中国桃叶珊瑚属植物叶表皮微形态特征及其分类学意义

Leaf epidermal micro-morphology of genus Aucuba (Garryaceae) in China and its taxonomic significance

关键词:  桃叶珊瑚属，物种鉴定，叶表皮微形态，系统分类，气孔

Key words:  Aucuba, species identification, leaf epidermal micro-morphological features, taxonomic significance, stoma

摘要:

为揭示桃叶珊瑚属（Aucuba）的叶表皮微形态特征，探讨其分类学意义，给该属植物的种类划分提供较客观的形态学证据，该研究以中国桃叶珊瑚属10种7变种为研究对象，利用光学显微镜和扫描电镜对其叶表皮微形态特征进行系统观察，结果表明：（1）桃叶珊瑚属植物气孔器均分布于叶片远轴面，形状从近圆形到椭圆形不等；保卫细胞为肾形，覆盖在5~7个未特化的表皮细胞上方，并被这些表皮细胞环绕，无副卫细胞，并揭示这是一种新的气孔器类型——悬铃木型气孔（Platanus-Type stoma）。（2）叶表皮微形态聚类分析结果表明，中国桃叶珊瑚属分为2组：Group Ⅰ 叶表皮角质层表面较光滑且近轴面存在乳突状突起，表皮细胞垂周壁以浅波状和波状为主，气孔器形状以近圆形为主；Group Ⅱ 叶表皮角质层表面附着较多蜡质，表皮细胞垂周壁以波状和深波状为主，气孔器形状以亚圆形和椭圆形为主。该结果支持依据综合形态特征划分的“绿花乔木组”和“红花灌木组”的分类处理。（3）该研究揭示了部分种间关系与分类处理，如倾向于将大花桃叶珊瑚（A. grandiflora）、凹脉桃叶珊瑚（A. cavinervis）处理为独立种；不支持狭叶桃叶珊瑚作为桃叶珊瑚（A. chinensis）的变种处理。综上认为，叶表皮微形态特征对中国桃叶珊瑚属植物在分组水平上有重要分类价值，在属内部分物种鉴定上具有一定参考价值。

Abstract:

To reveal the micro-morphological characteristics of leaf epidermis in the genus Aucuba, explore their taxonomic significance, and provide objective morphological evidence for species classification within this genus. This study examined 10 species and 7 varieties of Chinese Aucuba using light microscopy (LM) and scanning electron microscopy (SEM). The results are as follows: (1) Stomatal apparatuses in Aucuba occur exclusively on the abaxial leaf epidermis. They range from nearly round to oval in shape, lack subsidiary cells, and consist of kidney-shaped guard cells surrounded by 5-7 unspecialized epidermal cells. This represents a novel stomatal type termed the “Platanus-Type”. (2) Cluster analysis of micro-morphological traits revealed that Chinese Aucuba species can be divided into two groups: Group Ⅰ exhibits a relatively smooth cuticular surface, papillae adaxial epidermis, sinuolate to sinuous anticlinal walls, and predominantly round stomatal apparatuses; Group Ⅱ is characterized by cuticles with abundant wax, sinuous to sinuate anticlinal walls, and sub-round to oval stomatal apparatuses. These groupings align completely with the traditional morphological classification of “green-flowered tree group” and “red-flowered shrub group”. (3) Leaf epidermal features supported certain taxonomic revisions, such as recognizing A. grandiflora and A. cavinervis as distinct species, but do not support the recognition of A. chinensis var. angusta. In summary, the micro-morphological traits of leaf epidermis have significant taxonomic value at the group level in Chinese Aucuba and provide a useful reference for the identification of certain species within the genus.