峨眉双蝴蝶的胚胎学研究(英文)

Embryology of Tripterospermum cordatum(Gentianaceae)

首次报道了峨眉双蝴蝶Tripterospermumcordatum (Marq )H .Smith的胚胎学特征 ,研究结果用以讨论双蝴蝶属的系统演化关系。主要研究结果如下 :花药四室 ;药壁发育为双子叶型 ;绒毡层属单型起源 ,细胞具单核 ,属腺质型绒毡层 ,药隔处的绒毡层细胞形成类胎座 ,其余部位的绒毡层细胞仍为一层细胞 ;在花药成熟时 ,花药的药室内壁纤维状加厚且柱状伸长 ,表皮细胞减缩退化 ,纤维状加厚不明显。成熟花粉为 3-细胞型。子房为 2心皮 ,1室 ,侧膜胎座。胚珠为 4或 8列的Hypertropous胚珠类型。大孢子母细胞减数分裂形成的 4个大孢子呈直线式排列 ,合点端的大孢子具功能。胚囊发育为蓼型。珠孔受精。胚乳发育为核型。胚胎发育为茄型酸浆II变型。通过比较双蝴蝶属与蔓龙胆属和龙胆属的胚胎学特征表明 ,双蝴蝶属在一些重要的胚胎学特征上与蔓龙胆属和龙胆属均存在较大差异 。

The present paper reports embryological characters of Tripteropsermum cordatum (Marq ) H. Smith for the first time and discusses the systematic relationships of Tripterospermum . Anthers are tetrasporangiate. The development of anther walls conforms to the Dicotyledonous type. The tapetal cells origin from the primary parietal cells, and thus the tapetum is of single origin. The development of the tapetum with uninucleate cells is of the Glandular type. The tapetal cells on the connective side show radial elongation or periclinal division and intrude into the anther locule to form placenoids. The anther wall has only one middle layer; the endothecium persists and its cells become pillar and fibrous, and the epidermis degenerates. Cytokinesis at meiosis of microsporocytes is of the simultaneous type and the microspore tetrads are tetrahedral. Pollen grains are 3-celled. The ovary is bicarpellary and unilocular. The placentation is of reduced or typical parietal placentae with 4 or 8 rows of hypertropous ovules. The ovule is unitegmic and tenuinucellar. The embryo sac originates from a single archesporial cell. The one chalazal megaspore in linear tetrad becomes functional. The development of embryo sac is of the Polygonum type. Before fertilization, two polar nuclei fuse into a secondary nucleus. Three antipodal cells persist. Flowers are protandrous. Fertilization is porogamous. The development of the endosperm is of the Nuclear type. The embryogeny corresponds to the Solanad type Physalis Ⅱ variation type. Compared with Gentiana and Crawfurdia, Tripterospermum is different from Gentiana and Crawfurdia in embryological characters. The embryological data indicate that it is better to treat Tripterospermum as an independent genus.