黄荆叶表皮形态结构及其生态适应性研究

Structure of Leaf Epidermis and Ecology Adaptation of Vitex negundo L. at Karat Area in Southwest China

利用光学显微镜和扫描电镜观察我国西南岩溶区典型次生灌草丛建群种-黄荆成熟叶的上、下表皮形态,观察指标包括气孔器、表皮毛、表皮细胞等.研究结果表明：自然分布广、适应性强的黄荆在叶表皮形态上具有气孔密度大（气孔密度为370-500个/mm^2）并仅出现在下表皮、表皮细胞小、上下表皮被毛及具有蜡质文饰等特征,以上特征有利于减少黄荆体内水分的散失,进而适应岩溶干旱环境.

As an adaptive consequence, plants growing in drought habitats have developed various drought-resistant mechanisms on their leaf-structures such as well-developed epidermal hairs, numerous stomata and other characters. For finding valuable ecology-adoption characters of Vitex negundo L. , the leaf epidermis have been examined by scanning electron microscopes （SEM） and the optical microscopy （LM） to study the characteristics of stomata, trichomes and dermal cell, et al. Under SEM observation, the results show that leaf epidermis consisted of epidermis cells and stoma complexes. Two kinds of trichomes including cone-hairs and vertical-tine hairs exit on the upper epidermis, however on the lower epidermis only exit conehairs along the vein. Moreover, the stomata apparatus only distribute on the lower epidermis and are anisocytic and wax grains also appear on the lower epidermis. In addition, the dermal cells on the leaf epidermis are not only numerous, but also have the dense character. Evidences from the results by LM serve as another proof on drought-resistant mechanisms of Vitex negundo L.. The stomatal density of Vitex negundo L. is very high, which means there are about 370-500 stomata in one mm^2. According to its living condition, it can be seen that there is an intense relationship between the leaf epidermis of Vitex negundo L. and its ecological adaptability, which enables Vitex negundo L. to adapt to the droughty environment at karst area in southwest China.