126,385 research outputs found
Burmese amber fossils bridge the gap in the Cretaceous record of polypod ferns
No full textpublisher: Elsevier articletitle: Burmese amber fossils bridge the gap in the Cretaceous record of polypod ferns journaltitle: Perspectives in Plant Ecology, Evolution and Systematics articlelink: http://dx.doi.org/10.1016/j.ppees.2016.01.003 content_type: article copyright: Copyright © 2016 Elsevier GmbH. All rights reserved.Copyright © 2016 Elsevier GmbH. All rights reserved. This document is the authors' final accepted version of the journal article. You are advised to consult the publisher's version if you wish to cite from it.NHM Repositor
Distribution, habitat preferences and population sizes of two threatened tree ferns, Cyathea cunninghamii and Cyathea x marcescens, in south-eastern Australia
No full textThe distribution, population sizes and habitat preferences of the rare tree ferns Cyathea cunninghamii Hook.f. (Slender Tree Fern) and F1 hybrid Cyathea x marcescens N.A.Wakef. (Skirted Tree Fern) in south-eastern Australia are described, together with the extension of the known distribution range of Cyathea cunninghamii from eastern Victoria into south-eastern New South Wales. Floristic and ecological data, encompassing most of the known habitat types, vegetation associations and population sizes, were collected across 120 locations. Additional information was sought from literature reviews, herbarium collections and field surveys of extant populations.
Cyathea cunninghamii is widespread, with the majority of populations occurring in Tasmania and Victoria, one population in south-eastern NSW and a disjunct population in south-eastern Queensland; Cyathea x marcescens is confined to south and eastern Victoria and south and north eastern Tasmania. Both taxa occur on King Island in Bass Strait. Both taxa have a near coastal distribution with most populations occurring in sub-coastal hinterland and escarpment forests with a median altitude of 288 m. Hierarchical cluster analysis of floristic data across the species’ geographic range identified six vegetation communities ranging from rainforest to damp sclerophyll forest. Their micro-habitat preferences were consistently identified as steeply incised gullies of minor headwater streams of coastal and sub-coastal ranges with a plentiful moisture regime and geomorphic protection from extreme stream flow events, flooding and bank scouring. Sporophyte recruitment was associated with exposed soil of stream banks and edges of constructed walking tracks.
Population sizes of both taxa are small with the majority of populations consisting of less than five adult individuals, with total populations of Cyathea cunninghamii and Cyathea x marcescens estimated at 919 and 221 mature individuals respectively.
Population extinctions in Victoria and Tasmania have primarily been associated with outlier populations in regions subject to agricultural land clearance, habitat modification and changes to fire regimes in crown forests. Nonanthropogenic mortality was associated with land slips, tree falls and stream bank scouring by flood water. Conservation of the hybrid Cyathea x marcescens necessitates the preservation of habitats where both Cyathea cunninghamii and Cyathea australis occur in close proximity to substrates suitable for spore germination. In future, molecular techniques may prove useful for field identification of juvenile stages, facilitating selection of progeny of Cyathea cunninghamii and Cyathea x marcescens for cultivation and re-introduction to sites of previous or possible future extinctions
Differential distribution of hepatitis B core and E antigens in hepatocytes: analysis by monoclonal antibodies
No full textCurrent knowledge on the expression of HBeAg in hepatocytes is incomplete because of difficulties in obtaining monospecific antisera devoid of anti-HBc reactivity. In this study, we have examined by immunofluorescence the expression of HBcAg and HBeAg in cryostat liver sections from 25 chronic carriers of HBsAg using monoclonal antibodies. Although virtually all liver biopsies displayed concordance for HBeAg and HBcAg expression, the pattern of fluorescence differed markedly. Thus, monoclonal anti-HBc gave nuclear staining in all 13 reactive biopsies, while cytoplasmic staining was observed in only two of these. In contrast, monoclonal anti-HBe showed cytoplasmic reactivity coexisting with nuclear reactivity in 10 of 13 reactive biopsies. Hepatitis B virus DNA polymerase activity in the serum appeared to correlate better with the presence of HBcAg in hepatocytes rather than HBeAg. These results provide further evidence that HBeAg is expressed both in the nuclei and in the cytoplasm of infected hepatocytes. The observation that the number of cells expressing HBeAg exceeds those expressing HBcAg in carriers with active virus replication would suggest that assembly of core particles occurs in only a proportion of infected hepatocytes expressing HBeAg
What We Do (and Don't) Know About Ferns: Dryopteris (Dryopteridaceae) as a Case Study
No full textFerns are the second largest group of vascular land plants after the angiosperms, but remain chronically underrepresented in studies of plant phylogeny, biogeography, physiology, and genomics. The genus Dryopteris, the woodferns, is a large group with a worldwide distribution, and recent research has made it one of the better understood fern genera and a potential model for understanding many aspects of fern biology and evolution. Here we review historical and current understanding of the genus, and outline promising avenues of future research in ferns for which Dryopteris is an ideal study system, particularly for research on polyploid complexes, biogeographic distributions, and physiological ecology
Influência de fatores exógenos na germinação de esporos e da radiação ultravioleta B (RUV B) no desenvolvimento de gametófitos de Acrostichum Danaeifolium Langsd. & Fisch (Polypodiopsida, Pteridaceae): uma pteridófita do manguezal
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Biológicas. Programa de Pós-Graduação em Biologia VegetalA distribuição da vegetação mundial vem se alterando ao longo do tempo, mas atualmente as alterações climáticas estão ocorrendo rapidamente devido ao aumento da emissão de gases que causam o "efeito estufa" e o aquecimento global. Acrostichum danaeifolium Langsd. & Fisch. (Polypodiopsida, Pteridaceae) é uma pteridófita que cresce tipicamente em ambientes salobres ou salinos que cercam as costas, sendo também encontrada em alguns manguezais da Ilha de Santa Catarina. Considerados ecossistemas costeiros de transição entre os ambientes terrestre e marinho, os manguezais possuem riqueza e importância biológica como grandes "berçários" naturais. Esse ecossistema poderá ser severamente atingido pelas mudanças climáticas. Conhecer a fisiologia de sua vegetação e suas possíveis adaptações é de fundamental importância para sua preservação. Dessa forma o estudo da germinação de A. danaeifolium e de seu desenvolvimento gametofítico está implicado no conhecimento de suas características reprodutivas, visando à conservação e o manejo da espécie. O objetivo deste trabalho foi verificar os efeitos de variações no pH, temperatura, salinidade e da radiação UV B (RUV B) na porcentagem de germinação de esporos de A. danaeifolium, além de verificar alterações morfofisiológicas e bioquímicas em gametófitos jovens submetidos à RUV B. Frondes férteis da espécie foram coletadas na área de preservação permanente (APP) do manguezal do Itacorubi situado na região centro-oeste da Ilha de Santa Catarina, SC, Brasil. Esporos foram filtrados em papel entretela e armazenados a 7ºC. O teste de germinação foi realizado em sala de cultivo a 25ºC (27 mol m-2s-1). Não foram encontradas diferenças estatisticamente significativas na germinação de esporos nos diferentes pHs utilizados (4 a 9). Temperaturas amenas (15-20ºC) inibiram e/ou retardaram a germinação, enquanto que na temperatura de 30ºC encontrou-se a máxima germinação da espécie. Observou-se uma diminuição na porcentagem de germinação com o aumento da salinidade e um retardo na germinação de esporos, com 7 dias de cultivo, submetidos à RUV B. Pode-se observar também redução de crescimento em gametófitos submetidos à RUV B, bem como o surgimento de ramificações anômalas, em imagens capturadas por microscópio confocal de varredura a laser. Alterações ultraestruturais no sistema de membranas dos cloroplastos e maior presença de grãos de amido e plastoglóbulos foram observadas em gametófitos submetidos à RUV B. Não foram observadas diferenças nas curvas rápidas de luz, obtidas pelo fluorímetro PAM, tanto nos gametófitos submetidos à RUV B, quanto no controle. Houve variação na concentração de clorofilas com a diminuição de clorofila a e aumento de clorofila b em gametófitos submetidos à RUV B. Não houve diferença estatisticamente significativa com relação aos carotenóides, mas observou-se aumento de compostos fenólicos em gametófitos cultivados sob RUV BThe distribution of the global vegetation has been changing over time, but now climate change is occurring rapidly due to increased emission of gases causing the "greenhouse effect" and global warming. Acrostichum danaeifolium Langsd. & Fish. (Polypodiopsida, Pteridaceae) is a fern that typically grows in brackish or saline surrounding the coast being also found in some mangroves of the island of Santa Catarina. Coastal ecosystems considered transitional between terrestrial and marine environments, mangroves have wealth and great biological importance as natural "nurseries". This ecosystem may be severely affected by climate change. Knowing the physiology of its vegetation and its possible adaptations has fundamental importance to its preservation. Thus the study of germination and development of A. danaeifolium gametophyte is implicated in the knowledge of their reproductive characteristics, aiming at the conservation and management of the species. The objective of this study was to evaluate the effects of variations on pH, temperature, salinity and UV B radiation in the germination of spores of A. danaeifolium, correlating them the likely changes caused by climate change, and to identify morphophysiological and biochemical changes in young gametophytes undergo UV B radiation. Fertile fronds of this species were collected in permanent preservation areas (APP) of mangrove Itacorubi located in the central-west of Santa Catarina Island, SC, Brazil. Spores were filtered lens paper and stored at 7 º C. The germination test was conducted in culture room at 25°C (27 mol m-2s-1). There were no statistically significant differences in germination of spores used in the different pHs (4-9). Mild temperatures (15-20 º C) inhibited and / or delayed germination, while the temperature of 30°C was found maximum germination of the species. There was a decrease in germination with increasing salinity and a delay in spore germination, with 7 days of culture, under UV B radiation. One can also observe a reduction of growth in gametophytes subjected to UV B radiation as well as the emergence of anomalous branches in images captured by confocal laser scanning microscopy. Ultrastructural changes in the membrane system of chloroplasts and greater presence of starch grains and plastoglobules were observed in gametophytes subjected to UV B radiation. No differences were observed in the rapid light curves, obtained by the PAM fluorometer, both in gametophytes subjected to UV B radiation and in control. There were variations in chlorophyll concentration, with decreased of chlorophyll a and increase of chlorophyll b. There was no statistically significant difference with respect to carotenoids, but there was an increase of phenolic compounds in gametophytes grown under UV B radiatio
Niche, ferns (259-2)
No full textPhoto shows ferns growing in a crack in the red sandstone in Glen Canyon. Probably taken in June of 196
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Estudos morfofisiológicos de duas samambaias epífitas da Mata Atlântica: Elaphoglossum luridum (Fée) Christ (Dryopteridaceae) e Vittaria lineata (l.) Smith (Pteridaceae)
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Biológicas. Programa de Pós-Graduação em Biologia VegetalAs pteridófitas constituem um importante grupo de organismos da flora brasileira, muito dependentes das condições climáticas presentes na Floresta Atlântica. As epífitas são plantas que não possuem conexões diretas com o solo e utilizam-se de suporte, mas não dos nutrientes, dos forófitos em que se apoiam. Dentre a grande variedade de pteridófitas epífitas da Mata Atlântica, podemos citar as espécies Elaphoglossum luridum (Fée) H. Christ. (Dryopteridaceae) e Vittaria lineata (L.) Smith (Pteridaceae). Considerando-se o número reduzido de informações sobre a anatomia e a fisiologia de pteridófitas epífitas, foram realizadas as caracterizações anatômicas e estudos de diferentes aspectos da fisiologia, em ambas as espécies, através de análises de: conteúdo relativo de água (CRA), pigmentos fotossintéticos, fluorescência da clorofila a e a concentração de malato foliar, em plantas do grupo controle, submetidas ao estresse hídrico e à aplicação exógena de ácido abscísico (ABA); com o objetivo de observar caracteres importantes para a sobrevivência destas espécies em ambientes xéricos. Os materiais botânicos foram coletados na Unidade de Conservação Desterro - UFSC (UCAD), Florianópolis, SC, sendo cultivados na casa de vegetação do Departamento de Botânica - CCB - UFSC. Ambas as espécies estudadas apresentam características anatômicas relacionadas às condições xéricas, tais como: frondes coriáceas a cartáceas, que apresentam suculência, cutícula espessa, células epidérmicas com paredes periclinais espessas e estômatos, restritos a face abaxial. As análises fisiológicas demonstraram uma grande capacidade de manutenção hídrica em E. luridum e V. lineata, pois, mesmo em condições de estresse hídrico e aplicação de ABA exógeno, as espécies não apresentaram alterações significativas no CRA, mantendo altos níveis. Nas análises da concentração de pigmentos fotossintéticos, as plantas submetidas aos tratamentos de estresse demonstraram quedas significativas nos níveis de clorofila a e b, todavia as concentrações de carotenoides mantiveram-se estáveis. Os parâmetros fotossintéticos (?, Eoptimum e ETRmax), obtidos através das curvas rápidas de luz (RLC's), apresentaram quedas significativas após os tratamentos de estresse hídrico e aplicação de ABA. Em E. luridum, não foram encontradas evidências do metabolismo ácido das crassuláceas (CAM). Em V. lineata, plantas do grupo controle não apresentaram diferença no conteúdo de malato entre as amostras coletadas as 06h00min e as 18h00min, não demonstrando, assim, evidências do metabolismo CAM. Contudo, plantas submetidas ao estresse hídrico por sete dias e à aplicação exógena de ABA, apresentaram aumentos significativos nas concentrações de ?Malato, demonstrando uma acidificação noturna e revelando uma regulação positiva do metabolismo CAM. Assim, foram encontradas evidencias da possibilidade de alteração do modo de fixação de carbono da via C3 para o CAM, em resposta ao déficit hídrico e aplicação exógena de ABA, podendo, com isso, a espécie V. lineata apresentar o metabolismo CAM facultativo.Ferns are an important group of organisms of the flora, very dependent on climatic conditions present in the Atlantic Forest. Epiphytes are plants that do not have direct connections with the soil and utilize phorophytes just to support. Among the wide variety of epiphytic ferns of the Atlantic Forest, we can mention the species Elaphoglossum luridum (Fée) H. Christ. (Dryopteridaceae) and Vittaria lineata (L.) Smith (Pteridaceae). Considering the small number of information about the anatomy and physiology of epiphytic ferns, anatomical characterization and studies of different aspects of physiology in both species, were conduct through analysis of: relative water content (RWC), photosynthetic pigments, chlorophyll fluorescence, malate concentration of fronds. Three groups were analyzed: control group, group subjected to water stress and another subjected to exogenous application of abscisic acid (ABA), with the aim of observing important characters for the survival of these species in xeric environments. The botanical material was collected in the Environmental Desterro Park - UFSC (UCAD), Florianopólis, SC. The plants were kept in the greenhouse of the Botany Department - CCB - UFSC. Both species have anatomical features related to xeric conditions, such as coriaceous to chartaceous fronds that present succulence, presence of thick cuticle, epidermal cells with thick external periclinal walls and stomata restricted to the abaxial surface. The physiological analyzes showed a great ability to retain water in E. luridum and V. lineata, because even under conditions of water stress and exogenous abscisic acid (ABA) application, the species showed no significant changes in the RWC. In the analysis of the concentration of photosynthetic pigments, plants subjected to stress treatments showed significant decreases in levels of chlorophyll a and b, however the concentrations of carotenoids were kept stable. The photosynthetic parameters (á, Eoptimum and ETRmax), obtained by rapid light curves (RLC's), showed significant decreases after treatment of water stress and ABA application. In E. luridum, we did not found evidence of crassulacean acid metabolism (CAM). In V. lineata, the control group showed no difference in malate content of the samples collected between 06h00min and 18h00min, so there was no evidence of CAM metabolism. However, plants subjected to drought stress for seven days and the application of exogenous ABA showed significant increases in concentrations of ÄMalate, demonstrating a nocturnal acidification and revealing an up regulation of CAM metabolism. Thus, we found evidence of the possibility of changing the mode of carbon fixation pathway C3 to CAM in response to water stress and exogenous application of ABA and may, therefore, the species V. lineata present the facultative CAM metabolism
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Ferns of the Great Smoky Mountains National Park
No full textThis 16 page reference guide titled “Ferns of the Great Smoky Mountains National Park” was written by George B. Stevenson and includes descriptions and images of 36 different ferns found in the park
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