Embryology of Megacodon stylophorus and Veratrilla baillonii (Gentianaceae): descriptions and systematic implications

	Embryology of Megacodon stylophorus and Veratrilla baillonii (Gentianaceae): descriptions and systematic implications
	Xue, CY; Li, DZ
	2005-03-01
发表期刊	BOTANICAL JOURNAL OF THE LINNEAN SOCIETY
卷号	147 期号:3 页码:317-331
摘要	The embryological characters of Megacodon stylophorus (C. B. Clark) H. Smith and Veratrilla baillonii Franch. are described for the first time and the systematic relationships of Megacodon and Veratrilla are discussed. Both species share the following embryological features. The anthers are tetrasporangiate. The formation of anther walls is of the Dicotyledonous Type. The tapetum is of glandular type with uninucleate cells which have a dual origin. The tapetal cells on the connective side show radial elongation or periclinal division and intrude into the anther locule to form 'placentoids'. Cytokinesis in the microsporocyte meiosis is of the simultaneous type and the microspore tetrads are nearly always tetrahedral, rarely decussate. The ovary is bicarpellate and unilocular. The ovule is unitegmic and tenuinucellar. The formation of the embryo sac is of the Polygonum Type. Before fertilization, the two polar nuclei fuse into a secondary nucleus. Fertilization is porogamous. The development of the endosperm is of the Nuclear Type. However, the two species show variation in the following features: the number of cell layers which form the anther locule wall; construction of the wall of the mature anther; cell number in mature pollen grains; ovule number in cross sections of placentae; degree of ovule curvature; character of the hypostase and seed shape. In a comparison with the other taxa in the tribe Gentianeae using embryological features, Megacodon is referred to as an independent genus and should be treated as a member of the subtribe Swertiinae; Veratrilla is better separated from Swertia s.l. as an independent genus. Veratrilla is more derived than Swertia s.s. and shows a close relationship with S. tetraptera. (c) 2005 The Linnean Society of London.
关键词	Development Embryogenesis Gentianeae Megagametogenesis Microgametogenesis Phylogeny Swertiinae
学科领域	Plant Sciences
收录类别	SCI
语种	英语
WOS记录号	WOS:000227841700005
引用统计
文献类型	期刊论文
条目标识符	http://ir.kib.ac.cn/handle/151853/11203
专题	中国西南野生生物种质资源库
作者单位	Chinese Acad Sci, Kunming Inst Bot, Kunming 650204, Yunnan, Peoples R China
推荐引用方式 GB/T 7714	Xue, CY,Li, DZ. Embryology of Megacodon stylophorus and Veratrilla baillonii (Gentianaceae): descriptions and systematic implications[J]. BOTANICAL JOURNAL OF THE LINNEAN SOCIETY,2005,147(3):317-331.
APA	Xue, CY,&Li, DZ.(2005).Embryology of Megacodon stylophorus and Veratrilla baillonii (Gentianaceae): descriptions and systematic implications.BOTANICAL JOURNAL OF THE LINNEAN SOCIETY,147(3),317-331.
MLA	Xue, CY,et al."Embryology of Megacodon stylophorus and Veratrilla baillonii (Gentianaceae): descriptions and systematic implications".BOTANICAL JOURNAL OF THE LINNEAN SOCIETY 147.3(2005):317-331.

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