Effect of green synthesized silver nanoparticles on growth and physiological responses of pearl millet under salinity stress

Agricultural production and food security are hindered by abiotic stress in plants. Consequently, novel approaches are needed to overcome these problems and achieve sustainability. Crop production has been demonstrated to be improved by nanoparticles under several biotic and abiotic stress conditions. This experiment examined the effect of different concentrations of green synthesized silver nanoparticles AgNPs (15, 25, 35, 45, and 55 ppm) on the growth and physiological responses of pearl millet subjected to NaCl stress levels (50, 75, 100, 125, and 150 mM); (3) Results: In the current research, the NaCl stress levels significantly reduced the growth metrics (shoot length, root length, shoot fresh and dry weight, and root fresh and dry weight) chlorophyll a, chlorophyll b and soluble protein, compared to control. Contrary to this, all stress levels induced an increase in osmolytes (soluble sugars and proline) and antioxidant enzymes including superoxide dismutase, catalase, and ascorbate peroxidase. It is likely that the diminished growth metrics of NaCl-treated seedlings are due to the increased effort put forth in osmotic adjustment and antioxidant defense mechanisms to counteract reactive oxygen species and oxidative stress. The foliar spray of AgNPs, however, further enhanced osmotic and O2--H2O2 scavenging mechanisms in NaCl stressed seedlings to reduce the oxidative stress damages, resulting in improved growth. Overall, AgNPs application improved the growth metric, chlorophyll pigments, osmolytes, and antioxidant mechanism of salt-stressed seedlings in a dose-additive manner. However, further testing of AgNPs is required with pearl millet and other cereals in the field to validate these results.