Proactive attenuation of arsenic-stress by nano-priming: Zinc Oxide Nanoparticles in Vigna mungo (L.) Hepper trigger antioxidant defense response and reduce root-shoot arsenic translocation

Arsenic (As) stress is mainly responsible for hampering seed germination and plant development. Accumulation of As in grains poses a major threat to agricultural output and food security. This study sought to determine the feasibility of seed priming with biogenic Zinc Oxide Nanoparticles (ZnONPs) to alleviate As-phytotoxicity in both seedlings and plants before the reproductive stage in Vigna mungo (L.) Hepper (blackgram). This report is the first of its kind in depicting stress amelioration by nano-priming in blackgram. Under As stress, ZnONPs significantly enhanced blackgram seed germination rate (20–23.33%), and other morpho-physiological attributes. The incorporation of ZnONPs resulted in a decrease in reactive oxygen species build-up (hydrogen peroxide by 23–67%) and malondialdehyde (21–69%). Additionally, ZnONPs caused a surge in the accumulation of osmoregulators and activity of antioxidant enzymes (superoxide dismutase by 28–68%, catalase by 20–42%, guaiacol peroxidase by 19–49%, and ascorbate peroxidase by 26–39%). Results infer that ZnONPs play an immense role in mitigating As-toxicity by limiting its translocation from root to shoot. Together, this study offers the first evidence to show that nano-priming with ZnONPs can efficiently alleviate As-stress in blackgram, demonstrating its potential use as a stress-relieving agent in As-contaminated areas to increase growth and yield.