Abstract: The stem size of twig affects the number and size of leaves on it. It is of great significance to explore the relationship between stem architecture of twig and leaf expansion efficiency for understanding plant resource use strategies. In this study, nine Syringa species in Xining City were used as materials. The stem architecture was characterized by twig’s base diameter, stem length, and biomass, while leaf expansion efficiency was characterized by leaf expansion coefficient, leaf density, total leaf area, and average single leaf area. The relationship between stem architecture and leaf expansion efficiency was clarified. The results showed that there were significant interspecific differences in the relationship between stem architecture and leaf expansion efficiency. Stem diameter and stem biomass with shorter stem length better reflected the influence of stem architecture on leaf expansion efficiency. Leaf expansion coefficient and leaf density decreased with increasing stem length, while total leaf area and average leaf area increased. However, the intensity of such effect varied among species. The leaf expansion efficiency was significantly affected by the stem length of twig. There was obvious differentiation of strategies in the adaptation of heterologous plant species of same genus to alpine habitat.

Key words: plant twig, leaf area, leaf expansion index, stem length, Syringa