Effects of Alkaline Stress on the Growth and Physiological Characteristics of Caucasian Clover

Background: Saline-alkali soil seriously restricts plant growth. Caucasian clover (Trifolium ambiguum Bieb.) is a high-quality leguminous forage with strong adaptability and stress resistance. However, current research on Caucasian clover under saline-alkali stress remains limited. The purpose of this study is to use NaHCO3 solution to carry out alkali stress on Caucasian clover plantsand to understand the changes of plant growth and physiological characteristics under stress, which is of great significance for its popularization and cultivation in alkaline soil. Methods: To study the effects of alkaline stress on the growth and physiological characteristics of Caucasian clover, plants were subjected to varying concentrations (0, 50, 100, 150, 200 mmol/L) of NaHCO3 in pot experiments. Post-stress, parameters such as dry weight, root-to-shoot ratio, main root length, chlorophyll, malondialdehyde (MDA) contentand the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) were measured. Result: This study demonstrated that alkaline stress significantly affected the growth and physiological characteristics of Caucasian clover. With increasing alkaline stress, the aboveground and underground dry weights, as well as the main root length, decreased significantly. Photosynthesis was inhibited, with chlorophyll content increasing under low alkaline stress but decreasing sharply at higher concentrations. The activities of antioxidant enzymes (SOD, POD, CAT) increased significantly under low stress but gradually decreased under higher stress levels. Meanwhile, MDA content increased significantly under high alkaline stress. Correlation analysis showed a strong positive correlation between SOD activity and CAT activity, as well as between aboveground dry weight and main root length (P less than 0.01), while chlorophyll content was negatively correlated with MDA content (P less than 0.05).