Floral ontogeny of the Afro-Madagascan genus Mitrasacmopsis with comments on the development of superior ovaries in Rubiaceae

BACKGROUND AND AIMS: Members of Rubiaceae are generally characterized by an inferior ovary. However, Mitrasacmopsis is cited in the literature as having a semi-inferior to superior ovary. It has previously been hypothesized that the gynoecial development of Rubiaceae with semi-inferior to superior ovaries takes place in the same way as in Gaertnera, one of the most commonly cited rubiaceous genera with a superior ovary. To test this hypothesis, a floral ontogenetic study of Mitrasacmopsis was carried out with special attention paid to the gynoecial development. METHODS: Floral ontogeny and anatomy of Mitrasacmopsis were examined using scanning electron and light microscopy. KEY RESULTS: At an early developmental stage, a concavity becomes visible in the centre of the floral apex simultaneously with the perianth initiation. A ring primordium surrounding this concavity expands vertically forming the corolla tube (early sympetaly). Stamen primordia develop inside the corolla. From the bicarpellate gynoecium only two carpel tips are visible because the ovary is formed by a gynoecial hypanthium. In the basal part of each carpel, a placenta primordium is initiated. Two septa divide the ovary into two locules. In each locule, the placenta becomes mushroom shaped and distinctly stalked. Eventually, the inferior ovary of Mitrasacmopsis develops into a beaked capsule. Only very late in the fruiting stage, the continuously expanding ovary is raised above the insertion point of the persistent calyx, changing the ovary position of Mitrasacmopsis from basically inferior to secondarily semi-inferior. CONCLUSIONS: Mitrasacmopsis follows an epigynous pattern of floral development. However, the presence of a prominent beak in the fruiting stage gives the whole ovary a semi-inferior appearance. This kind of secondarily semi-inferior ovary is shown to be different from the secondarily superior ovary observed in Gaertnera.     

The development of the superior ovary in Tetraplasandra (Araliaceae)

Tetraplasandra is a small Hawaiian genus of seven species with remarkable diversity in ovary position, ranging from inferior to completely superior. Tetraplasandra gymnocarpa is the only member of the Araliaceae with a fully superior ovary. A comparative study of floral anatomy and development in superior and inferior ovary species of Tetraplasandra revealed that the superior ovary in T. gymnocarpa is unusual in that it develops within an epigynous ground plan. During the course of development, the ovary changes from inferior to secondarily superior primarily by an upward expansion of the ovary from the insertion point of the perianth and androecium to the ovary apex. The superior ovary of T. gymnocarpa, evident in late ontogeny, is a modified inferior ovary; thus it is not structurally homologous to a truly superior ovary. The adaptive significance of the switch from inferior to superior ovary is reexamined. A recent phylogeny of Tetraplasandra and the biogeography of the extant species provide evidence that the change in ovary position may be associated with a shift in pollination strategy that may have occurred as recently as 2.6 million years ago.     

Floral structure and development in Nartheciaceae (Dioscoreales), with special reference to ovary position and septal nectaries

We present a comparative study of the floral structure and development of Nartheciaceae, a small dioscorealean family consisting of five genera (Aletris, Lophiola, Metanarthecium, Narthecium, and Nietneria). A noticeable diversity existed in nine floral characters. Analyses of their respective character states in the light of a phylogenetic context revealed that the flowers of Nartheciaceae, whose plesiomorphies occur in Aletris and Metanarthecium, have evolved toward in all or part of Lophiola, Narthecium, and Nietneria: (1) loss of a perianth tube; (2) stamen insertion at the perianth base; (3) congenital carpel fusion; (4) loss of the septal nectaries; (5) unilocular style; (6) unfused lateral carpellary margins in the style; (7) flower with the median outer tepal on the abaxial side; (8) flower with moniliform hairs; and (9) flower with weak monosymmetry. We further found that, as the flowers developed, the ovary shifted its position from inferior to superior. As a whole, their structure changes suggest that the Nartheciaceae flowers have evolved in close association with pollination and seed dispersal. By considering inferior ovaries and the presence of septal nectaries as plesiomorphies of Nartheciaceae, we discussed evolution of the ovary position and septal nectaries in all the monocots.     

Systematic Placement of Dasypogonaceae Among Commelinid Monocots: Evidence from Flowers and Fruits

Despite progress in clarifying the relationships of Dasypogonaceae (four genera, Baxteria, Calectasia, Dasypogon, and Kingia), their infrafamilial relationships and precise affinities within the commelinid clade remain unsatisfactorily resolved. This paper reviews existing data on the systematic affinities of Dasypogonaceae. It also presents new data on floral structure in all four genera, and data on floral ontogeny in Dasypogon. In Dasypogon, Kingia, and Baxteria the ovary is trilocular and septal nectaries are present around the ovary base. In Calectasia, the ovary is unilocular and septal nectaries are entirely absent. Two subfamilial groupings within Dasypogonaceae (Calectasia–Dasypogon and Baxteria–Kingia) are proposed on the basis of leaf anatomy and ovule and ovary morphology. Many floral characters are plesiomorphic in Dasypogonaceae, but some morphological characters support a close relationship with the order Poales sensu lato, especially the epidermal location of the silica bodies. The unusual long-stalked “drumstick” inflorescences of Dasypogon and Kingia resemble those of some Poales, in which flowers are frequently borne on condensed inflorescences. A possible close relationship between Dasypogonaceae and some Poales such as Rapateaceae and Thurniaceae merits further exploration.     

Floral development of Iris decora Wall. (Iridaceae)

The outer tepal and stamen primordia arise as secondary primordia on the outer tepal-stamenprimordia, which are formed on the floral apex. The inner tepal primordia are formed directly on the floral apex. All the floral appendages are initiated in the second tunica layer and are homologous with regard to their origin and early development. A short perianth tube is formed as a result of intercalary growth in the common bases of the tepal primordia. The intercalary growth in the fused bases of the floral appendages elevates the peripheral zone. The floral apex thus appears as a shallow cup. Further intercalary growth results in the formation of an inferior ovary. The ovules are initiated as outgrowths on placental ridges from the lateral ovary wall, the trilocular appearance being the result of secondary cohesion of the parietal placentae.     

Comparative morphology of female flowers and systematics in Geonomeae (Arecaceae)

Female floral structure is compared in Geonomeae (Arecaceae). A perianth is formed by two alternate whorls of three basally congenitally united and imbricate sepals and three basally congenitally united and apically valvate petals. A sterile androecium is formed by a variable number of staminodes, which are united into a tube. The gynoecium shows three more or less equally developed carpels or is pseudomonomerous (Geonoma). The single anatropous ovule per carpel is median, either basal or at mid-height of the ovary. A septal nectary is present at the base and mid-height of the ovaries and exits at different levels of the ovary. Carpels in pseudomonomerous gynoecia seem to be basistylous, but the styles are more lateral or apical in gynoecia with all three carpels equally developed. Stigmas expose unicellular or multicellular (Welfia) papillae at anthesis. Pollen tube transmitting tracts and a compitum are present in the ventral slits of the postgenitally united styles. Floral structure in Geonomeae is compared with other Arecaceae, especially Arecoideae, in a morphological and systematic context.     

Floral morphology of Maloideae (Rosaceae) and its systematic relevance

Flowers of 169 species of Rosaceae subfamily Maloideae, which were chosen to represent the taxonomic and geographic diversity of the group, were studied to ascertain their morphological variation and its systematic relevance. We describe and illustrate variation in size, indumentum, color, and macroscopic structural features. Most maloid species have syncarpous flowers with two to five carpels in which the ovary is at least three-quarters inferior, whereas species of other Rosaceae subfamilies have apocarpous or unicarpellate flowers with superior ovaries. However, maloid flowers show significant variation in the degree of carpel connation and of ovary adnation to the hypanthium. Cotoneaster, Heteromeles, and Pyracantha are completely apocarpous, and Dichotomanthes is perigynous with a completely superior ovary. Thus, no one floral character is sufficient to separate the Maloideae from other subfamilies of Rosaceae. Differences among their flowers support our recognition of Malus, Pyrus, and Sorbus as separate genera. Further, we argue for removal of Docyniopsis and Eriolobus from Malus, division of Sorbus into several genera, and union of Aronia, Photinia, and Stranvaesia. No floral characters support the traditional dichotomy of the subfamily into tribes Crataegeae and Sorbeae.     

Structural homology and developmental transformations associated with ovary diversification in Lithophragma (Saxifragaceae)

Lithophragma, comprising only ten species, encompasses a remarkable diversity of ovary positions, reported to range from inferior to superior. The structural homology of the gynoecium and developmental transformations associated with ovary diversification are investigated for Lithophragma. Scanning electron and light microscopy indicate that all species of Lithophragma have epigynous flowers. Lithophragma campanulatum, L. glabrum, and L. heterophyllum have ovaries that externally appear nearly superior, but are actually shallowly inferior or "pseudosuperior." The inferior ovaries of Lithophragma species can be conceptually divided into superior and inferior regions that meet at the point of perianth and androecial insertion. Static and ontogenetic allometry reveal that across the species of Lithophragma the lengths of these two ovary regions are coordinated. Ovary regions in mature flowers display an approximately linear relationship that can be expressed through the allometric equation SL = -0.5314 IL + 2.0348 (where SL and IL are the lengths of the superior and inferior regions of the ovary, respectively; r = 0.7683, df = 35, P = 2.45 × 10). Mapping ontogenetic allometries onto a recent phylogeny for Lithophragma shows that ovary position evolution is bidirectional and has shifted toward greater superiority in some species and greater inferiority in others.     

澜沧荛花(瑞香科)的花部形态发生 及其系统学意义

通过扫描电镜对澜沧荛花Wikstroemia delavayi花部的形态发生过程进行了观察和分析,旨在为该属的系统学研究提供花部发育形态学资料。澜沧尧花花部的发生和早期发育呈远轴面向近轴面的顺序,但这一式样由于近轴面的器官在早期发育之后生长加速发生了转变。因此,花开放时所表现的所谓辐射对称,显然是由同一轮器官的异率生长所导致的次生现象。花盘发生于花萼筒基部的远轴面上,与花萼、雄蕊的发生间隔时间较长。花盘原基在下轮雄蕊着生处凹陷或间断,与之相对应,花盘裂片与下轮雄蕊呈互生。由此,花盘显然不是花托的一部分,也不是象花萼、雄蕊和心皮一样的独立结构,将其解释为雄蕊群的一部分更合理。花盘的发生和早期发育及其着生位置同其他花部器官的发生和发育式样具有明显的相关性,这种相关性对进一步阐明瑞香属Daphne和荛花属Wikstroemia的系统发育关系具有—定意义。根据对雌蕊群的发生和发育过程观察,该种的子房是由一个近轴面的可育心皮和一个远轴面的不育心皮融合而成的单室子房,为假单心皮雌蕊。尽管荛花属和瑞香属均属于单室产房,但澜沧荛花的子房维管束中的腹束排列于中轴位置,而目前资料显示瑞香属植物的腹束接近于侧膜位置,这方面仍需进一步研究。     

Floral structure and development and systematic aspects of some 'lower' Asparagales

 Floral structure and development of representatives of Asteliaceae, Blandfordiaceae, Boryaceae, Doryanthaceae, and Hypoxidaceae, all members of the `lower' Asparagales, were studied comparatively. The results are discussed in the light of new molecular systematic studies, but also with regard to established morphological characters in related groups. Stamen shape varies considerably within and between taxa: the shape of anthers is from X-shaped, sagittate to non-sagittate, they are either latrorse or introrse, basifixed, centrifixed or dorsifixed. Gynoecia are syncarpous up to the stigmatic region in all taxa. Ovaries of Doryanthaceae and Hypoxidaceae are inferior, but they are superior in Asteliaceae, Blandfordiaceae and Boryaceae. All ovaries have at least a short synascidiate zone. With the exception of Astelia alpina (Asteliaceae), the ovaries are trilocular. Ovaries of Asteliaceae contain mucilage, which is secreted from trichomes on the funicle and on the placenta. Although flowers are polysymmetric at anthesis, they are monosymmetric in earliest stages with a developmental gradient from adaxial to abaxial. Perianth organs arise individually from either a concave (taxa with inferior ovary) or convex (taxa with superior ovary) apex. Hypoxidaceae have pollen flowers with free stamens. One species, Curculigo capitulata, has Solanum-type flowers with postgenitally united stamens. It is most probably pollinated by buzzing bees. All other taxa have nectariferous flowers with internal or external septal nectaries. Received February 5, 2001 Accepted June 20, 2001     

Floral morphogenesis of Wikstroemia delavayi (Thymelaeaceae) and its phylogenetic implication

Floral morphogenesis of Wikstroemia delavayi Lecomte was investigated by scanning electron microscope (SEM) and compared with its allied groups. Initiation and early development of floral parts in W. delavayi followed unidirectional sequences from the abaxial side to the adaxial side. Because the floral parts grew faster at the adaxial side than at the abaxial one in following development, the zygomorphic pattern in the early development changed and finally became an almost actinomorphic form at anthesis. The disc was initiated from the abaxial base of the floral tube and itslobes were alternate with lower whorl stamens. According to this initiatial and developmental pattern, it is reasonable to interpret the disc as a part of the androecium rather than a modification of the receptacle. The located position and development of the disc was correlative with the development of other floral organs, which might provide insight to delimit Wikstroemia and Daphne based on different floral developmental pattern that might exist between the two genera. The developmental process of W. delavayi indicated that the syncarpous and uniloculate gynoecium was in fact bicarpellate, which consisted of a fertile carpel and a sterile one. It was pseudomonomerous. Even though the ovary in both Wikstroemia and Daphne was uniloculate, the location of the ventral bundles in the ovary was obviously different from each other according to data to date. In this respect, further investigation is undertaken between the two genera.     

澜沧荛花(瑞香科)的花部形态发生yh及其系统学意义(英文)

通过扫描电镜对澜沧荛花Wikstroemiadelavayi花部的形态发生过程进行了观察和分析 ,旨在为该属的系统学研究提供花部发育形态学资料。澜沧荛花花部的发生和早期发育呈远轴面向近轴面的顺序 ,但这一式样由于近轴面的器官在早期发育之后生长加速发生了转变。因此 ,花开放时所表现的所谓辐射对称 ,显然是由同一轮器官的异率生长所导致的次生现象。花盘发生于花萼筒基部的远轴面上 ,与花萼、雄蕊的发生间隔时间较长。花盘原基在下轮雄蕊着生处凹陷或间断 ,与之相对应 ,花盘裂片与下轮雄蕊呈互生。由此 ,花盘显然不是花托的一部分 ,也不是象花萼、雄蕊和心皮一样的独立结构 ,将其解释为雄蕊群的一部分更合理。花盘的发生和早期发育及其着生位置同其他花部器官的发生和发育式样具有明显的相关性 ,这种相关性对进一步阐明瑞香属Daphne和荛花属Wikstroemia的系统发育关系具有一定意义。根据对雌蕊群的发生和发育过程观察 ,该种的子房是由一个近轴面的可育心皮和一个远轴面的不育心皮融合而成的单室子房 ,为假单心皮雌蕊。尽管荛花属和瑞香属均属于单室子房 ,但澜沧荛花的子房维管束中的腹束排列于中轴位置 ,而目前资料显示瑞香属植物的腹束接近于侧膜位置 ,这方面仍需进一步研究     

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.     

黄连属(毛茛科)花的形态发生

本文运用扫锚电子显微镜(SEM)观察了黄连属(Coptis)植物花的形态发生和发育过程, 结果表明, 该属植物所有的花部器官均为螺旋状发生, 雄蕊为向心式发育, 花瓣原基有微弱的延迟发育, 心皮原基为对折型(即马蹄形), 子房为半封闭类型, 子房柄是在发育过程中形成的。通过与其它具T-型染色体类群在花形态发生上的比较, 认为黄连属表现出了某些原始的性状, 这一结果与分子系统学研究认为黄连属为毛茛科的基部类群的结论一致。     

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.     

FLORAL DEVELOPMENT IN MANGROVE RHIZOPHORACEAE

The flowers of mangrove Rhizophoraceae (tribe Rhizophoreae) are adapted to three different pollination mechanisms. Floral development of representative species of all four genera suggests that the ancestral flower of the tribe was unspecialized, with successively initiated whorls of separate sepals, petals, antisepalous stamens, and antipetalous stamens; at its inception, the gynoecium had a united, half-inferior ovary and separate stigmatic lobes. This developmental pattern is found in Rhizophora mangle (wind-pollinated) and Ceriops decandra (insect-pollinated). In Kandelia, all floral organs distal to the sepals are initiated simultaneously, and there has apparently been an evolutionary amplification in the number of stamens to about six times the number of petals. Explosive pollen release evolved independently in C. tagal and in Bruguiera. In the former, all stamens belong to one whorl and arise simultaneously upon a very weakly differentiated androecial ring primordium. In Bruguiera, the androecial ring is pronounced, and two whorls of stamens arise upon it; the primordia of the antisepalous whorl arise first but are closer to the center of the apex than the antipetalous stamen primordia. The antisepalous stamens bend toward and are enclosed by the petals early in development. In all genera, the inferior ovary develops by zonal growth of receptacular tissue; additional intercalary growth above the placenta occurs in Bruguiera. In general, floral specialization is accompanied by an increase in the width of the floral apex compared to the size of the primordia, increasing fusion of the stylar primordia, and decreasing prominence of the superior portion of the ovary. Apparent specializations of petal appendages for water storage, including the presence of sub-terminal hydathodes (previously unreported in any angiosperm), were found in two species in which flowers remain open during the day but were absent from two species normally pollinated at night or at dawn. Distinctive tribal characteristics that may aid in phylogenetic analysis include the mode of development of the inferior ovary; the aristate, bifid, usually fringed petals that individually enclose one or more stamens; the intrastaminal floral disc; and the initially subepidermal laticiferous cell layer in the sepals and ovary.     

Developmental morphology of the flower of <Emphasis Type="Italic">Dracontium polyphyllum</Emphasis> in the context of the phylogeny of the Araceae

The inflorescence of Dracontium polyphyllum consists of 150 – 300 flowers arranged in recognisable spirals. The flower has 5 – 6 (90% of observed specimens), or 7 broad tepals enclosing 9 – 12 stamens (occasionally 7) inserted in two whorls. The gynoecium is trilocular (90% of observed specimens) or tetralocular. The tetralocular gynoecia are found at random among the trilocular gynoecia. Each locule encloses an ovule inserted in an axile position, in the median portion of the ovary. Each carpel has its own stylar canal. However, in the upper portion of the style, there is only one common stylar canal. Floral organs are initiated in an acropetal direction in the following sequence: tepals, stamens, and carpels. During later stages of development, the tepals progressively cover the other floral organs. The first floral primordia are initiated on the upper portion of the inflorescence. During early stages of development, the floral primordia have a circular shape. The tepals are initiated nearly simultaneously. During later stages of development, the first whorl of stamens develops in alternation with the tepals and is followed by a second whorl of stamens. The trilocular or tetralocular nature of the ovary is clearly visible during early stages of development of the gynoecium. Recent molecular studies show that Anaphyllopsis A. Hay and Dracontium L. are closely related. However, although pentamerous flowers have been observed in Anaphyllopsis, the developmental morphology of the flower of Dracontium is different from that of Anaphyllopsis.     

Floral development and anatomy of Salvadoraceae

Background and Aims

This study is an investigation into the floral development and anatomy of two genera of the small family Salvadoraceae, which belongs to the Brassicales in a clade with Batis and Koeberlinia. Salvadoraceae remains little known, despite its wide distribution in arid areas of the globe. Floral morphological data are scarce, and information on floral anatomy is limited to a single study, although morphological and anatomical characters are now used increasingly as a counterpart of molecular data. There remain a number of controversial morphological questions, such as the fusion of the petals, the number of carpels and the nature of the nectaries.

Methods

Floral anatomy and ontogeny were studied in two species of Salvadora and one species of Dobera. Only for S. persica could a full floral developmental sequence be done.

Key Results

The floral development demonstrates that the ovary of Salvadoraceae is basically bicarpellate and pseudomonomerous with a single locule and parietal placenta. The ovary of Dobera resembles Azima tetracantha in the presence of a false apical septum. Evidence for a staminodial nature of the nectaries is not decisive. In Salvadora petals and stamens are lifted by a short hypanthium.

Conclusions

Salvadoraceae share several morphological and developmental synapomorphies with Batis (Bataceae) and possibly Koeberlinia (Koeberliniaceae), supporting their close relationship as indicated by molecular phylogeny.Key words: Batis, Brassicales, Dobera, Emblingia, floral development, floral anatomy, Koeberlinia, phylogeny, Salvadora, Salvadoraceae, SEM