Abstract: Leaves of seven species of Saussurea DC.(twentynine populations) from 2 100 m to 4 200 m altitude in the eastern of Qinghai-Tibetan were studied,the relation between the structure of leaves of seven species and their environment was discussed. We have discovered that all the leaves of species are bifacial, their epidermis were single layer and had thicker cutide; With the altitude increasing, the thickness of the leaves, palisade and spongy tissue increased, and all of them had well-developed aerenchyam. Our results indicated that leaves of seven species had the structural characters of the mesophytes with part of xerophytes and liydrophytes. All of these above showed that the characteristics of seven kinds of leaves were the results of adaptation to the stressful environment of the severe lack oxygen, cold climate and high solar radiation ect.

Key words: Qinghai-Tibetan plateau, Saussurea DC., altitude, leaves, anatomical structure