Fig. 10
From: Salinity stress amelioration through selenium and zinc oxide nanoparticles in rice
A conceptual illustration depicting the proposed mechanism by which nanoparticle (NP) application mitigates salinity stress in rice plants. Under saline conditions, excessive Na⁺ disrupts ion homeostasis and induces oxidative stress through the overproduction of reactive oxygen species (ROS) such as H₂O₂, O₂•⁻, and OH•. The application of Se-NPs and ZnO-NPs enhances the plant’s antioxidant defense system, which includes enzymatic antioxidants such as superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR). Moreover, monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR) play crucial roles in regenerating ascorbate (AsA) from its oxidized forms, maintaining the AsA–GSH (ascorbate–glutathione) cycle. This cycle is essential for scavenging ROS and restoring cellular redox balance. DHAR catalyzes the reduction of dehydroascorbate (DHA) to AsA using reduced glutathione (GSH) as an electron donor, while MDHAR reduces monodehydroascorbate (MDHA) back to AsA using NAD(P)H. Glutathione reductase (GR) maintains the GSH pool by reducing oxidized glutathione (GSSG) to GSH. The coordinated activity of these enzymes enhances the recycling of antioxidants, reduces lipid peroxidation (as indicated by decreased MDA levels), supports ion regulation (improved K⁺/Na⁺ ratio), and ultimately improves growth, stress tolerance, and grain mineral content in rice under salinity stress. HKTT-1, a Na+ transporter, is also upregulated, reducing sodium accumulation in shoots and maintaining ionic balance. KOR1 supports cell wall remodelling, preserving root growth and structural integrity under osmotic stress. Proline biosynthesis further contributes to osmotic adjustment, ROS scavenging, and cellular protection.
