Iron-Mediated Spatial Cadmium Resistance Mechanisms: Dual Shield and Spear Strategies in Soil–Plant Systems

Research on iron (Fe)-mediated plant mitigation of cadmium (Cd) stress has achieved significant progress. This review elucidates the dual role of Fe as both a "shield and spear" from a Spatial perspective. Initially, exogenous Fe acts as a rapid "shield" by immobilizing Cd, recruiting beneficial microorganisms, and forming iron plaque in the rhizosphere to inhibit Cd uptake, simultaneously initiating early defense by upregulating Fe uptake systems. Subsequently, Fe shifts to a "spear" function, enhancing long-term plant tolerance by inhibiting Cd transport at cellular levels, repairing photosystem damage, and strengthening antioxidant defenses at molecular levels. These mechanisms provide crucial insights for developing Fe-based agronomic strategies. However, the dose-response toxicity and the trade-off between defense and growth limit field practical application. To address this, we integrate the physicochemical properties of Fe-based materials with agronomic management practices to propose application guidelines, advancing sustainable agricultural development.