Eco-Friendly Synthesis of Selenium Nanoparticles via Sternbergia candida: Enhancing Antioxidant Defense and Mitigating Salt Stress in Pepper (Capsicum annuum L.) Plants.

Nanoparticles enhance agricultural applications with their bioactivity, bioavailability, and reactivity. Selenium mitigates the adverse effects of salinity on plant growth, boosting antioxidant defense, metabolism, and resilience to abiotic stress. Our study applied selenium nanoparticles to mitigate salinity-induced damage and support plant growth. We characterized green-synthesized nanoparticles and analyzed stress-related metabolites, antioxidant activities (DPPH, ABTS), phenolic content, and reducing powers (CUPRAC, FRAP). Nanoparticle applications reduced proline and MDA levels while boosting chlorophyll, carotenoids, antioxidant activity (DPPH, ABTS), and total phenolic content. An increase was also observed in CUPRAC and FRAP reducing capacities. In terms of phenolic content, the highest value was determined in SA1 (4.58±0.40 mg GAE g-1) application; DPPH free radical scavenging activity IC50 value was determined in A3 (0.13±0.007 mg mL-1) application, which was closest to the positive control. The lowest proline level was found in A3 (15.00±0.64 nmol g-1 FW) and the lowest MDA level was found in SA3 (10.08±0.42 nmol g-1). Comparing the results, green synthesis of selenium nanoparticles using Sternbergia candida (SC-SeNP) at different concentrations showed ameliorative effects on various parameters in plants, and it was determined that the effects of salt stress on pepper plants were reduced following SC-SeNP applications.