growth and morpho-physiological response of stevia seedlings to nano-chemical pretreatments and salt stress

The purpose of this study was to evaluate the effects of salinity stress on germination, growth, and physiological characteristics of stevia and to investigate whether pre-treatment with nano-compounds, specifically zinc oxide (zno), titanium oxide (tio2), and silicon (si), could enhance these traits. the study revealed a significant improvement in the germination, growth, and physiological properties of stevia seeds under varying levels of salinity stress (0, 2.5, 5, and 10 ds/m) using eight different seed priming treatments. the results showed that the effects of salinity stress and seed priming, as well as the interaction between these two factors, were significant on seed germination parameters and physiological characteristics. the most considerable germination percentage (54%) and rate (11.89 seeds/day), germination power (0.018), and seedling vigor index (609.6) were observed in seed priming with a combination of tio2 and si under normal conditions. under non-stress conditions, the combination of si and zno used for seed pre-treatment resulted in the highest mean photosynthetic pigments, including chlorophyll a, b, and total (17.49, 8.72, and 26.22 µg/g fw, respectively) as well as the lowest mean proline content (0.3µmol/g fw) and enzymatic activities of antioxidants such as catalase and peroxidase (8.82 and 16.72 u/mg protein . min). the integrated application of si + tio2 or si + zno was particularly effective in enhancing germination and growth indices, as well as improving physiological traits under salt stress conditions. these results suggest that nano-fertilization can be a promising approach to enhance seedling growth and development, particularly under stress conditions.