Nano-ceria priming ameliorates heavy metal nanoparticle toxicity in tomato

Abrupt urbanization and enhanced anthropogenic processes have resulted in severe soil contamination with heavy metals, especially nickel (Ni), which negatively impacts plant physiological and biochemical processes. Both the bulk and nanoparticle forms of Ni disrupt plant growth, which poses severe threats to agricultural productivity and food safety. In the background of these challenges, recent research has highlighted the improvement of sustainable techniques to promote crop yield under stresses. Seed nano-priming is one such promising technique that optimizes germination, seedling vigor, and overall plant tolerance. The current study was focused on the protective effect of seed priming with cerium oxide nanoparticles (CeO₂-NPs) against nickel oxide nanoparticles (NiO-NPs) stress in tomato ( Solanum lycopersicum L.) seedlings. Tomato seeds were primed with CeO₂-NP suspensions at 2, 4, and 8 mg L⁻¹ for 24 hours, with negative (water-treated) and positive (NiO-NP-treated) control groups. NiO-NP stress caused significant reductions in germination rate (by 48.33%), shoot and root growth, cell viability, mitotic activity, and genomic stability. In contrast, CeO₂-NP priming effectively reversed these detrimental effects. Of all the treatments, 4 mg L⁻¹ CeO₂-NP showed the greatest reduction in oxidative stress, as evidenced by a 30.85% drop in H₂O₂ content, besides significant increases in antioxidant activity, mitotic index (up by 85.71%), and genomic stability. The findings reveal the potential of CeO₂-NP seed priming in overcoming NiO-NP-induced phytotoxicity and genotoxicity. The study demonstrates CeO₂-NPs as an effective, eco-friendly technique for enhancing plant resistance in Ni-polluted soils.