Background: The construction of the Three Gorges-Gezhou Dam altered the water level fluctuation pattern in the downstream habitat of the endangered species Myricaria laxiflora. This study investigated how branch and leaf growth traits of M. laxiflora remnant populations changed to adapt the environmental stress caused by human-altered water level fluctuations.Results:Due to such disturbance, branch and leaf growth traits of M. laxiflora populations exhibited significant differences across water

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... level conditions. The number of secondary branches, plant height, and leaf number of the plants in the upper area of the habitat were significantly higher than that in the middle and lower river bank areas. The longest secondary branch length of the plants in the upper and middle region was significantly higher than that in the lower region. The branch and leaf volume of plants in the middle region was significantly higher than that in the upper and lower region. The maximum water content of plants in the middle and lower region was significantly higher than that in the upper region. Principal component analysis showed that the branch and leaf traits of plants changed with decreasing water level toward to decreasing plant height, leaf number and the number of secondary branches, and increasing maximum water content of branch and leaves. Conclusions: The phenotypic plasticity of M. laxiflora plants in branch and leaf growth traits alleviates the impacts of human-regulated water level fluctuations. However, the above ground growth of M. laxiflora plants distributed at the middle and lower areas of the fluctuation zone is still negatively affected.