白蜡虫七种寄主植物枝条树皮比较解剖研究

Comparative anatomical study of twig barks of seven host plant species of the pela wax scale，Ericerus pela（Chavannes）

关键词:  白蜡虫  寄主植物  树皮  解剖结构

Key words:  Ricerus pela(Chavannes)  Host plant  Bark  Anatomical structure

摘要:

采用常规石蜡切片法解剖观察了白蜡虫7种寄主植物一年生枝条树皮横切面结构特征，结果表明：白蜡虫7种寄主植物一年生枝条树皮从内到外由次生韧皮部、初生韧皮部纤维束、皮层和周皮组成；次生韧皮部横向系统均由筛管、伴胞和薄壁细胞组成；轴向系统由射线组成。木栓层以美国白蜡和流苏细胞层数最多，达10～12层；华南小蜡、紫药女贞和白枪杆次之，为5～8层；女贞和白蜡树最少，分别为2～3和3～4层。初生韧皮部纤维束排列整齐连接为带状或分散，女贞属纤维连接成带状，白蜡属和流苏属纤维分散。带状纤维层厚薄不均，厚度在26.93±13～59.15±7 μm之间，以白枪杆纤维层最厚，为59.15±7 μm；美洲白蜡次之，为50.05±7 μm；白蜡树最薄，为26.93±13 μm。分散型纤维束直径在25.12±13～76.15±36 μm之间，纤维束直径大小顺序为：流苏（76.15±36 μm）＞紫药女贞（43.44±10 μm）＞女贞(25.12±13 μm)。女贞、紫药女贞和流苏纤维束间距分别为78.53±39 μm、149.78±27 μm和212.02±95 μm。次生韧皮部厚度在48.52±12～377.44±24 μm之间，以女贞的次生韧皮部最厚，达377.44±24 μm，华南小蜡最薄，为48.52±12 μm。树皮次生韧皮部厚、木栓层数少和纤维束直径小为白蜡虫优良寄主植物的显著特征。

Abstract:

Anatomical structure and characteristics of transverse section of one year twigs of seven host plant species of Ericerus pela（Chavannes）were studied by paraffin method. Barks of seven species consisted of periderm，cortex，fibre bundies of primary phloem and secondary phloem from the inner to outer. The secondary phloem consisted of sieve elements，companion cells and phloem parenchyma cells within transverse system and phloem rays within axial system. Among seven host species，Fraxinus americana and Chionanthus retusa had the thickest phellems which were composed of 10-12 cell layers，followed by Ligustrum calleryanum，L.delavayanum and Fraxinus malacophylla，of which consisted of 5-8 cell layers，while F.chinensis and Ligustrum lucidum had the thinnest phellems，which were composed of 2-3 or 3-4 cell layers，respectively. There were two types of fiber bundies of primary phloem，ribbon like in Ligustrum or scattered in Fraxinus and Chionanthus. Thickness of ribbon like fibers were different between three Fraxinus species:59.15±7 μm for F.malacophylla，followed by 50.05±7 μm for F.americana，and 26.93±13 μm for F.chinensis. The diameter of scattered fibers of Fraxinus and Chionanthus were also different，ranging from the widest of 76.15±36 μm for C.retusa to the narrowest of 25.12±13 μm for L.lucidum. The spacing of fiber bundied of L.lucidum，L.delavayanum and C.retusa were 78.53±39 μm，149.78±27 μm and 212.02±95 μm，respectively. Thickness of secondary phloem layers differed wildly among species，ranging from the thickest of 377.44±24 μm for L.lucidum to the thickest of 48.52±12 μm for L.calleryanum. In summary，host plants with barks featured by thick secondary phloem，thin phellems，and small diameter fibers are likely to have higher suitability for the wax insect，E.pela.