夹竹桃叶的形态解剖学及其环境适应性意义

Morphological Anatomy and Environmental Adaptability of Nerium oleander Leaves

摘要:

为了解夹竹桃(Nerium oleander)叶结构的环境适应性，采用解剖学和组织化学方法对其叶的显微结构进行观察。结果表明, 夹竹桃叶上、下表面均被有非腺毛、角质层和蜡质，气孔窝只分布在下表面，气孔窝内密布非腺毛，气孔窝底部有气孔存在；叶的上、下表皮均为复表皮，栅栏组织2层细胞排列紧密；海绵组织细胞呈无规则排布，细胞间隙大，叶肉组织中有草酸钙簇晶分布；中脉向下突出，表皮外有角质层，表皮下有厚角组织，内部有大量薄壁细胞，中脉中央有双韧型维管束，维管束周围的薄壁细胞中有草酸钙簇晶和草酸钙方晶分布；维管束附近一些薄壁细胞充满淀粉粒，导管类型多样，有螺纹、梯纹、孔纹导管，可见无节不分枝乳汁管。夹竹桃叶的角质层、复表皮、气孔窝和草酸钙晶体等结构特征提示其有很强的保水、抗紫外线、抗病虫害能力，2层紧密的栅栏组织和疏松的海绵组织不仅支持其有较高的光合效率，同时还能防止高温干旱造成的伤害。夹竹桃叶解剖结构的研究表明夹竹桃具有较强的环境适应能力。

Abstract:

In order to understand the environmental adaptability of leaf structure of Nerium oleander, the microscopic structure of leaves was observed by anatomical and histochemical methods. The results showed that the upper and lower surfaces of leaves were covered with non-glandular hairs, cuticle and wax, and the stomatal nests were only distributed on the lower surface, densely covered with non-glandular hairs, and there were stomata at the bottom. The upper and lower epidermis of leaves were compound epidermis, and the two layers of palisade tissue cells were tightly arranged. The cells of sponge tissue were randomly arranged with large intercellular spaces, and calcium oxalate clusters were distributed in mesophyll tissue. There are cuticle outside the epidermis, thick angular tissue under the epidermis, and a large number of parenchyma cells inside. There are double pliable vascular bundles in the center of the midvein, and calcium oxalate clusters and calcium oxalate square crystals are distributed in the parenchyma cells around the vascular bundles. Some parenchyma cells near the vascular bundle were full of starch granules. The vessels were of various types, including spiral, scalariform and pitted vessels. The cuticle layer, compound epidermis, stomatal cavity and calcium oxalate crystal of N. oleander leaves indicate that it has a strong ability of water retention, ultraviolet resistance and insect resistance. The two layers of tight palisade tissue and loose spongy tissue not only support its high photosynthetic efficiency, but also prevent the damage caused by high temperature and drought. The anatomical structure of the leaves of N. oleander shows that oleander has strong adaptability to the environment.