Synergistic damage and antagonistic protection of arbuscular mycorrhizal fungi and nanoplastics on oxidative stress in rice.

BACKGROUND: The combined effects of arbuscular mycorrhizal fungi (AMF) and nanoplastics (NPs) on rice oxidative stress remain unclear, particularly regarding the synergistic or antagonistic nature of their interaction in different organs. This study investigated the interactive effects of AMF (Funneliformis mosseae) inoculation and polystyrene nanoplastic (PS-NP, 0.5 g kg-1 soil) exposure on oxidative stress, antioxidant systems, and gene expression in rice (Oryza sativa L.) roots and leaves. RESULTS: NP treatment alone increased leaf photosynthetic pigments but caused malondialdehyde (MDA) accumulation. AMF alone did not significantly alter leaf MDA levels; however, under combined NP + AMF treatment, leaf MDA increased by 153.8%, indicating synergistic damage. In roots, AMF exerted a clear protective effect, increasing superoxide dismutase (SOD) activity by 137% and phenolic content by 39.1%, while partially reducing NP-induced proline accumulation. Gene expression analysis revealed that AMF upregulated OsCAX family genes and antioxidant genes (OsPOD, OsAPX) in roots whereas, in leaves, antioxidant genes (OsFe-SOD, OsCAT, OsPOD) were predominantly suppressed. Correlation analysis confirmed a strong negative link between suppression of leaf antioxidant genes and elevated lipid peroxidation. CONCLUSION: This study demonstrates that AMF and NPs produce opposite effects in rice roots and leaves: antagonistic protection in roots versus synergistic damage in leaves. These findings provide theoretical support for managing microplastic pollution in agriculture and for the targeted application of AMF. © 2026 Society of Chemical Industry.