Embryology of Swertia (Gentianaceae) relative to taxonomy

The embryological features of three species of Swertia ( s.l.) – S. erythrosticta , S. franchetiana , and S. tetraptera – were characterized, and the observations were used, together with previously gathered data on other species, to evaluate a recently proposed polyphyly, based on molecular data, of Swertia s.l. Comparisons of species within the genus showed that they have diversified embryologically, and there are significant between-species differences. Notable features that vary between species include the number of cell layers that form the anther locule wall, the construction of the wall of the mature anther, tapetum origin, the cell number in mature pollen grains, the structure of the fused margins of the two carpels, the ovule numbers in placental cross-sections, the shape of the mature embryo sac, the degree of ovule curvature, antipodal variation and the presence of a hypostase, and seed appendages. They share characters that are widely distributed in the tribe Gentianeae, such as a dicotyledonous type of anther wall formation, a glandular tapetum with uninucleate cells, simultaneous cytokinesis following the meiosis of the microsporocytes, tetrahedral microspore tetrads, superior, bicarpellary and unilocular ovaries, unitegmic and tenuinucellar ovules, Polygonum -type megagametophytes, progamous fertilization, nuclear endosperm, and Solanad-type embryogeny. The presence of variation in embryological characters amongst the species of Swertia s.l. strongly supports the view that Swertia s.l. is not a monophyletic group. Frasera is better separated from Swertia s.l. as an independent genus, and is only distantly related to Swertia s.s. judging from the numerous differences in embryology. Swertia tetraptera is very closely related to Halenia , as they show identical embryology.  © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society , 2007, 155 , 383–400.     

大钟花属和黄秦艽属花部解剖

对大钟花属和黄秦艽属进行了花部解剖学研究,并以此讨论了它们的系统演化关系。大钟花属和黄秦艽属的雌花部分花萼维管束与花冠维管束来源于同一维管束迹,而雄蕊维管束来源于雄蕊迹,每心皮具1条背维管束2条腹维管束,因此,花被维管束为融合型;黄秦艽属的雄花每个花萼、花瓣和雄蕊的维管束均来源于单个维管束迹,每心皮具1条背维管束2条腹维管束,属于基本型。从花部解剖结构看出,大钟花属与假龙胆演化支关系较近;黄秦艽属较獐牙菜属进化。     

Sporogenesis and gametogenesis in Sladenia and their systematic implication

Sporogenesis and gametogenesis in the monotypic genus Sladenia is reported for the first time. The anther wall is of the monocotyledonous type of formation and consists of four-layers, namely a glandular tapetum, one middle layer, an endothecium, and an epidermis. Fibrous thickenings are developed in the epidermis at or near the stage of anther maturity rather than in the endothecium. Successive cytokinesis in microsporogenesis results in tetrahedral or rarely isobilateral tetrads of microspores. Pollen grains are two-celled when shed. The ovule is bitegmic, tenuinucellate, and anatropous. The nucellus degenerates during meiosis of the megaspore mother cell. The micropyle is formed by only the inner integument. Development of the female gametophyte conforms to the Adoxa type. Sladenia has been treated either as a member of Actinidiaceae, Dilleniaceae or Theaceae s.l. , or as belonging to an independent family, Sladeniaceae. Recent molecular studies have suggested that it belongs to Ternstroemiaceae within the Ericales s.l . Several noteworthy embryological characters are distinct from those of the other putatively related families and support the recognition of a separate family, Sladeniaceae. Additional embryological evidence confirms this conclusion.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 143 , 305–314.     

中国特有属藤山柳属(猕猴桃科)的花药和胚珠发育及其分类学意义

首次报道了刚毛藤山柳（Clematoclethra scandens subsp.scandens）的花药和早期胚珠发育的胚胎学特征：花药4室;发育完整的花药壁6层,为基本型花药壁,由外至内分别为表皮、药室内壁、两层中层和两层绒毡层;腺质型绒毡层为2核或3核,纤维性加厚发生于药室内壁;小孢子母细胞减数分裂为同时型胞质分裂,小孢子四分体多为四面体型;成熟花粉粒为2-细胞型,3孔沟或稀4孔沟。早期胚珠为近倒生,单珠被,薄珠心,珠孔由单珠被构成。比较胚胎学研究认为藤山柳属和猕猴桃科的其它两个属都具有单珠被胚珠及其他相似的花药发育特征,这些特征和形态分类系统范畴的第伦桃科和山茶科有明显区别。因此,本文支持花粉形态学、细胞学和分子系统学的观点,认为藤山柳属与水东哥属和猕猴桃属构成一个较好的单系,一并放在猕猴桃科。     

The embryology of <Emphasis Type="Italic">Xanthoceras</Emphasis> and its phylogenetic implications

Recent molecular analyses found the Chinese monotypic genus Xanthoceras to be either a sister genus to the rest of a broadly defined Sapindaceae sensu lato (s.l.) including Aceraceae and Hippocastanaceae or the only genus of the Xanthoceraceae. Here we investigate for the first time the embryology of Xanthoceras and compare the embryological data with related taxa to aid in understanding the phylogenetic relationships of this genus. The results indicate that Xanthoceras shares many embryological features with Sapindaceae sensu stricto (s.s.), Aceraceae, and Hippocastanaceae, including a glandular tapetum, simultaneous microsporogenesis, three-colporate pollen grains, a bitegmic and crassinucellate ovule, Polygonum type of embryo sac development, endosperm formation of the nuclear type, and exalbuminous mature seeds. The wide range of similarities in embryological features suggests that Xanthoceras is closely related to other members of Sapindaceae s.l. However, Xanthoceras differs from other Sapindaceae in several morphological characteristics, for instance, five to eight ovules in each locule in Xanthoceras versus one to two ovules in each locule in other Sapindaceae s.l., and five golden horn-like appendages present on both staminate and hermaphrodite flowers of Xanthoceras versus absent on the flowers of other Sapindaceae s.l. We propose that Xanthoceras merits recognition at the subfamily level as Xanthoceroideae, rather than at the family level as Xanthoceraceae. The present study also reveals that late-acting ovarian self-incompatibility (OSI) occurs in X. sorbifolium and that postzygotic OSI contributes to the self-sterility of the species.     

Embryological observations on Tipuana tipu (Benth.) O. Kuntze (Dalbergieae,Papilionaceae)

Abstract

The anther and ovule development of Tipuana tipu is described. Some embryological aspects previously not reported for the family have been pointed out, i.e. the Basic type of anther wall development; the constant occurrence of several megasporo-cytes undergoing meiosis, the concurrent development of more than one megaspore and finally the coexistence of three or four mature gametophytes in the same ovule.     

Sporogenesis and gametogenesis of Delavaya toxocarpa (Sapindaceae) and their systematic implications

In order to investigate the embryological characteristics of Delavaya toxocarpa Franch. and provide a basis for further understanding the phylogeny within Sapindaceae s.l., we studied the sporogenesis and gametogenesis of D. toxocarpa using the conventional paraffin section method. The results were as follows: anthers are tetrasporangium; tapetum is typically secretory type; cytokinesis in the microsporecyte meiosis is of the simultaneous type and microspore tetrads are tetrahedral; mature pollen contains two cells; the ovary is bilocular with two ovules per locule; placentation is axial; the ovule is amphitropous, bitegmic, and crassinucellate; the chalazal megaspore in a linear tetrad becomes functional; and the development of megaspore is of the polygonum type. Most similarities shared by the species observed suggest that the species and genera of Sapindaceae s.l. have phylogenetic consistency. The distinctive trait, lacking hypostase, indicatesDelavaya (and Handeliodendron) might be more primitive than other genera in Sapindaceae. Moreover, some characters, such as opposite palmate compound leaf, apical thyrse, rounded seed without wing, 2 hemitropous ovules per locule, and lacking aril, indicate the close relationship between Delavaya, Aceraceae, and Hippocastanaceae. The preliminary data about the embryological and morphological characteristics in Delavaya might justify the basic systematic position of this genus in the family Sapindaceae s.s.     

Anther wall development,placentation, sporogenesis and gametogenesis in Smilax davidiana A.DC: A contribution to the embryology of Smilax

Embryological characters can be used to address taxonomic relationships and complement molecular phylogenetics and are of special value at the genus level. However, embryological information is fragmentary in Smilax and completely unknown in Smilax davidiana, a Chinese species. Anther wall development, placentation, sporogenesis and gametogenesis of S. davidiana are characterized here. The anther is bisporangiate, anther wall formation is of the Dicotyledonous type, both epidermis and endothecium develop fibrous thickenings, and the tapetum is secretory and of dual origin. Cytokinesis in the microsporocyte meiosis is successive, the microspore tetrad is tetragonal, and mature pollen is two-celled. The ovary is mostly trilocular with an axile placentation (a small fraction of the ovaries are unilocular with parietal placentation), the ovule is anatropous, bitegmic and crassinucellate, with embryo sac development of the Polygonum type. This study documents for the first time the embryological characters of S. davidiana in detail and contributes much to the embryology of Smilax.     

藏药椭圆叶花锚的胚胎学

本文首次报道了藏药椭圆叶花锚的胚胎学特征。花药四室,药壁发育为双子叶型;绒毡层异型起源,腺质型绒毡层。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型;成熟花粉为３－细胞。子房２心皮,而二心皮连接处强烈膨大、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。承珠盘发达。果实成熟时,种子只发育至球型胚阶段。比较了该种与龙胆族其它属、种的胚胎学特征,发现它们大部分特征是相似的,但在如下３个特征上存在区别：子房二心皮连接处强烈膨大、内凸;直生胚珠;具有发达的承珠盘。其胚胎学特征的系统学和分类学意义有待进一步比较与评价     

Embryology of Zippelia begoniaefolia (Piperaceae) and its systematic relationships

Microsporogenesis and embryology of the monotypic Zippelia (Z. begoniaefolia) Blume (Piperaceae) is described for the first time to assess its systematic relationships. The formation of the anther wall is of Basic Type such that the anther wall, consisting of an endothecium with fibrous thickenings, two middle layers, and a glandular septum with 2‐nucleate cells, is derived from a primary parietal layer. Simultaneous cytokinesis follows meiosis of the microspore mother cell thence forming a tetrahedral tetrad of microspores. The single basal ovule is orthotropous, crassinucellate and bitegmic but only the inner integument forms the micropyle. The sporogenous cell of the nucellus functions directly as a megaspore mother cell. A coenocyte with four nuclei forms after meiosis of the megaspore mother cell. The formation of the embryo sac is tetrasporic ab initio and is of, or similar to, the Drusa Type of embryo sac in which the nuclei of the coenocyte undergo two successive mitoses and forms a 16‐celled or 16‐nucleate embryo sac that is ovoid in shape. The embryo sac has an egg apparatus consisting of an egg cell and two synergids (but one of the latter is less discernable). Two polar cells occur just beneath the egg apparatus and 11 antipodal cells or nuclei are arranged along the lower part of the inner wall of the embryo sac. They are linked by threads of cytoplasm. The two polar cells are separated or fused before fertilization. A large primary endosperm nucleus with many nucleoli, which resulted from the fertilized polar cells and with the participation of antipodal cells, divides into a free nuclei stage. The free nuclei are arranged along the lower part of the inner wall of the embryo sac or rarely assemble at the central part. The development of endosperm is thus of the Nuclear Type. The zygote remains undivided and fails to develop even when the seed is nearly mature. Frequently, the zygote and the endosperm abort later and leave an empty chamber in the top part of the seed. Most of the seed content is starchy perisperm. Only the inner integument forms the seed coat and the pericarp develops glochidiate hairs (anchor‐like hairs) when the endosperm begins to develop. By comparison with the other piperaceous taxa using embryological and botanical features, Zippelia is referred to as a basal taxon and a more isolated evolutionary line or a blind branch in the Piperaceae. © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society, 2002, 140 , 49–64.     

红直獐牙菜的胚胎学

首次报道了红直獐牙菜大小孢子发生,雌雄配子体形成和胚胎发育过程。主要结果如下：花药四室,药壁发育为双子叶型,绒毡层异型起源,接近腺质绒毡层,中层３层,花药壁表皮宿存,细胞柱状伸长,纤维状加厚,药室内壁退化,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,１室,１２列胚珠,侧膜胎座,薄珠心,单珠被,倒生胚珠,蓼型胚囊,反足细胞３个,宿存时间短,胚乳发育为核型     

Pollen morphology of the Swertiinae (Gentianaceae): phylogenetic implications

Recent molecular surveys of the Swertiinae (Gentianaceae–Gentianeae) revealed unexpected phylogenetic relationships, including polyphyly of the genera Gentianella , Jaeschkea , Lomatogonium and Swertia . To find new non-molecular characters supporting the phylogeny, we examined the exine variation of 73 species of all major lineages of subtribe Swertiinae using environmental scanning electron miscroscopy supplementing older, mainly light microscopical, studies. In contrast to previous studies, we were able to pick out taxa from phylogenetic key positions with particular focus on Swertia . Many distantly related taxa such as parts of Frasera , Gentianopsis , Halenia , Gentianella , Megacodon and several lineages of Swertia share a striate–reticulate or reticulate exine pattern. This is interpreted as the plesiomorphic character state of Swertiinae. There is also considerable variation of derived patterns; for example, different types of microechinate or almost smooth pollen was repeatedly observed in distantly related groups. Another extreme was the ring-shaped reticulation found in a North American species of Gentianopsis . Unfortunately, major relationships as revealed by molecular analyses were rarely supported because of the abundance of the plesiomorphic type and homoplasy even on low taxonomic levels; for example, within Lomatogonium . Exine variation was particularly useful in characterizing independent lineages of Swertia . For example, according to pollen characters and in agreement with other data, the Asian Swertia cuneata is a sister group of a strongly diversified African lineage and Swertia yunnanensis , which is rather aberrant in flower morphology, seems close to parts of Lomatogonium .  © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society , 2008, 157 , 323–341.     

Embryology of <Emphasis Type="Italic">Hemerocallis</Emphasis> L. and its systematic significance

The embryology of the genus Hemerocallis L. was studied to re-evaluate its current systematic position proposed by recent phylogenies based on molecular data. Using the improved carbol fuchsin–aniline blue staining method and conventional paraffin sectioning technique, we followed the development of anther and pollen grain, ovule and female gametophyte, and embryo and endosperm up to seed maturity. Our results showed that the (1) anther wall development is of the Monocot type, with a one cell-thick middle layer and a secretory tapetum, (2) microsporocytes cytokinesis is of the intermediate type, (3) microspore tetrads are tetragonal or decussate, (4) pollen grains are two-celled, (5) ovary is superior and trilocular, with axile placentas bearing two collateral ovules per locule, (6) ovules are anatropous, tenuinucellate, and bitegmic, with micropyle formed by the inner integument, (7) megaspore tetrads are linear, and only the chalazal one is functional, (8) embryo sac development is typically of Polygonum type, (9) embryogenesis is of Graminad type, and (10) endosperm development is of nuclear type. Overall, our study thus confirms that the embryological features of Hemerocallis support its exclusion from Liliaceae in Liliales, its inclusion in Asparagales, and its affinities with Asphodelaceae.     

山茶科核果茶属和石笔木属的胚胎学研究

观察了短叶核果茶,石笔木,粗毛石笔木和屏石笔木的大小孢子和雌雄配子体的发生和发育过程,４个种的胚胎学特征高度相似,均为基本型药壁发育,腺质线毡层,同时型小孢子母细胞胞质分裂,四面体形小孢子四分体,二细胞成熟花粉,倒生胚珠,双珠被,薄珠心,单孢原,蓼胚囊,卵细胞与助细胞区分明显,均具有珠被绒毡层和承珠盘,以蓼型胚囊区别于邻近的山茶属。     

Embryology of the Theaceae - anther and ovule development of Camellia, Franklinia, and Schima

The anther and ovule development of Camellia, Franklinia, and Schima (Theaceae, Camellioideae) were observed. The three genera share the following embryological traits: anther wall formation of basic type, tapetum of glandular type, walls of endothecial cells with secondary thickening, and production of pseudopollen grains in connective, which are dispersed into pollen sacs at anthesis, ovule bitegmic-tenuinucellate, micropyle formed by inner integument alone, hypostase present, and both integuments generally five-to-seven cell layered. One autapomorphy of the Camellioideae found in the present study is the production of pseudopollen. The three genera surveyed differ with respect to the number of middle layers in the anther, the presence or absence of stomata on connective epidermis, morphology of pseudopollen, type of embryo sac formation, form of ovule, ovular vasculature, and the proliferation of ovular epidermis, etc. Among the three genera, Franklinia and Schima are presumed to be closer embryologically, and Schima possesses more numerous specialized features.     

峨眉双蝴蝶的胚胎学研究

首次报道了峨眉双蝴蝶Ｔｒｉｐｔｅｒｏｓｐｅｒｍｕｍ ｃｏｒｄａｔｕｍ（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如厚且柱状伸长,表皮细胞减缩退化,纤维状加厚不明显。成熟花     

Embryology of Eusideroxylon (Cryptocaryeae, Lauraceae) and character evolution in the family

Lauraceae are relatively well-known embryologically and embryological data are available for 23 of about 50 genera. In this paper we present the embryology of Eusideroxylon , an unstudied and key genus within Cryptocaryeae, which are positioned basally in the evolution of Lauraceae, and discuss the evolution of embryological characters in the family. Based on comparisons of over 50 characters, it was found that Eusideroxylon is consistent with Aspidostemon , the core Cryptocaryeae ( Beilschmiedia , Cryptocarya , Endiandra and Potameia ), Caryodaphnopsis and Cassytha in having a glandular anther tapetum. The core Cryptocaryeae further agrees with both Caryodaphnopsis and Cassytha in having an embryo sac protruding from the nucellus. In light of the phylogenetic trees available, both the glandular tapetum and the embryo sac protruding from the nucellus have evolved as homoplasies in Lauraceae, once each in a clade of Cryptocaryeae, and the Caryodaphnopsis and Cassytha clade, respectively. Such character-state distributions suggest that it is better to place both Caryodapnopsis and Cassytha in the same clade as the core Cryptocaryeae. Embryologically, Eusideroxylon appears to have an intermediate state between Hypodaphnis , a genus positioned basal-most in the family, and the core Cryptocaryeae. Supplementary data on the anther and seed of Hypodaphnis are also provided.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 150 , 187–201.     

葱兰大小孢子发生和雌雄配子体发育及其系统学意义

采用常规石蜡切片技术,对石蒜科葱兰的花药壁发育、大小孢子的发生和雌雄配子体的发生过程进行了研究,并对葱兰属、石蒜科、百合科以及葱科的胚胎学特征进行比较讨论。结果表明:(1)葱兰花药四室,药壁由表皮、药室内壁、中层和绒毡层组成;药壁发育类型为单子叶型,绒毡层的类型为分泌型;花粉成熟时药室内壁径向加长并纤维状加厚,表皮宿存;小孢子母细胞在减数分裂过程中胞质分裂为连续型,小孢子四分体排列方式主要为四面体型,还有少数一些为左右对称型,成熟花粉为2-细胞型。(2)葱兰的雌蕊3心皮合生,子房下位,中轴胎座,3室,每室具2列倒生胚珠;胚珠双珠被,厚珠心,具蓼型胚囊。(3)葱兰属的胚胎学特征与石蒜科的其他种类存在较大的差异,如葱兰属花药壁发育为单子叶型,而石蒜科花药壁发育主要为双子叶型,但葱兰属的这些胚胎学特征却和百合科较为相似。