Soil cadmium (Cd) contamination pose a serious threat to global food safety. Boron (B) application effectively reduces Cd accumulation in crops via a dual defense mechanism. This review synthesizes the mechanisms of apoplastic barrier reinforcement and transmembrane transport regulation in plants. B promotes pectin biosynthesis, cross-linking and demethylation of the cell wall to immobilize more Cd2+. It also stimulates the deposition of lignin in the Casparian strip, physically blocking Cd2+ entry into the stele of rice, hot pepper and rape. Additionally, B acts as a transcriptional regulator to downregulate influx transporters (e.g., NRAMP1, IRT1) located at the plasma membrane. Consequently, the expression of vacuolar sequestration transporters (e.g., HMA3, ABCC2) is suppressed, reflecting an adaptive response to reduced cytosolic Cd. The concept of "external exclusion and influx inhibition" provides a theoretical basis for implementing B-based agronomic practices as a strategy to inhibit Cd uptake, ensuring safer food production in Cd-contaminated soils.
Junliang Xin (Wed,) studied this question.