Dynamic drivers of PAHs transformation in the spatial and temporal continuum of the rhizosphere: An analysis of plant-microbe synergistic mechanism

Abstract

The migration and transformation of polycyclic aromatic hydrocarbons (PAHs) in soil systems are inherently constrained by their low solubility, strong sorption affinity to soil particles, and limited bioavailability for biological uptake and degradation. As a critical ecological interface mediating plant-microbe interactions, the rhizosphere plays a pivotal role in facilitating PAHs mobilization and transformation processes. This review systematically examines the spatiotemporal dynamics of PAHs migration and transformation within rhizosphere systems under plant-microbe collaborative regulation, characterized by sequential temporal phases (initial desorption-solubilization, intermediate absorption-accumulation, and terminal degradation-transformation) and spatial stratification (rhizosphere soil-liquid interface, root surface microenvironment, and internal root tissues). We particularly emphasize the synergistic plant-microbe interactions that drive PAHs desorption, solubilization, phytoaccumulation, and biodegradation. Furthermore, we elucidate four potential mechanistic pathways: AHL analogs in root exudates activate bacterial quorum sensing systems to stimulate surfactant production and PAHs-degrading enzyme synthesis; Microbial-derived IAA enhances H⁺ -ATPase activity in plants, facilitating PAHs/H⁺ co-transport mechanisms; Coordinated AHL-IAA signaling promotes Ca²⁺ uptake and upregulates root nodule symbiosis-related gene expression; ROS in root exudates activate bacterial c-di-GMP signaling pathways to enhance microbial colonization and PAHs-degrading enzyme production. We also analyze the practical limitations affecting rhizoremediation efficacy, including climatic conditions, soil heterogeneity, and variations in pollutant types, and propose corresponding future research directions toward the end of the article. This comprehensive analysis establishes a theoretical framework for understanding the mechanistic basis of plant-microbe synergism in rhizospheric PAHs remediation, offering a foundation for advancing rhizosphere engineering and phytoremediation strategies.

Keywords: Biodegradation; Plant-microbe synergism; Polycyclic aromatic hydrocarbons; Rhizoremediation.