Abstract: Plant survival in cyclically changing water levels and the recovery after water recession reflect their adaptability to flooding. To better understand the tolerance to flooding stress of Artemisia selengensis, a typical wetland plant in Poyang Lake, we examined the morphological and physiological responses of A. selengensis to three kinds of water environment and after water withdrawal and recovery. The double-pot method was adopted, with three water levels (rising, falling and stabilizing) being set up. In the rising water level group, six water levels were set up, which all initially increased from 0 cm, with an increasing intensity of 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6 cm·d^-1, respectively, with final water levels being 5, 10, 15, 20, 25, and 30 cm respectively after 50 days. In the descending water level group, six water levels were set up, the water levels were decreased from 5, 10, 15, 20, 25 and 30 cm, with a decreasing intensity of 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6 cm·d^-1 respectively, and all the final water levels were 0 cm after 50 days. In the stable water level group, six water levels were set up, which were 5, 10, 15, 20, 25 and 30 cm respectively, and the water levels remained constant. A control group with the water level of 0 cm was set up (the water level in the pot just submerged the soil surface). The treatment time of water level fluctuation was 50 days and the normal moisture after waterlogging time was 10 days, resulting in a total of 60 days. Results showed that: (1) In the three water level environment types, when water level was lower than 15 cm, the increases of plant height and the number of leaves showed a gradual upward trend. However, when the water level was higher than 15 cm, the growth rate of plant height and the number of leaves decreased. In the rising water level group, plant height and the number of leaves with the treatment intensity of 0.1-0.3 cm·d^-1 were significantly higher than the control group. (2) In the rising water level, the treatment intensity of 0.3 cm·d^-1 was within the tolerance range of A. selengensis to waterlogging. When the treatment intensity was less than 0.3 cm·d^-1, the change of antioxidant enzyme activity was obviously different from that of more than 0.3 cm·d^-1. Affected by the initial water level, the activities of superoxide dismutase and catalase of A. selengensis in the falling water level reached the maximum at 10-20 days. In the stable water level, when the waterlogging depth was 10 and 15 cm, the antioxidant enzyme activity increased continuously. The activities of superoxide dismutase and catalase decreased with increasing waterlogging time and stress intensity, whereas peroxidase activity showed an increasing trend. (3) Among the three types of water level environment, the superoxide anion production rates and malondialdehyde content did not differ from that in the control group under low intensity stress (P>0.05), which were correlated to the antioxidant enzyme activity in the early stage of the experiment. The superoxide anion production rates and malondialdehyde content in high intensity treatment group increased with increasing waterlogging depth and duration, and were significantly higher than those in control group. (4) In normal moisture condition after waterlogging, all indices of low-intensity treatment group recovered quickly and had no significant difference with that of the control group (P>0.05). The indices of high intensity treatment group recovered slowly or not completely. Therefore, A. selengensis is suitable for ecological restoration and reconstruction in the short-term and in a low-intensity-alteration water environment.

Key words: Artemisia selengensis, water level fluctuation, adversity stress, water recession recovery.