Manganese oxide nanoparticles elicit cadmium tolerance in wheat seedlings by ionomic and phenomic adjustment, regulation of AsA–GSH pathway, cellular thickness recovery, and antioxidant modulation†

Abstract

This study evaluates the effects of cadmium (Cd) stress on wheat cultivars SKD-1 and Borlaug-16 and the use of manganese dioxide nanoparticles (MnO₂NPs) for remediation. Upon characterization, MnO₂NPs demonstrated colloidal stability and effectiveness, with an average size of 37.63 nm determined by the Scherrer equation and 41 nm by Rietveld refinement, flake-like shape, and a zeta potential of −10.9 mV. Both wheat cultivars were subjected to 50 mg kg⁻¹ Cd stress and treated with MnO₂NPs at 100, 250, and 500 ppm through nano-priming. MnO₂NPs significantly reduced Cd uptake by 20–50% in both root and leaf tissues. Cd exposure increased toxic elements like arsenic, chromium, copper, nickel, and lead in Borlaug-16 roots by up to 50% and decreased essential minerals by 30–60%. The 250 ppm MnO₂NPs treatment restored essential minerals by up to 45%. In SKD-1, Cd exposure raised H₂O₂ levels by 78.03% in roots and malondialdehyde by 40.03% in leaves. MnO₂NPs reduced H₂O₂ to 7.85 μmol g⁻¹ and malondialdehyde to 1.29 mmol g⁻¹, while increasing superoxide dismutase activity by 86.77%. Anatomical analysis revealed that Cd exposure increased epidermis thickness by 16.80% and decreased cortex thickness by 29.10% in SKD-1 roots, while MnO₂NPs promoted recovery by 50–80%. Ionomic analysis showed that MnO₂NPs improved ion distribution and reduced Cd uptake by 40–60%, with notable improvements in calcium, magnesium, and potassium levels. These findings highlight the potential of MnO₂NPs in mitigating Cd stress, enhancing physiological resilience, and elemental balance in wheat. Future research should focus on optimizing MnO₂NPs application to achieve sustainable crop production.