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.     

Embryology of Handeliodendron bodinieri (Sapindaceae) and its systematic value: development of male and female gametophytes

Embryological characters of Handeliodendron bodinieri (Sapindaceae) are reported for the first time. Anthers are tetrasporangiate. Cytokinesis in microsporocyte meiosis is of the simultaneous type and the microspore tetrads are tetrahedral. The tapetum is secretory and parietal. Mature pollen is bicellular. The ovary is trilocular. There are two ovules in each locule. The placenta is axile. The ovule is crassinucellate, bitegmic and hemitropous, without hypostase when mature. The development of the embryo sac is of the Polygonum type. The systematic significance of the embryological characters of Handeliodendron bodinieri is discussed.     

Microsporogenesis and megasporogenesis in Sinofranchetia (Lardizabalaceae)

Sinofranchetia Hemsl. (Lardizabalaceae) is a monotypic genus endemic to China. A recent combined analysis of molecular sequence data and morphology suggested that Sinofranchetia should be placed in tribe Sinofranchetieae. Embryology of taxa can be complementary to molecular phylogenetics and of special value at the genus level; however, embryological characters are completely unknown in Sinofranchetia. Here we characterize microsporogenesis and megasporogenesis in the male flowers and female flowers of Sinofranchetia, and provide embryological characters of the genus. In microspore development cytokinesis is simultaneous, the tetrads are tetrahedral and isolateral, and the mature pollens are two-celled and tricolpate (sometimes three-celled in the sterile anther of female flowers). Dicotyledonous-type and basic wall formations are found in Sinofranchetia, the tapetum is glandular. Megasporogenesis is successive, the female gametophyte of the Polygonum type. Anthers in female flowers degenerate at the tetrad stage, and some anthers produce two-celled or three-celled pollen. The newly revealed embryological characters are the basic type of anther wall formation, isolateral microspore tetrads, and both the epidermis and the parietal cell being involved in the formation of the crassinucellate ovules. The embryological peculiarities in Lardizabalaceae are discussed.     

基于ITS与 trn L-F序列探讨槭树科的系统发育

报道了槭树科41种(其中槭属39种)植物的 trn L-F和ITS序列(其中部分种的ITS序列为重新测定),以期通过分子手段对槭树科内部尤其是复杂的槭属的系统发育关系进行重建.以无患子科和七叶树科为外类群,基于对57个种单独的ITS序列(包括从GenBank下载的16种的序列)、41种 trn L-F序列及41种两者序列的联合数据,分别采用最大简约法(Maximum Parsimony Method)和邻接法(Neighbor-Joining Method)对槭树科的系统发育进行了分析.结果显示,整个槭树科为一单系类群;金钱槭位于槭树科的基部;但由于云南金钱槭( Dipteronia dyerana )聚在了槭属内部,认为金钱槭属和槭属均可能是非单系类群;槭属内组间关系的支持率普遍较低,但多数组的组内关系得到了较好的支持.将两个片段结合比单独的ITS或 trn L-F分析能更好地解决槭属内部的系统关系,其中sect.Palmata 和sect.Microcarpa ,sect.Platanoidea 、sect.Lithocarpa 和sect.Macrophylla ,sect.Integrifolia 、sect.Trifoliata 和sect.Pentaphylla ,以及sect.Acer 、sect.Goniocarpa 和sect.Saccharina (sensu Ogata)的组间亲缘关系得到了一定的支持,但对其中部分组的划分可能应做进一步调整.重新评价了徐廷志系统中对sect.Rubra 和sect.Saccharodendron 的处理.     

基于ITS与trnL—F序列探讨槭树科的系统发育

报道了槭树科41种（其中槭属39种0植物的trnL-F和ITS序列（其中部分种的ITS序列为重新测定），以期通过分子手段对槭树科内部尤其是复杂的槭属的系统发育关系进行重建。以无患子科和七叶树科为外类群，基于对57个种单独的ITS序列（包括从GenBank下载的16种的序列），41种trnL-F序列及41种两序列的联合数据，分析采用最大简约法（Maximum Parsimony Method)和邻接法（Neighbor-Joining Method)对槭树科的系统发育进行了分析。结果显示，整个槭树科为一单系类群；金钱槭位于槭树科的基部；但由于云南金钱槭（Dipteronia dyerana)聚在槭属内部，认为金钱槭属和槭属均可能是非单系类群；槭属内组间关系的支持率普遍较低，但多数组的组内关系得到了较好的支持。将两个片段结合比单独的ITS或trnL-F分析能更好地解决槭属内部的系统关系，其中sect,Palmata和sect.Micrcarpa,sect,Platanoidea,sect,Lithocarpa和sect.Macrophylla,sect,Integrifolia.Trifoliata和sect Pentaphylla,以及sect.Acer,sect.Goniocarpa和sect.Saccharina(sensu Ogata）的组间亲缘关系得到了一定的支持，但对其中部分组的划分可能应做进一步调整。重新评价了徐廷志系统中对sect.Rubra和sect.Saccharodendron的处理。     

Identification of asymmetrically winged samaras from the Western Hemisphere

A key is presented for use in identifying asymmetrically winged fruits (samaras) with either proximal or distal locules. It aids identification based on dispersed fuit morphology and can be used to identify undetermined extant herbarium specimens or fossil fruits to the correct extant family and genus. The 39 genera from 11 families (Aceraceae, Anacardiaceae, Fabaceae, Malpighiaceae, Phytolaccaceae, Polygalaceae, Polygonaceae, Rutaceae, Sapindaceae, Trigoniaceae, Ulmaceae) are distinguished on the basis of wing venation, size of fruit, presence and position of attachment surface, presence and type of subsidiary wings on the ovary wall. ornamentation, size and shape of the ovary, locule position, shape of locule cross section, style position and ornamentation, distinction between ovary wall and wing, and angle of attachment between individual samaras. The developmental origins of some of these features are discussed.     

Embryology and relationships of Akania (Akaniaceae)

We present the first extensive study of embryology of Akania , the only genus of Akaniaceae (one of the 15 glucosinolate-producing families). Akania has a distinctive combination of embryological features, which includes bitegmic and crassinucellate ovules; thick, multiplicative and vascularized outer integument; a Polygonum-type embryo sac; albuminous seed; 'exotestal' seed coat with a palisade of columellar, thick-walled cells and a thick and sclerotic mesotesta with the inner tissue aerenchymatous. A comparison of its embryological characteristics with those of some other groups indicates that Akania closely resembles Bretschneideraceae (another glucosinolate-producing family) and Sapindaceae, but it retains some archaic embryological features and is best treated as a separate family in or near Sapindales, as in most modern general classifications. Based on evidence from embryological and other data, Akaniaceae appear to be the sister group of Bretschneideraceae, possibly near to Sapindales. With the data at hand, we cannot fully assess the recent suggestion that Akaniaceae-Bretschneideraceae are a basal group in Capparales.     

Embryology of <Emphasis Type="Italic">Petrosavia</Emphasis> (Petrosaviaceae,Petrosaviales): evidence for the distinctness of the family from other monocots

The affinities of Petrosavia, a rare, leafless, mycoheterotrophic genus composed of two species indigenous to East to Southeast Asia, have long been uncertain. However, recent molecular analyses show that the genus is sister to Japonolirion osense. Japonolirion and Petrosavia comprise the Petrosaviaceae, which are now placed in its own order, Petrosaviales, distinct from other monocots based on molecular analyses. We conducted an embryological study of Petrosavia, comparing it to Japonolirion, as well as to basal monocots (Acorus and Araceae) and more derived monocots (Nartheciaceae, Velloziaceae, and Triuridaceae). Our results showed that Petrosavia is very similar in embryology to Japonolirion, with both genera sharing a glandular anther tapetum, simultaneous cytokinesis in microspore mother cells, anatropous and crassinucellate ovules, T-shaped tetrads of megaspores, ab initio Cellular-type endosperm, and a mature seed coat composed of the exotesta, endotesta, and endotegmen. The two genera of Petrosaviaceae are clearly distinct from Acorus, and all Araceae, Nartheciaceae, Velloziaceae, and Triuridaceae genera in various combinations of characters. Thus, both molecular and embryological evidence support the distinctness of the Petrosaviaceae from other monocots and its placement in its own order, Petrosaviales.     

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.     

Sapindales: molecular delimitation and infraordinal groups

An analysis of rbcL sequence data for representatives of families of putative sapindalean/rutalean affinity identified a robust clade of core “sapindalean” taxa that is sister to representatives of Malvales. The constitution of this clade approximates the broad concept of Sapindales (sensu Cronquist). Five lineages within the order are recognized: a “rutaceae” clade (Rutaceae, Cneoraceae, Ptaeroxylaceae, Simaroubaceae sensu stricto, and Meliaceae); a “sapindaceae” clade (Sapindaceae, Aceraceae, and Hippocastenaceae); Anacardiaceae plus Burseraceae; Kirkiaceae; and Zygophyllaceae pro parte. Relationships among these groups were only weakly resolved, but there was no support for the recognition of the two more narrowly defined orders, Rutales and Sapindales sensu stricto. Several families that have previously been allied to Sapindales or Rutales show no affinity to the core sapindalean taxa identified with the molecular data, and are excluded from the order: viz. Akaniaceae, Bretschneideraceae, Conneraceae, Coriariaceae, Melianthaceae, Meliosmaceae, Physenaceae, Rhabdodrendraceae, Sabiaceae, Staphyleaceae, Stylobasiaceae, Surianaceae, and Zygophyllaceae sensu stricto.     

The affinities of Lithophytum: A transfer from Solanaceae to Verbenaceae

Lithophytum violaceum Brandegee, until recently known only from a single Mexican collection, has been considered anomalous since it was first described in 1911. This genus was originally assigned to the Solanaceae, but our reexamination of it shows that this relationship is highly unlikely. A plant of xeric habit with small emarginate leaves, it is different from any other known genus. The flowers have five sepals, and the sympetalous corolla is campanulate or salverform. The five equal epipetalous stamens surround a unilocular ovary with two parietal anatropous ovules. Style and stigma are absent, and the locule of the ovary is exposed to the outside by an apical pore. The wood, young stem, leaf, floral anatomy, and pollen were studied in detail, and the aggregate of morphological features accords well with the Verbenaceae.     

Floral structure of Emmotum (Icacinaceae sensu stricto or Emmotaceae), a phylogenetically isolated genus of lamiids with a unique pseudotrimerous gynoecium,bitegmic ovules and monosporangiate thecae

Background and Aims

Icacinaceae sensu stricto consist of a group of early branching lineages of lamiids whose relationships are not yet resolved and whose detailed floral morphology is poorly known. The most bizarre flowers occur in Emmotum: the gynoecium has three locules on one side and none on the other. It has been interpreted as consisting of three fertile and two sterile carpels or of one fertile carpel with two longitudinal septa and two sterile carpels. This study focused primarily on the outer and inner morphology of the gynoecium to resolve its disputed structure, and ovule structure was also studied. In addition, the perianth and androecium were investigated.

Methods

Flowers and floral buds of two Emmotum species, E. harleyi and E. nitens, were collected and fixed in the field, and then studied by scanning electron microscopy. Microtome section series were used to reconstruct their morphology.

Key Results

The gynoecium in Emmotum was confirmed as pentamerous, consisting of three fertile and two sterile carpels. Each of the three locules behaves as the single locule in other Icacinaceae, with the placenta of the two ovules being identical, which shows that three fertile carpels are present. In addition, it was found that the ovules are bitegmic, which is almost unique in lamiids, and that the stamens have monosporangiate thecae, which also occurs in the closely related family Oncothecaceae, but is not known from any other Icacinaceae sensu lato so far.

Conclusions

The flowers of Emmotum have unique characters at different evolutionary levels: the pseudotrimerous gynoecium at angiosperm level, the bitegmic ovules at lamiid level and the monosporangiate thecae at family or family group level. However, in general, the floral morphology of Emmotum fits well in Icacinaceae. More comparative research on flower structure is necessary in Icacinaceae and other early branching lineages of lamiids to better understand the initial evolution of this large lineage of asterids.     

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.     

Embryology of Harrisonia (Cneoroideae,Rutaceae): a comparison with related genera and families

Harrisonia, a genus of three or more species distributed from tropical Africa and Southeast Asia to northern Australia, has long been considered a member of Simaroubaceae. Recent molecular analyses, however, have shown that the genus is assigned to subfamily Cneoroideae of Rutaceae, in which Cneoroideae (eight genera) are sister to the remainder of the family (‘core Rutaceae’). Here, we report embryological features of Harrisonia based on published and newly obtained data and provide morphological corroboration for the molecular affinities of the genus and Cneoroideae. We compared its embryological features with those of seven other genera of Cneoroideae and with those of the core Rutaceae and related families (Meliaceae, Simaroubaceae and Sapindaceae). Comparisons showed that Harrisonia fits within Cneoroideae through possessing campylotropous seeds with a multi‐cell‐layered endotesta. Embryological evidence, like molecular evidence, further shows that, in Cneoroideae, Harrisonia probably has affinities to a group of Bottegoa, Cedrelopsis, Cneorum and Ptaeroxylon by sharing a micropyle formed by the inner integument alone and solitary oil cells in the testa. Except for Harrisonia, Cneoroideae are still poorly understood embryologically and further investigations are needed.     

Floral organogenesis of Delavaya toxocarpa (Sapindaceae; Sapindales)

The floral organogenesis and development of Delavaya toxocarpa Franch. (Sapindaceae) were studied under scanning electron microscope and light microscope to determine its systematic position within Sapindaceae. Flowers arise in terminal thyrses. The sepal primordia initiate in a spiral (2/5) sequence, which are not synchronous. The five petal primordia initiate almost synchronously and alternate with sepal primordia. Eight stamens initiate almost simultaneously and their differentiation precedes that of the petals. The last formed petal and one stamen initiate from a common primordium. Mature stamens curve inwards and cover the ovary in bud. The gynoecium begins as a hemispheric primordium on which two carpellary lobes arise simultaneously. Later in development a single gynocium is formed with two locules and two ovules per locule. Floral morphology suggests a closer affinity with Sapindaceae, although certain features of floral ontogenesis are similar to those observed in certain members of the former Hippocastanaceae, such as Handeliodendron.     

Floral development of <Emphasis Type="Italic">Gonocaryum</Emphasis> with emphasis on the gynoecium

We investigated the floral development of Gonocaryum, a genus of Cardiopteridaceae that was segregated from Icacinaceae s.l., using scanning electron microscopy to clarify its gynoecial structure and facilitate morphological comparisons of Cardiopteridaceae. The key floral developmental characters include sepal initiation that follows a quincuncial spiral sequence; petals that are valvate with inflexed tips and are postgenitally fused at the base; a petal and stamen initiation sequence that is almost simultaneous; a globular protuberance on top of the connective; a gynoecium that is tricarpellate and pseudomonomerous, with the stigma produced by one abaxial lateral carpel; and two ovules that are unitegmic and anatropous with an obturator on the funicle. The floral developmental characters of Gonocaryum are discussed relative to Cardiopteris, which has been well studied and whose gynoecial vasculature is reinterpreted here, and are briefly compared to other members of Aquifoliales and Icacinaceae s.l. The imbricate sepals, initiated in a quincuncial spiral sequence, and the tricarpellate, pseudomonomerous gynoecium are common characters of Cardiopteridaceae. Unisexual flowers are an autapomorphy of Gonocaryum in Cardiopteridaceae.     

Fossil flowers of ericalean affinity from the Late Cretaceous of Southern Sweden

Charcoalified fossil flowers of a new genus and species (Paradinandra suecica) with affinities to Ericales s.l. (sensu lato) are described from the Late Cretaceous (Santonian-Campanian) from Southern Sweden. The flowers are pentamerous, hypogynous, and actinomorphic. Aestivation of sepals and petals is imbricate-quincuncial. The androecium consists of an outer whorl with single episepalous stamens and an inner whorl with paired epipetalous stamens. Pollen is small and probably tricolpate. Three carpels form a syncarpous ovary with numerous campylotropous ovules on parietal placentae. The styles are free for most of their length. The structure of mature fruits and seeds is unknown. Clear distinction of sepals and petals, possible dehiscence of anthers by restricted slits, presence of a nectary, and the general floral construction (salverform corolla) with a canalized access to the floral center clearly indicate insect pollination of the fossil flowers. Comparisons with extant taxa demonstrate that Paradinandra suecica shares many similarities with Ericales s.l. and in particular with members of Ternstroemiaceae, Theaceae, and Actinidiaceae. However, it is neither identical to any one genus of these families nor to any of the previously described ericalean taxa from the Cretaceous and thus provides further evidence of the diversity of Cretaceous ericalean plants.     

MORPHOLOGY,VASCULAR ANATOMY AND EMBRYOLOGY OF PISTILLATE AND STAMINATE FLOWERS OF ASPARAGUS OFFICINALIS

Flowers of three pistillate (female), two heterogametic staminate (male) and two homogametic male genotypes of Asparagus officinalis L. were compared for morphology and vascular anatomy of the flower and for embryological development to the stage of mature ovules and pollen. Flowers are liliaceous, the staminate with rudimentary pistils and the pistillate with collapsed anthers. The uncomplicated vascular pattern differs between staminate and pistillate flowers only in the size and degree of maturation of bundles to stamens and carpels. Longer styles appear to be correlated with a greater extent of ovule development in ovaries of staminate flowers. Microsporogenesis in males is normal with wall development corresponding to the Monocotyledonous type. The tapetum is glandular and binucleate, cytokinesis successive, the tetrads isobilateral or occasionally decussate, and the mature pollen grain two-celled. A pair of heteromorphic, possibly sex, chromosomes was observed in heterogametic male plants. Anther development is initially the same in pistillate flowers, but the tapetum degenerates precociously followed by collapse of microspore mother cells. In pistillate flowers the ovules are hemitropous, bitegmic, and slightly crassinucellate. Megasporogenesis-megagametogenesis conforms to the Polygonum type. In staminate flowers ovule development is like that in pistillate flowers until degeneration starts in nucellar and integumentary cells at the chalazal end. Ovules in both homogametic male genotypes rarely complete meiosis, while in the heterogametic males it is normally completed with about one ovule in 20 flowers forming a mature megagametophyte. Since manipulation of sex expression in Asparagus could be important in developing inbred male and female lines for breeding purposes, those aspects of the morphological and embryological observations presented which might be useful in planning experiments to induce sex changes are discussed briefly.     

Floral anatomy,embryology, seed,and fruit development in Cephalanthus (Naucleeae-Rubiaceae), with emphasis on C. glabratus

Information on the reproductive anatomy in genera of the tribe Naucleeae, particularly Cephalanthus, is scarce and fragmented. Of the six species in the genus, only the mature megagamethophyte of Cephalanthus occidentalis has been described. This study aims to provide information on embryological aspects in flowers of C. glabratus and to analyze the morphology and anatomy of the flowers, fruit, and seed in the six species of the genus. Cephalanthus glabratus have imperfect flowers: pistillate (PF) and staminate (SF). In the PF, the ovules are functional, while in the SF, they atrophy during the formation of the embryo sac. The mature ovule has a single integument, corresponds to the Phyllis type and the embryo sac is a Polygonum type, forming only in the PF. The presence of pollenkitt and secondary presentation of pollen were observed in the SF, as well as in the pollen formation previously described, whereas in the PF, they are absent, due to the collapse of the pollen grains inside the indehiscent anthers. The analysis of the ontogeny of the ovular excrescence in C. glabratus determined its funicular origin, calling it an aril. Its development is a pre-anthesis event, initiated during megasporogenesis. In seeds, the aril is a fleshy, white appendage which almost completely envelops the seeds of Cephalanthus, except for Cephalanthus natalensis where it is noticeably more reduced. Studies of the fruit in Cephalanthus species indicate that the infructescence is a dry schizocarp which separates into uni-seminated mericarps, except in C. natalensis that has fleshy indehiscent fruit.