Gender-specific carbon discrimination and stomatal density in the dioecious tree of Hippophate rhamnoides

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, δ13C 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 δ13C 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, δ13C value and thus water-use efficiency did not significantly change from 1978 to 2001. Consequently, gender-specific δ13C could play a decisive role in explaining gender differences in the developmental growth.