Integrated physiological, transcriptomic, and metabolic analysis reveals the effects of nanoplastics exposure on tea plants

Micro/nanoplastics (M/NPs) are emerging as hazardous environmental contaminants threatening crop safety and ecosystem resilience. They pose a global threat to ecosystems and compromise food security and human health by introducing unforeseen risks. Tea plants, which are perennial evergreens cultivated in more than 50 countries, face severe risks from M/NP contamination, which jeopardize their growth, development, and product quality/safety. However, the molecular mechanisms of tea plants to M/NPs remain largely unknown. In this study, we systematically investigated the effects of polystyrene nanoplastics (PS-NPs) on tea plants using hydroponics and integrated physiological, transcriptomic, and metabolomic analyses. We found that PS-NPs were absorbed by the roots and translocated to aerial tissues, with significant accumulation in tender tissues. PS-NPs exposure inhibited root elongation while inducing lignification in the root cortex and stele, and impaired photosynthesis via reduced efficiency, disrupted chlorophyll biosynthesis, altered stomatal dynamics, and ROS homeostasis dysregulation. Integrated transcriptomic and metabolomic analyses revealed the concurrent enrichment of phenylpropanoid/flavonoid biosynthesis, glutathione metabolism, and hormones signaling pathways in the roots/leaves, indicating their pivotal role in tea plant responses to PS-NPs exposure. Additionally, key response genes were identified, revealing the mechanistic targets for resilience enhancement in tea plants. Our findings offer mechanistic insights into how PS-NPs disrupt tea plants growth and development through the multi-level dysregulation of physiological and molecular homeostasis, thereby providing theoretical support for green development in the tea industry with consideration of the challenge of widespread M/NP contamination.