Antioxidant machinery modulation by phosphorus mitigates zinc oxide nanoparticle toxicity in Triticum aestivum and Solanum lycopersicum seedlings

Industrial products containing nano-zinc oxide (ZnONPs) enter the agricultural environment and pose hazardous effects on major crops. This study aimed to investigate the potential of 4 mM soil phosphorus (diammonium phosphate) to mitigate the adverse effects of ZnONPs stress on Triticum aestivum (wheat) and Solanum lycopersicum (tomato) seedlings. Under hydroponic conditions, 500 and 1000 µM ZnONPs were found to inhibit the growth of both crops by reducing root and shoot lengths. Additionally, physiological indices, including pigment content and endogenous nitric oxide (NO) levels, were reduced, accompanied by an increase in Zn accumulation. Enhanced activities of four antioxidant enzymes—Superoxide dismutase (EC 1.15.1.1), Catalase (EC 1.11.1.6), Ascorbate peroxidase (EC 1.11.1.11), and Glutathione-S-transferase (EC 2.5.1.18)—indicated oxidative damage in ZnONPs-exposed tomato and wheat seedling. Supplementation with phosphorus influenced NO generation, which subsequently up-regulated antioxidative enzymes and mitigated the effects on pigment content and growth. The ZnONPs-induced reactive oxygen species (ROS) were scavenged, and Zn accumulation in shoots and roots was reduced. Overall, the results suggest that phosphorus can reverse ZnONPs-induced oxidative stress by increasing endogenous NO levels, highlighting its potential for safe vegetable production in areas polluted with metal nanoparticles.