关键词: 胡杨, 塔里木河下游, 水分胁迫, 细胞和组织结构, 扫描和透射电镜

Abstract: The characteristics of the leaf cell and organ structures of Populus euphratica Oliv., inhabited in the lower reaches of Tarim River, in relation to water stress are studied under scanning election microscopy (SEM) and transmission election microscopy (TEM). P. euphratica exhibits a serious of quality characteristics adapted to aridity environment. It has well-developed roots and hydrotropism of lateral roots, heteromorphous leaves with the self-direction-adjusting ability, long florescence and strong root tiller as well as characteristics of setting seeds in autumn. More microstructures associated with drought resistance are observed: there are ruffles on the surface of leaves; cuticle and coat are separated by a network of cavities; coats extend out and change into structures shaped as root hairs; there is a big central vacuole or a lot of dense small vacuoles in cells; there are more abundance of plastids in the cytoplasm and more starch granules in the plastid; the osmiophilic substances are obviously displayed in the cytoplasm and in the posterior margin of the vacuole; conducting tissue in leaf is poorly developed; X-radical analyses of critical components show that calcium is the main and steady content. The relation between the microstructure of P. euphratic leaf and water table indicates that structural development would be influenced by water table below 4 m. The cell wall and plasmalemma of P. euphratica are tightly combined as a dentate form under election microscope, explaining why the cell could endure severe water or osmotic stress and resist to plasmolysis.

Key words: Populus euphratica, the lower reaches of Tarim River, water stress, structure of cell, tissue and organ, SEM and TEM