Abstract: The resource allocation pattern between leaf and flower in the process of plant growth is formed by the long-term interaction between plants and the environment, reflecting the comprehensive function of diversity. By using the ArcGIS established regional digital elevation model (DEM) and the method of standardized major axis estimation (SMA), this paper studied the relationship between the leaf and flower growth of Zygophyllum xanthoxylum population at different slope aspects on the northern slope of Qilian Mountains, Northwest China. The results showed that, with the slope aspect turning from north to east, west, and south, the plant density, height, aboveground biomass and soil moisture content of the plant community, the currentyear twig biomass, flower size, leaf area and leaf number of Z. xanthoxylum decreased, while the reproductive allocation increased. Significant positive relationships between the flower size and leaf area and leaf number were found at all slope aspects (P<0.05), the slope of the regressions was significantly less than 1.0 (P<0.01), and the growth speed of flower size was greater than those of leaf number and leaf area. With the aspect turning from north to east, west, and south, the allometric slope of leaf area and flower size decreased, and the allometric slope of leaf number and flower size increased. Slopeinduced gradual changes of environmental factors and vegetation community influenced the growth rates of leaf and flower of Z. xanthoxylum. This relationship reflected the phenotypic plasticity and the resource tradingoff mechanism of growth/reproduction of desert plants in coping with the environmental heterogeneity.

Key words: flooding, Distylium chinense, net photosynthetic rate, light response model, photosynthetic parameter.