Reconciling 14C and minirhizotron‐based estimates of fine‐root turnover with survival functions          下载免费PDF全文

Bernhard Ahrens  Markus Reichstein 《植物养料与土壤学杂志》2014,177(2):287-296

The turnover of fine‐roots is a crucial component for the input of C to the soil. The amount of root litter input is depending on estimates of turnover times from different techniques. Turnover times from fine‐root cameras (minirhizotrons) often yield 75% higher root litter input estimates than turnover times estimated with the bomb‐radiocarbon signature of fine roots. We introduce a generic framework for the analysis of fine‐root ¹⁴C with different survival functions. So far, mostly an exponential function has been used to estimate the turnover time and mean age of fine roots. In the context of the introduced survival function framework we clarify the terms turnover time, mean residence time, mean longevity, and mean age, which are commonly used in studies of root turnover. Using a unique time series of fine‐root ¹⁴C (Fröberg 2012), we test if survival functions other than the exponential function are better in accordance with turnover‐time estimates commonly found with other methods. A survival function that corresponds to a two‐pool model was best in agreement with minirhizotron‐based estimates (mean residence time of 1.9 y). We argue that using fine‐root ¹⁴C and minirhizotron time‐to‐death data together would give the best constraints on fine‐root turnover. At the same time this could allow quantifying systematic biases inherent to both techniques.  相似文献   

山西省新疆杨造林中其个体基因变异的研究     

汪清锐  Michael Mussong  Sonja Lǒffler  Bernhard Gǒtz 《山西农业大学学报(自然科学版)》2009,29(2)

新疆杨(Populus bolleana LAUCHE)是山西省北部乃至中国西北部重要的阔叶树造林树种,但目前发现只有雄性植株,它很可能是一个或几个无性系通过无性繁殖而大规模传播开来,基因变异狭窄,会给造林带来巨大的潜在危险。于2004年到2005年在山西省境内随机采集59个样树,在德国爱博斯瓦尔德大学(FH-Eberswalde)的生态实验室进行了同工酶分析。分析结果显示,在山西省境随机采样的59个新疆杨树中,88%的被猜测为是一个或同样的无性系。初步证实山西省境内的新疆杨造林基因变异有限,这就是说在山西境内新疆杨的造林潜在着巨大的风险。同时就避免或降低这种风险的可能性进行讨论。  相似文献   

Ocular abnormalities in a herd of Old Kladruber Horses: A cross‐sectional study     

Radka Andrysikova  Simon Pot  Simon Rüegg  Jitka Markova  Eliska Horackova  Filip Kolos  Katrin Voelter  Bernhard Spiess 《Veterinary ophthalmology》2019,22(4):462-469

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Chemistry and biology of novel amine fungicides: Attempts to improve the antifungal activity of fenpropimorph     

Alan Akers  Eberhard Ammermann  Ernst Buschmann  Norbert Gtz  Walter Himmele  Gisela Lorenz  Ernst-Heinrich Pommer  Costin Rentzea  Franz Rhl  Hardo Siegel  Bernhard Zipperer  Hubert Sauter  Matthias Zipplies 《Pest management science》1991,31(4):521-538

In spite of considerable efforts by many workers, there has been a lack of progress in the area of amine fungicides since fenpropimorph. Random synthesis of a large variety of different amine compounds, as well as intelligent structural modification of the lead structure fenpropimorph (well over 15 000 amines have been screened at BASF alone) have not led to a new market product so far. Further work has been focused on the reported mode of action of fenpropimorph, notably on the inhibition of the sterol Δ¹⁴-reductase. Although some doubt has to be cast on the hypothesis that fenpropimorph behaves as a sterol mimic, the concept of ‘high energy intermediate’ inhibitors has been employed successfully. Rational drug design of azasterol mimics has led to a number of very potent inhibitors of the sterol Δ¹⁴-reductase which also displayed high fungicidal activity in the greenhouse. Although many of these compounds are more powerful reductase inhibitors than fenpropimorph, under field conditions none showed significant advantages over this established fungicide. Most likely, fenpropimorph already exhibits the maximum fungicidal activity which can be attained by blocking the sterol Δ¹⁴-reductase. This would mean that, with the development of the ‘second generation’ amine fungicide fenpropimorph, this class of compounds has already virtually been optimized.  相似文献   

Zum Tode von Dr. Walter Bosshard     

Ulrich Ammer  Werner Kroth  Karl E. Rehfuess  Walter Schöpfer  Peter Schütt  Bernhard Ulrich  Friedrich Georgi  Rudolf Georgi 《European Journal of Forest Research》1986,105(1):445-445

Ohne Zusammenfassung  相似文献   

Microclimate in agroforestry systems in central Amazonia: does canopy closure matter to soil organisms?   总被引：7，自引：0，他引：7  

Christopher Martius  Hubert Höfer  Marcos V.B. Garcia  Jörg Römbke  Bernhard Förster  Werner Hanagarth 《Agroforestry Systems》2004,60(3):291-304

Microclimate was recorded and soil organisms were collected 1997-1999 in ecosystem stands of contrasting structure in central Amazonia (a primary forest, a 12-year secondary forest, two different agroforestry systems, a rubber tree (Hevea brasiliensis) plantation, and a peach palm (Bactris gasipaes) monoculture with a densely closed canopy). The aim was to look at the effects of canopy closure on microclimate and soil organisms. Monthly maxima temperature, average air and soil temperatures, and saturation deficit were highest in September 1997, and total annual rainfall in 1997 was 12-28% lower than in the other study years. The monthly average litter temperatures were consistently 2-4 °C higher in the plantation sites than in the rainforest and the secondary forest, and temperatures on single days (not the monthly averages) in the plantations were up to 10 °C higher than in the primary forest. The highest average litter and soil temperatures and the highest temperature maxima were recorded in the agroforestry plantations. Canopy closure strongly determined the litter temperatures in the sites. Soil macrofauna biomass was also strongly correlated to canopy closure (linear regression, P = 0.05). We conclude that a well developed canopy effectively protects the soil macrofauna from high temperature variation and drought stress. Therefore, optimizing these agroforestry systems for canopy closure may contribute to a better management of the beneficial soil decomposer community. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

Antimicrobial activity of Artemisia douglasiana leaf essential oil     

Setzer WN  Vogler B  Schmidt JM  Leahy JG  Rives R 《Fitoterapia》2004,75(2):192-200

Artemisia douglasiana leaf has been shown to be efficacious complementary herbal treatment for chronic bladder infection in a paraplegic youth. The leaf oil has been analyzed by GC-MS and the major components found to be camphor (29%), artemisia ketone (26%), artemisia alcohol (13%), alpha-thujone (10%), 1,8-cineole (8%), and hexanal (5%). The leaf oil and the major components have been tested for antimicrobial activity against Bacillus cereus, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Candida albicans, and Aspergillus niger. The essential oil shows limited antimicrobial activity in vitro, so it is unclear if the oil exerts a direct antimicrobial effect in vivo, or plays some role in stimulation of host defenses.  相似文献   

Comparison of 11 herpesvirus isolates from tortoises using partial sequences from three conserved genes     

Marschang RE  Gleiser CB  Papp T  Pfitzner AJ  Böhm R  Roth BN 《Veterinary microbiology》2006,117(2-4):258-266

Herpesviruses are an important cause of epidemic disease in tortoises. There are at least two serologically distinct herpesviruses capable of infecting tortoises. Methods for the diagnosis of herpesvirus infections in tortoises include virus isolation and a number of different PCRs. We have compared 11 virus isolates collected from various species in different countries over several years using sequences from three different viral genes. During this study we used four different PCR protocols described for the diagnosis of herpesvirus infections in tortoises. The protocols used included two based on portions of the DNA polymerase gene, one targeting the UL5 homologue, and one targeting the UL39 homologue. Comparison of the methods showed that the tortoise herpesvirus-specific protocols were all serotype specific. Sequences of the obtained amplicons were compared with one another and with sequences of herpesviruses available in GenBank. The sequence alignments showed that the tortoise herpesviruses were most closely related to members of the subfamily Alphaherpesvirinae. They also showed that the tortoise isolates could be clearly divided into two genogroups.  相似文献   

Conformational switches modulate protein interactions in peptide antibiotic synthetases     

Koglin A  Mofid MR  Löhr F  Schäfer B  Rogov VV  Blum MM  Mittag T  Marahiel MA  Bernhard F  Dötsch V 《Science (New York, N.Y.)》2006,312(5771):273-276

Protein dynamics plays an important role in protein function. Many functionally important motions occur on the microsecond and low millisecond time scale and can be characterized by nuclear magnetic resonance relaxation experiments. We describe the different states of a peptidyl carrier protein (PCP) that play a crucial role in its function as a peptide shuttle in the nonribosomal peptide synthetases of the tyrocidine A system. Both apo-PCP (without the bound 4'-phosphopantetheine cofactor) and holo-PCP exist in two different stable conformations. We show that one of the apo conformations and one of the holo conformations are identical, whereas the two remaining conformations are only detectable by nuclear magnetic resonance spectroscopy in either the apo or holo form. We further demonstrate that this conformational diversity is an essential prerequisite for the directed movement of the 4'-PP cofactor and its interaction with externally acting proteins such as thioesterases and 4'-PP transferase.  相似文献   

Where water is oxidized to dioxygen: structure of the photosynthetic Mn4Ca cluster     

Yano J  Kern J  Sauer K  Latimer MJ  Pushkar Y  Biesiadka J  Loll B  Saenger W  Messinger J  Zouni A  Yachandra VK 《Science (New York, N.Y.)》2006,314(5800):821-825

The oxidation of water to dioxygen is catalyzed within photosystem II (PSII) by a Mn(4)Ca cluster, the structure of which remains elusive. Polarized extended x-ray absorption fine structure (EXAFS) measurements on PSII single crystals constrain the Mn(4)Ca cluster geometry to a set of three similar high-resolution structures. Combining polarized EXAFS and x-ray diffraction data, the cluster was placed within PSII, taking into account the overall trend of the electron density of the metal site and the putative ligands. The structure of the cluster from the present study is unlike either the 3.0 or 3.5 angstrom-resolution x-ray structures or other previously proposed models.  相似文献