Mn ₃ O ₄ 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 (SiO 2, TiO 2, Fe 3 O 4, and Mn 3 O 4 ) were compared for alleviating nanoplastic-induced phytotoxicity. Mn 3 O 4 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. Mn 3 O 4 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 Mn 3 O 4 were validated across multiple plant species and cultivation systems, highlighting a nanomaterial-enabled strategy for improving plant resilience under nanoplastic stress.