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排序方式: 共有163条查询结果,搜索用时 218 毫秒
1.
Steven I. Higgins Robert B. O’Hara Olga Bykova Michael D. Cramer Isabelle Chuine Eva‐Maria Gerstner Thomas Hickler Xavier Morin Michael R. Kearney Guy F. Midgley Simon Scheiter 《Journal of Biogeography》2012,39(12):2132-2145
Aim To develop a physiologically based model of the plant niche for use in species distribution modelling. Location Europe. Methods We link the Thornley transport resistance (TTR) model with functions which describe how the TTR’s model parameters are influenced by abiotic environmental factors. The TTR model considers how carbon and nutrient uptake, and the allocation of these assimilates, influence growth. We use indirect statistical methods to estimate the model parameters from a high resolution data set on tree distribution for 22 European tree species. Results We infer, from distribution data and abiotic forcing data, the physiological niche dimensions of 22 European tree species. We found that the model fits were reasonable (AUC: 0.79–0.964). The projected distributions were characterized by a false positive rate of 0.19 and a false negative rate 0.12. The fitted models are used to generate projections of the environmental factors that limit the range boundaries of the study species. Main conclusions We show that physiological models can be used to derive physiological niche dimensions from species distribution data. Future work should focus on including prior information on physiological rates into the parameter estimation process. Application of the TTR model to species distribution modelling suggests new avenues for establishing explicit links between distribution and physiology, and for generating hypotheses about how ecophysiological processes influence the distribution of plants. 相似文献
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M. Leite T. Eremeeva A. Treimanis V. Egle T. Bykova L. Purina U. Viesturs 《Engineering in Life Science》1995,15(2):199-209
Some effects of the xylanase treatment on the separate birch ORGANOSOLV pulp fibre wall morphological layers were examined. These investigations were focused on the outer layers, i.e. the primary wall (P) and the outer layer of the secondary wall (S1), as well as the central layers, i.e. the central layer of the secondary wall (S2) and the tertiary wall (T). Step by step, the fractionation of the pulp components in the polar solvents N,N-dimethylformamide (DMFA), dimethylsulphoxide (DMSO) and DMSO/H3PO4 was used as a mild technique for the isolation of the lignin-carbohydrate complexes. The different residual amounts of lignin and hemicelluloses in the outer and central pulp fibre wall layers as well as the different lignin-hemicellulose ratios were determined. The size-exclusion chromatographical (SEC) analysis showed a higher initial lignin content in the region of the high molecular mass (MM) fibre wall fraction extracted with “DMSO/H3PO4” than the outer cell wall layers. In the central layers, the amounts of soluble lignin (calculated on the mass of total dissolved substance) were approximately the same for all the three solvents. The xylanase treatment brought the most considerable changes in the high MM part of the residual lignin (the lignin carbohydrate complex). This was true for both the P-S1 and S2-T layers. The careful brightness comparison of the outer and central fractions after the X-E-P-P bleaching sequence showed a surprisingly low bleachability of the outer layer fraction. The xylanase action depended on the composition of the lignin-carbohydrate complex (LCC) and the extent of the maintenance of the outer layers during the pulping process. 相似文献
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现有的分类系统尚缺乏可用于减少䶄属物种种间鉴定不确定性的形态学鉴别特征。鉴于此,本研究旨在筛选出能够对同域分布的棕背䶄(Myodes rufocanus), 红背䶄(M. rutilus)和堤岸䶄(M. glareolus)进行可靠鉴定的头骨形态指标和方法。为了达到以上目的,本文一方面筛选出能够用于种间鉴别的头骨和齿列形态特征,另一方面提出可用于鉴别以上三个物种的计算公式。对不同研究者提出来用于鉴别以上三个同域分布物种的35个特征进行筛选。头骨形态测量数据的获取需要花费较长的时间,而且结果变异很大。在本研究中,在分析中剔除15个形态特征,20个相对保守的特征被选择用于分析(包括来自头盖骨、牙齿和头骨其它部位的特征)。在20个特征中,有8个特征被选择出来,并使用Statistica 10 计算出判别公式。这些特征使准确鉴定不同个体各自所属种类成为可能。 相似文献
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Nemtsev SV Gamzazade AI Rogozhin SV Bykova VM Bykov VP 《Prikladnaia biokhimiia i mikrobiologiia》2002,38(6):609-615
Chitin isolated enzymatically from Antarctic krill shells was dissolved in aqueous NaOH by freezing and thawing to create homogenous conditions. Deacetylation was performed at room temperature or heating. The degree of deacetylation, molecular weight, and dynamic viscosity of solutions were estimated in chitosan samples. Deacetylation of chitin under homogenous conditions was optimized. Chitosans with molecular weights of 180-220 and 250-300 kDa were obtained from the chitins of Antarctic krill and Northern shrimps, respectively. 相似文献
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Pivovarova TA Kondrat'eva TF Batrakov SG Esipov SE Sheĭchenko VI Bykova SA Lysenko AM Karavaĭko GI 《Mikrobiologiia》2002,71(6):809-818
Earlier, we described a new family of mesophilic, strictly autotrophic Fe(2+)-oxidizing archaebacteria, Ferroplasmaceae, which belongs to the order Thermoplasmales and includes the genus Ferroplasma and species F. acidiphilum (strain YT) [1]. The present work is concerned with a comparative study of phenotypic characteristics of the type strain YT and a new strain, F. acidiphilum Y-2, isolated from dense pulps produced during oxidation of arsenogold concentrates from the Bakyrchikskoe (Kazakhstan) and Olimpiadinskoe (Krasnoyarsk Krai) ore deposits, respectively. The G + C content of DNA from strains YT and Y-2 comprised 35.1 and 35.2 mol%, respectively; the level of DNA-DNA homology between the strains was 84%. Restriction profiles of chromosomal DNA from both strains exhibited a similarity coefficient of 0.87. Genotypic characteristics of these strains indicate their affiliation to the same species. The cells of both strains are polymorphic and lack cell walls. Strains of F. acidiphilum oxidized ferrous oxide and pyrite as the sole source of energy and fixed carbon dioxide as the sole carbon source. Strains required yeast extract as a growth factor. Optimum pH for cell growth ranged from 1.7 to 1.8; the temperature optima for the growth of strains YT and Y-2 were 34-36 and 40-42 degrees C, respectively. Comparative analysis of total lipids revealed their close similarity in the strains; two glycophospholipids comprised 90% of total lipids: lipid I, beta-D-glucopyranosylcaldarchaetidylglycerol (about 55%), and lipid II, trihexosylcaldarchaetidylglycerol (26%), whose isopranyl chains contained no cyclopentane rings. The carbohydrate fraction of lipid I hydrolysate contained only D-glucose, whereas hydrolysate of lipid II contained both D-glucose and D-galactose in a molar ratio of 2:1. Thus, it was established that the intraspecific phylogenetic divergence within F. acidiphilum is manifested in two the strains by different temperature optima against the background of similarity in other phenotypic properties. 相似文献
9.
Briantseva IA Gorlenko VM Turova TP Kuznetsov BB Lysenko AM Bykova SA Gal'chenko VF Mitiushina LL Osipov GA 《Mikrobiologiia》2000,69(3):396-406
Two new species of heliobacteria isolated from cyanobacterial mats of two alkaline sulfidic hot springs are formally described. Strains BR4 and BG29 are assigned to anoxygenic phototrophic bacteria of the family Heliobacteriaceae, since they possess the unique properties of this taxon: strict anaerobiosis, formation of bacteriochlorophyll g, the lack of extensive intracytoplasmic membranes and chlorosomes, an unusual cell wall structure, and phylogenetic relatedness to the low G + C gram-positive eubacteria. Based on the 16S rDNA sequence similarity, strains BR4 and BG29 are assigned to the genus Heliobacterium and described as two new species of this genus: Heliobacterium sulfidophilum sp. nov. and Heliobacterium undosum sp. nov. The G + C content of the DNA is 51.3 mol % in Hbt. sulfidophilum and 57.2-57.7 mol % in Hbt. undosum. The cells of Hbt. sulfidophilum are rods, and the cells of Hbt. undosum are slightly twisted spirilla or short rods. Both new bacteria are motile by peritrichous flagella. Hbt. sulfidophilum produces endospores. The new bacteria are strict anaerobes growing photoheterotrophically on a limited range of organic compounds. In the dark, they can switch from photosynthesis to the slow fermentation of pyruvate. Biotin is required as a growth factor. Both species are highly tolerant to sulfide (up to 2 mM at pH 7.5) and oxidize it photoheterotrophically to elemental sulfur; photoautotrophic growth was not observed. The temperature optimal for growth of Hbt. sulfidophilum and Hbt. undosum is 30-35 degrees C, and the optimal pH is 7-8. 相似文献
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Total cell proteins of the nineteen halophilic and halotolerant eubacteria isolated from marine sediments and highly mineralized formation waters of oil fields were investigated by SDS gel electrophoresis. The microorganisms studied, phenotypically identified as belonging to the genera Dietzia, Rhodococcus, Staphylococcus, Cytophaga, Brevibacterium, and Archangium, were found to form clearly distinguishable clusters (20-30% similarity at the generic level) on the dendrogram derived from electrophoretic protein patterns. Protein similarity data confirmed the heterogeneity of Rhodococcus maris and its relatedness to the genus Dietza. 相似文献