Effects of foliar microplastic exposure on cherry radish: Photosynthesis inhibition mechanisms and multi-omics functional network analysis

The pervasive contamination of microplastics (MPs) represents a critical global environmental threat. However, their effect on the plant-soil-microbe system remains poorly understood. This study investigated the physiological and biochemical responses of cherry radish (Raphanus sativus L.) to foliar MPs exposure, elucidating tissue-specific metabolic mechanisms and rhizosphere microbial community shifts. Key findings demonstrate that foliar MPs exposure severely impaired photosynthesis, with polystyrene microplastics (PSMPs) reducing net photosynthetic rate by 63.1 %. Disruption of chlorophyll synthesis was evidenced by reduced Mg (7.2-18.4%) and Zn (13.5-29.3%) accumulation. Stomatal blockage and starch grain accumulation further compromised photosynthetic efficiency. Distinct oxidative stress responses between leaves and roots revealed differential metabolic adaptations. Leaves upregulated galactose metabolism while downregulating starch-sucrose metabolism and TCA cycle activity. Roots enhanced glyoxylate-dicarboxylate metabolism but suppressed butanoate metabolism. Under photosynthetic constraints, metabolomics confirmed redirected carbon allocation and energy conversion. Rhizosphere communities exhibited strengthened synergistic interactions, with bacterial alpha diversity increasing while fungal diversity decreased significantly. Partial least squares structural equation modeling (PLS-SEM) further uncovered complex feedback regulation within the plant-soil-microbe continuum. This study provides valuable insights for understanding the mechanism of "plant-soil-microbe" interactions under MPs stress.