Abstract: This paper provides a theoretical basis for the introduction of plant in the desert hinterland to study the changes of plant growth and physiological characteristics under salt, drought, and their interaction stress, to understand the adaptability of Buddleja alternifolia seedlings, and determine the reasonable irrigation method in the extreme habitat of the desert hinterland, Xinjiang, China. Experiments of random combinations of three field moisture gradients and four salt gradients were designed to control the growth and biochemical indicators. Finally, the drought resistance and salt tolerance of Buddleja alternifolia were evaluated based on the membership function method. The results showed as follows: (1) Under drought stress or low- salt stress, the growth of ground diameter, new shoots, and crown width of Buddleja alternifolia increased, but decreased under high salt stress; Under interaction stress, the salt concentration was different from the drought stress. With low salt concentration and drought interaction (W1S1, W2S1), the plant growth increased, while with high salt concentration and drought interaction (W1S3, W2S3), the plant growth decreased. (2) Regardless of the type of stress, the content of free proline (Pro) content of Buddleja alternifolia increased significantly with the increase of stress. (3) The changes of superoxide dismutase (SOD) and peroxidase (POD) activities were relatively complex. Except for the drought stress, the SOD activity and POD activity are significantly decreased. Inconsistent changes were observed under salt stress and salt-drought interaction stress. This indicated that under salt stress, cross stress, and drought stress, change in the corresponding osmotic adjustment substances and enzyme activities were observed, no obvious synchronization was found, a possibility of coordination exists, and the sensitivity of plant cells was found to be far stronger than the phenotypic growth. Changes in the phenotypic growth under high salt concentration damage did not appear in the external morphology of the plant. However, the enzyme activity and osmotic adjustment substances have significant changes. Finally, the analysis of the membership function showed that the most suitable water and salt conditions for the Buddleja alternifolia were: salt concentration of 8 g·L- 1, irrigation amount of 25 L·times- 1, and drought and salt tolerance to water and salt stress: drought stress > interaction stress > salt stress.

Key words: drought stress, salt stress, interaction stress, Buddleja alternifolia, physiological characteristic