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Abstract: For a long time dioecious plants have played an important role in examination of the reproduction cost and determination of the sexual dimorphism evolution in life history. Hippophae rhamnoides sinensis, a dioecious, outcrossing plant, occurs mainly in the arid regions of northwest China, contributes to maintain the local ecosystems in these regions. In this study, δ 13C and the stomatal density of herbarium sheet were measured in Hippophate rhamnoides sinensis. It was found that the plants showed gender-difference in carbon isotope compositions: the males maintained higher δ 13C values and thus higher water use efficiency as well as slightly higher stomatal density than the females, moreover, the between-sex difference is stable in different contexts through carbon isotope discrimination. Although we found that the stomatal density had being reduced and is sensitive to atmospheric CO2 level, δ 13C value and thus water-use efficiency did not significantly change from 1978 to 2001. Consequently, gender-specific δ 13C could play a decisive role in explaining gender differences in the developmental growth. [Copyright &y& Elsevier]