国产18种鳞盖蕨属植物叶表皮微形态特征及其系统学意义

Leaf epidermis micromorphology characters of 18 species of Microlepia from China and its taxonomic significance

关键词:  鳞盖蕨属, 叶表皮, 微形态, 光学显微镜, 扫描电子显微镜, 系统学意义

Key words:  Microlepia, leaf epidermis, micromorphology, light microscope(LM), scanning electron microscope(SEM), taxonomic significance

摘要:

鳞盖蕨属是一个自然类群,由于各类群之间的形态差异以及种内变异比较大,因此其分类一直存在争议。该研究利用光学显微镜(LM)和扫描电子显微镜(SEM)对鳞盖蕨属18种植物(含3变种)的叶表皮微形态进行了观察和比较,并结合形态学、孢粉学和分子系统学探讨其系统学意义。结果表明:在光学显微镜下,18种鳞盖蕨属植物叶上、下表皮的脉上均有毛,叶表皮细胞都为不规则形,垂周壁为深波状或波状; 气孔都分布在下表皮,气孔器类型主要有极细胞型和腋下细胞型两种,叶表皮微形态特征支持鳞盖蕨属是碗蕨科中的一个单系类群; 叶上、下表皮脉间毛的变异特征支持光叶鳞盖蕨、毛叶边缘鳞盖蕨和二回边缘鳞盖蕨处理为边缘鳞盖蕨变种; 在扫描电镜下,叶上表皮角质层多为脊状凸起,多数还具丝状纹饰,角质膜特征与叶片回数有一定的相关性; 共环极细胞型、聚腋下细胞型、不等细胞型和不规则四细胞型只在少数种出现,气孔外拱盖多数凹陷,光滑或有颗粒; 气孔外拱盖内缘平滑、浅波状或齿状; 保卫细胞两极大多数有“T”型加厚,不同种间叶表皮微形态特征表现出一定差异。该研究结果为其分类、演化、系统位置等进一步研究提供了参考。

Abstract:

The fern genus Microlepia is a natural fern group, while large morphological differences of this genus lead to some classification controversies. The leaf epidermal micromorphology of 18 species( include 3 varieties )of Microlepia was observed and compared under light microscope( LM )and scanning electron microscope( SEM ). Hairs were on the veins of the upper and lower epidermis. The form of epidermal cells was irregular, with the anticlinal walls sinuous or sinuate. The stomatal apparatus of all species were restricted to abaxial epidermises and generally could be described as polocytic and axillocytic type, and copolocytic, coaxillocytic, aisocytic and anomotetracytic type only appears in a few species. The similarity of the micromorphological characteristics of leaf epidermis support that the genus Microlepia is a monophyletic group in Dentaedtiaceae. The hairs characteristics between veins of the leaves support that M. calvescens, M. marginata var. villosa and M. marginata var. bipinnata should be treated as a variety of M. marginata. Under SEM, the cuticle of the upper epidermis was mostly ridged, and most of them had filiform ornamentation. The characteristics of leaf cuticle ornamentation were correlated with pinnate compound leaves. The inner margin of the outer stomatal rim was often smooth, sinuous or odontoid. “T” sharp, upright outer stomatal rims occurred in most species, and outer stomatal ledge was mostly depressed. The differences among the leaf micromorphology of these species were shown, which provides references for the classification, evolution and system location of Microlepia.