Constraints on development of fungal biomass and decomposition processes during restoration of arable sandy soils     

Annemieke van der Wal  Johannes A. van Veen  Richard C. Summerbell 《Soil biology & biochemistry》2006,38(9):2890-2902

In an earlier study we reported the apparent stabilization of a low fungal biomass in ex-arable lands during the first decades after abandonment. It was hypothesized that the lack of increase in fungal biomass was due to constraints on development of fungi with persistent hyphae such as lignocellulolytic basidiomycetes and ericoid mycorrhizal fungi. With respect to the former group, the slow increase of the pool of lignocellulose-rich organic matter was expected to be the major constraint for their development. To study this, we enriched soil samples of one arable land, of two recently abandoned arable lands, of one older abandoned arable land and of heathland with carbon substrates that differed in composition (glucose, cellulose and sawdust). In addition, we combined the effect of carbon addition on fungal biomass development in arable and recently abandoned lands with inoculation of 1% of soil from the older abandoned site and the heathland. All treatments induced a fast increase and a subsequent rapid decline in fungal biomass in the arable and ex-arable fields. Denaturing Gradient Gel Electrophoresis (DGGE) band patterns and enzyme activities did show differences between the carbon treatments but not between the recent and older abandoned field sites, indicating a similarly responding fungal community even after three decades of land abandonment and irrespective of soil inoculation. Identification of fungi by sequencing and culturing confirmed that decomposition processes were mostly dominated by opportunistic fungi in arable and ex-arable fields. In the heathland, only a very slow increase of microbial activity was observed after addition of carbon and sequencing of DGGE bands showed that ericoid mycorrhiza (ERM) fungi were responsible for carbon decomposition. We conclude that an increase of enduringly present fungal hyphae in ex-arable land may only be possible when a separate litter layer develops and/or when suitable host plants for ERM fungi become established.  相似文献   

Assessment of genetic relationships between <Emphasis Type="Italic">Rhus</Emphasis> L. species using RAPD markers     

Surya Prakash  Johannes Van Staden 《Genetic Resources and Crop Evolution》2007,54(1):7-11

Genetic diversity of seven Rhus L. species was assessed using random amplified polymorphic DNA (RAPDs) markers. Initially, 90 primers were screened, of which 25 produced reproducible amplification products. These primers generated a total of 296 bands, with an average of 11.8 bands per primer. Out of 296 bands scored, 236 (80%) were polymorphic and 62 (20%) were monomorphic. Primers OPC-05 and OPD-05 generated 100% polymorphic bands. The resolving power of primers ranged from 9.4 to 26.8. Similarity matrix values ranged from 0.45 to 0.63. The dendrogram generated using Unweighted Pair Group Method using Arithmetic Averages (UPGMA) grouped all the species of Rhus in one major group with two sister groups, whilst R. pyroides Burch. and R. dentata Thunb. were outliers. R. gerrardii (Harv. ex Engl.) Diels, R. glauca Thunb. and R. pentheri Zahlbr. constituted one sister group, while R. natalensis Bernh. ex C. Krauss and R. gueinzii Sond. were included in the other. The degree of genetic diversity observed between seven species of Rhus with RAPD markers suggest that this approach could be used for studying the phylogeny of the genus.  相似文献   

Lachgas(N2O)-Freisetzung durch Streptomyces nitrosporeus in einem sandigen Lehmboden in Abhängigkeit von pO2, pH und Angebot an leicht mineralisierbarem Kohlenstoff     

Frank Wenzhfer  Balazs Kriszt  Gero Benckiser  Johannes C. G. Ottow 《植物养料与土壤学杂志》1997,160(2):201-208

Nitrous oxide (N₂O) release by Streptomyces nitrosporeus in a sandy loam soil as affected by pO₂, pH and amount of easily decomposable organic carbon In model experiments under defined conditions (80%WHC, 300 μg nitrate-N g^?1 dry soil, 30°C) the effect of pO₂, pH and addition of easily decomposable organic matter on nitrous oxide production by Streptomyces nitrosporeus DSM 40023 from a sterilized sandy loam soil was studied. This streptomycete reduces nitrate to N₂O but not to N₂. The strain was inoculated into a sterilized sandy loam soil (pH 6), enriched with nitrate and incubated at approximately 20 and 10% (v/v) O₂ for 26 days. In another series of experiments the pH was increased with NaOH-solution up to pH 7 or the soil was enriched with pulverized leaves (1%) to increase mineralization activity and the demand for electron acceptors. In the headspace the concentration of O₂, CO₂ and N₂O was analysed by GC. The soil concentration of NO₃^?, NO₂^? and NH₄⁺ was measured as well as the pH value. The population density was determined by the plate count method. At a decreased oxygen concentration of about 2.5% (v/v) in the headspace, S. nitrosporeus increased the release of N₂O. In the experiments with an initial oxygen concentration of approximately 20% (v/v) this threshold of about 2.5% /(v/v) O₂ was hardly reached and consequently only little N₂O was produced. Apparently, S. nitrosporeus uses O₂ in preference to nitrate, which is characteristical of nitrate respiration. A pH increase from pH 6 to 7 reduced the lag phase significantly and increased the rate of oxygen consumption, CO₂ release and N₂O production. Maximum nitrous oxide production was reached after 13 days. The result indicated that streptomycetes like S. nitrosporeus may use nitrate alternativly to O₂ to maintain energy conservation (ATP synthesis) with the release of N₂O. So far, nothing is known about the role of streptomycetes in contributing to N₂O production in natural soils.  相似文献   

Digital image analysis of radial shrinkage of fresh spruce (Picea abies L.) wood     

Hansmann C  Konnerth J  Rosner S 《Wood material science & engineering》2011,6(1-2):2-6

Contact-free digital image analysis was performed of the radial shrinkage of fresh, fully saturated small spruce wood beams. An experimental test set-up was developed to ensure constant distance from the charge-coupled device camera to the sample surface as well as constant climate and light conditions during the whole experiment. Dimensional changes were observed immediately after the drying process began. An unexpected distinct effect could be observed which could not be explained by drying surface layers only. After a fast initial radial shrinkage a slowing down of the dimensional changes occurred at high mean moisture contents. A complete interruption of any dimensional changes followed. Finally, a recovery from shrinkage was even observed. It is assumed that strong negative pressure occurred in the fully saturated capillaries owing to dehydration which led to additional dimensional changes. As a consequence, the break of the water column and aeration in these capillaries finally resulted in a recovery period in the shrinkage rate due to the pressure release. After this effect, the dehydration was characterized by a phase of fast and almost linear shrinkage due to drying surface layers. Finally, the shrinkage slowed down to zero when reaching equilibrium moisture content.  相似文献   

A molecular basis for natural selection at the timeless locus in Drosophila melanogaster     

Sandrelli F  Tauber E  Pegoraro M  Mazzotta G  Cisotto P  Landskron J  Stanewsky R  Piccin A  Rosato E  Zordan M  Costa R  Kyriacou CP 《Science (New York, N.Y.)》2007,316(5833):1898-1900

Diapause is a protective response to unfavorable environments that results in a suspension of insect development and is most often associated with the onset of winter. The ls-tim mutation in the Drosophila melanogaster clock gene timeless has spread in Europe over the past 10,000 years, possibly because it enhances diapause. We show that the mutant allele attenuates the photosensitivity of the circadian clock and causes decreased dimerization of the mutant TIMELESS protein isoform to CRYPTOCHROME, the circadian photoreceptor. This interaction results in a more stable TIMELESS product. These findings reveal a molecular link between diapause and circadian photoreception.  相似文献   

A neutralizing antibody selected from plasma cells that binds to group 1 and group 2 influenza A hemagglutinins   总被引：2，自引：0，他引：2  

Corti D  Voss J  Gamblin SJ  Codoni G  Macagno A  Jarrossay D  Vachieri SG  Pinna D  Minola A  Vanzetta F  Silacci C  Fernandez-Rodriguez BM  Agatic G  Bianchi S  Giacchetto-Sasselli I  Calder L  Sallusto F  Collins P  Haire LF  Temperton N  Langedijk JP  Skehel JJ  Lanzavecchia A 《Science (New York, N.Y.)》2011,333(6044):850-856

The isolation of broadly neutralizing antibodies against influenza A viruses has been a long-sought goal for therapeutic approaches and vaccine design. Using a single-cell culture method for screening large numbers of human plasma cells, we isolated a neutralizing monoclonal antibody that recognized the hemagglutinin (HA) glycoprotein of all 16 subtypes and neutralized both group 1 and group 2 influenza A viruses. Passive transfer of this antibody conferred protection to mice and ferrets. Complexes with HAs from the group 1 H1 and the group 2 H3 subtypes analyzed by x-ray crystallography showed that the antibody bound to a conserved epitope in the F subdomain. This antibody may be used for passive protection and to inform vaccine design because of its broad specificity and neutralization potency.  相似文献   

Conjugation of bovine serum albumin and glucose under combined high pressure and heat     

Buckow R  Wendorff J  Hemar Y 《Journal of agricultural and food chemistry》2011,59(8):3915-3923

The effect of combined heat and pressure on the Maillard reaction between bovine serum albumin (BSA) and glucose was investigated. The effects in the range of 60-132 °C and at 0.1-600 MPa on the lysine availability of BSA were investigated at isothermal/isobaric conditions. The kinetic results showed that the protein-sugar conjugation rate increased with increasing temperature, whereas it decreased with increasing pressure. The reaction followed 1.4th order kinetics at most conditions investigated. A mathematical model describing BSA-glucose conjugation kinetics as a function of pressure and temperature is proposed. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry were used to verify BSA-glucose conjugation and to identify the glucosylated sites. These indicated that the application of combined high pressure and high temperature resulted in significant differences in the progression of the Maillard reaction as compared to heat treatments at atmospheric pressure.  相似文献   

Characterisation of T cell phenotypes,cytokines and transcription factors in the skin of dogs with cutaneous adverse food reactions     

Eveline Z. Veenhof  Edward F. Knol  Yvette M. Schlotter  Johannes C. Vernooij  Victor P. Rutten  Ton Willemse 《Veterinary journal (London, England : 1997)》2011,187(3):320-324

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Atmospheric deposition to remote receptors III. Statistical analysis of precipitation data from the ILWAS-network     

E. R. Altwicker  P. E. Shanaghan  A. H. Johannes 《Water, air, and soil pollution》1986,28(1-2):71-88

A statistical analysis of the precipitation data base from the Integrated Lake-Watershed Acidification Study (ILWAS) is presented. Included in this analysis are: equivalence of distributional form of the concentrations, ion pair concentration analysis, regression by site and season, precipitation type, and multiple regressions. The analysis emphasizes the ions: H, NH₄, SO₄, and NO₃. Variability in H is explained largely through SO₄ and NO₃; spatial variability for the species pairs SO₄-H, NO₃-H, SO₄-NH₄; and NO₃-NH₄ does not suggest significant differences between sites on a seasonal basis.  相似文献   

Species concepts and systematics of domesticated cereals     

Dr. Johannes M. J. De Wet 《Genetic Resources and Crop Evolution》1981,29(1):177-198

Summary Cultivated cereals are domesticated grasses. Wild progenitors of domestic cereals are aggressive natural colonizers and often become weedy in man disturbed habitats. Hybridization between cultivated cereals and their close wild relatives gives rise to mimetic cereal weeds that often accompany the domestic species well beyond its natural range. Similar weeds may also evolve from abandoned cultivars as a result of mutations that restore their ability for natural seed dispersal. Cultivated complexes of domestic species are typically variable. Man selects and isolates phenotypes to suit his fancies, with the result that different phenotypes of a cereal are often grown for different uses in the same village, and adjacent villages often grow different phenotypes for similar uses. Conventional species concepts do not hold for domestic species. It is proposed that wild, weed and cultivated complexes of individual domestic species be recognized respectively as subspecies. Major discontinuities in variation within the weed or cultivated subspecies are then identified as races without formal taxonomic recognition.

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Artbegriff und Systematik bei domestizierten Getreiden

Zusammenfassung Kultivierte Getreide sind domestizierte Gräser. Die wilden Vorfahren der domestizierten Getreide sind aggressive natürliche Besiedler und werden oft zu Unkräutern in vom Menschen beeinflußten Standorten. Bastardierung zwischen kultivierten Getreiden und ihren wilden Verwandten läßt mimetische Getreideunkräuter entstehen, die oft die domestizierten Arten außerhalb ihres natürlichen Verbreitungsgebietes begleiten. Ähnliche Unkräuter können sich auch aus aufgegebenen Sorten entwickeln als ein Ergebnis von Mutationen, die ihre Fähigkeit zur natürlichen Samenausstreuung wiederherstellen. Kultivierte Komplexe domestizierter Arten sind in typischer Weise variabel. Der Mensch selektiert und isoliert Phänotypen nach seinen Vorstellungen mit dem Ergebnis, daß verschiedene Phänotypen eines Getreides oft zu verschiedenen Zwecken im selben Dorf angebaut werden, und benachbarte Dörfer oft verschiedene Phänotypen für ähnliche Zwecke kultivieren. Der herkömmliche Artbegriff bewährt sich nicht bei domestizierten Arten. Es wird vorgeschlagen, daß Wild-, Unkraut- und Kulturformen einer domestizierten Art als entsprechende Unterarten angesehen werden. Größere Gruppen innerhalb der Unkraut- oder Kultur-Unterart sollten als Rassen ohne formale taxonomische Bezeichnung gehandhabt werden.

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