西南岩溶地区黄荆和檵木叶片结构对其生态环境的响应

应用常规石蜡切片法对生长于桂林毛村岩溶区和非岩溶区的黄荆(Vitex negundo)和檵木(Loropetalumchinense)的解剖特征进行了比较研究,并对两区的黄荆叶片表皮形态进行了扫描电镜观察.结果显示:(1)两地的黄荆叶片背面均有浓密的绒毛,但致密程度有差异,岩溶区黄荆叶片的气孔深藏于绒毛间隙,这种结构可减少水分蒸发,降低因岩溶干旱带来的水分缺失.(2)岩溶区黄荆和檵木的叶片厚度、上下表皮厚度、栅栏组织的厚度以及栅栏组织的致密程度均大于非岩溶区,这些特征有利于减少水分蒸腾.(3)岩溶区黄荆和檵木叶片的维管组织发达程度高于非岩溶区,有利于在蒸腾减小的情况下促进水分运输和营养元素的迁移,说明2种植物叶片结构特征在不同生境区的改变是其长期在岩溶区干旱环境条件下形成的适应性变化.

Ecological Responses of Vitex negundo and Loropetalum chinense Leaves in Southwest Karst Areas

The anatomical characteristics of Vitex negundo and Loropetalum chinense between karst areas and non-karst areas in Maocun of Guilin were investigated by light microscope and the configuration of V.negundo leaves was observed by scanning electron microscope.The results are as follows:(1) The anatomical characteristics of V.negundo leaves from both sites presented similarities and differences to some degree.The scanning electron microscope results showed that these leaves from both sites all have bushy tomenta,yet with different densities.Stomata of leaves in karst areas were found deeply stored in the gap of the tomenta,which could decrease the moisture evaporation,and thus reduce the moisture lose resulted from the karst drought.(2) The thickness of the leaves,the epidermis of both upside and downside,and the palisade parenchyma of V.negundo and L.chinense were much thicker in the karst areas than that in the non-karst areas.The tomenta of palisade parenchyma was more bushy in the karst areas than that in the non-karst areas.These characteristics were helpful to decrease water transpiration,which was consistent with the field observation results of daily average transpiration rate in karst areas being lower than that in non-karst areas.(3) The vascular tissues of the V.negundo and L.chinense leaves were highly developed in the karst areas than that in the non-karst areas,which make it advantageous to promote water transportation and nutrient elements migration under the condition of lower of transpiration.To sum up,the leaves characteristics of V.negundo and L.chinense reflected the ecological adaptation to the karst drought environment.