翼萼蔓属系统位置的研究

ON SYSTEMATIC POSITION OF PTERYGOCALYX (GENTIANACEAE)

对翼萼蔓属进行了外部形态、花部解剖学、大小孢子发生和雌雄配子体发育、花粉形态和染色体的研究，并以此为据，讨论了该属的分类等级和系统位置。翼萼蔓属的花具花冠腺体。花萼筒具１６条维管束，花冠筒具１２条维管束，二者的维管束是独立发生的。每心皮具１条背维管束和２条腹维管束。雄蕊先熟。花药四室；药壁发育为双子叶型；绒毡层异型起源，细胞具双核，属腺质型绒毡层；一层中层细胞；药壁表皮层宿存，细胞膨大，细胞壁纤维状加厚；药室内壁部分纤维状加厚。小孢子母细胞减数分裂的胞质分裂为同时型；成熟花粉为３细胞型。子房为２心皮，１室，超侧膜胎座；胚珠２５～４０列，倒生胚珠，腹维管束靠近腹缝线。薄珠心，单珠被。大孢子母细胞减数分裂形成的４个大孢子呈直线式排列，其中合点端的大孢子具功能。胚囊发育为蓼型。极核在受精前融合为次生核，反足细胞３个，具反足吸器。胚乳发育为核型。花粉球形，极轴长约３２．８μｍ，赤道轴长约３４．２μｍ，外壁纹饰为网状纹饰。体细胞染色体数为２ｎ＝２６，染色体基数为ｘ＝１３，核型公式为２ｎ＝２６＝１８ｍ＋４ｓｍ＋２ｓｔ＋２ｔ，属２Ａ型。比较翼萼蔓属、蔓龙胆属和扁蕾属的外部形态、花部解剖学、胚胎学、花粉形态和染色体特征，?

The gross morphology, floral anatomy, embryology, pollen and karyotypes of Pterygocalyx volubilis were studied. The results are used to reevaluate the taxonomic status of the monotypic genus Pterygocalyx. Pterygocalyx volubilis has epipetalous glands. There are 16 bundles in calyx tube and 12 bundles in corolla tube,the calyx and corolla bundles are different in origin. Each carpel has one dorsal and two ventral bundles. Flowers are protandrous.The anther is 4 sporangiate. The development of anther walls conforms to the dicotylendonous type . The tapetum is of glandular type, dual origin,and binucleate cells at the late stage. The epidermis and part of endothecium persist; epidermisis fibrous thickened. Cytokinesis in the microsporocyte meiosis is simultaneous, and tetrads are tetrahedral. Pollen grains shed at the 3 celled condition. The ovary is bicarpellate and unilocular. The placentation is of superficial placentae with 25～40 series of ovules. The ovule is unitegmic, tenuinucellar and anatropous. The embryo sac originates from a single archesporial cell. The chalazal megaspore in linear tetrad becomes the functional one. The development of embryo sac is of the Polygonum type. Before fertilization, two polar nuclei fuse into a secondary nucleus. Three antipodals persist, become much enlarged, and function as haustorium. The development of the endosperm is of the Nuclear type. Pollen grains of Pterygocalyx are spheroidal, 32.8×34.2 μm in size with exine ornamentation being reticulate. The chromosome number of Pterygocalyx is 2n=26, with the basic number x=13. The karyotype is formulated as 2n=26=18m+4sm+2st+2t, belonging to “2A” type in Stebbins'classification. The genus Pterygocalyx is closely related to Gentianopsis . It is better to treat Pterygocalyx as an independent genus.