SiO2 Nanoparticles Enhance Salt Tolerance, Yield, and Quality in Oat ( Avena sativa L.) by Regulating ROS Signaling and Na+/K+ Homeostasis

Salt stress disrupts photosynthesis, ion homeostasis, and antioxidant systems, thereby inhibiting plant growth and reducing the yield and quality. This study investigated the physiological and molecular mechanisms of salt stress alleviation by foliar application of different concentrations of silicon dioxide nanoparticles (SiO2 NPs) in oats under 150 mM NaCl. Physiological and transcriptomic analyses were performed. 300 ppm of SiO2 NPs significantly promoted growth and photosynthesis, enhanced antioxidant enzyme activities, reduced oxidative damage, and maintained Na+/K+ balance while improving nutritional quality. SiO2 NPs regulated genes involved in photosynthesis and carbon metabolism and upregulated the ion transporter genes HKT1;1, HKT7, and HKT9 and ROS signaling genes MPK6 and WRKY33. HKT proteins were localized to the plasma membrane. Weighted correlation network analysis (WGCNA) identified six hub genes associated with the growth and photosynthetic traits. Overall, SiO2 NPs enhance salt tolerance, yield, and quality in oat by maintaining Na+/K+ homeostasis, activating ROS signaling, and sustaining photosynthesis and carbon metabolism.