Mn ₃ O ₄ Nanozymes Mitigate Salt Stress in Tomato ( <i>Solanum lycopersicum</i> ) by Scavenging Reactive Oxygen Species and Enhancing Photosynthesis

The mitigation of salinity stress by Mn3O4 nanoparticles (NPs) has been reported in plants, yet their integrated effects on tomato─spanning seed germination, vegetative growth, fruit yield, and underlying molecular mechanisms─remain largely unexplored. This study employed physiological, transcriptomic, and metabolomic analyses to systematically evaluate tomato responses to 100 mM NaCl stress following Mn3O4 NP application. Seed priming with 100 mg/L Mn3O4 NPs significantly enhanced the germination rate by 103.02% (p <0.05), while foliar spraying significantly improved seedling biomass and chlorophyll content and reduced oxidative stress markers. Under saline conditions, Mn3O4 NP treatment increased fruit yield by 19.05% (p <0.05). Multiomics data revealed that Mn3O4 NPs induced coordinated upregulation of pathways related to systemic acquired resistance, phytohormone signaling, and antioxidant defense. These findings clarify the physiological and molecular basis of Mn3O4 NP-induced salt tolerance and provide a foundation for developing nanoenabled strategies to enhance crop performance in saline environments.