Accumulation of nanoplastics in wood plants presenting cell type preference

Despite the increasing nanoplastics (NPs) pollution in terrestrial ecosystems, the absorption, translocation, accumulation, and adverse effects of NPs in forest trees remain unclear. Three types of fluorescent-labeled nanoparticles were applied to Phoebe bournei: polystyrene (PS) and polymethyl methacrylate (PMMA) as nanoplastics, and silicon dioxide (SiO₂) as an inorganic reference. The accumulation mechanisms of NPs were investigated using confocal microscopy and transcriptomic analysis. The results show that PS-NP inhibited the photosynthetic rate by affecting the primary quinone electron acceptor (Q_A) reduction of photosystem II (PSII). The concentrations of glutathione (GSH) increased in P. bournei to alleviate oxidative stress. NPs penetrated the roots and translocated to the aboveground parts, where they accumulated specifically in tissues with thickened or cuticle-enriched secondary cell walls, such as the endodermis, xylem, phloem, epidermis and glandular trichome. However, the cell type-specific accumulation patterns observed in NPs-treated roots were not observed in the SiO₂ nanoparticle treatment group. NPs inhibited the expression of photosynthesis genes and disturbed the cutin and wax metabolic pathways by downregulating the expression of the fatty acid elongase PbCER1 and upregulating the expression of lipid transportation genes such as PbLTPG8 and PbABCG22. This study sheds light on NPs stress responses and translocation pathways in woody perennials, informing their potential use in NPs phytoaccumulation.