Abstract

PS-MPs (0.1 and 0.5 μm) were absorbed by tomato roots and translocated to stems and leaves. • High concentrations of small-sized PS-MPs significantly inhibited tomato growth and activated oxidative stress responses. • Transcriptomic analysis revealed disruptions in hormone signaling, MAPK cascade, and phenylpropanoid biosynthesis pathways. • Metabolomic profiling showed alterations in antioxidant systems, alkaloid metabolism, and membrane lipid biosynthesis. • Integrated omics revealed PS-MPs interfere with growth, stress adaptation, and metabolic homeostasis in tomato seedlings. Microplastics (MPs) are increasingly recognized for their uptake by plants and associated risks to human health through the food chain. However, the underlying mechanisms governing MP absorption and physiological impacts in crop plants remain inadequately understood. This study systematically examined for the first time the uptake, translocation, accumulation, physiological alterations, and molecular mechanisms elicited by polystyrene MPs (PS-MPs) in tomato ( Solanum lycopersicum L.). Results showed that both sized PS-MPs were absorbed by root tissues and then translocated to aerial parts, accumulating preferentially in roots > stems > leaves. Smaller particles and higher exposure concentrations significantly enhanced internal accumulation. PS-MPs stress reduced root elongation, plant height, and fresh biomass, while upregulating oxidative stress markers concentration-dependently. Transcriptomic analyses showed that high concentrations of smaller-sized PS-MPs induced more differentially expressed genes, particularly those involved in key pathways such as plant hormone signal transduction, MAPK signaling pathway-plant, and phenylpropanoid biosynthesis. Metabolomic profiling verified disruptions in phenylpropanoid biosynthesis, ascorbate and aldarate metabolism, and glycerophospholipid metabolism, suggesting compromised membrane integrity and antioxidant capacity. This study advances our u