Anatomical and Morphological Characteristics of Populus Euphratica in the Lower Reaches of Tarim River under Extreme Drought Environment

Populus euphratica Oliv. is an old desert tree species that has been naturalized and invades zones along the watercourses in many arid and semiarid regions. The plant species developed some plasticity to adapt to the gradual environmental gradients. The aim of this study was to test the hypothesis that the changes in leaf morphology of P euphratica reflect the adaptability of the plant to the unique environment of the lower reaches of Tarim River in China. The foliar architecture, blade epidermal and internal anatomies of P euphratica were analyzed at different sites along the Tarim River. Compared with the abaxial surface of the leaves, their adaxial surface has more hairs, a greater stomatal density and opening, higher mesophyll proportion, and increased blade thickness, palisade width, and epidermal thickness. The long trichome of the roots found at site 6 in the Yinsu section may be an adapted structure of the plants in arid areas. The mature leaves of P euphratica have comparatively more epidermis and cuticles, well developed palisades and more chloroplasts at different sites compared to the young leaves. Foliar morphological and anatomical variability in P euphratica may be considered an adaptive advantage that enables leaves to develop and function in different habitats, marked by strong variations in solar radiation, air temperature, humidity and water table.