Type-dependent effects of microplastics on tomato (Lycopersicon esculentum L.): Focus on root exudates and metabolic reprogramming

Much attention has been paid to the prevalence of microplastics (MPs) in terrestrial systems. MPs have been shown to affect the physio-biochemical properties of plants. Different MPs may have distinctive behaviors and diverse effects on plant growth. In the present study, the effects of polystyrene (PS), polyethylene (PE), and polypropylene (PP) MPs on physio-biochemical properties, root exudates, and metabolomics of tomato (Lycopersicon esculentum L.) under hydroponic conditions were investigated. Our results show that MPs exposure has adverse effects on tomato growth. MPs exposure had a significant type-dependent effect (p < 0.001) on photosynthetic gas parameters, chlorophyll content, and antioxidant enzyme activities. After exposure to MPs, the content of low molecular weight organic acids in tomato root exudates was significantly increased, which was considered as a strategy to alleviate the toxicity of MPs. In addition, MPs treatment significantly changed the metabolites of tomato root and leaf. Metabolic pathway analysis showed that MPs treatment had a great effect on amino acid metabolism. We also found that plants exposed to PS and PP MPs produced more significant metabolic reprogramming than those exposed to PE MPs. This study provides important implications for the mechanism studies on the toxic effect of various MPs on crops and their future risk assessment.