20种胡椒属植物叶表皮微形态特征及其分类学意义

Micromorphological characteristics of leaf epidermis and taxonomic significance of 20 species of Piper L.

关键词:  叶表皮，胡椒属，微形态，扫描电镜，分类

Key words:  leaf  epidermis, Piper  L., micromorphology, scanning  electron microscope, taxonomy

摘要:

为解决我国胡椒属植物分类学问题，探究叶表皮微形态特征的分类学意义，该研究利用光学显微镜和扫描电镜对栽培种胡椒和19种国产胡椒属植物的叶表皮微形态特征进行了观察比较。结果表明：（1）大多数物种叶表皮细胞呈多边形，垂周壁平直或弓形，仅少数物种下表皮细胞形状不规则，垂周壁呈浅波状。（2）气孔器均仅分布于下表皮，类型为不等型、双环列型及中间过渡类型，气孔器大小、密度在种间表现出一定差异，可作为种间区分的辅助指标。（3）角质层纹饰有近光滑、条纹状、乳突状及微乳突状四类，该特征能够在一定程度上反映物种间亲缘关系，在胡椒属下分组中具有一定价值。（4）表皮毛包括腺毛与非腺毛两种类型，多数物种具腺毛，非腺毛含单毛与复毛，少数物种无毛，表皮毛特征可以作为胡椒属植物种间分类的重要依据。（5）依据叶表皮微形态特征和其他性状对一些物种的分类问题进行了探讨，倾向于将小叶球穗胡椒（Piper thomsonii var. microphyllum）处理为独立物种，不支持将细苞胡椒（P. curtipedunculum）处理为角果胡椒（P. pedicellatum）的异名，支持将水晶胡椒（P. semi-transparens）划分为独立种，支持黄花胡椒（P. flaviflorum）与胡椒（P. nigrum）具有较近的亲缘关系。该研究结果表明叶表皮微形态特征可为胡椒属植物分类提供重要依据。

Abstract:

The genus Piper is characterized by a notable degree of interspecific morphological similarity coupled with considerable intraspecific variation, which presents significant challenges for accurate species classification. This study aimed to investigate the taxonomic significance of leaf epidermal micromorphological characteristics and address unresolved taxonomic issues within the genus Piper. The leaf epidermal micromorphological characteristics of Piper nigrum and 19 native Piper species were systematically examined and compared using light microscopy (LM) and scanning electron microscopy (SEM). The results were as follows: (1) The leaf epidermal cells of most species were polygonal in shape, exhibiting straight-arched anticlinal walls. In contrast, only a few species displayed irregularly shaped epidermal cells with sinuolate anticlinal walls on the upper epidermis. (2) Stomata were exclusively located on the lower epidermis and could be classified into three distinct types: anisocytic, amphicyclocytic, and the transitional type between these two categories. Stomatal size and density showed significant interspecific variation, serving as auxiliary diagnostic features for species differentiation. (3) The cuticular ornamentation was categorized into four main types: nearly smooth, striate, papillate, and micropapillate. These distinct patterns of ornamentation partially reflect the phylogenetic relationships among species and provide valuable insights for the infrageneric classification within the genus Piper. (4) Trichomes were classified into two broad categories: glandular and non-glandular types. The majority of species exhibited glandular trichomes, while non-glandular trichomes included both simple and branched types. A small number of species were glabrous. The characteristics of trichomes were demonstrated to be critical and informative taxonomic criterion for interspecific classification within Piper. (5) Based on the leaf epidermal micromorphological characteristics and other relevant traits, the taxonomic status of certain species was re-evaluated. This study supported the recognition of P. thomsonii var. microphyllum as a distinct species and rejected the synonymization of P. curtipedunculum with P. pedicellatum. Additionally, it affirmed P. semi-transparens as a separate species, while also confirming the close phylogenetic relationship between P. flaviflorum and P. nigrum. This study indicates that the critical taxonomic importance of leaf epidermal micromorphological characteristics, particularly the traits of trichomes. These features provide essential insights into species differentiation, phylogenetic relationships, and the resolution of longstanding taxonomic debates within the genus Piper.