Abstract
Salinity is one of the most dominant abiotic stresses limiting growth and productivity in rice (Oryza sativa L.), thereby posing a serious threat to global food security. To enhance plants' tolerance to salinity stress, the application of green-synthesized nanoparticles presents a novel and eco-friendly approach. This research article investigates the ameliorative effects of selenium (Se-NPs) and zinc oxide (ZnO-NPs) nanoparticles, both individually and in combination, on rice plants under salinity stress. Our results revealed that salinity stress significantly impaired rice growth and productivity, reducing plant height, root length, and yield-related traits, including tiller count, number of grains per spike, and grain weight. Furthermore, it induced oxidative stress, as evidenced by elevated levels of malondialdehyde and proline. The elevated levels of reactive oxygen species were visibly confirmed through histochemical staining. However, treatment with Se-NPs and ZnO-NPs significantly alleviated these adverse effects by enhancing the plant's antioxidant defense mechanism. Activities of key antioxidant enzymes such as superoxide dismutase (50.06%), catalase (59.92%), ascorbate (104.28%), and peroxidase (85%) were significantly elevated, contributing to efficient ROS scavenging and reduced lipid peroxidation. The combined nanoparticle application was particularly effective in restoring physiological and biochemical parameters to near-normal levels, with increases of 46.32% in plant height, 70.53% in root length, and 100.7% in grains per spike under salinity stress. Furthermore, the enhanced accumulation of minerals such as Zn (31.8 ppm), Se (0.57 ppm), and Fe (7.4 ppm) in rice grains was also observed, indicating a dual benefit of stress alleviation and nutritional enrichment. Green-synthesized Se-NPs and ZnO-NPs, particularly when combined, offer a promising strategy for mitigating salinity stress in rice. Beyond enhancing stress tolerance and growth, the nanoparticles also contribute to the biofortification of rice grains, thereby improving both crop resilience and nutritional value in saline environments.