Unveiling the Dual Effects of Aluminum Oxide (Al ₂ O ₃ ) Nanoparticles at Varying Doses: Assessing Low- vs High-Dose Impacts on <i>Pisum sativum L</i> . Seedlings and Their Potential in Lead Mitigation

In this study, we revealed a dose-dependent response of aluminum oxide nanoparticles (Al2O3 NPs) for evaluating their toxicity and for harnessing their potential beneficial application in lead (Pb) remediation in germinating pea (Pisum sativum L.). Our findings showed that at high concentrations of 200 and 500 mg/L Al2O3 NPs, root and shoot lengths decreased by 80% and 75%, respectively, compared to controls. However, Al2O3 NPs at a low concentration of 10 mg/L increased root length by 50%, and fresh biomass and dry biomass of shoots by 15% to 30%, respectively, as compared to controls. In addition, when Al2O3 NPs were assessed under Pb stress, a stimulation of the embryonic axis length and fresh biomass was revealed, by 30% and 15%, respectively, as compared to Pb. Al2O3 NPs at a low concentration seem to counteract Pb-induced toxicity and promote seed germination and early growth dynamics. This was attributed to the significant decline in oxidative stress indicators and improved protection of proteins against oxidation. Al2O3 NPs also acted via the enhancement of the recovery of cellular redox homeostasis and the antioxidant defense system. This resulted in the decline of cell death by 25% with Al2O3 NPs treatment as compared to Pb. This nanoparticle-induced physiological and metabolic modulation, enhancing seedlings’ stress tolerance, seems to be complemented by Pb surface adsorption, which reduces Pb bioavailability. This dual mechanism suggests a synergistic interaction that underscores the combined physicochemical and biological roles of Al2O3 NPs in mitigating Pb toxicity.