Metal nutrition and transport in the process of symbiotic nitrogen fixation

Symbiotic nitrogenfixation(SNF)facilitated by the interaction between legumes and rhizobia is a well-documented and eco-friendly alternative to chemical nitrogen fertilizers.Host plants obtainfixed nitrogen from rhizobia by providing carbon and mineral nutrients.These mineral nutrients,which are mostly in the form of metal ions,are implicated in various stages of the SNF process.This review describes the functional roles played by metal ions in nodule formation and nitrogenfixation and specifically addresses their trans-port mechanisms and associated transporters within root nodules.Future research directions and poten-tial strategies for enhancing SNF efficiency are also discussed.