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1.
Mycologia ; 108(2): 303-12, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-26740543

RESUMO

Litter layers in the Lower Devonian (~ 410 Ma) Rhynie chert were inhabited by a wide variety of saprotrophic fungi, however, only a few of these organisms have been described formally. A new microfungus, Trewinomyces annulifer gen. et sp. nov., occurs as tufts on decaying land plant axes from the Rhynie chert. The fungus consists of an intramatrical rhizoidal system and an erect extramatrical hypha (stalk) that bears a single, terminal sporangium. One or two successive rings often are present in the stalk immediately below the sporangium base. Overall morphology of T. annulifer resembles the extant genera Macrochytrium (Chytridiomycota) and Blastocladiella (Blastocladiomycota). However, the rhizoids are septate or pseudoseptate, a feature not known in extant zoosporic fungi, and thus render the systematic affinities of T. annulifer unresolved. Trewinomyces annulifer offers a rare view of the morphology of a distinctive Early Devonian saprotrophic microfungus.


Assuntos
Blastocladiomycota/citologia , Quitridiomicetos/citologia , Fósseis , Blastocladiomycota/classificação , Quitridiomicetos/classificação , Especificidade da Espécie
2.
Mycologia ; 108(5): 1028-1046, 2016 09.
Artigo em Inglês | MEDLINE | ID: mdl-27738200

RESUMO

Zygomycete fungi were classified as a single phylum, Zygomycota, based on sexual reproduction by zygospores, frequent asexual reproduction by sporangia, absence of multicellular sporocarps, and production of coenocytic hyphae, all with some exceptions. Molecular phylogenies based on one or a few genes did not support the monophyly of the phylum, however, and the phylum was subsequently abandoned. Here we present phylogenetic analyses of a genome-scale data set for 46 taxa, including 25 zygomycetes and 192 proteins, and we demonstrate that zygomycetes comprise two major clades that form a paraphyletic grade. A formal phylogenetic classification is proposed herein and includes two phyla, six subphyla, four classes and 16 orders. On the basis of these results, the phyla Mucoromycota and Zoopagomycota are circumscribed. Zoopagomycota comprises Entomophtoromycotina, Kickxellomycotina and Zoopagomycotina; it constitutes the earliest diverging lineage of zygomycetes and contains species that are primarily parasites and pathogens of small animals (e.g. amoeba, insects, etc.) and other fungi, i.e. mycoparasites. Mucoromycota comprises Glomeromycotina, Mortierellomycotina, and Mucoromycotina and is sister to Dikarya. It is the more derived clade of zygomycetes and mainly consists of mycorrhizal fungi, root endophytes, and decomposers of plant material. Evolution of trophic modes, morphology, and analysis of genome-scale data are discussed.


Assuntos
Fungos/classificação , Fungos/genética , Genoma Fúngico , Filogenia
3.
Proc Natl Acad Sci U S A ; 109(51): 20971-4, 2012 Dec 18.
Artigo em Inglês | MEDLINE | ID: mdl-23213234

RESUMO

Our understanding of the evolution of life on Earth is limited by the imperfection of the fossil record. One reason for this imperfect record is that organisms without hard parts, such as bones, shells, and wood, have a very low potential to enter the fossil record. Occasionally, however, exceptional fossil deposits that preserve soft-bodied organisms provide a rare glimpse of the true biodiversity during past periods of Earth history. We here present an extraordinary find of a fossil ciliate that is encased inside the wall layer of a more than 200 Ma leech cocoon from Antarctica. The microfossil consists of a helically contractile stalk that attaches to a main body with a peristomial feeding apparatus and a large C-shaped macronucleus. It agrees in every aspect with the living bell animals, such as Vorticella. Vorticellids and similar peritrichs are vital constituents of aquatic ecosystems worldwide, but so far have lacked any fossil record. This discovery offers a glimpse of ancient soft-bodied protozoan biotas, and also highlights the potential of clitellate cocoons as microscopic "conservation traps" comparable to amber.


Assuntos
Biodiversidade , Fósseis , Sanguessugas/fisiologia , Animais , Regiões Antárticas , Evolução Biológica , Ecossistema , Geografia , Invertebrados , Paleontologia/métodos
4.
Proc Natl Acad Sci U S A ; 108(33): 13630-4, 2011 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-21808011

RESUMO

Mycorrhizal root nodules occur in the conifer families Araucariaceae, Podocarpaceae, and Sciadopityaceae. Although the fossil record of these families can be traced back into the early Mesozoic, the oldest fossil evidence of root nodules previously came from the Cretaceous. Here we report on cellularly preserved root nodules of the early conifer Notophytum from Middle Triassic permineralized peat of Antarctica. These fossil root nodules contain fungal arbuscules, hyphal coils, and vesicles in their cortex. Numerous glomoid-type spores are found in the peat matrix surrounding the nodules. This discovery indicates that mutualistic associations between conifer root nodules and arbuscular mycorrhizal fungi date back to at least the early Mesozoic, the period during which most of the modern conifer families first appeared. Notophytum root nodules predate the next known appearance of this association by 100 million years, indicating that this specialized form of mycorrhizal symbiosis has ancient origins.


Assuntos
Micorrizas , Nódulos Radiculares de Plantas , Traqueófitas , Regiões Antárticas , Fósseis , Micorrizas/citologia , Micorrizas/fisiologia , Raízes de Plantas , Nódulos Radiculares de Plantas/citologia , Nódulos Radiculares de Plantas/fisiologia , Solo , Simbiose
5.
Mycologia ; 105(3): 521-9, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23233506

RESUMO

The Eocene (~ 48.7 Ma, Ypresian-Lutetian) Princeton Chert of British Columbia, Canada, has long been recognized as a significant paleobotanical locality, and a diverse assemblage of anatomically preserved fossil plants has been extensively documented. Co-occurring fossil fungi also have been observed, but the full scope of their diversity has yet to be comprehensively assessed. Here, we present the first of a series of investigations of fossilized fungi associated with the silicified plants of the Princeton Chert. This report focuses on saprotrophic, facultative-aquatic hyphomycetes observed in cortical aerenchyma tissue of an enigmatic angiosperm, Eorhiza arnoldii. Our use of paleontological thin sections provides the opportunity to observe and infer developmental features, making it possible to more accurately attribute two hyphomycetes that were observed in previous studies. These comprise multiseptate, holothallic, chlamydospore-like phragmoconidia most similar to extant Xylomyces giganteus and basipetal phragmospore-like chains of amerospores like those of extant Thielaviopsis basicola. We also describe a third hyphomycete that previously has not been recognized from this locality; biseptate, chlamydosporic phragmoconidia are distinguished by darkly melanized, inflated apical cells and are morphologically similar to Brachysporiella rhizoidea or Culcitalna achraspora.


Assuntos
Fósseis , Magnoliopsida/microbiologia , Fungos Mitospóricos/isolamento & purificação , Fungos Mitospóricos/fisiologia , Fungos Mitospóricos/genética , Fungos Mitospóricos/ultraestrutura , Paleontologia
6.
Mycologia ; 105(5): 1100-9, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23709575

RESUMO

Tissues of the extinct aquatic or emergent angiosperm, Eorhiza arnoldii incertae sedis, were extensively colonized by microfungi, and in this study we report the presence of several types of sterile mycelia. In addition to inter- and intracellular proliferation of regular septate hyphae, the tissues contain monilioid hyphae with intercalary branching. These filamentous mycelia are spatially associated with two distinct morphotypes of intracellular microsclerotia. These quiescent structures are morphologically similar to loose and cerebriform microsclerotia found within the living tissues of some plants, which have been attributed to an informal assemblage of dematiaceous ascomycetes, the dark-septate endophytes. While there are significant challenges to interpreting the ecology of fossilized fungi, these specimens provide evidence for asymptomatic endophytic colonization of the rooting structures of a 48.7 million year old aquatic angiosperm.


Assuntos
Magnoliopsida/microbiologia , Fungos Mitospóricos/ultraestrutura , Endófitos/isolamento & purificação , Endófitos/ultraestrutura , Fósseis , Hifas/isolamento & purificação , Hifas/ultraestrutura , Fungos Mitospóricos/isolamento & purificação , Paleontologia , Rizoma/microbiologia
7.
J Am Pharm Assoc (2003) ; 53(4): 373-81, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23892810

RESUMO

OBJECTIVE: To describe the relationship between state-level Aggregate Demand Index (ADI) data and market factors reflecting both supply and demand: unemployment rates, pharmacy graduates, community pharmacy prescription growth rates, and Medicare Part D. DESIGN: Cross-sectional time series analysis using state-level data. SETTING: U.S. labor market for pharmacists, from 2001 to 2010. INTERVENTION: Model ADI data for states (dependent variable) against five independent variables: previous year ADI, unemployment rates, pharmacy graduates, prescription growth rates, and Medicare Part D. MAIN OUTCOME MEASURES: Significance and predictive ability of the model, sign of the variables studied, and R2. RESULTS: In the two-way (state and time) fixed-effects model, all variables were significant and R2 was 0.79. Contributions to state-level ADIs were, in rank order, previous year ADI, unemployment rates, pharmacy graduates, and prescription growth rates. The model predicted 2010 ADI values for 44 of 51 states within ±10%. The model depicts the independent contributions of each variable for the short (∼1 year) and longer term. Although the nature of ADI data precludes quantitative predictions about the pharmacist job market, the model results show marketplace directions (up or down) and comparative impacts. CONCLUSION: The model demonstrated that unemployment rates, pharmacy graduates, prescription growth rates, and Medicare Part D contributed significantly to state-level ADIs between 2001 and 2010. The relationships uncovered should be monitored and reexamined as new data emerge in order to anticipate the directions of the pharmacist job market.


Assuntos
Emprego , Necessidades e Demandas de Serviços de Saúde , Assistência Farmacêutica , Farmácias , Farmacêuticos/provisão & distribuição , Estudos Transversais , Prescrições de Medicamentos , Emprego/estatística & dados numéricos , Necessidades e Demandas de Serviços de Saúde/estatística & dados numéricos , Humanos , Medicare Part D , Modelos Estatísticos , Assistência Farmacêutica/estatística & dados numéricos , Farmácias/estatística & dados numéricos , Farmacêuticos/estatística & dados numéricos , Fatores de Tempo , Desemprego , Estados Unidos , Recursos Humanos , Carga de Trabalho
8.
Med Care ; 50(8): 685-91, 2012 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-22354211

RESUMO

BACKGROUND: There have been a number of studies relating medication adherence to patient characteristics. There is less research on influence of health care providers on patients' medication-taking behavior. OBJECTIVES: To evaluate the pharmacy-level effect on medication adherence for patients receiving antidiabetic medications. RESEARCH DESIGN: This was a hypothesis-driven retrospective study using cross-sectional design and insurance claims data. The main analytical interest was the pharmacy-level effect on proportion of days covered as the measure of medication adherence. Multilevel random and mixed-effect models were used to tease out the pharmacy-level effect on patient outcomes. SUBJECTS: The study population consisted individuals aged 18-64 years, insured under employer-sponsored private health plans. RESULTS: We estimated models with and without covariates. In both models, pharmacy cluster effect was statistically significant (P<0.001). In the model without covariates, pharmacy cluster effect accounted for 12.8% (95% confidence interval, 12.4%-13.1%) of total variance in adherence, whereas in the model with covariates pharmacies accounted for 12.1% (95% confidence interval, 11.6%-12.4%) of total variance. Covariates associated significantly with adherence were age, sex, mail order pharmacy, and prescription drug copay. CONCLUSIONS: The results suggest significant variation in medication adherence attributable to pharmacy factor, independent of other effects. The underlying reason could be varying level of influence from pharmacies' efforts to inform or influence patients to take medications in prescribed manners. More research is necessary to better understand the effect of specific pharmacy characteristics and practice styles differences.


Assuntos
Diabetes Mellitus/tratamento farmacológico , Hipoglicemiantes/administração & dosagem , Adesão à Medicação/estatística & dados numéricos , Assistência Farmacêutica/organização & administração , Assistência Farmacêutica/estatística & dados numéricos , Adolescente , Adulto , Fatores Etários , Estudos Transversais , Feminino , Humanos , Hipoglicemiantes/uso terapêutico , Revisão da Utilização de Seguros/estatística & dados numéricos , Masculino , Pessoa de Meia-Idade , Modelos Estatísticos , Relações Profissional-Paciente , Estudos Retrospectivos , Fatores Sexuais , Fatores Socioeconômicos , Adulto Jovem
9.
Am J Bot ; 99(9): 1531-40, 2012 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-22922397

RESUMO

PREMISE OF THE STUDY: The glossopterids are a group of plants that thrived during a time of global warming similar to what is happening on the Earth today as well as the transition from archaic plant groups to the ancestors of modern groups. The diversity of the glossopterid clade is based on the megasporangiate structures assigned to the group, because the vegetative and pollen-bearing structures vary little. The presence of numerous reproductive genera from a single Upper Permian locality in the central Transantarctic Mountains provides important data on local glossopterid diversity in Antarctica. METHODS: Impression/compression fossils were imaged with a Leica 5000C digital camera on a dissecting microscope or a Fujifilm FinePix S1pro digital camera. KEY RESULTS: Two megasporangiate taxa are described: Scutum leiophyllum, which represents the first confirmed record of the genus in Antarctica, and Lidgettoniopsis ramulus, a new morphology consisting of a pinnate structure with oppositely attached megasporophylls. Plumsteadia ovata specimens indicate that this genus can be larger than previously recorded and illustrate the vegetative surface with a distinct midrib. CONCLUSIONS: The presence of a laminar, multiovulate structure and a pinnate structure at the same site indicates that local-level glossopterid diversity in Antarctica is greater than previously hypothesized. The discovery of a new megasporophyll morphology in Antarctica (confirming the presence of three distinctive morphologies on the continent) shows that Antarctic glossopterid heterogeneity is on a par with other Gondwanan continents. The diversity of the Antarctic landscape reveals that high polar latitudes can sustain a diverse ecosystem during times of global warming.


Assuntos
Biodiversidade , Óvulo Vegetal/anatomia & histologia , Plantas/anatomia & histologia , Plantas/classificação , Regiões Antárticas , Ecossistema , Fósseis , Fatores de Tempo
10.
J Thromb Thrombolysis ; 33(1): 28-37, 2012 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-21960323

RESUMO

No formal recommendations support bridging patients taking warfarin for a subtherapeutic international normalized ratio (INR). This study aimed to: (1) characterize practices at one anticoagulation clinic, (2) evaluate adverse events, and (3) compare cost of bridging versus withholding bridging for subtherapeutic INR. A retrospective chart review of 320 patients having 546 isolated subtherapeutic INR episodes included patients with an INR below their therapeutic range, preceded by two INRs within or above range. Bridged episodes required more frequent follow-up visits to achieve therapeutic INR (2.5 ± 1.0 vs. 2.2 ± 0.6; P = 0.097), but fewer days until the INR returned to therapeutic range (6.8 ± 5.0 vs. 18.9 ± 16.0; P < 0.0001). The strongest predictor of bridging was the magnitude the INR fell below the therapeutic range, where those with a severely-low INR were 30-fold more likely to be bridged (P < 0.0001), and moderately-low INR episodes were 6-fold more likely to be bridged compared with mildly-low INR (P < 0.0001). Those at high thromboembolic risk were more likely to be bridged than at low-risk (OR 3.39 [1.50-7.68]; P = 0.0034). Increasing age reduced the likelihood of being bridged (OR 0.97 [0.95-0.99]; P = 0.0118). Adverse events were infrequent in both the bridged and non-bridged; thrombosis (2.0 vs. 0.7%), major bleeding (2.0 vs. 1.3%), minor bleeding (4.1 vs. 3.1%) and bruising (18.4 vs. 3.6%). Incremental cost difference of bridging was significantly greater for total cost ($967.13) and its components, direct medical ($951.32), transportation ($2.73) and productivity cost ($13.08). It is unclear if bridging for an isolated subtherapeutic INR reduces thrombosis risk, but it is associated with higher costs.


Assuntos
Instituições de Assistência Ambulatorial , Anticoagulantes/administração & dosagem , Coeficiente Internacional Normatizado/métodos , Padrões de Prática Médica , Varfarina/administração & dosagem , Idoso , Instituições de Assistência Ambulatorial/economia , Anticoagulantes/economia , Custos e Análise de Custo , Feminino , Humanos , Coeficiente Internacional Normatizado/economia , Masculino , Pessoa de Meia-Idade , Padrões de Prática Médica/economia , Estudos Retrospectivos , Fatores de Risco , Trombose/economia , Trombose/prevenção & controle , Resultado do Tratamento , Varfarina/economia
11.
Mycologia ; 104(4): 835-44, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22453117

RESUMO

Documented fossil evidence of zygomycetous fungi is rare. A conspicuous fungal fossil, Jimwhitea circumtecta gen. et sp. nov., occurs in permineralized peat from the Middle Triassic of Antarctica. The fossil is interpreted as a mantled zygosporangium that buds from a macrogametangium subtended by a sac-like macrosuspensor. The macrogametangium is united at its tip with a microgametangium which is subtended by a micro-suspensor. This configuration is strikingly similar to the zygosporangium-gametangia complexes seen in certain modern Endogonaceae. Co-occurring with J. circumtecta are isolated propagules closely resembling the zygosporangium of J. circumtecta and a portion of a sporocarp containing zygosporangia embedded in a gleba. Several of the sporangia are borne on ovoid or elongate structures, which we interpret as gametangia. These fossils offer an exceptionally detailed view of the morphology and reproductive biology of early Mesozoic zygomycetes.


Assuntos
Fósseis , Fungos/classificação , Fungos/isolamento & purificação , Microbiologia do Solo , Regiões Antárticas , Evolução Biológica , Parede Celular/fisiologia , Fungos/fisiologia , Hifas/fisiologia , Especificidade da Espécie , Esporângios/anatomia & histologia , Esporos Fúngicos/fisiologia
12.
Am J Obstet Gynecol ; 205(5): 460.e1-8, 2011 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-21903192

RESUMO

OBJECTIVE: The objective of the study was to estimate the potential reduction of neural tube defects (NTDs) through the use of Metafolin-fortified oral contraceptives (OCs) in the United States. STUDY DESIGN: A population-based decision analytic model was developed to estimate the benefits of increased red blood cell (RBC) folate levels through the use of Metafolin-fortified OCs on NTD risk during pregnancy. We modeled women who began the year taking Metafolin-fortified or traditional OCs. Folate levels were derived from the National Health and Nutrition Examination Survey and clinical trial data. NTD risk was estimated by applying a published risk equation to respective RBC folate levels. RESULTS: The number of predicted NTD cases declined by 23.7% to 31.4%, depending on median baseline folate levels in women taking a fortified OC compared with taking a traditional OC. CONCLUSION: Metafolin-fortified OCs have the potential to reduce the number of folate-dependent NTDs among current and recent OC users.


Assuntos
Anticoncepcionais Orais Hormonais/uso terapêutico , Ácido Fólico/uso terapêutico , Defeitos do Tubo Neural/prevenção & controle , Adulto , Feminino , Ácido Fólico/sangue , Humanos , Modelos Teóricos , Defeitos do Tubo Neural/sangue , Inquéritos Nutricionais , Gravidez , Estados Unidos
13.
Am J Bot ; 98(7): 1222-5, 2011 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-21700798

RESUMO

PREMISE OF THE STUDY: Although root suckering and other types of sprouting are well studied in extant woody plants, little is known about the distribution of these traits at a macroevolutionary scale. Anatomically preserved fossil plants represent an excellent but understudied source of information of the distribution of sprouting behavior through time and across taxa. METHODS: A block of silicified peat collected in the Middle Triassic Fremouw Formation at the Fremouw Peak locality, Central Transantarctic Mountains, Antarctica, contains a group of anatomically preserved roots of the fossil conifer Notophytum krauselii that bear young shoots. The specimen was prepared using the standard acetate peel technique and studied in reflected and transmitted light. KEY RESULTS: Young sucker shoots bearing well-preserved leaves are produced in groups in some areas of the Notophytum roots. CONCLUSIONS: The production of root suckers in Notophytum indicates that some of the trees growing in polar forests during the Triassic could respond to environmental stresses by regenerating their vegetative structures and had the potential to reproduce vegetatively. The specimens also represent the first anatomical evidence of root suckering in any fossil seed plant, and its occurrence in an early putative podocarp supports the idea that this trait might be ancestral in at least some extant conifer families.


Assuntos
Evolução Biológica , Ecossistema , Fósseis , Paleontologia , Raízes de Plantas/crescimento & desenvolvimento , Traqueófitas/crescimento & desenvolvimento , Regiões Antárticas , Raízes de Plantas/anatomia & histologia , Fatores de Tempo , Traqueófitas/anatomia & histologia
14.
Mycologia ; 103(3): 455-7, 2011.
Artigo em Inglês | MEDLINE | ID: mdl-21289104

RESUMO

Evidence of fossil Peronosporomycetes has been slow to accumulate. In this review various fossils historically assigmed to the Peronosporomycets are dicussed briefly and an explanation is provided as to why the fossil record of this grouop has remained inconsistent. In recent year there has been several new reports of fossil peronosporomycetes based on structurally preserved oogonium-antheridium complexes from Derovonian and Carboniferous rocks that demonstrate the existence of these organisms as fossils and refute the long-standing assumption that they are too delicate to be preserved. Among these are serral tyoes characterized by oogonial surface members of the group. To date at last three groups of fossil vascular plants (i.e. lycophytes, ferns and seed ferns) are known to host peronosporomycetes aas endophytes; however only one form has been identified as a parasite.


Assuntos
Fósseis , Oomicetos , Evolução Biológica , Gleiquênias , Oomicetos/classificação , Paleontologia , Phaeophyceae , Filogenia
17.
Mycologia ; 97(3): 725-9, 2005.
Artigo em Inglês | MEDLINE | ID: mdl-16392260

RESUMO

The Carboniferous microfungus Protoascon missouriensis has been interpreted variously as an ascomycete, chytridiomycete, zygomycete and oomycete. We offer a more complete interpretation based on a re-examination of the type material that suggests the fossil represents an (a)zygosporangium-suspensor complex of a zygomycete comparable to some modern members of the Mucorales.


Assuntos
Fósseis , Fungos/classificação , Fungos/citologia , Microscopia
18.
New Phytol ; 108(1): 3-25, 1988 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33873915

RESUMO

The fossil record is a long-neglected source of valuable information concerning the diversity, structure, evolution and activities of ancient fungi. However, interest in these organisms has increased in recent years as their importance in a wide variety of interactions with plants, animals and the geological environment has been recognized. Evidence from the fossil record now implicates fungi in such processes as the establishment of terrestrial plants, degradation of lignin in Devonian forests, parasitic relationships with plants and animals, and the development of ancient soils. Although fossil fungi remain difficult to study, their geological record is rich and rewarding. Recent advances in the study of fungi from the Palaeozoic and early Mesozoic (exclusive of palynological research) are presented in this review. CONTENTS Summary I. Introduction 3 II. Fungal diversity 4 III. Interactions between fungi and their environment 7 IV. Evolution of fungi 12 V. Special problems in studying fossil fungi 14 VI. Future research in palaeomycology 16 Acknowledgements 17 References 17.

19.
Am J Bot ; 80(5): 500-516, 1993 May.
Artigo em Inglês | MEDLINE | ID: mdl-30139146

RESUMO

Stems and buds of Glossopteris skaarensis Pigg and buds of G. schopfii Pigg from the Permian Skaar Ridge locality in the central Transantarctic Mountains, Antarctica demonstrate the first anatomically preserved glossopterids known with stem/leaf attachment. Stems of G. skaarensis are 1-12 mm in diameter ( = 3.1 mm) with a broad pith, poorly defined primary xylem, and a zone of secondary xylem up to 6 mm thick. Pycnoxylic wood conforming to Araucarioxylon Kraus is composed of tracheids with uni- to biseriate oval to hexagonal bordered pits on radial walls, uniseriate rays one to a few cells high, and cupressoid to taxodioid cross-field pitting. Stems have a narrow zone of secondary phloem, aerenchymatous cortex with scattered sclereids, and sometimes a narrow periderm. Two wedge-shaped leaf traces each bifurcate to form four strands in the base of each petiole. Small axillary branches are vascularized by double branch traces that fuse at the margin of the main axis. Buds of G. skaarensis have leaves with narrow lateral laminae and a thickened midrib containing a wide lacuna, delicate vascular strands, and a prominent hypodermis. In contrast, buds of G. schopfii have uniformly thick leaves with prominent, circular vascular bundle sheaths. These anatomical details are used to reconstruct individual types of glossopterid plants, providing new information toward understanding the ecology and evolution of this important group of Permian seed plants.

20.
Am J Bot ; 70(1): 106-112, 1983 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30139065

RESUMO

Each sporangium in the Upper Devonian taxon Barinophyton citrulliforme contains both microspores and megaspores. Microspores range up to 50 µm in diam and possess a homogeneous sporoderm characterized by an outer separable layer. The sporoderm of the megaspores (up to 900 µm) is constructed of sporopollenin units that are loosely arranged in the outer portion of the wall, and that give the megaspore wall a spongy organization. Ultrastructural evidence suggests that the small spores were not abortive megaspores, but that both spore types were functional. The spores of this plant, as well as other Devonian spores that show less dramatic size differences, are suggested as demonstrating a phase in the evolution of heterospory where sex determination was established in spores within the same sporangium prior to the evolution of micro- and megasporangia.

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