RESUMO
The presence of mucilage cells in plants, studied mainly in vegetative organs, is a condition shared by several taxonomic groups and aspects related to their diversity have been discussed with systematic purposes. This study explores the flower distribution and classification of mucilage cells in Rosales species, with inferences about flower functions. Floral buds from fifty-seven species representing seven of nine families recognized in the Rosales were sampled and processed for light and transmission electron microscopy. Mucilage cells were found in about 40% of the studied species of Cannabaceae, Rhamnaceae, Ulmaceae, and Urticaceae families, whereas no floral mucilage cells were found in species of Elaeagnaceae, Moraceae, and Rosaceae. Mucilage cells were found in the epidermis and internal tissues of many organs of different floral morph types. There is a great diversity of forms of presentation of mucilage in cells, from smaller individualized single cells to very bulky cells and to completely filled mucilage reservoirs. In some cases, cells with mucilage apparently in the cell wall and others with mucilage in the vacuole seem to occur side by side. This diversity challenges the existing classifications of mucilage cells and reinforces the importance of ontogenetic and ultrastructural studies following the path of mucilage in cells in order to propose a more natural classification and to elucidate the evolution of mucilage cells in plants.
Assuntos
Cannabaceae , Mucilagem Vegetal , Rosales , Humanos , Flores/ultraestrutura , Polissacarídeos , Microscopia Eletrônica de TransmissãoRESUMO
Cyperus prophyllatus, an endangered new species of Cyperus (Cyperaceae) from an aquatic ecosystem of the Atlantic Forest, Espírito Santo State, southeastern Brazil, is described and illustrated. The spikelet morphology of Cyperus prophyllatus is unique among the c. 950 species of Cyperus in having both a conspicuous spikelet prophyll and a corky rachilla articulation, which remain persistent at the base of the spikelet after disarticulation. Our molecular phylogenetic data support the placement of C. prophyllatus in the C3 Cyperus Grade and more precisely in the clade representing Cyperus sect. Oxycaryum, which also includes C. blepharoleptos and C. gardneri. Anatomical and (micro)morphological analyses corroborate the phylogenetic results, provide a better understanding of ecology and taxonomy, as well as reveal compatibility of structures with survival and dispersion in aquatic environments. A distribution map, table with distinctive characters of allied species, and conservation status are made available.
Assuntos
Cyperus/anatomia & histologia , Espécies em Perigo de Extinção , Organismos Aquáticos , Brasil , Cyperus/classificação , Cyperus/genética , Cyperus/ultraestrutura , DNA de Plantas/genética , Flores/anatomia & histologia , Flores/ultraestrutura , Microscopia Eletrônica de Varredura , FilogeniaRESUMO
Secretory structures were little studied in Gentianaceae. Glandular areas on the calyx dorsal region are commonly reported for Helieae species, the main tribe of Gentianaceae. So, the elucidation of nature of glandular areas is particularly relevant. Trichomes secreting mucilage, interpreted as colleters, are reported only for the sepals of Gentianinae species. We aimed to anatomically characterize and identify the nature of the calycinal secretory structures in Calolisianthus pedunculatus. Samples from floral buds, flowers, and fruits were collected, fixed, and processed following usual procedures for light and scanning electron microscopies. Histochemical tests were performed to determine the nature of the secretion. Glucose, fructose, and sucrose were measured with an ELISA reader. Colleters occur on the sepal ventral region and are composed of a multicellular secretory head and a stalk. These structures secrete polysaccharides and proteins, and the secretion is probably released through cuticle microchannels. Nectaries, on the other hand, occur on the sepal dorsal region. They are formed by 3-5 cells arranged in rosettes circling a central cell or pore. These structures also secrete polysaccharides (mainly fructose), lipids, and proteins. The identification of the secretory structures in the sepals of Calolisianthus pedunculatus highlights the importance of anatomical studies in this family. The interpretation of the glandular areas on the calyx of the Helieae species as nectaries has been proven, as well as the confirmation of colleters as common structures in the sepals of Gentianaceae. Besides the taxonomic and phylogenetic importance of nectars and colleters, we highlight the importance of the secretion for the protection of floral buds against dehydration.
Assuntos
Flores/anatomia & histologia , Flores/citologia , Gentianaceae/anatomia & histologia , Gentianaceae/citologia , Histocitoquímica , Flores/ultraestrutura , Frutas/anatomia & histologia , Frutas/ultraestrutura , Gentianaceae/ultraestruturaRESUMO
Acianthera section Pleurobotryae is one of ten sections of the genus Acianthera and include four species endemic to the Atlantic Forest. The objective of this study was to describe comparatively the anatomy of vegetative organs and floral micromorphology of all species of Acianthera section Pleurobotryae in order to identify diagnostic characters between them and synapomorphies for the section in relation of other sections of the genus. We analyzed roots, ramicauls, leaves and flowers of 15 species, covering eight of the nine sections of Acianthera, using light microscopy and scanning electron microscopy. Acianthera section Pleurobotryae is a monophyletic group and the cladistic analyses of anatomical and flower micromorphology data, combined with molecular data, support internal relationship hypotheses among the representatives of this section. The synapomorphies identified for A. sect. Pleurobotryae are based on leaf anatomy: unifacial leaves, round or elliptical in cross-section, round leaves with vascular bundles organized in concentric circles, and mesophyll with 28 to 30 cell layers. Within the section, the clade (A. crepiniana + A. mantiquyrana) presented more differences in vegetative organ morphology and higher support values in combined analyses when compared to the second clade, (A. atropurpurea + A. hatschbachii). For each of these clades an exclusive set of homoplasies of vegetative and floral organs were also identified. The results support the argument that vegetative organs are more evolutionarily stable in comparison to reproductive organs and thus helpful for inference of internal phylogenetic relationships in Acianthera, while flowers are highly variable, perhaps due to the diversity of pollinator attraction mechanisms. The analyses indicate that the elliptical leaves observed in A. crepiniana have originated from round leaves observed in the other species of this section, suggesting an adaptation to increase the area of exposure of the leaf and better the efficiency of capture of sunlight in shaded environments such as the Atlantic Forest. The presence of papillose regions in both vegetative and floral organs indicated that micromorphological characters are also useful for the delimitation of species and sections within the genus.
Assuntos
Evolução Biológica , Flores , Orchidaceae , Filogenia , Folhas de Planta , Polinização , Flores/fisiologia , Flores/ultraestrutura , Microscopia Eletrônica de Varredura , Orchidaceae/classificação , Orchidaceae/fisiologia , Orchidaceae/ultraestrutura , Folhas de Planta/fisiologia , Folhas de Planta/ultraestrutura , Polinização/fisiologiaRESUMO
Caryocar brasiliense is a flagship species of the Brazilian Cerrado. It produces flowers with a strong peculiar scent, which are pollinated by bats and occasionally moths with short mouthparts. However, the cues responsible for attracting these nocturnal pollinators remain unknown. We aimed to identify osmophores of C. brasiliense, describe the ultrastructure of the cells involved in the synthesis and release of floral odour, and identify the constituents of the floral bouquet. We performed field observations and histochemical and ultrastructural analyses of flowers focusing on the androecium. Gas chromatography-mass spectrometry was used to analyse the scents emitted. Filament epidermal cells were found to possess an unusual shape and be responsible for the main production and release of odour. These cells, called foraminous cells, are elongate and possess pores where their cell walls are abruptly thin. The cuticle is practically absent over the pores, which facilitates odour emission. The foraminous cells have conspicuous nuclei and organelle-rich cytoplasm where oil droplets can be seen prior to anthesis. The features of these cells remain similar during anthesis, but many vesicles fuse with the plasma membrane and the number of oil droplets in the cytosol decreases. Twenty-nine components were found in the scent, especially fatty acid derivatives and N- and S-bearing compounds. Our analyses revealed that the androecium of C. brasiliense has a particular structure that acts as an osmophore. The scent from the androecium resembles that of the entire flower, which is an unprecedented finding for a plant with single flowers as the pollination unit.
Assuntos
Ericales/ultraestrutura , Flores/ultraestrutura , Odorantes/análise , Compostos Orgânicos Voláteis/análise , Ericales/fisiologia , Flores/química , Flores/citologia , Flores/fisiologia , Cromatografia Gasosa-Espectrometria de Massas , Humanos , Células Vegetais/fisiologia , Células Vegetais/ultraestrutura , Polinização , Compostos Orgânicos Voláteis/químicaRESUMO
The morpho-anatomical structure of nectaries, osmophores, and elaiophores, and the anatomical and micromorphological features of floral pieces of Cohniella cepula Hoffmans. and Cohniella jonesiana Rchb.f. were comparatively analyzed. In both species, bracteal and sepal nectaries are structured, i.e., they present a secretory epidermis, secretory parenchyma, and vascular bundles. Nectar secretion is released through stomata. The anatomical and micromorphological traits are similar in both nectaries, which can be detected only if the nectar drops are secreted. Considering the location of these nectaries, the secreted nectar would not be a reward to pollinators. Osmophores are located at the base of both callus and laterals lobes, and consist of a layer of secretory epidermis composed of quadrangular cells and papillae. Elaiophores are found on the callus of the labellum and are of the epithelial type. The anatomical features of floral pieces are similar in both species. The anatomical analysis of sepals and petals showed a few differences, which could be of potential taxonomic value. Our results contribute valuable and novel information for the knowledge of these species and the genus, which will be useful in future taxonomic evaluations.
Assuntos
Flores/anatomia & histologia , Orchidaceae/anatomia & histologia , Néctar de Plantas/fisiologia , Flores/citologia , Flores/ultraestrutura , Orchidaceae/citologia , Orchidaceae/ultraestruturaRESUMO
Pollination in Solanum (Solanaceae) species is commonly performed by female bees, which vibrate anthers to extract pollen. Another pollen removal type is by male euglossine bees, milking the anthers when searching for floral scents produced by secretory tissues (osmophorous) at the swollen connective of the anthers of species in the Cyphomandra clade. Some species of this clade, however, are buzz-pollinated and present papillate anthers that should also have secretory activity, a hypothesis here tested. The anthers of Solanum luridifuscescens were fixed at different stages of development and analysed under light microscopy, SEM and TEM. Histochemical tests for the detection of starch and lipids were done. Epidermal cells of the abaxial surface of the anthers were visibly papillose, had large nuclei and dense cytoplasm rich in organelles such as mitochondria and plastids, typical features of secretory tissues. In this site, lipid droplets were detected, concomitantly with starch consumption, compatible with the secretory process in osmophores. No exudate or accumulation of substances was seen on the surface; in agreement with a previous pollination study performed in field conditions, where no pollinators were observed collecting floral scents, only pollen. The histochemical and structural analyses have evidenced the lipidic composition of the secretion, strongly pointing to terpenes as the secreted compounds. Ours findings show that papillae of the anthers have secretory activities that produce lipophilic compounds. This does not result in resources for bees, but could be an evolutionary step to the development of more specialised anthers in the Cyphomandra clade.
Assuntos
Flores/anatomia & histologia , Solanum/anatomia & histologia , Solanum/fisiologia , Animais , Abelhas , Flores/citologia , Flores/metabolismo , Flores/ultraestrutura , Gotículas Lipídicas , Microscopia Eletrônica de Varredura , Microscopia Eletrônica de Transmissão , Células Vegetais/ultraestrutura , Polinização , Terpenos/metabolismoRESUMO
The family Malpighiaceae, particularly in the Neotropic, shows a similar floral morphology. Although floral attraction and rewards to pollinators are alike, stigmas and styles show more diversity. The stigmas were described covered with a thin and impermeable cuticle that needs to be ruptured by the mechanical action of the pollinators. However, this characteristic was only mentioned for a few species and the anatomy and ultrastructure of the stigmas were not explored. In this work, we analyze the morphology, anatomy, and ultrastructure of the stigma and style of Callaeum psilophyllum. Moreover, we identify the potential pollinators in order to evaluate how the disposition of the stigmas is related with their size and its role in the exposure of the receptive stigmatic surface. Our observations indicate that Centris flavifrons, C. fuscata, C. tarsata, and C. trigonoides are probably efficient pollinators of C. psilophyllum. The three stigmas are covered by a cuticle that remained intact in bagged flowers. The flowers exposed to visitors show the cuticle broken, more secretion in the intercellular spaces between sub-stigmatic cells and abundant electron-dense components inside vacuoles in stigmatic papillae. This indicates that the stigmas prepares in similar ways to receive pollen grains, but the pollinator action is required to break the cuticle, and once pollen tubes start growing, stigmatic and sub-stigmatic cells release more secretion by a granulocrine process.
Assuntos
Malpighiaceae/fisiologia , Flores/metabolismo , Flores/fisiologia , Flores/ultraestrutura , Malpighiaceae/metabolismo , Malpighiaceae/ultraestrutura , Polinização/fisiologiaRESUMO
We present a comparative flower ontogenetic study in five species of the genus Eucryphia with the aim of testing whether differences in the organ number observed can be explained by changes in the meristematic size of floral meristem and floral organs. Species native to Oceania, viz. E. milliganii, E. lucida and E. moorei, have the smallest gynoecia with ca. 6 carpels, while the Chilean E. glutinosa and E. cordifolia present more than ten carpels. E. milliganii has the smallest flower with the lowest stamen number (ca. 50), while the other species produce around 200 stamens and more. Standardized measurements of meristematic sectors were taken in 49 developing flowers that were classified into three well-defined ontogenetic stages. Sizes of meristems varied significantly among species within each developmental stage as revealed by ANOVA analyses. Significant regressions between organ number and corresponding meristem size were consistent with the premise that a larger meristem size prior to organ initiation could be determining for a higher organ number. Flower organogenesis in Eucryphia also involves relevant meristem expansion while the organs are initiated, which results in a particular androecium patterning with a chaotic stamen arrangement. Meristem expansion also appears to be slower but more extensive in species with larger initial meristematic size, suggesting that flower phenotype can be determined in ontogeny by this heterochronic interplay of space and time.
Assuntos
Flores/crescimento & desenvolvimento , Magnoliopsida/crescimento & desenvolvimento , Meristema/crescimento & desenvolvimento , Organogênese Vegetal , Flores/genética , Flores/fisiologia , Flores/ultraestrutura , Magnoliopsida/genética , Magnoliopsida/fisiologia , Magnoliopsida/ultraestrutura , Meristema/genética , Meristema/fisiologia , Meristema/ultraestrutura , FenótipoRESUMO
Genlisea violacea is a Brazilian endemic carnivorous plant species distributed in the cerrado biome, mainly in humid environments, on sandy and oligotrophic soil or wet rocks. Studies on reproductive biology or pollination in the Lentibulariaceae are notably scarce; regarding the genus Genlisea, the current study is the first to show systematic and standardised research on reproductive biology from field studies to describe the foraging of visiting insects and determine the effective pollinators of Genlisea. We studied two populations of G. violacea through the observation of flower visitors for 4 months of the rainy and dry seasons. Stigmatic receptivity, pollen viability, and breeding system were evaluated together with histochemistry and morphological analyses of flowers. The flowers showed stigmatic receptivity of 100% in open buds and mature flowers, reducing to 80% for senescent flowers. Nearly 80% of pollen grains are viable, decreasing to 40-45% after 48 h. Nectar is produced by glandular trichomes inside the spur. Two bee species are effective pollinators: one of the genus Lasioglossum (subgenus Dialictus: Halictidae) and the other of the genus Ceratina (subgenus Ceratinula: family Apidae). Moreover, bee-like flies of the Syrphidae family may also be additional pollinators. Genlisea violacea is an allogamous and self-compatible species. The differences in flower-visiting fauna for both populations can be attributed to factors such as climate, anthropogenic effect, seasonal factors related to insects and plants, as well as the morphological variation of flowers in both populations.
Assuntos
Lamiales/fisiologia , Polinização/fisiologia , Brasil , Carnivoridade/fisiologia , Flores/anatomia & histologia , Flores/fisiologia , Flores/ultraestrutura , Lamiales/anatomia & histologia , Reprodução/fisiologiaRESUMO
The perianth organs of six species of Nymphaeaceae, representing Euryale, Nymphaea and Victoria, were studied on the basis of macroscopical, micromorphological, and anatomical characters. The aims were to determine whether perianth is differentiated among tepal whorls considering the presence of sepaloid and petaloid characters, and to evaluate the occurrence of both features in individual tepals. Selected perianth series were examined macroscopically, with light microscopy, and scanning electron microscopy. Osmophores were detected using neutral red and Sudan. In all tepals examined, stomata and hydropotes were present on the abaxial and adaxial surfaces. These are anomocytic or stephanocytic; hydropotes of irregular type are also present. The outer series of tepals display morpho-anatomical characters in most part related with photosynthetic and protective functions. Osmophore activity is very scarce and petaloid epidermal morphology is present only in N. lotus, thus allowing interpretation of this whorl as primarily sepaloid. The second series exhibits both petal-like and sepal-like characters; in N. amazonum and N. gardneriana sepaloid and petaloid group of cells are present on the abaxial surface of individual tepals. Therefore, this whorl is transitional between the outer and the innermost ones. Both the morpho-anatomy and presence of osmophore activity indicate that the innermost series is entirely petaloid. Inner tepals of E. ferox, N. alba, and V. cruziana share the presence of epidermal cells with predominantly smooth cuticle, whereas those of N. amazonum, N. gardneriana, and N. lotus share a cuticular ornamentation consisting of numerous papillae on each cell. Morphological characters of the perianth epidermis are in some respects congruent with the molecular phylogeny of Nymphaeaceae. Our results support the co-expression of sepaloidy and petaloidy within individual tepals and the mosaic model of perianth evolution proposed for the angiosperms.
Assuntos
Flores/ultraestrutura , Nymphaeaceae/ultraestrutura , Flores/genética , Microscopia Eletrônica de Varredura , Nymphaeaceae/genética , Epiderme Vegetal/genética , Epiderme Vegetal/ultraestrutura , Estômatos de Plantas/genética , Estômatos de Plantas/ultraestruturaRESUMO
We investigated the morphology and structure of the floral nectary in 11 Neotropical genera belonging to the subfamilies Dodonaeoideae and Paullinioideae (Sapindaceae) from southern South America representing three tribes (Dodonaeaeae, Paullinieae, and Melicocceae), in relation to other floral traits in species with contrasting morphological flower characteristics. Nectary organization was analyzed under light, stereoscopic, and scanning electron microscopes; Diplokeleba floribunda N.E. Br. was also observed using transmission electron microscopy. Our comparative data may contribute to the understanding of floral nectary evolution and systematic value in this family. The nectaries were studied in both staminate and pistillate flowers. All the floral nectaries are typical of Sapindaceae: extrastaminal, receptacular, structured, and persistent. The anatomical analysis revealed a differentiated secretory parenchyma and an inner non-secretory parenchyma; the nectary is supplied by phloem traces and, less frequently, by phloem and xylem traces. Nectar is secreted through nectarostomata of anomocytic type. The anatomical analysis showed the absence of nectary in the three morphs of Dodonaea viscosa flowers. Nectary ultrastructure is described in D. floribunda. In this species, the change in nectary color is related to progressive accumulation of anthocyanins during the functional phase. We found relatively small variation in the nectary structural characteristics compared with large variation in nectary morphology. The latter aspect agreed with the main infrafamilial groupings revealed by recent phylogenetic studies, so it is of current valuable systematic importance for Sapindaceae. In representatives of Paullinieae, the reduction of the floral nectary to 4-2 posterior lobes should be interpreted as a derived character state.
Assuntos
Flores/ultraestrutura , Sapindaceae/ultraestrutura , Flores/metabolismo , Microscopia Eletrônica de Varredura , Microscopia Eletrônica de Transmissão , Epiderme Vegetal/ultraestrutura , Néctar de Plantas/biossíntese , Feixe Vascular de Plantas/ultraestrutura , Sapindaceae/metabolismoRESUMO
PREMISE OF THE STUDY: Pentaclethra and Dimorphandra (Leguminosae) have long been considered a possible enigmatic link between caesalpinioids and mimosoids because they both have an imbricate calyx and heteromorphic androecium, floral features that are rare among mimosoids but common among caesalpinioids. This study compared the developing flowers of Dimorphandra mollis and Pentaclethra macroloba to determine whether the shared floral conditions also have the same ontogenetic origin. METHODS: Buds of different sizes and flowers were processed for surface (scanning electron microscopy) and histological (light microscopy) examination. KEY RESULTS: The floral meristem initiates five sepal primordia in a modified helical order in both species. The median sagittal sepal is adaxial. The overlap of the sepals during elongation culminates with the formation of the imbricate calyx. Heteromorphic androecia arise in the intermediate stages of development. In P. macroloba, the fertile pollen-bearing stamens are antesepalous, robust and short, and the anthers carry a robust apical gland; the staminodes are long and white with a vestigial apical gland. In contrast, in D. mollis the fertile pollen-bearing stamens are antepetalous without glands and as long as the staminodes. The staminodes are thinner with an expanded apical region. CONCLUSIONS: The imbricate calyx and the heteromorphic androecium in the studied species originated via distinct pathways, favoring the hypothesis of homoplasy of these conditions. The pathways observed in P. macroloba are more similar to those observed in caesalpinioids than to those observed in mimosoids, indicating that although the floral development differs between the species studied, it supports the basal placement of Pentaclethra among mimosoids.
Assuntos
Fabaceae/crescimento & desenvolvimento , Flores/crescimento & desenvolvimento , Meristema/crescimento & desenvolvimento , Fabaceae/classificação , Fabaceae/genética , Flores/anatomia & histologia , Flores/ultraestrutura , Meristema/anatomia & histologia , Meristema/ultraestrutura , Microscopia Eletrônica de Varredura , Filogenia , Pólen/citologia , Pólen/crescimento & desenvolvimento , Pólen/ultraestrutura , Reprodução , Especificidade da EspécieRESUMO
PREMISE OF THE STUDY: Loranthaceae, Santalaceae, and Viscaceae are the most diversified hemiparasitic families of Santalales in the Andes. Their partial inflorescences (PIs) vary from solitary flowers, or dichasia in most Santalales, to congested floral groups along articles in most Viscaceae. The atypical articled inflorescences in Phoradendreae (Viscaceae), a phylogenetic novelty restricted to this tribe, have been variously described as racemes, spikes, fascicles, or as intercalary inflorescences, but no developmental studies have been performed to compare them with the construction of PIs across Santalales. METHODS: We used standard light microscopy and scanning electron microscopy to record the inflorescence development in members of Phoradendreae (Viscaceae) in comparison to those in species of Aetanthus, Gaiadendron, Oryctanthus, Passovia, and Peristethium (Loranthaceae) and Antidaphne (Santalaceae). KEY RESULTS: Morphological and developmental comparisons as well as optimization onto a phylogenetic framework indicate that individual inflorescences in Santalales are indeterminate and are formed by axillary cymose PIs. The latter correspond to dichasia, either simple, compound, or variously reduced by abortion of lateral flowers, abortion of the terminal flower, or loss of bracteoles. CONCLUSIONS: Dichasia are plesiomorphic in Santalales. These results favor the interpretation that inflorescences in Phoradendreae are formed by the fusion of serial dichasia (=floral rows) with the main inflorescence axis via syndesmy. We compared this interpretation with the competing one based on the co-occurrence of collateral and serial floral buds.
Assuntos
Flores/anatomia & histologia , Inflorescência/anatomia & histologia , Magnoliopsida/anatomia & histologia , Flores/crescimento & desenvolvimento , Flores/ultraestrutura , Inflorescência/crescimento & desenvolvimento , Inflorescência/ultraestrutura , Loranthaceae/anatomia & histologia , Loranthaceae/classificação , Loranthaceae/ultraestrutura , Magnoliopsida/classificação , Magnoliopsida/ultraestrutura , Microscopia Eletrônica de Varredura , Santalaceae/anatomia & histologia , Santalaceae/classificação , Santalaceae/ultraestrutura , Especificidade da Espécie , Viscaceae/anatomia & histologia , Viscaceae/classificação , Viscaceae/ultraestruturaRESUMO
BACKGROUND AND AIMS: Recent developments in DNA sequencing, so-called next-generation sequencing (NGS) methods, can help the study of rare lineages that are known from museum specimens. Here, the taxonomy and evolution of the Malagasy grass lineage Chasechloa was investigated with the aid of NGS. METHODS: Full chloroplast genome data and some nuclear sequences were produced by NGS from old herbarium specimens, while some selected markers were generated from recently collected Malagasy grasses. In addition, a scanning electron microscopy analysis of the upper floret and cross-sections of the rachilla appendages followed by staining with Sudan IV were performed on Chasechloa to examine the morphology of the upper floret and the presence of oils in the appendages. KEY RESULTS: Chasechloa was recovered within tribe Paniceae, sub-tribe Boivinellinae, contrary to its previous placement as a member of the New World genus Echinolaena (tribe Paspaleae). Chasechloa originated in Madagascar between the Upper Miocene and the Pliocene. It comprises two species, one of them collected only once in 1851. The genus is restricted to north-western seasonally dry deciduous forests. The appendages at the base of the upper floret of Chasechloa have been confirmed as elaiosomes, an evolutionary adaptation for myrmecochory. CONCLUSIONS: Chasechloa is reinstated at the generic level and a taxonomic treatment is presented, including conservation assessments of its species. Our study also highlights the power of NGS technology to analyse relictual or probably extinct groups.
Assuntos
Espécies em Perigo de Extinção , Poaceae/genética , DNA de Plantas/genética , DNA de Plantas/isolamento & purificação , Flores/ultraestrutura , Sequenciamento de Nucleotídeos em Larga Escala , Madagáscar , Microscopia Eletrônica de Varredura , Filogenia , Poaceae/classificação , Poaceae/ultraestruturaRESUMO
Utricularia cornigera and Utricularia nelumbifolia are giant, aquatic-epiphytic species of carnivorous bladderwort from southeastern Brazil that grow in the central 'urns' of bromeliads. Both species have large, colourful flowers. The main aim of our study is to ascertain whether the prominent floral palate of U. cornigera and U. nelumbifolia functions as an unguentarius-i.e. an organ that bears osmophores. Floral tissues of both species were investigated using light microscopy, scanning electron microscopy, transmission electron microscopy and histochemistry. Floral palates of U. cornigera and U. nelumbifolia provide clear visual signals for pollinating insects. In both species, the palate possesses diverse micro-morphology, comprising unicellular, conical to villiform papillae and multicellular, uniseriate, glandular trichomes that frequently display terminal branching. The most characteristic ultrastructural feature of these papillae was the presence of relatively large, polymorphic plastids (chromoplasts) containing many plastoglobuli. Similar plastids are known to occur in the fragrance-producing (osmophores) and oil-producing (elaiophores) tissues of several orchid species. Thus, these palate papillae may play a key role in providing the olfactory stimulus for the attraction of insect pollinators. Nectariferous trichomes were observed in the floral spurs of both species, and in U. nelumbifolia, free nectar was also recorded. The location, micro-morphology, anatomy and ultrastructure of the floral palate of the two species investigated may thus indicate that the palate functions as an unguentarius. Furthermore, the flowers of these taxa, like those of U. reniformis, have features consistent with bee pollination.
Assuntos
Organismos Aquáticos/virologia , Flores/ultraestrutura , Lamiaceae/ultraestrutura , Organismos Aquáticos/ultraestrutura , Brasil , Flores/anatomia & histologia , Flores/citologia , Imuno-Histoquímica , Lamiaceae/anatomia & histologia , Lamiaceae/citologia , Néctar de PlantasRESUMO
Cabomba Aubl. is a genus that presents a range of features that have made it to be considered a potential genetic model for studies of early angiosperm evolution. Therefore, any study that expands our knowledge of this genus is potentially useful for the understanding of the evolution of early angiosperms. This paper reports the study of the anatomy and the ultrastructure of the stigma and the style of Cabomba caroliniana Gray during the 2 days of anthesis using bright-field microscope, fluorescence microscope and transmission electron microscope. The stigma is dry and has pluricellular papillae. The style is hollow with a central canal coated by an epithelium. The papillae have fewer organelles than those typical of glandular cells, and they are covered by a cuticle that is broken when pollen germinates. The ultrastructure of epithelial cells indicates that the cells lining the canal are secretory. The canal is filled with a fibrillar and granular substance. The pollen tubes grow inside the canal through this substance. The results are discussed in the context of what is known for other species of angiosperms.
Assuntos
Flores/ultraestrutura , Magnoliopsida/ultraestrutura , Epitélio/ultraestrutura , Flores/citologia , Germinação , Magnoliopsida/citologia , Tubo Polínico/citologia , Tubo Polínico/crescimento & desenvolvimento , Tubo Polínico/ultraestruturaRESUMO
Postbloom fruit drop (PFD) is an important disease caused by the fungus Colletotrichum acutatum. PFD is characterised by the formation of necrotic lesions on the petals and stigmas of flowers as well as premature abscission of the fruit in Citrus spp. We compare the ultrastructure of the epidermis of uninoculated Citrus sinensis petals with that of petals inoculated with the fungus to understand the changes that occur upon C. acutatum infection. Healthy petals have a cuticle with parallel striations covering the uniseriate epidermis. This pattern consists of vacuolated parietal cells whose cytoplasm contains mitochondria, plastids with an undeveloped endomembrane system and a slightly dense stroma, a poorly developed rough endoplasmic reticulum, polysomes, few lipid droplets, and a nucleus positioned near the inner periclinal wall. In damaged regions, the cytoplasm of some cells is densely packed with well-developed endoplasmic reticulum, a large number of hyperactive dictyosomes, numerous mitochondria, and many lipid droplets. The plastids have an electron-dense stroma, starch grains, and a large amount of electron-dense lipid droplets, which can be released into vacuoles or the endoplasmic reticulum. Multivesicular bodies and myelin bodies are frequently observed in the vacuole, cytoplasm, and periplasmic space. Vesicles migrate through the cell wall and are involved in the deposition of cuticular material. In the later stages of infection, there is deposition of new cuticle layers in plaques. The outer periclinal walls can be thick. These observations indicate that epidermal cells respond to the pathogen, resulting in cuticular and parietal changes, which may limit further infection.
Assuntos
Citrus sinensis/microbiologia , Colletotrichum/patogenicidade , Flores/ultraestrutura , Doenças das Plantas/microbiologia , Epiderme Vegetal/ultraestrutura , Núcleo Celular/ultraestrutura , Citoplasma/ultraestrutura , Retículo Endoplasmático/patologia , Flores/microbiologia , Microscopia Eletrônica de Varredura , Microscopia Eletrônica de Transmissão , Mitocôndrias/ultraestrutura , Epiderme Vegetal/microbiologia , PlastídeosRESUMO
Biotic pollination is critical for tropical ecosystem functioning, and nectar plays an essential role as it represents the main trophic resource for pollinators. Nevertheless, little is known about the mechanisms that underlie its production, which is essential for understanding the basis of nectar-mediated interactions in ecological and evolutionary approaches. Therefore, this study explores the relationship between the nectar secretion pattern and nectary functional changes in Anemopaegma album, a bee-pollinated species. We analysed the pattern of nectar production under field conditions and investigated floral nectary structural changes in two different developmental stages using light, transmission and scanning electron microscopy. We measured 30.95 ± 23.02 µl (mean ± SD, n = 30) of nectar accumulated inside the nectar chamber (29.26 ± 3.48% sucrose equivalents) at the moment of flower opening. Nectar removal did not influence the pattern of floral nectar production in terms of volume or total sugar but reduced the concentration of the nectar produced during the first 24 h of anthesis. The nectary consisted of an epidermis, a nectary parenchyma and a subnectary parenchyma supplied only by phloem. Starch grains decreased in size and abundance from the subnectary parenchyma toward the epidermis. We observed the degradation of starch grains and incorporation of amyloplasts into vacuoles at the pre-anthesis stage as well as the transformation of amyloplasts into elaioplasts during anthesis. Nectar secretion was continuous during the A. album flower life span, which was related to the functional features of its floral nectary, especially the presence of starch stored in the parenchyma.
Assuntos
Bignoniaceae/fisiologia , Flores/fisiologia , Néctar de Plantas/metabolismo , Polinização , Animais , Abelhas , Brasil , Flores/anatomia & histologia , Flores/ultraestrutura , Microscopia Eletrônica de Varredura , Néctar de Plantas/química , Plastídeos/ultraestrutura , Amido/metabolismoRESUMO
UNLABELLED: ⢠PREMISE OF THE STUDY: In angiosperms, several carpel tissues are specialized to facilitate pollen-tube elongation to achieve fertilization. We evaluated the possible evolutionary pathways of the diverse female reproductive tracts in Nyctaginaceae.⢠METHODS: We studied the anatomy of a range of species representing different tribes, using light, fluorescence, scanning electron, and transmission electron microscopy.⢠KEY RESULTS: Stigmas have multicellular, multiseriate papillae, except for Boerhavia diffusa with unicellular papillae. The styles are solid, with a strand of transmitting tissue linking the stigma with the ventral ovary wall. In Allionia, Boerhavia, and Mirabilis, the transmitting tissue branches into two independent tracts at the base of the ovary and continues across the lateral margins of the funicle to the micropyle; it is composed of cells with thick walls surrounded by abundant extracellular matrix. Bougainvillea, Pisonia, and Pisoniella have a diffuse transmitting tissue and an obturator, a proliferation of cells covered by a layer of secretory papillae that encloses the funicle, placenta, and ventral wall of the gynoecium and contacts with the micropyle.⢠CONCLUSIONS: We propose two models of female reproductive tract, (A) one in which an obturator is absent and the transmitting tissue is compact and branched and (B) one in which an obturator is present and the transmitting tissue is diffuse. On the basis of character optimization, we hypothesize that model B represents the ancestral (plesiomorphic) condition in the family and model A originated once during evolution, within the tribe Nyctagineae.