四数獐牙菜的胚胎学及其系统学意义
摘要：
四数獐牙菜花药四室，药壁发育为双子叶型；绒毡层腺质型。小孢子母细胞减数分裂为同时型，
四分体的排列方式为四面体形；成熟花粉为3-细胞。子房2心皮，2心皮连接处强烈内凸，4列胚珠。薄
珠心，单珠被，直生胚珠。胚囊发育为蓼型。胚乳发育为核型。胚胎发育为茄型酸浆I变型。反足细胞
在胚囊成熟时期宿存。果实成熟时，种子只发育至球型胚阶段。承珠盘存在。与已研究的獐牙菜种类
的胚胎特征相比较，该种存在三个显著的特点：直生胚珠，心皮连接处强烈内凸，承珠盘存在。这三个特
征目前仅在龙胆族中的花锚属中发现。经过性状分析，它们均是演征，此三个共有演征表明四数獐牙菜
与花锚属是一单系群，它们的亲缘关系最近。这与Yun & Kupfer(1995)的分子证据部分吻合，因为分
子系统树上的花锚单系支包括花锚、四数獐牙菜和北美的密花属(广义獐牙菜属中的密花组)，而后者的
胚胎学特征未有任何报道。胚胎学研究暗示四数獐牙菜的分类学等级有待重新评价，广义的獐牙菜属
有可能不是一单系发生群。
关键词: 四数獐牙菜, 胚胎学, 系统学
Abstract:
The embryology of Swertia tetraptera is reported for the first time. The anther
is tetrasporangiate and its wall, of which the development conforms to the dicotyledonous
type, is composed of epidermis, endothecium, middle layer and tapetum at the mature stage.
The tapetum has dual origin and is similar to the glandular type. Cytokinesis is of the simul-
taneous type and microspore tetrads are mostly tetrahedral. Pollen grains are mostly 3-celled
when shed. The ovary is bicarpellate and unilocular with four series of ovules. The fused
margins of two carpels intensively protrude into the locule. The ovule is unitegmic, tenuinu-
cellate and orthotropous. The development of embryo sac is of the Polygonum type. The de-
velopment of endosperm conforms to the nuclear type and the embryogeny corresponds with
the Physalis I variation of Solanad type. Three antipodal cells persist at the mature embryo
sac. The embryo is at the globular stage when seeds are released from the capsule. Compared
with the other studied species in Swertia, S. tetraptera shows differences from them in
three distinctive embryological traits: enlargement and protrusion of the fused margins of two
carpels into the ovary locule; orthotropous ovules and a developed hypostase. These three
characters were previously only found in the genus Halenia of the tribe Gentianinae in the
Gentianaceae,and thus suggest that S. tetraptera should be related to Halenia. The results
partly correspond with the molecular evidence (Yuan & Kupfer, 1995). The monophyletic
Halenia clade in Yuan & Kupfer's molecular cladogram includes Halenia, S. tetraptera
and Frasera (section Frasera in Swertia s. l.); nevertheless, up to now, no embryological
study on Frasera has been reported. The embryological results imply that the taxonomic sta-
tus of S. tetraptera needs to be revaluated and the genus Swertia s. l. may not be a mono-
phyletic group.Key words: Swertia tetraptera, Embryology, Systematics
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