Effect of zinc ferrite nanoparticles and plant growth promoting rhizobacteria on growth and performance of okra under induced cadmium stress.

Cadmium (Cd) contamination of agricultural soils presents a severe threat to global food security by impairing crop productivity and introducing toxins into the food chain. Seeking an effective and sustainable remediation strategy, this study investigated the synergistic potential of zinc ferrite nanoparticles (ZnFe₂O₄NPs) and plant growth-promoting rhizobacteria (PGPR; Citrobacter sp. NCCP-668) in enhancing cadmium stress tolerance and the productivity of okra (Abelmoschus esculentus). A pot experiment was designed employing two levels of Cd stress (30 µM and 60 µM), simulating conditions from moderately to highly contaminated soils. Ten distinct treatment groups were established, including controls, individual applications of ZnFe₂O₄ NPs (100 mg/L) and PGPR, and their combined application. The results unequivocally demonstrated that exposure to Cd stress alone significantly inhibited key germination metrics, vegetative traits, and anatomical features by 16% to 79% compared to the non-stressed control. However, the co-application of ZnFe₂O₄ NPs and PGPR significantly mitigated these deleterious effects. Under 30 µM Cd stress, the combined treatment increased the germination rate index by 125.3%, leaf area by 99%, and stomatal length by 130%. PGPR treatments, both individually and in combination, were particularly effective at enhancing moisture retention in vegetative tissues under Cd stress. These findings establish the co-application of ZnFe₂O₄ NPs and PGPR as a highly promising, eco-compatible strategy for the remediation of Cd-contaminated soils and the sustainable production of crops like okra, ensuring both food safety and security.