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排序方式: 共有216条查询结果,搜索用时 15 毫秒
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Potato late blight is still an unsolved problem in organic farming. Up to now the disease can only be controlled by copper fungicides. Our project is aiming to reduce the application of copper-containing pesticides by introduction of a blight forecasting system based on meteorological parameters. Primary stem infections should be reduced by seed treatment with copper fungicides thus to postpone the beginning of the blight epidemic as well as the start of spraying. To control secondary infections on the foliage, fungicide strategies should be elaborated to achieve best efficacy with reduced amounts of pesticides. Therefore copper amounts and spraying intervals should be adjusted to the infection pressure. Based on the biological and epidemiological conditions for primary and secondary infections with special emphasis on soil moisture, the potato blight forecast system ÖKO-SIMPHYT should be developed. 相似文献
23.
Junt T Schulze H Chen Z Massberg S Goerge T Krueger A Wagner DD Graf T Italiano JE Shivdasani RA von Andrian UH 《Science (New York, N.Y.)》2007,317(5845):1767-1770
Platelets are generated from megakaryocytes (MKs) in mammalian bone marrow (BM) by mechanisms that remain poorly understood. Here we describe the use of multiphoton intravital microscopy in intact BM to visualize platelet generation in mice. MKs were observed as sessile cells that extended dynamic proplatelet-like protrusions into microvessels. These intravascular extensions appeared to be sheared from their transendothelial stems by flowing blood, resulting in the appearance of proplatelets in peripheral blood. In vitro, proplatelet production from differentiating MKs was enhanced by fluid shear. These results confirm the concept of proplatelet formation in vivo and are consistent with the possibility that blood flow-induced hydrodynamic shear stress is a biophysical determinant of thrombopoiesis. 相似文献
24.
Successful selection of interspecific hybrid progenies with superior ability to regenerate shoots from apical meristems was
performed in sunflower which now allows for the development of lines for improved biotechnological applications. Early generations
of interspecific hybrids originating from crosses between the two H. annuus CMS lines ‘HA89’ and ‘Baso’, and 9 wild species were screened for their ability to regenerate in vitro. Evaluation of 36 progenies allowed to identify seven progenies from crosses involving H. mollis, H. giganteus, H. strumosus, and H. decapetalus which showed a significantly higher regeneration potential than the commercial hybrid ‘Albena’ regarding the number of shoots
per explant. Among these progenies, 47.2 to 62.4% of explants produced shoots with an average of 2.3 to 3.5 shoots per cultured
explant. Regeneration in vitro was significantly determined by the genotype. More than half of the investigated interspecific hybrids performed better than
the inbred ‘HA89’ demonstrating that the high regeneration potential available in the wild species can be efficiently transferred
to cultivated sunflower. The seven progenies with high regeneration potential in vitro were characterised by agronomic performance in the field. Two of the interspecific hybrids derived from H. strumosus and H. decapetalus not only showed a superior regeneration potential but also proved to be competitive to commercial hybrids with regard to
important agronomic traits, e.g. fat content and TGW.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
25.
Wood modification with alkoxysilanes 总被引:4,自引:0,他引:4
Steffen?Donath Holger?Militz Carsten?MaiEmail author 《Wood Science and Technology》2004,38(7):555-566
Wood was treated with three different alkoxysilanes which are able to undergo a sol–gel process: tetraethoxysilane (TEOS), methyl triethoxysilane (MTES) and propyl triethoxysilane (PTEO). Two types of treatments were compared: impregnation of fibre saturated wood with monomeric silane solutions, and impregnation with pre-hydrolysed partly oligomeric silanes. Wood properties such as cell wall bulking, anti-swelling efficiency (ASE), moisture uptake and durability were more significantly improved in samples treated with monomeric silanes than in samples treated with oligomeric silanes. SEM-EDX mapping showed that this treatment resulted in a higher degree of silicon incorporation into the cell wall, although the weight percent gain (WPG) was lower compared to the treatment with pre-hydrolysed partly oligomeric silanes. The resistance against soil micro-organisms was enhanced in the initial phase of incubation especially in those samples treated with organo-functional-alkoxysilanes. In miniaturised block tests with the white-rot basidiomycete Trametes versicolor, an improved durability was observed within the test period. During an air conditioning step, a weight loss of the treated samples occurred which was accompanied by a reduction in bulking and ASE. The initial reduction of moisture uptake observed after treatment diminished almost completely. This effect was explained by an ageing of the gels in the wood cell wall which is a consequence of uncompleted hydrolysis and condensation of the silanes during the treatment. 相似文献
26.
27.
Marcin K. Widomski Steffen Beck Broichsitter Alexander Zink Heiner Fleige Rainer Horn Witold Stępniewski 《植物养料与土壤学杂志》2015,178(3):401-412
At the end of waste disposal in 2005, a temporary mineral system was constructed to cover the waste body of the municipal landfill in Rastorf (N Germany). The aim of this study was to evaluate the effectiveness of this temporary cover system in limiting the infiltration of surface water into the waste body. The numerical modeling for the hydrological year 2012 was performed in FEFLOW 6.0. The required input data for modeling were achieved by laboratory measurements of the saturated hydraulic conductivity and the water retention characteristics of the mineral layers. The assumed initial and boundary conditions were based on in‐situ measurements of matrix potential and volumetric water content at three different measuring points by tensiometers, FDR sensors and observed meteorological conditions. The model was applied according to Darcy's and Richards' equations for variably saturated flow. Our results allowed assessing the components of water balance for a temporary cover system, especially water seepage into the waste body. The correlation between the measured and modeled volumetric soil water content in the layered temporary cover system was observed (R2 = 0.56 to 0.90). Deviations between the measured and modeled values are superficially related to the soil´s heterogeneity. In conclusion, the measured and modeled water balance parameters indicate that the temporary coverage system remains effective in limiting the infiltration rate. However, our studies revealed that the calculated and measured water seepage exceeded the values allowable by the German regulations. Additional studies have to assess variations in the soil water characteristics caused by weather‐related wetting and drying cycles and influence of waste settlement changing the profile of slope. 相似文献
28.
Edith K. Hüttner Fabio Dal Bello Emanuele Zannini Jean Titze Steffen Beuch Elke K. Arendt 《Cereal Chemistry》2011,88(6):602-608
The breadmaking potential of six oat varieties was compared with and related to their physicochemical properties. The most significant differences in the bread characteristics were found in the crumb structure. The varieties Buggy, Energie, and Zorro resulted in good bread quality with an even gas‐cell distribution characterized by a high number of relatively small pores. In contrast, Typhon, Ivory, and Nord 08/311 each had a large hole in the center of the crumb and accordingly poor quality. Breads differed little in specific volume, bake loss, and density. Rheological analysis revealed positive effects of low batter resistance to deformation on oat bread quality. On the basis of the physicochemical characterization, protein and fat contents were identified as key factors responsible for differences observed in bread quality, provided that starch damage and water‐hydration capacity were low. Additionally, high setback and final viscosity, as determined by Rapid Visco Analyser (RVA) analysis, positively affected oat bread quality. High α‐amylase activity was found to influence negatively the breadmaking performance of oats. Overall, protein, fat, dietary fiber content, starch pasting properties, and α‐amylase activity were responsible for the breadmaking properties of oat varieties. 相似文献
29.
Zerihun Nigussie Atsushi Tsunekawa Nigussie Haregeweyn Enyew Adgo Makoto Nohmi Mitsuru Tsubo Dagnachew Aklog Derege Tsegaye Meshesha Steffen Abele 《Small-Scale Forestry》2017,16(2):219-233
The development of woodlots as an additional source of livelihood and as a land management option for small-scale farmers is a challenging issue in the cereal-based subsistence farming systems of north-western Ethiopia. There is a need to understand why and which factors determine the decisions of small-scale farmers to grow short-rotation woodlots on their land. Data used in this study were collected from a survey of 200 randomly selected households in the region. A Tobit regression model was used to determine predictor variables for farmers’ decisions to allocate land to planting Acacia decurrens (J.C. Wendl.) Willd. and at what density trees are planted on the respective plots. The most important motivations for planting A. decurrens were income, soil fertility management, and soil and water conservation. Having a male head of household, long distance to markets and plots being on marginal land, among other factors, increased the allocation of land to A. decurrens woodlots. Having a male head of household, access to credit and plots being on marginal land, among other factors, increased tree planting density. Age had a negative effect on both allocation of land to woodlots and tree density, whereas farm size had an inverted U-shaped relationship with both decisions. These results suggest that wider expansion of A. decurrens-based plantation systems could be achieved through improving extension, credit access and road infrastructure to connect small-scale farmers to markets and finance. 相似文献
30.
Development of two microsatellite multiplex PCR systems for high throughput genotyping in Populus euphratica 总被引:1,自引:0,他引:1
Eighteen microsatellite primer pairs previously developed at Oak Ridge National Laboratory for Populus tremuloides Michx. and Populus trichocarpa Torr. & Gray were screened for amplification in Euphrates poplar, Populus euphratica Oliv. Thirteen loci were found to express polymorphisms ranging from two to 17 alleles. The eight most variable loci were
selected to set up and optimize two multiplex polymerase chain reaction (PCR) assays. Three populations containing altogether
436 trees were used to characterize the selected loci and ascertain their applicability for parentage analysis and genotyping
studies. Through cross-checking of clonal identity against sex of the genotyped trees we estimated the maximum error rate
for merging genotypes to be less than 0.045.
Foundation project: This study was supported by the Deutsche Forschungsgemeinschaft DFG (grant number SCHN 1080/1-1) 相似文献