Root traits and rhizosphere responses as emerging bioindicators of microplastic pollution in agricultural soils: A...

In agricultural soils, crop roots are central to regulating soil health, nutrient cycling, and long-term carbon sequestration through rhizosphere-driven processes such as root exudation, microbial modulation, and litter decomposition. However, the increasing prevalence of microplastics (MPs) in farmlands arising from mulching films, sewage sludge, composts, and atmospheric deposition is increasingly recognized as a pervasive threat to root-soil-microbe interactions. This review focused on how crop root traits (architecture, chemistry, turnover) are influenced by MPs and explores their cascading impacts on rhizosphere functionality, with a specific focus on their potential as emerging bioindicators of MPs pollution in agricultural soils. MPs disrupt root morphology, alter microbial communities, reduce carbon inputs as exudates, and interfere with organo-mineral associations, and reshape rhizosphere responses that govern soil aggregation, nutrient availability, and microbial carbon stabilization. These responses vary across crop functional types, including grasses, legumes, vegetables, and fodder crops, reflecting differences in root architecture, turnover, and rhizosphere regulation. Collectively, these trait-based responses provide integrative and sensitive indicators of MPs stress in agroecosystems. We highlight future research strategies emphasizing rhizosphere engineering such as microbiome manipulation, exudation modulation, breeding for resilient root traits, and multi-indicator integration, to mitigate MPs stress and enhance overall ecosystem resilience. Collectively, this review underscores the potential of root-based bioindicators and rhizosphere responses as robust tools for monitoring MPs pollution and supporting sustainable soil management in plastic-impacted agroecosystems.