Biogenic chitosan–selenium nanoparticles for improved stress resilience in rice seedlings

Abstract

Salt stress is a major limiting factor in global agricultural production, severely affecting rice yield and quality, particularly during the seedling stage. Although extensive studies have been conducted on salt stress in rice, there is still limited understanding of how different types of green-synthesized nanoparticles influence salt tolerance mechanisms under controlled conditions. Nanoparticles (NPs), including green-synthesized metallic-based selenium nanoparticles (SeNPs) and organic-based chitosan nanoparticles (CTSNPs), have shown potential in mitigating salt stress. This study uniquely compares SeNPs and CTSNPs synthesized from the same plant source (Calotropis procera) to identify a more effective nano-based approach for improving rice resilience to salinity. The biosynthesized SeNPs and CTSNPs, confirmed through UV-vis spectra at 350 nm and 300 nm, respectively, and FTIR analysis indicated nanoparticle stabilization. Dynamic light scattering (DLS), X-ray diffraction (XRD), and scanning electron microscopy (SEM) with EDS confirmed their physical stability. Rice seedlings were grown hydroponically and subjected to 50, 100 and 150 mM NaCl stress at the 3-leaf stage (14 days after sowing) and morphological parameters were recorded to determine the most deleterious concentration. After 3 days of 150 mM salt stress, SeNPs and CTSNPs (0, 6, 12, and 24 ppm) were applied to roots. SeNPs showed superior performance in improving root and shoot lengths, biomass, photosynthetic pigments, and antioxidant enzyme activity (SOD, POD, APX, CAT, and proline) compared to CTSNPs. Among all treatments, 24 ppm SeNPs showed the most pronounced improvement in plant growth and defense responses, indicating their higher efficiency in mitigating oxidative damage caused by salinity. The findings indicate that the root application of SeNPs and CTSNPs mitigates salinity stress by enhancing the antioxidant system. These results highlight SeNPs as a promising eco-friendly nanomaterial for enhancing salt stress tolerance in rice, offering new insights into sustainable crop stress management.