From energy collapse to chemical defense: Microplastics reshape the metabolic landscape of Tetrastigma hemsleyanum (Vitaceae).

Microplastics have emerged as widespread terrestrial contaminants, yet their mechanistic effects on medicinal plants remain largely unresolved. Here, we investigated the uptake, intracellular movement, and multi-level stress responses of Tetrastigma hemsleyanum, a flavonoid-rich medicinal species, under exposure to polystyrene microplastics. Confocal imaging confirmed extensive microplastic accumulation in the roots and vascular transport to the leaves. Microplastic stress induced pronounced oxidative damage, as evidenced by a 45.2 percent increase in malondialdehyde, enhanced peroxidase and catalase activities, and a 42.5 percent reduction in total chlorophyll content and photosynthetic efficiency. Multi-omics integration revealed coordinated suppression of photosynthetic energy metabolism, exemplified by the strong repression of RPN2A, along with pronounced activation of PER31 and key genes of the flavonoid biosynthetic pathway. These transcriptional shifts corresponded with elevated accumulation of antioxidant metabolites, including catechin, dihydrokaempferol, and quercetin. Collectively, this study supports a mechanistic model in which microplastics disrupt redox homeostasis and constrain ATP supply, initiating a whole plant reallocation of metabolic resources from carbon fixation toward flavonoid-centered antioxidant defense. This adaptive shift provides insight into plant resilience to emerging pollutants and highlights the potential vulnerability of medicinal quality under microplastic contamination.