以国家植物园中水杉（Metasequoia glyptostroboides Hu et Cheng）为研究对象，对比根部淹水和非淹水生境中水杉的叶片形态特征、化学计量特征、气体交换参数及非结构性糖类的差异，分析水杉对2种生境的适应策略。结果表明：水杉根部淹水和非淹水生境土壤含水量差异显著（P<0.05），土壤化学计量特征中除C/N比外均具有显著差异。根部淹水生境水杉叶面积和比叶面积均显著大于根部非淹水生境，但叶干物质含量显著低于非淹水生境，这主要通过叶长的增加实现。同一径级内，根部淹水生境仅Ⅰ〔20 cm≤胸径（DBH）＜30 cm〕径级水杉叶片净光合速率显著高于非淹水生境；3个径级水杉叶片胞间CO₂浓度在2种生境间无显著差异；气孔导度和蒸腾速率在2种生境间均存在显著差异，且除Ⅰ径级的蒸腾速率外均为根部淹水生境显著高于根部非淹水生境。同一生境内，水杉叶片净光合速率、气孔导度和蒸腾速率随着径级的增大呈上升趋势，而胞间CO₂浓度的变化趋势相反。同一径级内，根部淹水生境水杉叶片有机碳、全氮和全磷含量均高于根部非淹水生境，且除有机碳含量外均存在显著差异；根部淹水生境水杉叶片N/P比、C/N比和C/P比总体小于根部非淹水生境，其中，Ⅰ径级水杉叶片N/P比和C/N比在2种生境间差异显著，Ⅰ和Ⅱ（30 cm≤DBH＜40 cm）径级水杉叶片C/P比在2种生境间差异显著。根部淹水生境水杉叶片非结构性糖类含量显著高于非淹水生境，主要表现为可溶性糖含量的升高。综上所述，水杉对淹水胁迫具有良好的适应能力，能够通过改变叶片形态、可溶性糖含量及气孔开放程度来保证正常的生命活动，在今后的迁地保护过程中可通过增加土壤含水量和光照帮助水杉适应环境的变化。

Taking Metasequoia glyptostroboides Hu et Cheng in the National Botanical Garden as the research subject, the differences in morphological characteristics, stoichiometric characteristics, gas exchange parameters, and non-structural carbohydrates of leaves of M. glyptostroboides in flooded and non-flooded habitats of roots were compared, and the adaptation strategies of M. glyptostroboides to these two habitats were analyzed. The results show that there are significant (P<0.05) differences in soil water content between flooded and non-flooded habitats of roots of M. glyptostroboides, and all soil stoichiometric characteristics except C/N ratio have significant differences. The leaf area and specific leaf area of M. glyptostroboides are significantly greater in flooded habitat of roots than in non-flooded habitat of roots, but the leaf dry matter content is significantly lower in non-flooded habitat of roots, and this is mainly achieved through the increase of leaf length. Within the same diameter class, only the leaf net photosynthetic rate of M. glyptostroboides at diameter class Ⅰ 〔20 cm≤diameter at breast height (DBH)<30 cm〕 in flooded habitat of roots is significantly higher than that in non-flooded habitat of roots; there are no significant differences in leaf intercellular CO₂ concentration of M. glyptostroboides at three diameter classes between the two habitats; there are significant differences in stomatal conductance and transpiration rate between the two habitats, and they are significantly higher in flooded habitat of roots than in non-flooded habitat of roots except for the transpiration rate at diameter class Ⅰ. Within the same habitat, the net photosynthetic rate, stomatal conductance, and transpiration rate of leaves of M. glyptostroboides show a tendency to increase with the increase of diameter class, while the variation tendency of intercellular CO₂ concentration is the opposite. Within the same diameter class, the contents of organic carbon, total nitrogen, and total phosphorus in leaves of M. glyptostroboides in flooded habitat of roots are all higher than those in non-flooded habitat of roots, and there are significant differences except for organic carbon content; the N/P ratio, C/N ratio, and C/P ratio of leaves of M. glyptostroboides in flooded habitat of roots are generally lower than those in non-flooded habitat of roots, in which, there are significant differences in N/P ratio and C/N ratio of leaves of M. glyptostroboides at diameter class Ⅰ between the two habitats, and there are significant differences in C/P ratio of leaves of M. glyptostroboides at diameter classes Ⅰ and Ⅱ (30 cm≤DBH<40 cm) between the two habitats. The non-structural carbohydrates content in leaves of M. glyptostroboides is significantly higher in flooded habitat of roots than in non-flooded habitat, and is mainly manifested as an increase in soluble sugar content. In summary, M. glyptostroboides has good adaptive ability to flooding stress, and it can ensure normal life activities by changing leaf morphology, soluble sugar content, and stomatal opening degree. In the future ex situ conservation process, it is possible to help M. glyptostroboides adapt to environmental changes by increasing soil water content and light.