The embryology and taxonomic relationships of Bretschneidera (Bretschneideraceae)

TOBE, H. & PENG, C.-I, 1990. The embryology and taxonomic relationships of Bretschneidera (Bretschneideraceae). We present the first report on the embryology of Bretschneidera , the only genus of Bretschneideraceae (which are one of 15 glucosinolate-producing families), to clarify its relationships. Embryologically Bretschneidera is characterized by the following features: ovule campylotropous, bitegmic and crassinucellate; outer integument thick, multiplicative and vascularized; embryo sac formation of the Allium type; seed exalbuminous; seed coat 'exotestal' with a palisade of columellar, thick-walled exotestal cells; mesotesta thick with the inner half aerenchymatous. These features suggest that Bretschneidera is distinct from any of the taxonomically related families but resembles both Hippocastanaceae and Sapindaceae (Sapindales) more closely than Moringaceae or Capparaceae (Capparales) which have been considered alternative allies, supporting most of the modern taxonomic treatments that place Bretschneidera as a separate family in Sapindales.     

Embryology and probable relationships of Eriospermum (Eriospermaceae)

Three South African species of the African genus Eriospermum Jacq ., which makes up Eriospermaceae Endl., have been studied in connection with the project "Families of Vascular Plants", partly to establish the phylogenetic relationships of the family. The embryology is unusual in several features reflecting the advanced character of the genus in this respect. The following features are the most important: the tapetum is secretory; microsporogenesis is successive; the ovules are anatropous and crassinu-cellate; the primary archesporial cell cuts off a parietal cell; the embryo sac formation is of the Polygonum type; endosperm formation is nuclear, but the endosperm is soon consumed, nucellus cells bordering on the sides of the chalazal half of the embryo sac divide to form a perispermal sheath around the embryo; embryo formation follows the Nicotiana variation of the Solanad type; the embryo of the mature seed is large and cylindrical-obconical, reaches above the perisperm. The seed coat is formed by both the outer and the inner integuments, both 2-layered; the epidermal cells of the test a grow out into long trichomes. The embryology and seed shape of Eriospermum is compared to those in Cyanastrum, Walleria , and genera of Tecophilaeaceae and some other families as far as details in these are known.     

Morphology and systematics of the Scytopetalaceae

The present study is based on a re-investigation of the vegetative and reproductive structures of the West African family Scytopetalaceae. Special emphasis is paid to inflorescence morphology and seed anatomy. The inflorescences of all genera of Scytopetalaceae can be interpreted as derived from panicles through reductions and structural changes. Thyrsoids prevail, but panicles, botryoids and racemes occur as well. Within the family cauliflory appears as the derived condition. Seed coat structure is extremely simplified and very stable in the Scytopetalaceae. The horny endosperm contains amyloid as the main storage compound. The presence of two obviously different forms of ruminate endosperm indicates that rumination arose twice within the family. The neotropical genus Asteranthos (Lecythidaceae) agrees in almost all relevant characters with the Scytopetalaceae. Therefore the proposed inclusion of Asteranthos in the latter family is fully confirmed. Scytopetalaceae, Lecythidaceae, Foetidiaceae and Napoleonaeaceae apparently form a natural alliance. Two new subfamilies (Scytopetaloideae, comprising Scytopetalum, Oubanguia , and Asteranthos; Rhaptopetaloideae comprising Rhaptopetalum, Pierrina and Brazzeia ) are proposed and fully described.     

THE DELIMITATION OF BIGNONIACEAE AND SCROPHULARIACEAE BASED ON FLORAL ANATOMY,AND THE PLACEMENT OF PROBLEM GENERA

The delimitation of Bignoniaceae and Scrophulariaceae has long been a taxonomic problem. Several genera, including Paulownia, Schlegelia, Gibsoniothamnus, and Synapsis, have been variously placed in one or the other family. Differences between these two families have been noted with regard to the presence of endosperm, embryo and seed morphology, and placentation; however, the lack of comprehensive data on the distribution of such characters within these two families left the delimitation problem unsolved. A comprehensive study of floral anatomy confirmed a basic difference in the placentation of these two families, as well as a basic difference in gynoecial vascularization. Paulownia has a floral anatomy, embryo morphology, and seed morphology consistent with placement in Scrophulariaceae. While reminiscent of Bignoniaceae, Paulownia is not an intermediate genus linking the two families. Schlegelia and Gibsoniothamnus have a floral anatomy consistent with placement in Scrophulariaceae. Schlegelia also has a scrophulariaceous seed morphology. Considered anomalous in the Bignoniaceae, the Schlegelieae similarly are distinct in the Scrophulariaceae.     

Embryology of Koeberlinia (Koeberliniaceae): Evidence for core-Brassicalean affinities

Koeberlinia, comprising a single xerophytic species K. spinosa, had previously been placed in various families, mainly Capparaceae. Current molecular evidence now places it in its own family Koeberliniaceae, thought to be related to the Bataceae/Salvadoraceae among the 17 other families of the Brassicales. We investigated 55 embryological characters of the genus, most of which are not understood yet, and thereby assessed its systematic relationships. Koeberlinia has many embryological features in common with the Capparaceae and seven other core-Brassicalean families (i.e., Brassicaceae, Cleomaceae, Emblingiaceae, Gyrostemonaceae, Pentadiplandraceae, Resedaceae, and Tovariaceae), specifically by possessing a campylotropous ovule with a nonmultiplicative (two-cell-layered) outer integument, reniform seeds with a curved embryo, and a fibrous exotegmen in the mature seed coat. However, Koeberlinia is clearly distinguished from them by a tenuinucellate rather than crassinucellate ovule as previously reported, markedly enlarged apical nucellar epidermal cells, and an "exotestal" seed coat. Embryologically, Koeberlinia resembles neither the Bataceae nor the Salvadoraceae, although only limited embryological data are available for these two families. Embryological evidence thus favors its joining the core Brassicales, but additional molecular analyses and embryological studies on the missing data of the Bataceae and Salvadoraceae are needed for final confirmation of its phylogenetic position.     

Glucosinolates of nine cruciferae and two capparaceae species

Autolysis products of nine species of the Cruciferae and two species of the Capparaceae were analysed by high sensitivity GC/MS. Four of the Cruciferae species were examined for glucosinolates for the first time. One new glucosinolate, 9-methylthiononylglucosinolate, was identified in Arabis purpurea and many known glucosinolates were identified for the first time in previously studied plant species. 5-Methylthiopentylglucosinolate appears to be characteristic of the genus Alyssum.     

Comparative anatomy and systematics of woody Saxifragaceae. Aphanopetalum Endl.

The floral and vegetative anatomy of the small Australian genus Aphanopetalum were studied. Wood is described for the first time and is characterized by predominantly solitary pores, scalariform vessel element perforation plates with low bar numbers, imperforate tracheary elements with distinctly bordered pits, sparse axial parenchyma, and a combination of homocellular and heterocellular rayS. Starch occurs in both axial and ray parenchyma of the wood. Stems possess unilacunar, one-trace nodes and the uncommon feature of an endodermis with well-defined Casparian stripS. Leaves have anomocytic stomata, a bifacial mesophyll and semicraspedodromous venation or a combination of semicraspedodromous and brochidodromous venation. The tetramerous flowers are apetalous or have minute petals. The compound, half-inferior gynoecium consists of essentially totally united carpels. The pattern of floral vascularization resembles different Saxifragaceae sensu lalo in that the compound sepal-plane and petal-plane traces give rise to staman bundles as well as sepal, petal, and carpel wall venation in their respective planes. The ventral ovarian bundles are fused into a single ventral complex that subdivides at the top of the ovary to form ventral bundles and to supply the one ovule in each locule. Vegetative and floral features provide compelling evidence to suggest that Aphanopetalum has its nearest relatives among the Saxifragaceae sensu lato rather than Cunoniaceae. The genus is probably best treated as forming its own subfamily (or family) among the saxifragaean alliance.     

Early reproductive developmental anatomy in Decaisnea (Lardizabalaceae) and its systematic implications

Background and Aims

Decaisnea insignis, known as ‘dead man''s fingers’ (Lardizabalaceae), is widely distributed in China and the Himalayan foothill countries. This economically important plant, which is the only species in the genus, has not been the subject of any embryological studies aside from one brief, older paper that lacks micrographs. Data on Decaisnea are also important because its systematic position has been unstable since the genus was established in 1855. Therefore, the objectives of this study were: (a) to use modern microscopy to document early reproductive anatomical development in Decaisnea; and (b) to compare qualitatively these early embryological characters with allied taxa in a systematic context.

Methods

Decaisnea insignis floral buds and inflorescences were regularly collected from Shaanxi Province, China and prepared for light microscopy. The embryological characters studied were qualitatively compared with those of allied taxa via a thorough examination of the existing literature.

Key Results

Early reproductive anatomy in Decaisnea was documented and novel revelations made. It was discovered that the pollen is shed when three-celled (not two-celled, as previously reported), and that endosperm formation is nuclear (not cellular or helobial, as previously reported). These two newly revealed embryological characters are not found in any other members of Lardizabalaceae. Furthermore, neither are persistent antipodal cells, which we confirmed to be present in Decaisnea.

Conclusions

Decaisnea and other Lardizabalaceae characteristically have tetrasporangiate anthers, a secretory tapetum, simultaneous microsporocyte cytokinesis, primarily bitegmic, crassinucellate ovules, and a Polygonum type embryo sac. However, in the family, persistent antipodals, nuclear endosperm, and pollen shed at the three-celled stage are only found in Decaisnea. These embryological data prompted the suggestion that Decaisnea needs elevation above the level of genus.     

An embryological study and systematic significance of the primitive gymnosperm Ginkgo biloba

Ginkgo biloba L.is considered one of the most ancient seed plants,with several primitive features of plant reproductive process.However,the phylogenetic position of Ginkgo and its relationship with other extant seed plants remain unclear.To gain a better understanding of these issues,we observed the embryological development of G.biloba using semi-thin sections and scanning electron microscopy.In late August,the zygote moved from the end of the micropylar to the middle of the archegonium,and mitosis resulted in many free nuclei distributed randomly in the archegonium.Afterwards,the cell wall was formed and the proembryo began to differentiate into the embryonal region and the underdeveloped presuspensor region.In early October,the embryo differentiated into two cotyledons,plumule,hypocotyl,radicle,and suspensor tissues.Subsequently,the two cotyledons grew rapidly,but the undeveloped suspensor began to degenerate and gradually disappear,indicating that the embryo had begun to mature.During early embryo development,the main supply of nutrients was carbohydrate in the cells of the jacket,tentpole,and surrounding endosperm,whereas endosperm provided nutrients during embryo maturation.Our results indicate that Ginkgo is extremely similar to cycads in terms of embryology but more similar to conifers in macromorphology and vegetative anatomy,suggesting that the Ginkgo lineage may have an intermediate phylogenetic position between cycads and conifers.     

The morphology,taxonomy and evolution ofRhodocoma (Restionaceae)

The vegetative and reproductive morphology, culm and rhizome anatomy and seed surface micromorphology ofRhodocoma are described. It is shown that this variation is best contained by recognizing three new species in the genus. These new taxa are described, and the phylogeny of the genus is investigated by cladistic analysis. The environmental parameters and distributions of the species are related to the cladogram. This suggests that the species are at present ecologically separated, and indicates that the speciation may have been sympatric. This is the first support for the hypothesis that sympatric speciation may have been important in the speciose Cape flora.     

姜目芭蕉群植物种子解剖学研究及其系统学意义

研究了姜目芭蕉群代表植物象腿蕉属象腿蕉(Ensete glaucum)、旅人蕉属旅人蕉(Ravenala madagascariensis)与蝎尾蕉属Heliconia faranmansis?D6肿咏馄侍卣鳌＝峁砻鳎笸冉段藜僦制ぃ制し只霰砥ぁ⒑癖谧橹赴褪赴悖赴瞿谇邢虮谟刖断虮谠龊瘢缓系闱哂泻系闶矣牒系愣眩谥制ち恢榭浊兄榭琢旌涂赘堑姆只榭琢煳涡停赘侵挥赡谥制は赴钩桑褐榭浊制ぱ由煨纬芍制昵唬和馀呷?层细胞：内胚乳细胞径向延长,细胞内充满淀粉粒。旅人蕉具假种皮,种皮分化出外种皮、中种皮和内种皮,外种皮细胞纵向延长,中种皮为7-9层切向延长的薄壁细胞,内种皮为石细胞型：合点区无合点室,内种皮在此出现缺口,缺口为整体轮廓呈喇叭形的近等径薄壁细胞群填充;珠孔区无珠孔领与孔盖的分化：外胚乳缺,内胚乳发达。蝎尾蕉属的Heliconia faranmansis?D6肿游藜僦制ぃ制の薹只墒闾寤闲∏揖断蜓映げ⑴帕形だ缸吹谋”谙赴钩桑褐榭锥酥制は蛲庋由欤纬衫嗨平浦肿拥闹指纷唇峁梗何蘅赘怯胫榭琢斓哂杏晒ば纬傻挠不牵缓系闱肼萌私断嗨疲煌馀呷樵?-4层细胞,细胞壁波浪形弯曲,内胚乳发达。综合作者对兰花蕉(Orchidanha chinensis)和前人对芭蕉群的种子解剖学研究结果,初步总结了芭蕉群种子解剖学特征及其进化式样,讨论了姜目芭蕉群四科种子解剖学特征的系统分类学意义。     

The morphology and relationships of the Sphaerosepalaceae (Malvales)

The comparative vegetative and reproductive morphology and anatomy of the Malagasy endemic family Sphaerosepalaceae is examined in light of two current competing hypotheses of relationship from recent molecular studies. Sphaerosepalaceae are similar to Thymelaeaceae on the basis of leaf architecture, calyx vasculature and in having endostomal micropyles. Comparisons with Tepuianthus and Thymelaeaceae subfamily Octolepidoideae are drawn on the basis of seed structure, indument type, perianth structure and pollen. Resin-filled, sclerenchymatous idioblasts, floral (positional) monosymmetry, a single series of stamen trunk bundles and a well-developed bixoid chalaza in the seed of Dialyceras parvifolium link Sphaerosepalaceae with its other putative sister group: a clade containing Bixaceae, Cochlospermaceae and Diegodendraceae. Synapomorphies of Sphaerosepalaceae include: fused, intrapetiolar stipules, embryo structure, pollen with endoapertures encompassing the ectoapertures and a tetramerous perianth. The extremely well-developed apical septum in the eusyncarpous gynoecium of Rhopalocarpus suggests that the gynoterminal style present in this genus has been secondarily derived from an ancestor with a fully syncarpous, basistylous gynoecium, as in Dialyceras . The morphological and evolutionary nature of basistylous and apically septate gynoecia is discussed. A rosette arrangement of ovules in each carpel coccus of D. coriaceum expands the bauplan concept of Sphaerosepalaceae and is probably unique among angiosperms as a whole.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 144 , 1–40.     

Are there symplastic connections between the endosperm and embryo in some angiosperms?—a lesson from the Crassulaceae family

It is believed that there is symplastic isolation between the embryo (new sporophyte) and the endosperm (maternal-parental origin tissue, which nourishes the embryo) in angiosperms. However, in embryological literature there are rare examples in which plasmodesmata between the embryo suspensor and endosperm cells have been recorded (three species from Fabaceae). This study was undertaken in order to test the hypothesis that plasmodesmata between the embryo suspensor and the endosperm are not so rare but also occur in other angiosperm families; in order to check this, we used the Crassulaceae family because embryogenesis in Crassulaceae has been studied extensively at an ultrastructure level recently and also we tread members of this family as model for suspensor physiology and function studies. These plasmodesmata even occurred between the basal cell of the two-celled proembryo and endosperm cells. The plasmodesmata were simple at this stage of development. During the development of the embryo proper and the suspensor, the structure of plasmodesmata changes. They were branched and connected with electron-dense material. Our results suggest that in Crassulaceae with plasmodesmata between the endosperm and suspensor, symplastic connectivity at this cell-cell boundary is still reduced or blocked at a very early stage of embryo development (before the globular stage). The occurrence of plasmodesmata between the embryo suspensor and endosperm cells suggests possible symplastic transport between these different organs, at least at a very early stage of embryo development. However, whether this transport actually occurs needs to be proven experimentally. A broader analysis of plants from various families would show whether the occurrence of plasmodesmata between the embryo suspensor and the endosperm are typical embryological characteristics and if this is useful in discussions about angiosperm systematic and evolution.     

The progamic phase of an early-divergent angiosperm, Annona cherimola (Annonaceae)

Background and Aims

Recent studies of reproductive biology in ancient angiosperm lineages are beginning to shed light on the early evolution of flowering plants, but comparative studies are restricted by fragmented and meagre species representation in these angiosperm clades. In the present study, the progamic phase, from pollination to fertilization, is characterized in Annona cherimola, which is a member of the Annonaceae, the largest extant family among early-divergent angiosperms. Beside interest due to its phylogenetic position, this species is also an ancient crop with a clear niche for expansion in subtropical climates.

Methods

The kinetics of the reproductive process was established following controlled pollinations and sequential fixation. Gynoecium anatomy, pollen tube pathway, embryo sac and early post-fertilization events were characterized histochemically.

Key Results

A plesiomorphic gynoecium with a semi-open carpel shows a continuous secretory papillar surface along the carpel margins, which run from the stigma down to the obturator in the ovary. The pollen grains germinate in the stigma and compete in the stigma-style interface to reach the narrow secretory area that lines the margins of the semi-open stylar canal and is able to host just one to three pollen tubes. The embryo sac has eight nuclei and is well provisioned with large starch grains that are used during early cellular endosperm development.

Conclusions

A plesiomorphic simple gynoecium hosts a simple pollen–pistil interaction, based on a support–control system of pollen tube growth. Support is provided through basipetal secretory activity in the cells that line the pollen tube pathway. Spatial constraints, favouring pollen tube competition, are mediated by a dramatic reduction in the secretory surface available for pollen tube growth at the stigma–style interface. This extramural pollen tube competition contrasts with the intrastylar competition predominant in more recently derived lineages of angiosperms.Key words: Annona cherimola, Annonaceae, embryo sac, endosperm, Magnoliid, ovule, pollen–pistil interaction, pollen tube     

Contribution of vegetative anatomy to the systematics of the Zygophyllaceae R.Br

SHEAHAN, M. C. & CUTLER, D. F., 1993. Contribution of vegetative anatomy to the systematics of the Zygophyllaceae R.Br. The Zygophyllaceae sensu lato are a heterogeneous family of trees, shrubs and herbs growing in arid and semi-arid areas of the world. There has been disagreement about the systematic status of some groups within the family, and the position of Balanites has also been disputed. The vegetative anatomy of the family was examined to see if it could throw light on current systems of classification. The anatomy of 37 species in 19 genera is described, and the results of tests of C₄ activity in 27 species are given. There is anatomical evidence to support the exclusion of Balanites into a separate family, and some groups (Engler's Peganoideae and Nitrarioideae) have characteristics which set them apart from the rest of the family. This is in accordance with other analyses of the family based on morphological, palynological and biochemical studies. There is also evidence that the tribuloid genera Tribulus, Kallstroemia and Kelleronia should be separated from the zygophylloid genera, at least at subfamily level; however, Neoluederitzia and Sisyndite should remain in the Zygophylloideae. Brief reference is made to relationships with other families in the Geraniales.