Abstract: We used light microscope, scanning electron microscope and histochemical localization techniques to study the relations between secondary vascular tissue and the ecological adaptation of Populus euphratica. P.euphratica has many structural characteristics and tuber member characteristics, which are adapt to ecological environment. The ratio of secondary phloem with developed phloem fiber to secondary xylem is 1/7 in width, and much cells with rich protein distributed in parenchyma. Less vessels in large diameter, with thick wall and multiple-pore distributed in the wood arranged radially, as a result, the tubal complex, mainly multiple-pore, supplemented by tracheid or bundle tracheid, was formed in secondary xylem of P.euphratica’ stem, while the xylem ray remained or evolved into fibrous tracheid. There are mainly pitted vessels in stem, occasionally trapeziform-pitted type, and both type vessels are very short with truncatus and leveled-perforation. The characteristics descripted above can explain the evolution and adaptation of secondary vascular tissue and tuber members of P.euphratica in a specific habitat.

Key words: Populus euphratica, secondary vascular tissue, anatomical structures, tuber members, habitat