Zinc oxide nanoparticles at low dose mitigate lead toxicity in pea (Pisum sativum L.) seeds during germination by modulating metabolic and cellular defense systems

Addressing lead (Pb) pollution and contamination in soil and agriculture is urgent due to its widespread and long-lasting impacts on human health, food safety, and the environment. In the current study, we assessed the potential use of Zinc oxide nanoparticles (ZnONPs) in alleviating Pb toxicity in germinating seedlings. Pea (Pisum sativum L.) seedlings were exposed to Pb (83 mg/L) over a 7-day period, without and with ZnONPs amendment. Our results showed that the application of ZnONPs at 10 mg/L restored the morphological parameters affected by Pb, 34 %, 26 % and 23 %, for the length, fresh, and dry biomass of embryonic axis, respectively. ZnONPs decreased the activities of antioxidative enzymes of catalase (87.5 %), guaiacol peroxidase (60 %), and glutathione peroxidase (25 %), but increased the activities of ascorbate peroxidase (60 %) and glutathione reductase (25 %). These changes were associated with the increase (7 %) in the thiol groups, and reductions in the malondialdehyde (23 %), hydrogen peroxide (33 %), and carbonyl group levels (78 %), in addition to the stimulation of the activities of ROS-associated enzymes, including glycolate oxidase (40 %) and NADPH oxidase (by 89 %). Consequently, cell viability was increased by 66 %, while cellular death was reduced by 10 %, with ZnONPs, relative to the Pb-stressed seedlings. These findings highlight the mechanisms surrounding the ability of nanosized ZnO to mitigate the harmful effects of Pb on the growth and physiology of plants. Further investigation is needed to understand the mitigating effects of ZnONPs on Pb on the molecular and genomic levels in seedlings and plants, and ensure the sustainability of agricultural practices and food safety. Besides, site and sourcespecific integrated approaches must be practiced to formulate suitable remediation strategies.