Abstract
Barley (Hordeum vulgare L.) is a vital cereal crop that is highly susceptible to a range of abiotic stresses, including low temperatures, drought, salinity, and particularly heat stress, which can significantly impair its growth and productivity. This study aimed to assess the impact of elevated temperature on the germination and physiological responses of the Astana 2000 barley cultivar. Seeds were germinated under controlled growth room conditions at an optimal temperature of 25°C (control) and a high temperature of 40°C to simulate heat stress. We evaluated several physiological and biochemical parameters, including chlorophyll content, malondialdehyde (MDA), and proline levels. Heat stress led to a noticeable decline in photosynthetic pigments, indicating reduced photosynthetic efficiency. In contrast, MDA and proline concentrations increased, reflecting enhanced lipid peroxidation and osmotic stress, respectively. Additionally, the activities of antioxidant enzymes such as aldehyde oxidase and catalase were significantly elevated under high temperature, suggesting an adaptive defense mechanism to counteract oxidative damage by detoxifying reactive oxygen species.