Embryology and relationships ofSuriana maritima L. (Surianaceae)

An intensive study of the embryology ofSuriana maritima L. is made to provide the information for discussing relationships and systematic position of the genus which is uncertain yet. Notable embryological features ofSuriana include: ovular archesporium multi-celled; ovule unitegmic, campylotropous, and crassinucellate with a nucellar cap; obturator not formed; ovule and seed pachychalazal; chalazal haustorium of endosperm formed; mature seed exalbuminous. Comparisons with possibly related families suggest thatSuriana is distinct from any of the families discussed but best resembles Rutaceae (and Simaroubaceae). Until a study onStylobasium and several other genera, which might be closer toSuriana, comes up in future, we tentatively support the placement ofSuriana as a monotypic family Surianaceae in Rutalessens. Takhtajan.     

中国特有种苦绳(广义夹竹桃科)的大小孢子发生和雌雄配子体发育及其分类学意义

近年来的分子系统学把狭义萝藦科和狭义夹竹桃科合并为广义夹竹桃科,包括5个亚科和25个族,但亚科和族间的亲缘关系较为复杂,亟待多学科证据澄清。本文利用常规石蜡切片技术观察了马利筋亚科南山藤属中的中国特有植物苦绳(Dregea sinensis var. sinensis)的孢子发生和配子体发育,结合已有资料比较了5个亚科的胚胎学特征。结果表明:(1)苦绳的花药由一对侧生并列药室组成,各有一个花粉团。(2)花药壁有6层,由外至内分别为表皮、2层药室内壁、中层和2层绒毡层,花药壁发育模式属于多层型。(3)绒毡层细胞单核,排成2列,为腺质型; 在小孢子四分体形成时期,药室内壁发生明显纤维状加厚; 花药成熟时,位于药室远轴最外侧处的花药壁发生断裂,准备散粉。(4)小孢子母细胞减数分裂中,胞质分裂方式为连续型,小孢子四分体排列方式为左右对称; 成熟花粉粒为3-细胞型,排列紧密,形成花粉团。(5)雌蕊含有两枚离生心皮,具边缘胎座,胚珠倒生,单珠被,薄珠心,蓼型胚囊。本文观察到的这些胚胎学特征为牛奶菜族提供了新资料。同时,胚胎学特征在5个亚科间的区别和联系,支持广义夹竹桃科的成立。     

Molecular evidence for the inclusion of the Korean endemic genus “<Emphasis Type="Italic">Echinosophora</Emphasis>” in<Emphasis Type="Italic"> Sophora</Emphasis> (Fabaceae), and embryological features of the genus

Although Echinosophora Nakai has been known as a monotypic and endemic genus of Papillionoideae of Fabaceae in Korea, it has been controversial whether it is distinct from or merged with Sophora. To resolve this matter, we conducted molecular phylogenetic analyses using nucleotide sequence data from the plastid rbcL gene and trnL (UAA) intron. Parsimony analysis, using a total of 53 taxa of the Papillionoideae (including E. koreensis [Nakai] Nakai and several species of Sophora and related genera) and using 20 taxa of Caesalpinioideae and Mimosoideae as outgroups, showed that, although the examined species of Sophora are split into two clades, E. koreensis formed a common clade with S. tomentosa (the type species of the genus) and S. flavescens. E. koreensis therefore should be treated as S. koreensis Nakai, and the generic name Echinosophora be eliminated. We also investigated the embryology of S. koreensis (=E. koreensis) and S. flavescens and found that no differences existed between them. Our molecular study, like other studies, strongly suggested that Sophora is polyphyletic. In this study we presented a summary of embryological features of the core Sophora for future critical comparison with related and unrelated taxa.     

Female reproductive organization and systematic position ofPlumariella yoshikawae Okamura (Ceramiaceae,Rhodophyta)

A detailed account of female reproductive features ofPlumariella yoshikawae is presented.Plumariella yoshikawae is recognized as morphologically similar toDelesseriopsis elegans in several features, particularly in the sequence of branch initiation, the presence of gland cells on the abaxial sides of the basal segments of the lateral branches, having carpogonial branches on the basal segments of unmodified lateral branches, and the maturation of the carposporophyte at well below the thallus apices. These features indicate thatPlumariella yoshikawae is best removed from the Ptiloteae and is correctly placed in the tribe Delesseriopsideae. The generaPlumariella andBalliella are retained along withDelesseriopsis within the tribe Delesseriopsideae.     

Embryology ofCrocus thomasii (Iridaceae)

The embryology ofCrocus thomasii is described. Male meiosis is of simultaneous type, and gives rise to starchy microspores which develop into lipoid pollen grains; these are two-celled and show a spinulate acolpate, abaculate exine lacking apertures. The tapetum is glandular and its cells become bi- or sometimes multinucleate. The ovule is anatropous and bitegmic; the inner integument forms the micropyle. Megasporogenesis is heteropolar with starch accumulation in the functional chalazal megaspore. Embryo sac development conforms to thePolygonum type. The endosperm development is nuclear. The embryo develops according to the Caryophyllad type. In the ripe seed it is differentiated and enveloped by a starchy cellular endosperm. The embryological characters observed strongly favour a close relation betweenC. thomasii andC. sativus.     

EMBRYOLOGY AND SYSTEMATIC POSITION OF HETEROPYXIS (MYRTALES)

We present here the first study of the embryology of Heteropyxis, in order to evaluate its relationships with Myrtaceae, a family in which it has often been placed. On the basis of embryology, Heteropyxis is undoubtedly very closely allied to Myrtaceae, but is distinct in possessing 1) a bisporic Allium type embryo sac, 2) a condition in which the two microsporangia of the theca are remotely separate from each other and dehisce by their respective longitudinal slits instead of by a common slit, and 3) an ovule and seed that has wings on both ends. All of these embryological characteristics are apomorphic features; they contrast with many other characteristics of the genus, such as its completely superior ovary and separate staminal traces, which are clearly primitive ones. Like the unique monotypic Psiloxylon, an endemic of Mauritius, Heteropyxis clearly diverged early from the evolutionary line leading to Myrtaceae before the origin of the common ancestor of that family (excluding Heteropyxis and Psiloxylon). Heteropyxis could logically be regarded either as a subfamily of Myrtaceae distinct from all other members of the family or as a separate but related family. We shall return to this question when our review of the embryological features of Psiloxylon has been completed.     

Embryological studies inGlaucidium palmatum Sieb. et Zucc. with a discussion on the taxonomy of the genus

Embryological features ofGlaucidium palmatum are as follows: the ovule is anatropous and bitegmic; the archesporium is hypodermal and multicelled, consisting of about 10 to 15 cells; all the archesporial, cells develop directly into megaspore mother cells, only three or four of which, however, generally complete meiotic divisions; before and during meiosis, dermal cells of the nucellar apical part undergo successive periclinal divisions forming a thick nucellar cap of as many as 20 cell-layers; embryo sac formation is of the Polygonum type; multiple embryo sacs occur frequently; antipodal cells are small in size and ephemeral or persistent; the inner integument is 3 to 5 cell-layers thick, and the outer integument 7 to 13 cell-layers thick; the outer integument is vascularized; a micropyle is formed by the inner integument alone; the endosperm is of the Nuclear type; embryogeny is of a type similar to the Onagrad type. In light of evidence from embryology and other sources it seems that there is ample reason for recognizing the family Glaucidiaceae which is distinct from the Ranunculaceae and its related families. Several common embryological features suggest an affinity between the Glaucidiaceae and the Paeoniaceae.     

Embryology of Gomortegaceae (Laurales): characteristics and character evolution

The embryological characteristics of Gomortegaceae, which are poorly understood, were investigated on the basis of Gomortega nitida, the only species of the family, to understand better the evolution of this group within Laurales. Comparisons with other Laurales and Magnoliales (a sister group of Laurales) show that Gomortega has many embryological features in common with the other lauralean families. Notably, Gomortega shares a testa without or with at best only a poorly developed mesotesta as a synapomorphy with all other Laurales. The genus further shares anthers dehisced by valves as a synapomorphy with the other Laurales (except for Calycanthaceae and Monimiaceae), and a non-multiplicative testa and bisporangiate anther as synapomorphies with Atherospermataceae and Siparunaceae (although the non-multiplicative testa occurs as a homoplasy in Monimiaceae, and the bisporangiate anther in Monimiaceae pro parte, Lauraceae pro parte and Hernandiaceae, respectively). Gomortega shows simultaneous cytokinesis to form pollen grains, a one-celled ovule archesporium and non-specialized chalaza, all or part of which may be synapomorphies shared with Atherospermataceae. Gomortega appears to have no embryological autapomorphies, but further comparison with Atherospermataceae is required.Kweon Heo and Yukitoshi Kimoto contributed equally to this work.     

Embryology of tribeDrypeteae, an enigmatic taxon ofEuphorbiaceae

The tribeDrypeteae, whose traditional assignment inPhyllanthoideae ofEuphorbiaceae is now doubtful, is studied embryologically on the basis of a literature survey and examination of six additional species in two of the four constituent genera.Drypeteae are characterized by having several embryological features that are unknown in otherPhyllanthoideae, such as a two- or three-celled ovule archesporium; a thin, two cell-layered parietal layer in the nucellus; no nucellar beak or cap; an early disintegrating nucellar tissue; thick, multiplicative, inner and outer integuments; an endothelium; a few discrete vascular bundles in the outer integument; and a fibrous exotegmen (or its derived state). EmbryologicallyDrypeteae do not fit within thePhyllanthoideae and, as available nucleotide sequence data from therbcL gene suggest, are rather placed nearErythroxylaceae, Rhizophoraceae, Chrysobalanaceae, andLinaceae. Drypeteae share with those families a combination of the fibrous exotegmen, the endothelium, and the thick, multiplicative inner integument.     

The phylogenetic position of Apterosperma (Theaceae) based on morphological and karyotype characters

Classifications of Theaceae have usually placed the endangered monotypic genus Apterosperma in tribe Schimeae (x=18), whereas recent molecular phylogenetic evidence supports its transfer to tribe Theeae (x=15). Molecular data have not resolved the phylogenetic position of Apterosperma within Theeae. We investigated the chromosome number and karyotype of Apterosperma in the context of molecular and morphological phylogenetic evidence to provide further insight into the placement of Apterosperma within Theaceae. The chromosome number and karyotype was found to be 2n = 30 = 26m + 4sm, consistent with the transfer of Apterosperma to tribe Theeae. When the chromosome data were incorporated into a data set of 46 other nonmolecular characters, Apterosperma was placed as the first-diverging lineage within the clade comprising tribe Theeae. This supports its placement based on molecular data. The low intrachromosomal asymmetry (type 1A) of Apterosperma, presumably ancestral for the family, is also consistent with this placement. Character optimization strongly supports a base chromosome number of x=15 for tribe Theeae. Because of variable and sometimes conflicting chromosome count reports of species in tribes Schimeae and Stewartieae, the base chromosome number of Theaceae could be either x=15 or 17.     

Phylogenetic significance of stylar features in genus Vicia (Leguminosae): an analysis with molecular phylogeny

Tribe Fabeae consists of five genera, Lathyrus (160 spp.), Lens (4–6 spp.), Pisum (2–3 spp.), Vavilovia (monotypic), and Vicia (160 spp.), and shows a diversity in stylar features. At least six different stylar types are known in the tribe. In order to reclassify the tribe at the rank of genus, we tried to discover apomorphies in stylar features using a molecular phylogenetic study. We surveyed internal transcribed spacer (ITS) sequences of nuclear ribosomal DNA of representative species, selected from each group having different types of styles in the tribe. We paid particular attention in sampling to members of Vicia section Vicilla, as stylar features are heterogeneous within this section. Consequently, our sample set included 15 species of section Vicilla, 23 species of other Fabeae, and two species of Trifolieae, which were used as a sister group of Fabeae. Based on our analysis, we found that a laterally compressed style and an abaxially tufted hairy style would be advanced against a dorsiventrally compressed style and an evenly hairy style, respectively, in genus Vicia. The species group, which shares the latter apomorphy, is composed of 56 species and was dispersed into 11 sections of two subgenera in the recent system of genus Vicia. We consider future revision of Fabeae should treat this species group as a single higher taxon.     

On the origin of the woody buckwheat Fagopyrum tibeticum (=Parapteropyrum tibeticum) in the Qinghai-Tibetan Plateau

Here we tested whether ‘insular woodiness’, a striking evolutionary pattern that commonly occurs on islands, has also appeared in QTP continental endemics. Parapteropyrum, a monotypic shrubby genus occurring in the central QTP, has been previously placed in the tribe Atraphaxideae of the family Polygonaceae, while all the other woody species of this tribe mainly occur in western and central Asia. We studied sequence variations of nuclear ITS (internal transcribed spacer) and cp (chloroplast) DNA (rbcL and accD) of this genus and the other ten genera. The constructed phylogenies based on ITS, cpDNA or a combination of both datasets, suggest that the woody Parapteropyrum is nested within and most likely evolved from the herbaceous Fagopyrum. We propose that the large-scale uplift of the QTP not only promoted continental species radiation, but also the secondary feature of woodiness in a few herbaceous lineages in response to strong selection pressures, similar to those acting on island flora. In addition, the confirmation of Parapteropyrum within Fagopyrum highlights its potential use as a new, perennial source of buckwheat.     

Embryology and systematic position ofLiparis (Orchidaceae)

The embryology ofLiparis paradoxa andL. rostrata has been studied. The young anther wall consists of an epidermis, endothecium, three middle layers and secretory tapetum with uninucleate cells. In the mature anther, two or three sub-epidermal layers develop fibrous thickenings. The anther wall development corresponds to the massive type. Simultaneous cytokinesis results in decussate, isobilateral, linear, T-shaped and tetrahedral pollen tetrads. The pollinia are compact and at anthesis the pollen grains are 2-celled. Ovules are anatropous, bitegmic and tenuinucellate. Both the integuments are dermal in origin and 2-layered. Development of female gametophyte is of the monosporic, 8-nucleate type. Double fertilization occurs. The primary endosperm nucleus degenerates. The mature embryo is organized from the derivatives of tiers 1, 1, m, and n. Its development conforms to a variation of the Onagrad type. The seed coat is formed entirely by the outer layer of the outer integument. There are three sterile and three fertile valves in the ovary. In the prefertilization stages valves consist of parenchymatous cells. After fertilization, the sterile valves become sclerenchymatous whereas the fertile valves remain parenchymatous. The embryological characters support the disputed systematic position ofLiparis within subtribeLiparidinae ofEpidendreae.     

The systematic relationships ofAegialitis (Plumbaginaceae) as revealed by pollen morphology

Light and first SEM observations on the pollen ofAegialitis indicate that the two species of the genus are clearly distinguishable from all other genera of the tribeStaticeae to whichAegialitis presently is relegated. Intraspecific exine or aperture dimorphism which appears frequently in this tribe, is not recorded in this genus.A. annulata andA. rotundifolia have distinct monomorphic pollen and show a great resemblance in exine features with the tribePlumbagineae, particularly species ofPlumbago. Considering these and other features, separate subtribal status forAegialitis within thePlumbagineae is proposed.     

The embryology and relationships ofPenaeaceae (Myrtales)

Two species ofPenaeaceae (Penaea mucronata andSaltera sarcocolla), a unique South African family ofMyrtales, were investigated embryologically.Penaeaceae clearly agrees with otherMyrtales in its basic embryological characteristics, and further is characterized by its highly specialized features: ephemeral endothecium, 16-nucleatePenaea-type embryo sac, and unique ovular form. A wider range of affinities of families includingPenaeaceae, Oliniaceae, Rhynchocalycaceae, Alzateaceae, andCrypteroniaceae sensu stricto, as well as a possible common divergence from an ancestral line leading toLythraceae and/orMelastomataceae, are discussed on embryological and other grounds.     

Systematic position of Asteropyrum (Ranunculaceae) inferred from chloroplast and nuclear sequences

Sequences of chloroplast gene rbcL and partial nuclear 26S rDNA were used to evaluate phylogenetic relationships of Asteropyrum. Four primary clades were recognized in Ranunculaceae, corresponding to subfamilies Hydrastidoideae, Coptidoideae, Thalictroideae, and Ranunculoideae. Our results place Asteropyrum in Ranunculoideae, sister to the tribe Actaeeae, which includes Beesia, Cimicifuga, and Eranthis. This is supported by chromosome characters, including chromosome size and basic number, and the stainability of prophase chromosomes and interphase nuclei. Our results do not support previous placements of Asteropyrum in either Coptidoideae or Thalictroideae. Considering its uniqueness in a few characters (e.g. simple peltate leaves, accumulating benzylisoquinoline alkaloids, vessel elements with only typical scalariform perforation plates), we recognize Asteropyrum as a monotypic tribe of Ranunculoideae, Asteropyreae W. T. Wang et C. Y. Chang.     

EMBRYOLOGY AND KARYOMORPHOLOGY OF LACTORIDACEAE

The embryology and karyomorphology of Lactoris fernandeziana, representing the monotypic family Lactoridaceae, were studied in an attempt to clarify its relationships. Embryologically, Lactoris is characterized by a combination of many generalized, plesiomorphic features, which are mostly shared with Magnoliales and partly shared with Laurales and Piperales, and some specialized, apomorphic features including a tenuinucellate ovule, a small nucellus with early disintegrating nucellar tissue, a nonmultiplicative outer integument, an endothelium, and haustorial endosperm. Karyomorphologically Lactoris is confirmed to have 2n = 40 at metaphase, probably as a tetraploid of x = 10, and more or less distinctive features at inter- and prophase. Comparisons based on its embryological and karyomorphological features suggest that Lactoris is not closely related to any other family. Based on evidence from various sources, we hypothesize that an evolutionary line was derived from a common ancestor with Magnoliales, and then diverged into Lactoris, which retains many primitive magnolialean features, and Piperales (and possibly other groups) with more specialized characteristics. Lactoris seems best placed in its own order, Lactoridales, near Piperales.     

Phylogenetic relationships in Peniocereus (Cactaceae) inferred from plastid DNA sequence data

The phylogenetic relationships of Peniocereus (Cactaceae) species were studied using parsimony analyses of DNA sequence data. The plastid rpl16 and trnL-F regions were sequenced for 98 taxa including 17 species of Peniocereus, representatives from all genera of tribe Pachycereeae, four genera of tribe Hylocereeae, as well as from three additional outgroup genera of tribes Calymmantheae, Notocacteae, and Trichocereeae. Phylogenetic analyses support neither the monophyly of Peniocereus as currently circumscribed, nor the monophyly of tribe Pachycereeae since species of Peniocereus subgenus Pseudoacanthocereus are embedded within tribe Hylocereeae. Furthermore, these results show that the eight species of Peniocereus subgenus Peniocereus (Peniocereus sensu stricto) form a well-supported clade within subtribe Pachycereinae; P. serpentinus is also a member of this subtribe, but is sister to Bergerocactus. Moreover, Nyctocereus should be resurrected as a monotypic genus. Species of Peniocereus subgenus Pseudoacanthocereus are positioned among species of Acanthocereus within tribe Hylocereeae, indicating that they may be better classified within that genus. A number of morphological and anatomical characters, especially related to the presence or absence of dimorphic branches, are discussed to support these relationships.     

The embryology and relationships ofOliniaceae

Two of the five species ofOliniaceae (Olinia emarginata andO. ventosa), a monotypic and problematic family of theMyrtales, were investigated embryologically.Oliniaceae clearly agree with otherMyrtales in their basic embryological characteristics, and are characterized further by having an ephemeral endothecium, a campylotropous ovule, and a thick, three-five-layered, outer integument. A combination of these three characteristic features is unknown elsewhere inMyrtales, so that embryological features do not support a close relationship with any other member of the order. Shared distinctive anther characteristics (i.e. ephemeral endothecium) suggest thatOliniaceae are derived from the common ancestor ofCrypteroniaceae s. str.,Rhynchocalycaceae, Alzateaceae, andPenaeaceae.