黄耆属裂萼亚属6种植物叶表皮微形态特征研究

Micro-morphological Characteristics of Leaf Epidermis for Astragalus Subgen. Cercidothrix and the Taxonomical Significance

为了明确黄耆属裂萼亚属内部类群的关系,该研究采用光学显微镜和扫描电镜,观察了黄耆属裂萼亚属6个组6种植物的叶表皮特征。结果表明:(1)在光学显微镜下,裂萼亚属6种植物的表皮毛密度、长度、臂长比以及气孔频率都存在较大差异:除莲山黄耆和地八角上表皮无毛外,其他种上下表皮都有毛分布并且下表皮毛密度较大;表皮毛臂长比在1.22~2.15之间;表皮毛的长度为104.7~902.0μm,同一个种的同一叶片上表皮毛长度差异在200~400μm之间,但上下表皮毛长度没有明显差别,其中短序组地八角的表皮毛长度最短(195.5μm),剑叶组鸡峰山黄耆的表皮毛长度最长(781.6μm)。(2)在光学显微镜下,裂萼亚属6种植物的表皮细胞形状和垂周壁式样也各不相同,其中灰叶黄耆和地八角垂周壁平直,莲山黄耆和鸡峰山黄耆为明显的波状,而斜茎黄耆和糙叶黄耆的垂周壁介于两者之间,相对应的表皮细胞形状分别为:多边形、不规则形和近多边形,这些特征可以作为物种鉴别的依据。(3)扫描电镜下,裂萼亚属6种植物的微形态特征基本一致,表皮毛均呈圆柱状,表面具有棱状条纹或乳头状突起,其中地八角的棱状条纹最为明显,其他各种之间的毛表面特征差异不明显;表皮细胞的蜡质层纹饰均为薄片状,气孔器外拱盖边缘平滑或微波状,其中地八角的气孔器周围角质层有明显的"T"型加厚。(4)比较不同环境下6种植物的气孔频率和密度发现,采自水边的地八角气孔频率最大,且上下表皮气孔频率一致,而采自黄土高原干旱地区鸡峰山黄耆的气孔频率却最小,与前人研究结果不一致。

In order to understand the relationship of groups of Subgen.Cercidothrix,we investigated the leaf epidermis of6species from different sections by the light microscopy(LM)and the scanning electron microscopy(SEM).The result shows that:(1)the densities,length,arm ratio of trichromes from different species are quite different.All leaves of species are hairiness except upper epidermis of A.leansanicus and A.bhotanensis,and hairs of lower epidermis are denser,hair arm ratio is between1.22to2.15.The length of trichromes is between104.7μm and902.0μm,the length of trichromes of one leaf is between200μm and400μm,but there is no obvious difference between upper and lower epidermis.A.bhotanensis have the shortest hairs which average length is195.5μm;A.kifonsanicus have longest hairs which average length is781.6μm.(2)The stomatal frequency,the shape of the epidermal cells and the anticlinal walls of different species are not the same.The anticlinal walls of A.discolor and A.bhotanensis are straight,while A.leansanicus and A.kifonsanicus are significant sinuate,and A.adsurgens and A.scaberrimus were intermediate.The corresponding epidermal cells are polygons,irregularity and nearly polygons respectively,which can be used for species identification.(3)Under SEM,the characteristics of these species are almost the same:the trichromes are cylindric,with papillae or striation ornamentation on surface.Waxy layer of epidermal cells are textured flake.Inner margin of outer stomatal rim was nearly smooth or sinuolate,while the stomatal of A.bhotanensis is surrounded by“T”type thickening of guard cells.(4)The stomatal frequencies and densities of six species under different environments shows that A.bhotanensis from waterside have the largest stomatal frequency,336/mm2,but the stomatal frequencies of A.kifonsanicus from arid areas was the lowest,120/mm2and the upper and lower epidermis were the same.This is inconsistent with the results of previous studies.