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51.
Gap percolation in rainforests 总被引:1,自引:0,他引:1
52.
Oxygen isotope fractionations across individual leaf carbohydrates in grass and tree species 下载免费PDF全文
Marco M. Lehmann Bruno Gamarra Ansgar Kahmen Rolf T.W. Siegwolf Matthias Saurer 《Plant, cell & environment》2017,40(8):1658-1670
Almost no δ18O data are available for leaf carbohydrates, leaving a gap in the understanding of the δ18O relationship between leaf water and cellulose. We measured δ18O values of bulk leaf water (δ18OLW) and individual leaf carbohydrates (e.g. fructose, glucose and sucrose) in grass and tree species and δ18O of leaf cellulose in grasses. The grasses were grown under two relative humidity (rH) conditions. Sucrose was generally 18O‐enriched compared with hexoses across all species with an apparent biosynthetic fractionation factor (εbio) of more than 27‰ relative to δ18OLW, which might be explained by isotopic leaf water and sucrose synthesis gradients. δ18OLW and δ18O values of carbohydrates and cellulose in grasses were strongly related, indicating that the leaf water signal in carbohydrates was transferred to cellulose (εbio = 25.1‰). Interestingly, damping factor pexpx, which reflects oxygen isotope exchange with less enriched water during cellulose synthesis, responded to rH conditions if modelled from δ18OLW but not if modelled directly from δ18O of individual carbohydrates. We conclude that δ18OLW is not always a good substitute for δ18O of synthesis water due to isotopic leaf water gradients. Thus, compound‐specific δ18O analyses of individual carbohydrates are helpful to better constrain (post‐)photosynthetic isotope fractionation processes in plants. 相似文献
53.
Catiana Dudiuk Laura Theill Soledad Gamarra Guillermo Garcia-Effron 《Current fungal infection reports》2017,11(4):176-183
Purpose of Review
The aim of this review is to evaluate these molecular-based methods able to identify pathogenic cryptic Candida spp. focusing on those that demonstrated to be useful in clinical laboratory settings.Recent Findings
It is long known that some Candida spp. are genetically heterogeneous. Firstly, individual species were divided into groups based on differences on the sequence of some genes. Later, those groups were designated as cryptic species and defined as phenotypically indistinguishable species that are only identified by their DNA sequences. Many common Candida spp. are now considered complexes formed by several cryptic species. Some of them have been recognized as human pathogens. The identification of these species is problematic but necessary since they have different host range, infection sites, infection severity, and antifungal susceptibility. Several independent DNA markers were proposed as tools for the differentiation of highly related species. We will concentrate on the three species complexes most frequently associated with human infections including Candida albicans, C. glabrata, and C. parapsilosis complexes and a fourth group of less common but multiresistant species including C. haeumulonii complex and C. auris.Summary
We review the clinically useful molecular tools able to differentiate the cryptic species of C. albicans, C. glabrata, and C. parapsilosis complexes and designated to uncover emerging multiresistant species.54.
Florian Wittmann Bianca Thaís Zorzi Fernando Augusto Tambelini Tizianel Marcus Vinicius Santiago Urquiza Rogério Rodrigues Faria Nathália Machado e Sousa Érica de Souza Módena Roberto Macedo Gamarra Augusto Lisboa Martins Rosa 《Folia Geobotanica》2008,43(4):397-411
The aboveground wood biomass (AWB) of tropical forests plays an important role in the global carbon cycle, and local AWB estimates provide essential data that enable the extrapolation of biomass stocks to ecosystem or biome-wide carbon cycle modelling. Few AWB estimates exist in Neotropical freshwater floodplains, where tree species distribution and forest structure depend on the height and duration of periodic inundations. We investigated tree species composition, forest structure, wood specific gravity, and AWB of trees ≥10 cm dbh in 16 plots totalling an area of 1 ha in a seasonally inundated riparian forest of the lower Miranda River, southern Pantanal, Brazil. The 443 tree individuals belonged to 46 species. Four species (Inga vera, Ocotea suaveolens, Tabebuia heptaphylla and Cecropia pachystachya) comprised more than 50% of the Total Importance Values (TIV), and floristic similarities between the plots averaged 38%. Although we detected an overall increase in species diversity correlated with decreasing flood levels, the most important tree species had almost identical distribution patterns along the flooding gradient. The stand basal area per plot (±?s.d.) amounted to 3.0?±?1.1 m2 (47.8?±?18.1 m2/ha), and the tree heights averaged 10.9?±?1.4 m. Multiplying the individual basal areas by individual tree heights and a form factor of 0.6, we estimated the aboveground wood volume (AWV) for each individual, and for each plot (24.4?±?11.7 m3, 391.1?±?188 m3/ha). Wood specific gravity (SG) varied between 0.39 g/cm3 (Cecropia pachystachya) and 0.87 g/cm3 (Tabebuia heptaphylla), with a stand level average of 0.63?±?0.12 g/cm3. Multiplying the individual AWV with species SG, we estimated the plot AWB to be 16.2?±?6.4 Mg (259.4?±?102 Mg/ha). This value is comparable to that reported for late-successional forest stands of Amazonian floodplain forests, and it is close to the worldwide tropical average AWB. Because tree heights in the present forest were comparatively low when compared to other Neotropical forests, we found that resprouting of stems accounted for comparatively high basal areas. We argue that stem resprouting is an adaptation of tree species originating in non-flooded Cerrado to the seasonal inundations of riparian forests. 相似文献
55.
Yuansha Chen Peter Bystricky Jacob Adeyeye Pinaki Panigrahi Afsar Ali Judith A Johnson CA Bush JG MorrisJr OC Stine 《BMC microbiology》2007,7(1):20
Background
In V. cholerae, the biogenesis of capsule polysaccharide is poorly understood. The elucidation of capsule structure and biogenesis is critical to understanding the evolution of surface polysaccharide and the internal relationship between the capsule and LPS in this species. V. cholerae serogroup O31 NRT36S, a human pathogen that produces a heat-stable enterotoxin (NAG-ST), is encapsulated. Here, we report the covalent structure and studies of the biogenesis of the capsule in V. cholerae NRT36S. 相似文献56.
Gamarra JG 《Proceedings. Biological sciences / The Royal Society》2005,272(1574):1815-1822
The use of fractals in ecology is currently pervasive over many areas. However, very few studies have linked fractal properties of landscapes to generating ecological mechanisms and dynamics. In this study I show that lacunarity (a measure of the landscape texture) is a well suited ecologically scaled landscape index that can be explicitly incorporated in metapopulation models such as the classical Levins equation. I show that the average lacunarity of an aggregated landscape is linearly correlated to the habitat that a species with local spatial processed information may perceive. Lacunarity is a computationally feasible index to measure, and is related to the metapopulation capacity of landscapes. A general approach to multifractal landscapes has been conceived, and some analytical results for self-similar landscapes are outlined, including the specific effect of landscape heterogeneity, decoupled from that of contagion by dispersal. Spatially explicit simulations show agreement with the semi-implicit method presented. 相似文献
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59.
Andrew JG Simpson 《Genome biology》2000,1(1):reports411.1-reports4112
A meeting report of the sessions on human, eukaryotic and bacterial genome sequencing at the American Society for Microbiology and Institut Pasteur joint conference: Genomes 2000 International Conference on Microbial and Model Genomes, Paris, April 11-15, 2000 相似文献
60.
One of the most popular data sets in ecology, that of lynx fur returns, is analysed in order to look for evidence for a bifurcation process. This bifurcation seems to be present from the observation of sudden shifts in the amplitude of oscillations of the lynx time series. Schaffer first proposed the possibility for such a bifurcation in 1985, and suggested that a possible source for the qualitative change of lynx's fluctuations was an increased trapping effort, which eventually lead to high-amplitude, chaotic dynamics. By studying the available information from the Hudson Bay Company records, we have found evidence for such an increased trapping pressure that (i) rapidly rose close to the shift from low-amplitude to large-amplitude fluctuations around 1820, and (ii) decreased around 1910, when there is another shift again to damped small oscillations. Although an increase in the top-predator mortality in a three-species food web typically leads to simpler dynamics and eventual predator extinction, here we show that a recent model involving a minimum bound in the lynx population, due to the presence of alternative prey in the lynx diet, consistently supports the presence of a bifurcation phenomenon. 相似文献