Nano-silica improves the emergence of pepper seeds and the growth of seedlings under waterlogging stress by reducing oxidative damage

Waterlogging stress is an important environmental factor that limits global agricultural productivity. Silica nanoparticles (SiNPs) have been proven to enhance the tolerance of plants to waterlogging stress. However, the exact SiNPs-regulated waterlogging stress response mechanism in pepper remains unknown. The present study examined the influence of 300 mg/L silicon nanoparticles (SiNP300) on germination, emergence, and subsequent growth of pepper seedlings under waterlogging stress. During the early developmental phase, SiNP300 accelerated germination (36.70%) and enhanced cotyledon expansion (150.00%), while maintaining membrane integrity through reduced lipid peroxidation in radicles. Expression levels of CaAP2/ERF86 (23.79%) and CaAP2/ERF113 (29.89%) were elevated, suggesting a role in strengthening tolerance to waterlogging. At the seedling stage, foliar application of SiNP300 promoted root system development, as evidenced by increases in total root length (15.71%), surface area (14.83%), and root tip number (101.24%). In parallel, total chlorophyll content rose by 87.06%, the net photosynthetic rate improved by 251.72%, and visible chlorosis and wilting were mitigated. SiNP300 also reduced oxidative injury by lowering H₂O₂ (hydrogen peroxide) and O₂˙⁻ (superoxide anion) levels in leaves through modulation of SOD (superoxide dismutase), POD (peroxidase), and CAT (catalase) activities, thereby elevating soluble protein accumulation. Collectively, these findings clarify the mechanism by which SiNP300 alleviates waterlogging stress in pepper and provide a theoretical basis for applying exogenous SiNPs to enhance plant resistance.