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Freeze-thaw differentially modulates the impact of agricultural film-derived microplastics on soil-crop system: Microbiome and metabolome responses
Summary
This study investigated how freeze-thaw cycling alters the properties and phytotoxicity of agricultural film-derived microplastics in soil, using both microbiome and metabolome analyses in wheat and soil systems. Freeze-thaw aging changed MP surface chemistry and differentially altered microbial community composition and plant metabolic responses compared to un-aged MPs.
Agricultural films derived microplastics (MPs) can persistently contaminate soil ecosystems in mid- to high-latitude regions, where freeze-thaw (FT) aging alters their physicochemical properties. Nevertheless, the phytotoxicity mechanism of FT-aged-MPs remains unclear. This study investigates the phytotoxicity of FT-aged low-density-polyethylene (PE) and poly(butylene-adipate-co-terephthalate) (PBAT) MPs to maize after 45-day of FT treatment, using plant physiological analysis, oxidative damage, metabolomics, and microbiome analyses. Results showed that FT-aged 500 μm PE-MPs increased root reactive oxygen species by 31.4 %, while FT-aged-PBAT-MPs reduced malondialdehyde content by 29.3-34.1 %. FT-aged-PE-MPs enriched Ideonella, a plasticizer-degrading microbes in the rhizosphere, with a relative abundance of 0.18 %. In contrast, FT-aged-PBAT-MPs enriched Sphingobacterium in the rhizosphere that degrade other pollutants and Kosakonia in the phyllosphere that promote plant growth. Sphingobacterium exhibited a nine-fold increase in abundance under FT-PBAT-MPs compared with pristine MPs, while Kosakonia had a relative abundance of 12.99 %. FT-aged-MPs induced higher migration rates of rhizosphere communities (Nm=388.6) compared with pristine MPs. FT-aged-PE-MPs alleviated oxidative stress via activated phenylalanine accumulation and caffeic acid biosynthesis. Conversely, FT-aged-PBAT-MPs suppressed phloretin production but increased glutathione production to strengthen plant defense. These findings demonstrate that FT-aging differentially alters MPs toxicity to crops, providing critical insights into ecotoxicological risks of aged-MPs in cold-region agroecosystems.