Amelioration of salt induced toxicity in pearl millet by seed priming with silver nanoparticles (AgNPs): The oxidative damage, antioxidant enzymes and ions uptake are major determinants of salt tolerant capacity

Abiotic stresses in plants reduce crop growth and productivity. Nanoparticles (NPs) are effectively involved in the physiochemical processes of crop plants, especially under the abiotic stresses; whereas, less information is available regarding the role of AgNPs in salt-stressed plants. Therefore, in the current study, we investigated the effects of seed priming with commercially available silver nanoparticles (AgNPs) (size range between 50 and 100 nm) on plant morphology, physiology, and antioxidant defence system of pearl millet (Pennisetum glaucum L.) under different concentrations of salt stress (0, 120 and 150 mM NaCl). The seed priming with AgNPs at different levels (0, 10, 20 and 30 mM) mitigated the adverse impacts of salt stress and improved plant growth and defence system. The results demonstrated that salt-stressed plants had restricted growth and a noticeable decline in fresh and dry weight. Salt stress enhanced the oxidative damage by excessive production of hydrogen peroxide (H₂O₂), malondialdehyde (MDA) contents in pearl millet leaves. However, seed priming with AgNPs significantly improved the plant height growth related attributes, relative water content, proline contents and ultimately fresh and dry weight at 20 mM AgNPs alone or with salt stress. The AgNPs reduced the oxidative damage by improving antioxidant enzyme activities in the pearl millet leaves under salt stress. Furthermore, sodium (Na⁺) and Na⁺/K⁺ ratio was decreased and potassium (K⁺) increased by NPs, and the interactive effects between salt and AgNPs significantly impacted the total phenolic and flavonoid content in pearl millet. It was concluded that seed priming with AgNPs could enhance salinity tolerance in crop plants by enhancing physiological and biochemical responses. This might boost global crop production in salt-degraded lands.

Keywords: Antioxidants; Plant growth; Salinity; Seed priming; Silver nanoparticles.