| Carex (Cyperaceae) is a large genus of angiosperms, with about 2000 species in the world and about 500 species in China, widely distributed. Due to the wide distribution, variety of species, scattered type specimens and confusion of names, It's difficult in classification and identification, especially in classification of species and intrageneric levels, and in geographical distribution. different divisions were made in Carex sect. Rhomboidales by different taxonomists, and the delimitation of section and placement of species were agued. Our study was made based on extensive literature searching, field collection and specimen identification, with the concept of population as a guide. A taxonomic revision of Sect. Rhomboidales was made, combined with leaf epidermal morphology, leaf anatomy and achene micromorphology features, and discussed their systematic and taxonomic significance. The main results are as follows:1. Leaf epidermal morphology and its systematic and taxonomic significanceLeaf epidermis of 53 samples (39 species, two subspecies and one varieties from Carex Sect. Rhomboidale in China) were observed under the microscope. The shape of epidermic cells were generally rectangular, and the anticlinal walls were mostly sinuate. Stomata almost distributed under the abaxial epidermis. Sometimes siliceous papillae were obvious on adaxial and abaxial epidermis. Epidermal appendages could be divided into two types, viz. prickle and trichome. Leaf epidermal characters between samples from different localities had no significant difference, it showed that leaf epidermic morphology was stable within species. According to morphological characteristics and leaf epidermis observation, it indicated that C. longerostrata and C. pseudolongerostrata should be placed in Sect. Rhomboidales. C. macrandrolepis and C. tatsutakensis were different from members of Sect. Rhomboidales. C. chinensis, C. chinensis var. longkiensis and C. diplodon were also significantly different from members of Sect. Rhomboidales, so they should be placed in the other section. Leaf epidermal characters between closely related species in this section were significantly different. They could be used to distinguish species and intraspecies.2. Leaf anatomy and its systematic and taxonomic significanceLeaf anatomical structure of 53 samples (39 species, two subspecies and one varieties from Carex Sect. Rhomboidale in China) were observed under the microscope. The outline of leaf transverse section was mostly V-shaped, shallow V-shaped or flat V-shape. Air cavities were developed, and bulliform cells were well developed on the midrib. The sclerenchyma developed of different degrees was around the midrib vascular bundles. The cells of adaxial surface were larger than those of abaxial surface. Epidermal appendages could be divided into two types, viz. tubercule and Epidermis hairs. Mesophyll cells under the epidermis had different degrees of differentiation. Leaf anatomical characteristics between samples of different populations, such as the transverse shape, epidermial appendages, bulliform cells layers, the midrib bundle sheath cell layers and the development degree of sclerenchyma. had shown intraspecific stability. Leaf anatomical characteristics also support the treatment of C. longerostrata and C. pseudolongerostrata being placed in Sect. Rhomboidales. Leaf anatomical characteristics had significant distinction between related species, could be used to distinguish species which are morphologically similar.3. Achene micromorphology and its systematic and taxonomic significanceAchene morphology of 44 samples (33 species, two subspecies and one varieties from Carex Sect. Rhomboidale in China) were observed by SEM, the results showed that the achene were mostly obovate or ovate in shape, with straight or curved beak, usually stipitate, constricted at the middle or not, and concaved at the lateral surface. Achene epidermal cells were polygonal or irregular in shape. The patterns of anticlinal walls are straight, sinuous or sinuate. Most species had one silica central body and concave, flat or convex silica platform. Micromorphological characters of achenes were compared within species between different populations, it turned out that the achene micromorphologic features were constant within species. Achene characteristics also provided that C. macrandrolepis and C. tatsutakensis were different from members of Sect. Rhomboidales. Achene micromorphology was different between closely related species, was useful to distinguish species and intraspecies.4. Taxonomic revisonCombining with the study on all above and consulting a large number of specimens (especially type specimens), a worldwide taxonomic revision of Sect. Rhomboidales was made, with 34 species recognized, including three new species, C. chorda, C. canina and C. rivulorum, one subspecies. C. harlandii subsp. hoozaensis and two varieties. C. brevicuspis var. funingensis and C. canina var. kaoi. C. takasagoana and C. longqishanensis were merged into C. manca, and C. basiflora was reduced to synonyms of C. taipaishanica。... |
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