In this study, soil containing four different concentrations of salt was used to grow Leymus chinensis, which was sampled over 120 days between the beginning of spring and the end of fall. During this time, its physiological and morphological characteristics were analyzed. Maximal superoxide dismutase and betaine content were observed under moderate saline‐alkaline stress treatment (A3), and with increasing saline‐alkaline stress, there was a linear increase in the contents of Na+, proline, malondialdehyde (MDA), organic acids (OAs), catalase, peroxidase, soluble protein and total soluble sugar. However, the K+ content and the K+/Na+ ratio decreased significantly. Under saline‐alkaline stress, the K+, betaine, OA and soluble protein levels in the leaves were higher than those in the rhizomes, whereas the proline, MDA, protective enzyme and total soluble sugar levels in the leaves were lower than those observed in the rhizomes. The node density varied with increases in saline‐alkali stress, and each node index was maximal at A3. Under saline‐alkali stress, the rhizome biomass, leaf biomass and root–shoot ratio first decreased and then increased, whereas the change in root biomass showed a contrary tendency, and the specific root length increased gradually. There was a significant correlation between the root–shoot ratio, specific root length, and the physiological indexes. These results show that under different degrees of saline‐alkali stress, L. chinensis is likely to use a series of adaptive physiological and morphological responses; the physiological responses were primarily related to the allocation of biomass and energy, root length, and the allocation of biomass between the aboveground and belowground organs.
