Floral morphology of southern African Orchideae. II. Habenariinae

The floral morphology of the southern African genera of Orchideae-Habenariinae (Bonatea, Cynorkis, Habenaria, Platycoryne, Stenoglottis, Centrostigma and Roe-perocharis) is surveyed paying special attention to the gynostemium. Ontogenetic data are provided for the species from which adequate material was available. It is shown that the floral architecture is essentially an elaboration and complication of that found in the better known Orchidinae. The structural similarities are particularly evident in the early ontogeny. Although the tribe Orchideae is commonly said to have gynostemia with erect anthers, a few Habenariinae are reported here to have reflexed anthers. In most cases both 'auricles' (filament excrescences) and 'basal bulges' (staminodes) are united to form the lateral gynostemium appendages. The primordia of both structures are clearly recognizable in the early ontogeny in all species studied. In Habenaria dregeana the basal bulges are only basally fused to the auricles, but in their main portion become adnate to the lip and petal bases: the auricles then solely form the lateral gynostemium appendages. It is suspected that this occurs also in other species not studied here. Systematic and phylogenetic aspects of the southern African representatives of the Habenariinae are discussed: the generic separation of Bonatea, Platycoryne and Centrostigma from Habenaria does not appear justified. Cynorkis, Roeperocharis and Stenoglottis are morphologically dissimilar to Habenaria. Based on the findings in the southern African taxa the status of the Habenariinae, Orchidinae, Orchideae and Diseae is discussed: there is no clear distinction between Habenariinae and Orchidinae; while the Diseae seem to represent a monophyletic group, the Orchideae are possibly polyphyletic.     

Floral morphology and ontogeny in Orchidaceae subtribe Disinae

Floral morphology and ontogeny in Orchidaceae subtribe Disinae. The flower structure and development of 24 species of the orchid subtribe Disinae are described and illustrated by drawings and scanning electron micrographs with special attention being paid to the gynostemium. The morphogenesis of this subtribe is fundamentally similar to that of the closely related tribe Orchideae. This includes the initiation of the auricles on the anther base in a dorsolateral position, and hence their interpretation as being mere appendages of the filament. The keel connecting the petals and the gynostemium plus its protrusion is considered homologous to the inner lateral staminodeS. Presumed vestiges of the adaxial staminodes were detected in one specieS. A peculiarity of the Disinae is that the entire apex of the median carpel develops into the rostellum, whereas its stigmatic portion emerges from the median carpel below the rostellum in later stages. The main diagnostic feature of the group is the reflexed position of the mature anther. However, it is shown here that this anther movement occurs in the later stages and that the initial anther is erect.     

Developmental studies in orchid flowers III: Neottioid species

The floral development of 19 species of Neottioideae (sensu Rasmussen 1985) was studied by means of scanning electron microscopy, paying special attention to the early differentiation of the organs that constitute the gynostemium. The gynostemium development of the Epipactieae proved to be similar to that of the Epidendroi deae and Vandoideae, in particular in that massive primordia corresponding to inner lateral staminodes are differentiated in early stages and later constitute the lateral appendages of the gynostemium. In the Neottieae a progressive reduction and delayed initiation of these staminodes was observed: the lateral teeth of the gynostemium originate from large staminode primordia in one species ( Corymborkis veratrifolia ), in the remaining species they are initiated in later stages or are missing.     

Developmental morphology and structural homology of corolla-androecium synorganization in the tribe Amorpheae (Fabaceae: Papilionoideae)

Comparative developmental morphology was used to assess structural homology of flowers in Dalea, Marina, and Psorothamnus of the tribe Amorpheae (Fabaceae: Papilionoideae). Dalea, Marina, and some species of Psorothamnus have an unusual petal-stamen synorganization (stemonozone) in which free petals are inserted on a region that is continuous with fused stamen filaments. Developmental studies of these three genera demonstrated similarity during organogenesis. Zonal growth results in several synorganized regions, including the stemonozone of Dalea, Marina, and some Psorothamnus. Psorothamnus species that lack a stemonozone have fused stamens and free petals inserted on the hypanthium, as in most other papilionoid legumes. We concluded that the stemonozone is not strictly homologous to either androecium or receptacle, but that it is the product of a modified androecial developmental program. In the prairie clover daleas, petaloid structures positioned between the stamens have been variously interpreted as petals or as staminodes; we infer that they have an extreme form of the daleoid stemonozone, on which five petals (no staminodes) and five stamens are inserted. Assessing structural homology of these flowers allows us to characterize accurately daleoid morphology for evolutionary studies in the tribe Amorpheae.     

The gynostemium of Hemipiliopsis purpureopunctata and Senghasiella glaucifolia, two taxonomically disputed species of Habenariinae (Orchidaceae)

The gynostemium structure and ontogeny of two taxonomically disputed orchids, Hemipiliopsis (= Habenaria ) purpureopunctata and Senghasiella (= Habenaria ) glaucifolia , are described and illustrated by scanning electron micrographs. The early gynostemium ontogeny of Hemipiliopsis purpureopunctata is shown to be fundamentally similar to that of the species of the tribe Orchideae that have been previously studied. This includes the initiation sequence of sepals, petals and lip, form and orientation of anthers, three-lobed condition of median carpel apex, and presence of auricles and basal bulges. During the later developmental stages some differences occur. The stigma processes of Senghasiella glaucifolia are united into a tongue-shaped organ, and the lateral rostellum lobes of Hemipiliopsis purpureopunctata protrude forwards with their viscidia positioned above the spur-mouth. Based on gynostemium characters, the generic rank of Hemipiliopsis was confirmed, but that of Senghasiella was not supported.  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 147 , 191–196.     

Subterranean axes in tribe Diurideae (Orchidaceae): Morphology,anatomy, and SYSTEMATIC SIGNIFICANCE

The morphological and anatomical nature of perennating storage organs of the predominantly Australasian orchid tribe Diurideae (Orchidoideae: Orchidaceae) as well as anatomical concepts in tribes Orchideae and Diseae of Orchidoideae have been problematic for 150 yr, reflected in conflicting or vague terminology and questions about polystely and even monophyly of Orchidoideae. From a representative survey of underground organs of 145 species in 37 ingroup genera (Diurideae) and two outgroup genera (Spiranthes and Disa), the so-called “root-stem tuberoids” are here interpreted as root tubers (except for the stem tubers of Rhizanthella) borne on either droppers or stolonoid roots. All root tubers examined are bounded by a 1–4 layered velamen and exodermis, whereas droppers and stolonoid roots may have velamen-exodermis or a simple epidermis depending on the taxon and often bear multiseriate or uniseriate trichomes associated with mycorrhiza (as do roots of some taxa). The “polystely” reported in tubers of many Orchideae also occurs in tubers of many Diurideae but represents only dissection of the siphonostele into 2–13 traces. Cladistic analyses of data show extraordinarily high levels of homoplasy in characters related to root, dropper/stolonoid root, and tuber, so that these characters alone are of limited usefulness.     

Phylogenetics of tribe Orchideae (Orchidaceae: Orchidoideae) based on combined DNA matrices: inferences regarding timing of diversification and evolution of pollination syndromes

Background and aims

Tribe Orchideae (Orchidaceae: Orchidoideae) comprises around 62 mostly terrestrial genera, which are well represented in the Northern Temperate Zone and less frequently in tropical areas of both the Old and New Worlds. Phylogenetic relationships within this tribe have been studied previously using only nuclear ribosomal DNA (nuclear ribosomal internal transcribed spacer, nrITS). However, different parts of the phylogenetic tree in these analyses were weakly supported, and integrating information from different plant genomes is clearly necessary in orchids, where reticulate evolution events are putatively common. The aims of this study were to: (1) obtain a well-supported and dated phylogenetic hypothesis for tribe Orchideae, (ii) assess appropriateness of recent nomenclatural changes in this tribe in the last decade, (3) detect possible examples of reticulate evolution and (4) analyse in a temporal context evolutionary trends for subtribe Orchidinae with special emphasis on pollination systems.

Methods

The analyses included 118 samples, belonging to 103 species and 25 genera, for three DNA regions (nrITS, mitochondrial cox1 intron and plastid rpl16 intron). Bayesian and maximum-parsimony methods were used to construct a well-supported and dated tree. Evolutionary trends in the subtribe were analysed using Bayesian and maximum-likelihood methods of character evolution.

Key Results

The dated phylogenetic tree strongly supported the recently recircumscribed generic concepts of Bateman and collaborators. Moreover, it was found that Orchidinae have diversified in the Mediterranean basin during the last 15 million years, and one potential example of reticulate evolution in the subtribe was identified. In Orchidinae, pollination systems have shifted on numerous occasions during the last 23 million years.

Conclusions

The results indicate that ancestral Orchidinae were hymenopteran-pollinated, food-deceptive plants and that these traits have been dominant throughout the evolutionary history of the subtribe in the Mediterranean. Evidence was also obtained that the onset of sexual deception might be linked to an increase in labellum size, and the possibility is discussed that diversification in Orchidinae developed in parallel with diversification of bees and wasps from the Miocene onwards.     

On the Systematic Position of Paradombeya Stapf

The systematic position of Paradombeya Stapf has been debated until now. The studies on gross morphology, anatomy, palynology and cytology were undertaken to confirm the systematic position and affinities of this genus. The combination of features, e. g., umbel-like cyme, 2-celled anther, presence of staminodes, staminal tube, 15 stamens, bifid cotyledons, wood anatomy, chromosome number of 2n=20, triporate, spiny and spheroidal pollen grains, suggests that the genus be better placed in the tribe Dombeyeaeof the Sterculiaceae.     

Molecular phylogenetics of Diseae (Orchidaceae): a contribution from nuclear ribosomal ITS sequences

We present here the first molecular phylogeny of tribe Diseae (Orchidoideae: Orchidaceae). Nuclear ribosomal ITS1, 5.8S rDNA, and ITS2 sequences were compared for 30 Diseae, 20 Orchideae, and four Cranichideae and Diurideae outgroups. ITS - rDNA sequences exhibited a transition:transversion ratio of 1.3 and extensive ITS length polymorphism. Phylogenetic analyses using maximum parsimony identified seven major core orchidoid groups. The branching order of the five Diseae and two Orchideae clades was weakly supported but indicated paraphyly of Diseae, with Disperis sister to the rest, followed by successive divergence of Brownleea, Disinae, Coryciinae sensu stricto (s.s.), Satyriinae, and terminated by Orchidinae plus Habenariinae. Within the monophyletic Disinae, Herschelia and Monadenia were nested within a paraphyletic Disa and clustered with D. sect. Micranthae. Within monophyletic Satyriinae, Satyridium rostratum plus Satyrium bicallosum was sister to the rest of Satyrium, and then Satyrium nepalense plus S. odorum was distinct from a cluster of six species. Coryciinae are paraphyletic because Disperis is sister to all other core orchidoids. Coryciinae s.s. are sister to Satyriinae plus Orchideae, with Pterygodium nested within Corycium. Maximum likelihood analysis supported possible affinities among Disinae, Brownleeinae, and Coryciinae but did not support monophyly of Diseae or an affinity between Disinae and Satyriinae. Morphological characters are fully congruent with the well-supported groups identified in the ITS phylogeny.     

Floral morphology of southern African Orchideae. I. Orchidinae

The floral morphology of the southern African genera of Orchidaceae-Orchideae-Orchidinae ( Brachycorythis, Schwartzkopffia, Neobolusia, Schizochilus, Holothrix and Bartholina ) is surveyed paying special attention to the gynostemium. Ontogenetic data are provided for a number of species that appear to be essential in formulating a proper interpretation of the gynostemium. The floral architecture is shown to be basically similar to that of the (much better known) European representatives of the subtribe. This, however, does not fully apply to the homology of the lateral gynostemium appendages ("auricles"): In Brachycorythis, Neobolusia and Schizochilus these develop like in Orchis and Dactylorhiza. Their prominent sculptured portions originate from dorsal stamen outgrowths and correspond to filament excrescences. Structures obviously homologous to lateral inner stamens can be recognized in the early ontogeny, but are in the mature flower incorporated in the 'arch' connecting the lip with the gynostemium. In contrast, in Holothrix and Bartholina the gynostemium appendages correspond entirely to staminodes, while the filament excrescences are missing. It is also shown that the 'concave' stigma said to be characteristic of the Orchidinae is in fact ± convex or even pad-like, but is generally positioned in a cavity under the rostellum. The 'erect' anther (the main diagnostic feature of the Orchideae) is reflexed up to 45° in some taxa. Affinities of the genera are briefly discussed. The generic separation of Schwartzkopffia and Neobolusia from Brachycorythis does not appear justified. Neobolusia virginea is obviously misplaced in the respective genus, and eventually merits generic status. The affinities of Schizochilus remain ± obscure at the moment. Bartholina appears to be merely a small group of specialized Holothrix species.     

Floral organogenesis and the developmental basis for pollinator deception in the asiatic dayflower, Commelina communis (Commelinaceae)

The upper half of flowers in Commelina communis deceptively lures potential pollinators with its showy petals and staminodes on the false promise of abundant pollen. This paper presents evidence that staminodization in the upper half is associated with a severe retardation of the entire upper floral hemisphere early in development. Possible consequences of this developmental retardation are seen also in the gynoecium, where the upper carpel of the three-carpellate ovary is underdeveloped and sterile at maturity. Only late in development do the upper petals and staminodes expand and acquire pigments necessary for their attractive function. We surmise that retardations of this severity are unlikely to be found for functionally fertile organs such as stamens and ovule-producing carpels, because key preparatory events preceding sporogenesis might otherwise be disrupted. Such differential growth about the floral apex resembles that known in some eudicots to be regulated by the TCP gene family; thus, future molecular developmental studies in Commelina may help to extend our understanding of the evolutionary genetics of floral monosymmetry to monocots.     

The evolution of staminodes in angiosperms: patterns of stamen reduction, loss, and functional re-invention

Stamens that have lost their primary function of pollen production, or staminodes, occur uncommonly within angiosperms, but frequently fulfill important secondary floral functions. The phylogenetic distribution of staminodes suggests that they typically arise during evolutionary reduction of the androecium. Differences in the genetic control and patterns of stamen loss between actinomorphic and zygomorphic flowers shape staminode development. In clades with actinomorphic flowers, staminodes generally replace an entire stamen whorl and staminode loss seems irreversible. In contrast, in clades with zygomorphic flowers staminodes evolve from a subset of the stamens in a whorl and staminodes can reappear in a lineage after being lost (e.g., Cheloneae, Scrophulariaceae). If staminodes do not adopt new functions during androecium reduction they are lost quickly, so that nonfunctional staminodes appear only in recently derived taxa. Alternatively, when staminodes assume new floral roles, either directly or indirectly after a nonfunctional period, they can become integral floral components which perpetuate within clades (e.g., Orchidaceae). Indirect evolution of staminode function allows greater flexibility of function by allowing staminodes to take over roles not performed by stamens, such as involvement in mechanisms to prevent self-pollination and mechanisms of explosive pollination. Multifunctional staminodes characterize lineages with universal or widespread staminodes.     

Cytological studies on some representative species of the tribe Orchideae (Orchidaceae) from China

Cytological studies were carried out on 14 taxa belonging to Amitostigma , Chusua , Galearis , Habenaria , Hemipilia , Hemipiliopsis , Herminium , Peristylus and Ponerochis , collected mostly from the south-eastern part of the Hengduan Mountain Region, south-west China. Cytological data on 11 of the taxa are reported for the first time. The interphase nuclei were either of the simple chromocentre type or intermediate between simple and complex chromocentre types. The nuclear morphology of Hemipiliopsis at interphase supports the conclusion that it is related more closely to Chusua and Ponerochis than to Habenaria . At the whole tribe level, however, the results did not indicate a clear correlation between morphological features of the interphase nuclei and phylogeny. The somatic chromosome numbers were 2 n  = 42 in ten species and 2 n  = 32, 38, 40, 64 and 72 in four species. The chromosome counts of 2 n  = 32 and 64 in Habenaria aitchsonii are rare in the genus. It is proposed that the repeated change of chromosome number from x  = 7 to x  = 8 has played an important role in the evolution of the tribe Orchideae. This change has occurred mainly in the European subtribe Orchidinae, but also in the Asian subtribe Habenariinae.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 145 , 231–238.     

Study of homeosis in the flower of Philodendron (araceae): a qualitative and quantitative approach

This study deals specifically with floral organogenesis and the development of the inflorescence of Philodendron squamiferum and P. pedatum. Pistillate flowers are initiated on the lower portion of the inflorescence and staminate flowers are initiated on the distal portion. An intermediate zone consisting of sterile male flowers and atypical bisexual flowers with fused or free carpels and staminodes is also present. This zone is located between the sterile male and female floral zones. In general, the portion of bisexual flowers facing the male zone forms staminodes, and the portion facing the female zone develops an incomplete gynoecium with few carpels. The incomplete separation of some staminodes from the gynoecial portion of the whorl shows that they belong to the same whorl as the carpels. There are two levels of aberrant floral structures in Philodendron: The first one is represented by the presence of atypical bisexual flowers, which are intermediates between typical female flowers and typical sterile male flowers. The second one is the presence of intermediate structures between typical carpels and typical staminodes on a single atypical bisexual flower. The atypical bisexual flowers of P. squamiferum and P. pedatum are believed to be a case of homeosis where carpels have been replaced by sterile stamens on the same whorl. A quantitative analysis indicates that in both species, on average, one staminode replaces one carpel.     

爪哇蒙蒿子(Anaxagorea javanica)内轮退化雄蕊形态结构及功能

利用扫描电子显微镜、光学显微镜对爪哇蒙蒿子（Anaxagorea javanica Blume）可育雄蕊、内轮退化雄蕊和雌蕊的形态、结构进行了观察,并利用组织化学染色法对内轮退化雄蕊和柱头顶端腺毛化学成分进行了检测。结果显示,内轮退化雄蕊顶端为长条状腺毛,柱头顶端有头状和盾状腺毛,两者顶端的腺毛形态和结构明显不同,但分泌物成分类似,都含有蛋白质和脂类物质。内轮退化雄蕊的横切面为一层表皮细胞包围着薄壁组织,中央有一束维管束,与可育雄蕊花丝部位的横切面十分相似,是介于可育雄蕊和雌蕊之间的过渡结构。在雌蕊阶段,退化雄蕊顶端腺体释放的黏液供传粉昆虫觅食;在雄蕊阶段,退化雄蕊顶端覆盖柱头,呈S型,防止自花授粉。爪哇蒙蒿子薄片状可育雄蕊、内轮退化雄蕊以及可育雄蕊和退化雄蕊腹面上存在气孔等原始性状,是连接番荔枝科和其外类群的同源特征。     

单性木兰（木兰科）花的形态发生

报道了单性木兰(Kmeria septentrionalis Dandy)花的形态发生过程。发现过去一直被认为是雌花条状披针形的“内轮花被片”,实际为退化雄蕊,它形态发生的时间与位置均与雄花的雄蕊相同,在成熟结构中仍可见药室残迹,说明单性木兰的雌性花是由两性花退化而来。通过与K. duperreana(Pierre) Dandy和Magnolia thailandica Noot. &; Chalermglin雌花的比较,发现它们雌花的形态相同,从而得知人们长期以来对此3种植物雌花的认识有误,原一直认为的“内轮花被片”实为退化雄蕊。     

Scent emissions and floral nutrients of Carludovicoideae (Cyclanthaceae) and their importance for associated beetles

To better understand the complex pollination biology of Carludovicoideae (Cyclanthaceae), four species from French Guiana were investigated in both the field and laboratory. The pistillate flowers of all species of the subfamily have long staminodes up to 10 cm long or more, which emit scent and apparently attract beetles during anthesis. Scent was collected by standard headspace methods and analyzed in the laboratory by GC/MS. The histology of staminodes, measurements of inflorescence temperatures, and analyses of the floral nutrients were performed. The staminodes have two ducts with a mucilage-like liquid containing sugar, which provides nourishment for beetle visitors. In Evodianthus funifer, four of the six beetle morphospecies (Curculionidae: Acalyptini) were pollinators and oviposited in staminate flowers. The remaining pair of morphospecies were non-pollinators, and avoided entering the inflorescence, while only cutting the staminodes for possible oviposition on the ground. Staminate flowers and staminodes have a high energy content, providing for larval development of the beetles. Our findings revealed that the staminodes released aromatic components, miscellaneous cyclic components, and terpenoids. Some of the major scent compounds of E. funifer and Ludovia lancifolia, i.e., (E,E)-α-farnesene-2(3),9(10)-diepoxid and 3-methylen-2-(pent-2(Z)-enyl)-cyclopentanol, are new to science. Also, Carludovicoideae are a subfamily of plants that attract beetle pollinators through highly specific scent compounds, making them comparable to species of Araceae, Magnoliaceae, and Annonaceae.     

Homeosis in Araceae Flowers: The Case of Philodendron melinonii

The early stages of development of the inflorescence of Philodendronmelinonii were examined using scanning electron microscopy.Pistillate flowers are initiated on the lower portion of theinflorescence and staminate flowers are initiated on the distalportion. The male flowers have four to five stamens. The femaleflowers have a multilocular ovary consisting of four to sixlocules. A transition zone consisting of sterile male flowersand bisexual flowers with fused or free carpels and staminodesis also present on the inflorescences. This zone is locatedbetween the male and female flower zones. Generally, the portionof the bisexual flower facing the male zone forms stamens, andthe portion facing the female zone develops an incomplete gynoeciumwith few carpels. In P. melinonii, the incomplete separationof staminodes from the gynoecial portion of the whorl showsthat the staminodes and carpels belong to the same whorl. Thebisexual flowers of P. melinonii are believed to be a case ofhomeosis where carpels have been replaced by sterile stamenson the same whorl. At the level of the inflorescence, pistillateand staminate flowers are inserted on the same contact parastichiesalong the inflorescence; there is no discontinuity between thefemale zone, the bisexual zone, and the male zone. The presenceof bisexual flowers is believed to correspond to a morphogeneticgradient at the level of the inflorescence as a whole. Copyright2000 Annals of Botany Company Flower, development, gradient, inflorescence     

Staminodes: Their morphological and evolutionary significance

Different approaches to circumscribe staminodial structures in the angiosperms are reviewed. The need for a morphological distinction between “true staminodes” (derived from stamens or homologous to stamens) and “pseudostaminodes” (nonhomologous to stamens) is emphasized. In phylogenetic studies the term “staminode” is often used uncritically, without knowledge of the true homology of these structures. Staminodes are either whole organs (outer tiers or whorls, namely petals, intermediate tiers, or organs within a tier), or partial organs. This article aims to discuss the shortcomings of the past and current approach of staminodes and proposes definitions of staminode types for use as characters in phylogenetic analyses. Staminodial structures should be classified according to their position and function in the flower. Both aspects are intricately linked and make the identification of staminodes sometimes problematic. Shifts in time (heterochrony) and space (heterotopy or homeosis) make that a regressing organ either aborts completely or becomes remodeled into something new. Petals are included in the definition of staminodes as they combine function and heterotopy. A hierarchical ordering of staminodial types is given and discussed. Three interdependent but possibly complementary functions are attached to the occurrence of staminodes: an attractive, nutritional, and structural function. The importance of staminodes for the evolution of the androecium and flower is demonstrated. The difficulty in unmasking pseudostaminodes, comprising receptacular disks, is demonstrated. The value and shortcomings of molecular-based interpretations of staminodes are discussed. It is shown that the decision to recognize a staminode from receptacular emergences often relies on unstable grounds and remains largely dependent on the acceptance of a given phylogenetic background.     

Phylogenetic relationships in Disa based on non-coding trnL-trnF chloroplast sequences: evidence of numerous repeat regions

Sequence data from the intron and spacer of the trnL-F chloroplast region elucidate the phylogenetic relationships of the tribe Diseae (Orchidoideae: Orchidaceae). Within Diseae, 41 species of Disa, two of Brownleea, three of Satyrium, and two of Corycium were included, with five species of Habenaria sensu lato (Orchideae) and one epidendroid as outgroups. The sequences revealed substitutions and considerable length variation, due mainly to the presence of repeat motifs. Phylogenetic analysis using parsimony revealed five distinct clades. The branching order of the five weakly supported the paraphyly of Diseae, with the successive divergence of Brownleea, Corycium, Habenaria, Satyrium, and Disa. Within the monophyletic Disa, three main groupings appeared, two strongly supported clades representing sect. Racemosae and sect. Coryphaea and the third grouping containing several clades currently grouped into sections based on morphological phylogenies. Some discrepancies between the molecular phylogeny and the phylogeny based on morphological characters may require reevaluation of some of the morphological characters. The presence of different numbers of repeat motifs, both among different taxa and within taxa, indicates that these characters may be phylogenetically informative at the population level.