Leaf Anatomical Structure of Populus euphratica in Tarim River Basin
HUNG Wen-Juan, JIAO Pei-Pei, HUANG Jin-Hua, ZHANG Dan
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From the regional scale, three natural ranges of Populus euphratica in Alar, Luntai and Yuli County with different climate and soil conditions were chosen from the upper, middle and lower reaches of Tarim River Basin, respectively. In each site, 8 plots with the same size of 50 m×50 m were chosen and within each plot, leaves from 3 adult trees of P.euphratica were selected randomly. Routine paraffin sectioning method was used to observe and compare the leaf anatomical characters of P.euphratica, and explore their adaptive strategies and anatomical features to adapt to different environmental conditions. The results showed:(1)The basic leaf anatomical characters from 3 distribution areas were consistent with each other, and showed:a. The upper and lower epidermis were both mutiple epidermis and consisted of double layer of cells; b. Palisade tissue of mesophyll was differentiated close to upper and lower epidermis, and the leaf belonged to isolateral leaf. The mucous cells which relatively deep stained were also visible in the mesophyll tissue. c. The "bundle sheath" consisting of thick-walled cells was visible outside the vein vascular bundle. (2)From the whole point of the Tarim River Basin, there were vary degrees of variations among the leaf anatomical structure indexes. The range of variation coefficient was from 0.029 to 1.786, and the thickness variation coefficient of upper epidermal cells was smallest, while the blade thickness was largest. (3)The quantitative values of leaf anatomical structure index varied in different areas:leaf thickness, palisade tissue thickness, cuticle layer thickness, lower epidermis thickness and the grid/sea showed Yuli County >Luntai County >Alar County, which indicated that P.euphratica stored water and reduced water loss to adapt to the relatively dry environment through increasing the thickness of leaf, cuticle layer and epidermal cells. (4)There was significant correlation between the structure indexes and altitude, latitude and longitude. The thickness of upper epidermal and upper cuticle layer were positively correlated with longitude significantly(P<0.05)and highly significantly(P<0.01). The leaf thickness, mesophyll thickness, palisade tissue thickness and grid/sea were negatively correlated with longitude highly significantly(P<0.01). The thickness of upper epidermal, upper cuticle layer and grid/sea were negatively correlated with altitude significantly(P<0.05)or highly significantly(P<0.01).