Polypropylene Microplastics Bidirectionally Modulate Copper Toxicity in <i>Jasminum sambac</i> by Rewiring Glutathione and Porphyrin‐Photosynthetic Networks

Copper is essential yet phytotoxic when excessive, and polypropylene microplastics (PP-MPs) are increasingly co-occurring with Cu in soils, but their mechanistic impact on woody ornamentals remains unclear. Jasminum sambac in Cu spiked soil across a PP-MPs gradient and found a dose-dependent, non-monotonic modulation of Cu toxicity. PP-MPs accumulated on root surfaces, shifting Cu partitioning along the soil-root-shoot axis: an intermediate load reduced shoot Cu and translocation, lowered membrane lipid peroxidation, and was accompanied by coordinated adjustment of glutathione redox metabolism (GSR, G6PD, PGD) and GSH turnover (GGT, GGCT). Transcriptomics indicated that moderate PP-MPs partially restored genes for chlorophyll biosynthesis (CHLI/CHLH/CHLM) and light-harvesting (Lhcb1/2), aligning with improved photosynthesis and chlorophyll a/b balance. However, high dose PP-MPs weakened this protection: root Cu rebounded, antioxidant enzymes (SOD/POD) dropped below control levels, PetC expression remained low, and chlorophyll a/b imbalance reoccurred. At a higher load, protection weakened root Cu rebounded, SOD and POD fell below control levels, PetC associated electron transport remained constrained, and Chl a/b imbalance re-emerged. The data suggest that PP-MPs act as both an interfacial sorptive buffer and a regulator of redox photosynthetic networks, informing risk assessment of metal-microplastic co‑contamination in soils.