Freeze-thaw aged film-derived polyethylene and poly(butylene adipate-co-terephthalate) microplastics differentially regulate the toxicity of acetochlor on maize

Microplastics (MPs) from agricultural films and herbicides persistently coexist within the agroecosystem. Freeze-thaw (FT) cycles can induce changes in the surface properties of MPs at mid- and high-latitudes, which may affect the phytotoxicity of co-existing herbicides. This study investigated the mechanisms by which original and FT-aged low-density polyethylene (PE) and poly(butylene adipate- co -terephthalate) (PBAT) MPs regulate the toxicity of acetochlor (ACT) on maize. Results showed that the regulation of original and FT-aged MPs on maize biomass and oxidative stress could reflect changes in ACT toxicity. Overall, original and FT-aged MPs alleviated ACT toxicity on maize by triggering glutathione production and enhancing microbial community stability. However, compared with original MPs, FT-aged PE-MPs exhibited a reduced alleviation capacity (14.88–53.31%), associated with suppressed eugenol (26.52–40.20%) and caffeic acid (30.18–30.77%) synthesis and decreased abundance of Pseudobdellovibrio and Luteolibacter . In contrast, FT-aged PBAT-MPs enhanced the alleviation of ACT stress on maize (48.52–365.93%) by enhancing microbial network stability, upregulating growth hormones (32.13–120.46%), and elevating oxidative stress-related phenolic compounds. FT-aged MPs also alleviated the adverse effect of ACT on photosynthetic capacity (7.14–340.47%) relative to original MPs by increasing the abundance of pollutant-degrading bacteria. This study offers new insights into how FT-aged MPs differentially regulate the toxicity of ACT on maize and provides guidance for sustainable agricultural development. • Original and freeze thaw aged microplastics (MPs) alleviated ACT toxicity on maize. • Original and freeze thaw (FT) aged MPs enhanced glutathione-mediated detoxification. • FT-aged PBAT alleviated ACT toxicity by regulating microbial activity and hormones. • Relative to original MP, FT-aged PE diminished its capacity to alleviate ACT toxicity. • FT-aged PE-MPs suppressed phenolic antioxidants and plant-beneficial bacteria.