Objective To study the dynamic physio-ecological response and salt tolerance differences of plants under salt stress to select proper greening species in saline-alkali areas.

Method Pot experiment was conducted with 2-year-old seedlings of Taxodium hybrid 'Zhongshanshan', Ficus microcarpa and Hibiscus hamabo, and three salt gradients were set to compare the dynamic characteristics of seedling growth and morphology, antioxidant enzyme system and osmoregulation system, and the principal component analysis (PCA) was conducted to determine the differences of salt tolerance among the three species.

Result Short-term salt stress (14 d) showed little influence on the survival rate, leaf shape and leaf color of the three species, but long-term salt stress (56 d) showed a significant effect on F. microcarpa, and the dynamic characteristics of comparative branch lengths differed obviously under salt stress. With increasing salt treatment time, leaf SOD activities of the three species showed a decreasing trend, the POD and APX activities increased at first and then decreased, and the MDA contents showed a general decreasing trend. The leaf soluble sugar and soluble protein contents of the three species decreased at first and then increased under salt stress, and the leaf comparative conductance increased significantly with the increase of salt concentration. The interaction of salt treatment time and species had significant effects on leaf SOD, POD activities and MDA contents. Principal components of salt tolerance in three species were distinct, indicating their different tolerance response characteristics.

Conclusion The eco-physiological response characteristics of the three species show that the salt treatment has the greatest impact on F. microcarpa and less impact on A. hybrid and H. hamabo, consequently, H. hamabo and A. hybrid can be potentially prioritized as greening species in saline areas in Eastern China.