Comparative studies on leaf epidermal micromorphology and mesophyll structure of Elaeagnus angustifolia L. in two different regions of desert habitat

In order to obtain qualitative and quantitative characteristics of leaf epidermal micromorphology and mesophyll structure to evaluate the responses of Elaeagnus angustifolia L. to different environmental factors, epidermal micromorphology was observed by scanning electron microscopy (SEM), and mesophyll structure was studied by light microscopy (LM) and transmission electron microscopy (TEM). Materials were selected from Linze County, Gansu Province (material A) and Qitai County, Xinjiang Uygur Autonomous Region (material B) of China. Results show that lamina thickness was higher in material A, with one layer of epidermal cells in both adaxial and abaxial surfaces, and epidermal cell radial length was significantly longer in the adaxial surface. E. angustifolia leaves are typically bifacial, with a higher ratio of palisade to spongy tissue in material A. The thickness of trichome layer of epidermis was thicker in material A. In contrast, cell wall and cuticular wax of the epidermal cells were thinner in material A than in material B. Chloroplast ultrastructure was different with the approximate spherical chloroplast containing numerous starch grains and osmiophilic granules in material A, while only the spindly chloroplast contained starch grains in material B. Multiple layers of peltate or stellate-peltate trichomes occupied both leaf surfaces in material A and the abaxial surface in material B, while the adaxial surface of material B contained few trichomes. Stomata were not observed on the leaf surfaces in materials A and B by SEM because of trichome obstruction. Our results indicate that the leaf structure of E. angustifolia is closely correlated with environmental factors, and the combination of leaf epidermal micromorphology and mesophyll structure afford resistance to environmental stress.