Iron oxide nanoparticles ameliorated the cadmium and salinity stresses in wheat plants, facilitating photosynthetic pigments and restricting cadmium uptake

Cadmium and salinity are the major threats to environmental resources and agricultural practice worldwide. The present work aims green synthesis, characterization, and application of iron oxide nanoparticles for co-alleviation of Cd and salt stresses in wheat plants. The iron oxide NPs were synthesized from a native bacterial strain, Pantoea ananatis strain RNT4, yielding a spherical FeO-NPs with a size ranging from 19 to 40 nm evidenced by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images. Results showed that application of 100 mg kg⁻¹ of the bioengineered FeO-NPs in an original saline soil stimulated wheat plant growth, gaining 36.7% of additional length as compared with the control scenarios, via alleviating the detrimental effects of abiotic stresses and thereby reprogramming the morpho-physiological state of wheat plants. In addition, the presence of FeO-NPs in soil significantly increased the nutrient concentrations of N, P and K⁺, while reducing the Na⁺ and Cl⁻ components in the wheat grain. Interestingly, application of the FeO-NPs in Cd-polluted soils eventually reduced wheat plant uptake of Cd by 72.5%, probably due to the adsorption of Cd onto the large surface of NPs and thereby, constraining Cd bioavailability to the plants. It provides the first evidence that a FeO-NPs-based treatment could be a candidate agricultural strategy for mitigating the Cd and salt stresses in Cd-polluted saline soils for safe agriculture practice.