塔里木河下游胡杨叶片变化与环境异质性

通过电子显微镜观测对塔里木河下游三个取样点胡杨(Populus euphratica Oliv.)叶片的细胞显微结构进行了研究。通过电镜观察到许多与抗旱性相关的结构:叶表面具有皱褶状纹饰;角质层和表皮之间由网格状空腔隔离开;表皮向外突出形成根毛状结构;细胞内含一中央大液泡或密布小液泡;输导组织不发达;细胞中质体和质体内淀粉粒非常丰富;在细胞质中和液泡内发现嗜锇颗粒;细胞核很大,核仁明显;组织细胞中晶簇成分X-射线微区分析表明,其成分主要是钙,而且含量稳定。叶片显微结构与地下水位的关系表明,4 m以下的地下水位会影响其组织结构的建成。在超微结构研究中还发现,胡杨细胞膜与细胞壁之间呈齿状结合。说明细胞膜与壁之间结合的牢固性和稳定性,解释了胡杨细胞在水分胁迫下不易发生质壁分离的原因。

Ultramicroscopic Structure of Populus euphratica Leaves Related to Environmental Heterogeneity in the Lower Reaches of Tarim River

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.