The coexistence of microorganisms in complex soil environments greatly affects the environmental behavior and ecological effects of microplastics (MPs). However, relevant studies are sparse, and internal mechanisms remain unclear. Herein, arbuscular mycorrhizal fungi (AMF), a common symbiotic microorganism in the soil–plant system, was proved to significantly affect MPs absorption and migration with a “size effect”. Specifically, the existence of AMF accelerated small-sized MPs (0.5 μm) uptake but slowed large-sized MPs (2 μm) uptake in lettuce. The content of 0.5 μm MPs absorbed by plants with AMF was 1.26 times that of the non-AMF group, while the content of 2 μm MPs was only 77.62 % that of non-AMF group. Additionally, the different effects of microorganisms on the intake content of MPs with different particle sizes in plants also led to different toxic effects of MPs on lettuce, that is, AMF exacerbated small-size MPs toxicity in lettuce (e.g., reduced plant biomass, photosynthesis, etc), and it weakened large-sized MPs toxicity (e.g., increased plant height, antioxidant enzyme activity, etc). The above phenomenon mainly because of the change in AMF on the plant root structure, which can be visually observed through the intraradical and extraradical hyphae. The symbiotic structure (hyphae) formed by AMF and host plants root could enhance the absorption pathway for small-sized MPs in lettuce, although not for large-sized MPs. Additionally, the effects of AMF varied with the soil environment of differently sized MPs, which promoted the migration of small-particle MPs to plants but aggravated large-particle MPs fixation at the soil interface. These findings could deepen the understanding of MPs pollution in terrestrial systems and provide theoretical basis and technical support to accurately assess soil MPs pollution.

中文翻译：

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共生微生物介导的微塑料在土壤-植物系统中的迁移积累及其生态效应


复杂土壤环境中微生物的共存极大地影响了微塑料（MPs）的环境行为和生态效应。然而，相关研究很少，内部机制尚不清楚。其中，丛枝菌根真菌（AMF）是土壤-植物系统中常见的共生微生物，被证明能够显着影响 MPs 的吸收和迁移，并具有“尺寸效应”。具体而言，AMF 的存在加速了生菜中小尺寸 MP（0.5 μm）的吸收，但减缓了大尺寸 MP（2 μm）的吸收。 AMF植物吸收的0.5 μm MPs含量是非AMF组的1.26倍，而2 μm MPs含量仅为非AMF组的77.62%。另外，微生物对植物体内不同粒径MPs摄入量的影响不同，也导致MPs对生菜的毒害作用不同，即AMF加剧了生菜中小粒径MPs的毒性（如降低植物生物量、光合作用降低等）。等），并且减弱了大尺寸MP的毒性（如增加株高、抗氧化酶活性等）。上述现象主要是因为AMF对植物根系结构的改变，可以通过根内菌丝和根外菌丝直观地观察到。 AMF 与寄主植物根部形成的共生结构（菌丝）可以增强生菜中小型 MP 的吸收途径，但对大型 MP 的吸收途径则不然。此外，AMF的作用随不同粒径MPs的土壤环境而变化，促进了小颗粒MPs向植物的迁移，但加剧了大颗粒MPs在土壤界面的固定。 这些研究结果可以加深对陆地系统MPs污染的认识，为准确评估土壤MPs污染提供理论依据和技术支撑。