Mn3O4 Nanoparticles Modulate Redox Homeostasis to Mitigate Nanoplastic-Induced Phytotoxicity

Nanoplastics are emerging stressors to terrestrial plants, yet effective mitigation strategies remain limited. Here, representative oxide nanoparticles (SiO2, TiO2, Fe3O4, and Mn3O4) were compared for alleviating nanoplastic-induced phytotoxicity. Mn3O4 showed the strongest protective effects against polystyrene nanoplastics (PS-NPs) with distinct surface charges, which induced oxidative stress, impaired photosystem II function, and weakened antioxidant defenses. Mn3O4 mitigated these effects by modulating reactive oxygen species levels and spatial distribution at the nanoplant interface, rather than acting solely as a passive radical scavenger. Physiological analyses showed improved photosynthetic efficiency, reduced lipid peroxidation, and enhanced antioxidant capacity. Transcriptomic profiling further revealed redox-related, metabolic, and structural adjustments consistent with an adaptive stress response. The protective effects of Mn3O4 were validated across multiple plant species and cultivation systems, highlighting a nanomaterial-enabled strategy for improving plant resilience under nanoplastic stress.