Synergistic Promotion of Phosphorus Uptake by Root Architecture and Exudates in Legume–Cereal Intercropping Systems: A Review

Phosphorus, a non-renewable nutrient and limiting factor for crop growth, has drawn considerable attention due to the need to improve its use efficiency. Intercropping enhances phosphorus use efficiency by increasing biodiversity, thereby maintaining high productivity and ecosystem sustainability. The primary mechanisms through which intercropping systems enhance phosphorus uptake and utilization in crops encompass adaptive modifications in root morphology, the secretion of a variety of root exudates (including organic acids, phytosiderophores, and phosphatases), and the recruitment of beneficial microorganisms, such as plant growth-promoting rhizobacteria (PGPR). In this context, the remodeling of root architecture increases the soil contact area, while root exudates not only directly mobilize soil phosphorus reserves but also supply energy and signaling molecules to microorganisms, facilitating the targeted assembly of rhizosphere communities. These microorganisms further augment phosphorus transport and uptake through a series of processes involving “chemical dissolution, enzymatic mineralization, and hyphal transport.” This review systematically explores the synergistic interaction between root architecture and exudates in promoting efficient phosphorus utilization, with the aim of enhancing the understanding of the regulatory mechanisms governing subterranean inter root interactions. Future research should investigate the biological underpinnings of subterranean interactions within intercropping systems that improve phosphorus efficiency. This can be achieved by concentrating on gene interaction networks associated with phosphorus uptake, transport, and utilization; rhizosphere metabolites; beneficial functional microorganisms; real-time monitoring of high-throughput phenotypes; and simulations and optimizations based on artificial intelligence.