Enhanced denitrification in plots of N2-fixing faba beans compared to plots of a non-fixing legume and non-legumes     

S. Kilian  D. Werner 《Biology and Fertility of Soils》1996,21(1-2):77-83

Denitrification rates were studied using the C₂H₂ inhibition technique in a 2-year field experiment within plots of nodulated and non-nodulated faba beans, ryegrass, and cabbage. Denitrification rates ranged from 14.40 to 0.02 ng N₂O–N g^–1 soil dry weight h^–1. Mean denitrification increased fourfold in plots of N₂–fixing Vicia faba compared to non-nodulated V. faba mutant F48, Lolium perenne, and Brassica oleracea. The results with and without C₂H₂ treatment indicate that in the field the major part of this enhanced denitrification led to the endproduct N₂ rather than to the ozone-degrading N₂O. Higher denitrification rates of plots with N₂–fixing plants in September seemed to be caused by an increase in soil NO _inf3 ^sup- of about 20 kg ha^–1 found between July and August. Soil NO _inf3 ^sup- and soil moisture explained 67% of the variation in denitrification rates of the different soil samples over the growing seasons in the 2 years. Soil moisture explained 44% of the variation for soil planted with N₂–fixing plants and 62% for soil planted with non-fixing plants. Positive exponential relationships were obtained between denitrification rates and soil nitrate (r=0.71) and soil moisture (r=0.82).  相似文献   

Effect of silicon fertilizers on silicon accumulation in wheat     

Joanna Mecfel  Simone Hinke  Werner Andreas Goedel  Günter Marx  Rüdiger Fehlhaber  Ernst Bäucker  Otto Wienhaus 《植物养料与土壤学杂志》2007,170(6):769-772

The effect of fertilization with silicon (Si) compounds on accumulation of Si in wheat (Triticum aestivum L.) has been studied. Wheat plants were grown under identical growing conditions, but subjected to fertilization with various Si compounds (pyrolitic fine silica particles [aerosil®], sodium silicate, silica gel), and the Si content of the above ground plants was analyzed via X‐ray microanalysis (EDX) and atomic‐absorption spectroscopy (AAS). Silicon was predominantly deposited in the epidermis cells of the leaves and their cell walls. The efficiency of the Si compounds used as fertilizers to augment the Si content of the plants increased in the order sodium silicate > silica gel > aerosil® and thus seemed to correlate with the ease of formation of orthosilicic acid from these compounds.  相似文献   

Quantitative analysis of trace and major elements in thin sections of soils with the secondary ion microscope (Cameca)     

E.B.A. Bisdom  S. Henstra  H.W. Werner  P.R. Boudewijn  W.F. Knippenberg  H.A.M. de Grefte  J.M. Gourgout  H.N. Migeon 《Geoderma》1983,30(1-4):117-134

A series of experiments have been performed for a number of years to obtain quantitative microchemical analysis by secondary ion microscopy of materials in thin sections of soils. The first successful quantification was obtained from an area with a diameter of 300 μm in bauxite and done with an IMS 300 at Philips Research Laboratories. Such an area, however, is frequently too large for most soil samples which are extremely heterogeneous even on a microscale. A second generation IMS 3F was tested for soils at the Cameca factory in Paris. This instrument allows the quantification of trace and major elements of soil constituents in a spot with 1.5 μm diameter, using a computer program developed by Philips Research Laboratories. Calcite and clay from a Petrocalcic Xerochrept were used for this test. Ion spectra, ion images and linear traverses were made giving information on the nature and distribution of both major and trace elements. The possibility of investigating a larger number of chemical elements simultaneously in linear traverses is of considerable help in the study of thin sections. Various submicroscopic and other techniques are discussed to give some insight into the position of ion microscopy amongst these.  相似文献   

Pflanzenschutzprobleme im Spiegel der Qualitätsforschung     

Werner Schuphan 《Journal of pest science》1965,38(7):97-104

Ohne Zusammenfassung  相似文献   

Structure,mechanism, and regulation of the Neurospora plasma membrane H+-ATPase   总被引：1，自引：0，他引：1  

Kühlbrandt W  Zeelen J  Dietrich J 《Science (New York, N.Y.)》2002,297(5587):1692-1696

Proton pumps in the plasma membrane of plants and yeasts maintain the intracellular pH and membrane potential. To gain insight into the molecular mechanisms of proton pumping, we built an atomic homology model of the proton pump based on the 2.6 angstrom x-ray structure of the related Ca2+ pump from rabbit sarcoplasmic reticulum. The model, when fitted to an 8 angstrom map of the Neurospora proton pump determined by electron microscopy, reveals the likely path of the proton through the membrane and shows that the nucleotide-binding domain rotates by approximately 70 degrees to deliver adenosine triphosphate (ATP) to the phosphorylation site. A synthetic peptide corresponding to the carboxyl-terminal regulatory domain stimulates ATPase activity, suggesting a mechanism for proton transport regulation.  相似文献   

Predators' effects on ecosystem entropy     

Flueck WT 《Science (New York, N.Y.)》2011,333(6046):1092-1093

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Materials science. Designer nanotubes by molecular self-assembly     

Blau WJ  Fleming AJ 《Science (New York, N.Y.)》2004,304(5676):1457-1458

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Marine biodiversity hotspots and conservation priorities for tropical reefs   总被引：1，自引：0，他引：1  

Roberts CM  McClean CJ  Veron JE  Hawkins JP  Allen GR  McAllister DE  Mittermeier CG  Schueler FW  Spalding M  Wells F  Vynne C  Werner TB 《Science (New York, N.Y.)》2002,295(5558):1280-1284

Coral reefs are the most biologically diverse of shallow water marine ecosystems but are being degraded worldwide by human activities and climate warming. Analyses of the geographic ranges of 3235 species of reef fish, corals, snails, and lobsters revealed that between 7.2% and 53.6% of each taxon have highly restricted ranges, rendering them vulnerable to extinction. Restricted-range species are clustered into centers of endemism, like those described for terrestrial taxa. The 10 richest centers of endemism cover 15.8% of the world's coral reefs (0.012% of the oceans) but include between 44.8 and 54.2% of the restricted-range species. Many occur in regions where reefs are being severely affected by people, potentially leading to numerous extinctions. Threatened centers of endemism are major biodiversity hotspots, and conservation efforts targeted toward them could help avert the loss of tropical reef biodiversity.  相似文献   

van der waals interactions in the Cl + HD reaction     

Skouteris D  Manolopoulos DE  Bian W  Werner HJ  Lai LH  Liu K 《Science (New York, N.Y.)》1999,286(5445):1713-1716

The van der Waals forces in the entrance valley of the Cl + HD reaction are shown here to play a decisive role in the reaction's dynamics. Exact quantum mechanical calculations of reactive scattering on a potential energy surface without Cl-HD van der Waals forces predict that the HCl and DCl products will be produced almost equally, whereas the same calculations on a new ab initio potential energy surface with van der Waals forces show a strong preference for the production of DCl. This preference is also seen in crossed molecular beam experiments on the reaction. The study of chemical reaction dynamics has now advanced to the stage where even comparatively weak van der Waals interactions can no longer be neglected in calculations of the potential energy surfaces of chemical reactions.  相似文献   

Frequency and mechanisms of 2n egg formation in haploid tuberosum-wild species F1 hybrids     

Joanna E. Werner  S. J. Peloquin 《American Journal of Potato Research》1987,64(12):641-654

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