating the salinity (75 mM NaCl and 75 mM NaHCO3) caused strong detrimental effects on mineral ions uptake and the oxidative damage in cucumber (Cucumis Sativus L.) plants. Salinity and alkalinity stresses reduced macro and micro elements content which were significantly improved by Si and Se supplementation. Further, peroxide hydrogen was more in salinity- alkalinity stressed plants without Si and Se as compared to those supplemented with Si and Se. Si protected cucumber plants from NaCl induced oxidative damage by improving the activity of antioxidant enzymes (glutathione reductase, guaiacol peroxidase, ascorbate peroxidase).  More importantly Si and Se supplementation improved the accumulation of P, Mg, Ca, Fe, Zn, Mn and Cu. In conclusion, Si and Se mitigate the negative effects of NaCl and NaHCO3 in cucumber plants by modifying nutrient uptake and up-regulating antioxidant system.