Abstract: To investigate the effects of exogenous salicylic acid（SA）on the growth of watermelon seedlings under drought stress, with watermelon as the research material, foliar spraying of SA was used to study the effects of different concentrations [0 mmol/L（T0）, 0.5 mmol/L（T1）, 1 mmol/L（T2）, 2 mmol/L（T3）, and 3 mmol/L（T4）]of SA on the growth of watermelon seedlings under drought stress conditions. The results showed that under drought stress, the growth status of watermelon seedlings was significantly inhibited, with a significant increase of 40.50% and 52.10% in malondialdehyde（MDA）and relative conductivity, an increase in total photosynthetic pigment content, soluble protein and proline content, and an increase in peroxidase（POD）and catalase（CAT）activities. With the increase of SA concentration, the growth and physiological characteristics of watermelon seedlings were significantly affected. Plant height, stem thickness, leaf width, leaf length, proline content, soluble protein content, photosynthetic pigment content, stomatal conductance, and antioxidant enzyme activity（CAT and POD）showed a trend of first increasing and then decreasing; The content of malondialdehyde, relative conductivity, and transpiration rate showed a trend of first decreasing and then increasing. Compared with drought stress, the T1 group of watermelon seedlings had the highest plant height, leaf width, CAT activity, photosynthetic pigments, and proline content, with increases of 56.02%, 2.46%, 32.20%, 23.30%, and 40.70%, respectively; The T2 group of watermelon seedlings showed the highest stem diameter, POD activity, and soluble protein content, with increases of 24.03%, 12.80%, and 10.00%, respectively; The growth and physiological characteristics of T4 group watermelon seedlings were severely inhibited. In summary, the application of low to medium concentrations of exogenous SA can alleviate the damage caused by drought stress to watermelon seedlings. T1 treatment in this experiment is the most suitable concentration to improve the drought resistance of watermelon seedlings.

Key words: watermelon, drought stress, salicylic acid, physiological characteristics