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Pseudomonomerous gynoecia with three (or four) carpels are unknown in the species-rich core group of Apiales, but this condition is shared by three species-poor families (Pennantiaceae, Torricelliaceae, Griseliniaceae) that form the basal grade of the order. Testing a hypothesis on the ancestral nature of carpel dimorphism in Apiales requires comparative data for all three lineages in this grade. We provide the first detailed description of flowers, including floral vasculature and gynoecium development, in a member of Pennantiaceae (Pennantia corymbosa). In contrast to many other Apiales, the inflorescence of Pennantia is paniculate and therefore has an unstable number of phyllomes in axes terminated by flowers. All phyllomes in the inflorescence are shifted onto lateral branches they subtend exhibiting recaulescence, a pattern that has not been reported elsewhere in Apiales. Plants are dioecious with functionally unisexual flowers. There are normally five stamens alternating with five petals. Anthers are present and produce pollen in stamens of male as well as female flowers, but ventral microsporangia are reduced in some anthers of female flowers. Anther morphology sometimes varies even among stamens of the same flower. Two types of synthecal anthers are recorded. Pollen dimorphism is confirmed: inaperturate pollen produced by stamens of female flowers supposedly acts as the only reward for pollinators in the absence of nectaries. The gynoecium of the female flower is syncarpous and pseudomonomerous: only one of three carpels is fertile. The gynoecium is initiated as three carpel primordia (future stigmas). One of them is smaller than the other two and occupies an alternistaminal (and antepetalous) position. The two large carpel primordia are located in the radii of stamens that are generally smaller (early in development) than the three other stamens. The carpel dimorphism is maintained at anthesis. The carpel with the smaller stigma is fertile, and those with larger stigmas are sterile. The carpels are congenitally united below the stigmas. The ovary is superior, unilocular (vs. inferior and plurilocular in Torricelliaceae and Griseliniaceae) and usually uniovulate with pendent ovule(s) inserted at the cross-zone level of the fertile carpel. As in most other Apiales, the short symplicate zone is sealed by postgenital fusion at anthesis and forms an internal compitum. The fertile carpel of the members of the basal grade of Apiales investigated so far is uniformly arranged in a petal radius. This is consistent with the idea that pseudomonomery is associated with stable patterns of flower groundplan in Apiales. Our data do not provide any clear structural or developmental evidence of independent origins of carpel dimorphism in Pennantiaceae, Torricelliaceae and Griseliniaceae. [ABSTRACT FROM AUTHOR]

This research provides a description and illustrations for a new species from the Phong Nha-Ke Bang National Park, Cynanchum quangbinhense. The distribution, habitat, phenology and conservation assessment for the species are also presented. The new species differs from closely related species, C. ovalifolium in many characters such as leaf shape, inflorescence type, fewer and smaller flowers, colour of petals, margins of the corona, and anthers appendages shape, and differs from C. kwangsiense in having small leaves, umbellate inflorescences, triangular sepals, retuse apex of petals, and plicate margin of corona. Our discovery raises the known species of this genus in Vietnam to seven. In addition, a key to species of Cynanchum in Vietnam, and notes on morphological variation of C. officinale are presented in this paper. [ABSTRACT FROM AUTHOR]

Thismia is characterized by an exceptionally complicated floral morphology that is currently not understood properly. In the taxonomic literature, descriptive rather than morphological terms are often applied to parts of the flower in Thismia , relating to the general appearance of the floral organs instead of their precise homologies. Precise understanding of the floral structure is complicated by the rarity of Thismia spp. and the paucity of appropriate material. Here we provide a comprehensive study of reproductive organs of three Thismia spp. (T. annamensis , T. javanica and T. mucronata) including the first investigation of inflorescence architecture and early floral development in Thismiaceae. We found a hitherto unknown diversity of the reproductive shoots in the genus, manifested in the number of floral prophylls (two or three, in contrast to a single prophyll in the vast majority of monocots) and in the branching plane resulting in two distinct inflorescence types, a drepanium and a bostryx. We report the non-acropetal sequence of initiation of floral whorls (with stamens being the last elements to initiate), never previously described in monocots, and the gynoecium composed of completely plicate carpels, also a rare feature for monocots. Floral vasculature is relatively uniform in Thismia , but significant interspecific differences are found in tepal innervation, including the number of tepal traces; some of these differences are not immediately related to the external tepal morphology. We argue that the annulus, which acts as a roof of the hypanthium, possesses an androecium nature and represents congenitally fused bases of stamen filaments. We describe the stamens as laminar structures, which are also shortly tubular in the distal part of the supraconnective with the adaxial tubular side forming a skirt-like appendage. Finally, the placentas, which are column-like when mature, are initially parietal, becoming secondarily similar to free-central placentas through schizogenous separation from the ovary wall. [ABSTRACT FROM AUTHOR]

The paper presents new data on the orchid diversity in Vietnam obtained in 2016--2020. It contains descriptions of one genus (Apetalanthe) and two species new to science (Apetalanthe gracilis, Nervilia appressifolia), as well as one genus (Neottianthe) and four species (Calanthe tricarinata, Collabium yunnanense, Dendrobium praecinctum, Neottianthe secundiflora) new for the flora of Vietnam. Apetalanthe is particularly remarkable for the reduction of petals. The accepted name, synonyms, type, citations of relevant regional taxonomic publications, data on ecology, phenology and distribution, estimated IUCN Red List status, studied specimens, brief taxonomic notes, and illustrations are provided for each recorded species. [ABSTRACT FROM AUTHOR]

Here we present revised taxonomy, morphological variation and geographical distribution of Jasminum pedunculatum Gagnep. (Oleaceae). Type material of this species was analyzed and a specimen from P (P00644297) was designated as a lectotype. Jasminum albicalyx Kobuski is reduced to a taxonomic synonym of J. pedunculatum on the basis of morphological features and geographical occurrence. A full list of all available specimens of J. pedunculatum s. lato and a map of its distribution are provided. The species is widely distributed throughout Guangxi (China) and in northern Vietnam. A drawing and colour photographs of J. pedunculatum are provided to aid identification. [ABSTRACT FROM AUTHOR]

Elatostema (Urticaceae) comprises several hundred herbaceous species distributed in tropical and subtropical Africa, Asia, Australia and Oceania. The greatest species richness occurs on limestone karst in Southeast Asia. Taxonomic revisions of Elatostema are largely out of date and contradict each other with respect to the delimitation of Elatostema and Pellionia. Most herbaria in SE Asia and worldwide contain significant amounts of unidentified material. As part of a broader revision of Elatostema in SE Asia, we present an updated checklist for Vietnam based on field visits, a review of specimens in herbaria worldwide, a review of type material and nomenclature. We recognize 77 taxa (75 species and two infraspecific taxa) of Elatostema in Vietnam, 23 of which were previously ascribed to Pellionia. Nineteen of these are new records for the country, i.e., E. attenuatoides, E. austrosinense, E. backeri, E. brunneinerve, E. crassiusculum, E. crenatum, E. fengshanense, E. glochidioides, E. malacotrichum, E. nanchuanense, E. oblongifolium, E. obtusum, E. oppositum, E. pergameneum, E. pruni-folium, E. pseudolongipes, E. pycnodontum, E. salvinioides and E. xichouense. We place E. baviensis in synonymy of E. platyphyllum, E. colaniae in synonymy of E. myrtillus, P. macroceras in synonymy of E. hookerianum, and P. tetramera in synonymy of E. dissectum for the first time. Fourteen taxa (18% of all the recognized taxa) are endemic to Vietnam, which makes Elatostema one of the richest genera for endemic species in this country; this level of endemism is comparable to levels observed in Orchidaceae. Our checklist suggests that the highest diversity and endemism of Elatostema occurs in northern Vietnam, and that there is the greatest floristic similarity of northern Vietnam to SW China. The relationship among floristic regions is also investigated. We could find no records of Elatostema for 33 out of 63 provincial units of Vietnam, including all the southernmost provinces. We propose that further studies on the diversity of Elatostema in central and southern Vietnam are severely needed. [ABSTRACT FROM AUTHOR]

Gross morphology and the development of flowers in Schefflera subintegra ( Araliaceae) are examined. The floral groundplan of this species is found to be very similar to that of Tupidanthus calyptratus representing a case of most extreme floral polymery within Araliaceae. Schefflera subintegra differs from T. calyptratus with respect to a lower floral merism (19-43 versus 60-172 stamens and 15-33 versus 60-138 carpels respectively) and by transformation from polysymmetry to disymmetry of flower in the course of its development. Close relationships between S. subintegra, T. calyptratus, and Schefflera hemiepiphytica have been confirmed by phylogenetic analysis based on nuclear ribosomal internal transcribed spacer sequences. These species form a subclade within the Asian Schefflera clade, with T. calyptratus as a sister taxon to two other species. Apart from more or less pronounced floral polymery, the species of this subclade share calyx and corolla without any traits of individual sepals and petals, and also a massive calyptra. As these data suggest, the extremely polymerous flowers of Tupidanthus apparently evolved in two steps: (1) the saltational multiplication of floral elements together with a loss of individuality of sepals in the calyx and petals in the corolla and (2) further polymerization of androecium and gynoecium. Mutation(s) in CLAVATA-like gene(s) are suggested as a possible mechanism of the saltation event. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 175, 553-597. [ABSTRACT FROM AUTHOR]

Vietorchis furcata, an achlorophyllous orchid, discovered in southern Vietnam is described and illustrated as new for science. This is the second species of the genus regarded earlier as monotypic. A key for identification of both species of the genus and short notes on their taxonomy and biology are provided. Closely related genera - Vietorchis and Silvorchis are segregated in rank of subtribe Vietorchidinae due to their isolated taxonomical position. [ABSTRACT FROM AUTHOR]

Floral symmetry is widely known as one of the most important structural traits of reproductive organs in angiosperms. It is tightly related to the shape and arrangement of floral parts, and at the same time, it plays a key role in general appearance (visual gestalt) of a flower, which is especially important for the interactions of zoophilous flowers with their pollinators. The traditional classification of floral symmetry divides nearly all the diversity of angiosperm flowers into actinomorphic and zygomorphic ones. Within this system, which is useful for ecological studies, many variations of symmetry appear to be disregarded. At the same time, the diversity of floral symmetry is underpinned not only by ecological factors, but also by morphogenetic mechanisms and constraints. Sometimes it is not an easy task to uncover the adaptive or developmental significance of a change of the floral symmetry in a particular lineage. Using the asterid order Apiales as a model group, we demonstrate that such changes can correlate with the merism of the entire flower or of its particular whorl, with the relative orientation of gynoecium to the rest of the flower, with the presence of sterile floral elements and other morphological characters. Besides, in some taxa, the shape and symmetry of the flower change in the course of its development, which should be taken in consideration in morphological comparisons and evaluations of synapomorphies in a particular clade. Finally, we show that different results can be obtained due to employment of different approaches: for instance, many flowers that are traditionally described as actinomorphic turn out to be disymmetric, monosymmetric, or asymmetric from a more detailed look. The traditional method of division into actinomorphy and zygomorphy deals with the general appearance of a flower, and mainly considers the shape of the corolla, while the geometrical approach handles the entire three-dimensional structure of the flower, and provides an exact number of its symmetry planes. [ABSTRACT FROM AUTHOR]