Abstract
Freezing stress is one of the major abiotic factors limiting plant growth and productivity. This study evaluates the effects of diatomite (DTM) as a natural silicon-rich amendment on growth performance, physiological responses, and cold stress tolerance in barley (Hordeum vulgare L.). Seed priming and substrate application of DTM at different concentrations (5–20%) were used to assess morphological, biochemical, and ultrastructural changes under normal and low-temperature conditions. Results showed that DTM significantly enhanced root growth and biomass accumulation, with the most pronounced effect at 10% concentration. Treated plants exhibited improved survival under freezing stress, along with better preservation of leaf cellular structure and photosynthetic pigments. Biochemical analyses revealed reduced proline accumulation and decreased activity of key antioxidant enzymes, indicating alleviation of oxidative stress and improved redox balance. Electron microscopy confirmed the integration of diatomite particles into seed and tissue structures, providing physical reinforcement and thermal protection. Overall, diatomite acts as a multifunctional, environmentally safe soil amendment that enhances plant growth and improves tolerance to cold stress through combined physical and physiological mechanisms.