Modification of sunflower oil quality by seed-specific expression of a heterologous Δ9-stearoyl-(acyl carrier protein) desaturase gene     

P. Rousselin    J. Molinier    C. Himber    D. Schontz    P. Prieto-Dapena  J. Jordano    N. Martini    S. Weber    R. Horn    M. Ganssmann    R. Grison    M. Pagniez    A. Toppan    W. Friedt  G. Hahne 《Plant Breeding》2002,121(2):108-116

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Fertility restoration of new CMS sources in sunflower (Helianthus annum L.)     

R. Horn  W. Friedt 《Plant Breeding》1997,116(4):317-322

The development of commercial sunflower hybrids based on new CMS sources is of special interest for reducing the potential risk of vulnerability to pathogens and for increasing genetic diversity. From 263 test crosses involving nine new CMS sources, i.e. ANL1, ANL2, MAX1, PEF1, PET2, ANN1, ANN2, ANNS and ANN4, five lines were selected as potential restorers for PEF1, PET2 and ANN4. In test crosses between all nine CMS sources and these five restorer lines evaluated in 2 years, seven fully restored hybrids could be identified. These hybrids, based on ANL1, ANL2, MAX1, PEF1, PET2, and ANN4, showed good agronomic performance for plant height, days to flowering, maturity and oil content. Segregation analyses of the F2 populations indicate that a single dominant restorer gene was sufficient to restore pollen production of hybrids based on ANL2, PEF1 and PET2. For restoration of ANN4, two dominant complementary genes are required. In restoration of fertility in the crosses of ANL1 and MAX1 investigated, two dominant genes are involved each of which on its own allows the production of fertile plants.  相似文献   

Modern forestry vehicles and their impacts on soil physical properties     

R. Horn  J. Vossbrink  S. Becker 《Soil & Tillage Research》2004,79(2):207-219

“Close-to-nature forest stands” are one central key in the project “Future oriented Forest Management” financially supported by the German Ministry for Science and Research (BMBF). The determination of ecological as well as economical consequences of mechanized harvesting procedures during the transformation from pure spruce stands to close-to-nature mixed forest stands is one part of the “Southern Black Forest research cooperation”. Mechanical operations of several typical forest harvesting vehicles were analysed to examine the actual soil stresses and displacements in soil profiles and to reveal the changes in soil physical properties of the forest soils. Soil compaction stresses were determined by Stress State Transducer (SST) and displacement transducer system (DTS) at two depths: 20 and 40 cm. Complete harvesting and trunk logging processes accomplished during brief 9-min operations were observed at time resolutions of 20 readings per second. Maximum vertical stresses for all experiments always exceeded 200 kPa and at soil depths of 20 cm for some vehicles and sequences of harvesting operations approached ≥500 kPa. To evaluate the impacts of soil stresses on soil structure, internal soil strengths were determined by measuring precompression stresses. Precompression stress values of forest soils at the field sites ranged from 20 to 50 kPa at soil depths of 20 cm depth and from 25 to 60 kPa at soil depths of 40 cm, at a pore water pressure of −60 hPa. Data obtained for these measured soil stresses and their natural bearing capacities proved that sustainable wheeling is impossible, irrespective of the vehicle type and the working process. Re-occurring top and subsoil compaction, increases in precompression stress values in the various soil horizons, deep rut depths, vertical and horizontal soil displacements associated with shearing stresses, all affected the mechanical strengths of forest soils. In order to sustain naturally “unwheeled” soil areas with minimal compaction, it is recommended that smaller machines, having less mass, be used to complete forest harvesting in order to prevent or at least to maintain currently minimal-compacted forest soils. Additionally, if larger machines are required, permanent wheel and skid tracks must be established with the goal of their maximum usefulness for future forest operations. A first step towards accomplishing these permanent pathways requires comprehensive planning with the Federal State Baden-Württemberg. The new guideline for final opening with skid tracks (Landesforstverwaltung Baden-Württemberg, 2003) proposes a permanent skid track system with a width of 20–40 m.  相似文献   

Removing an exotic shrub from riparian forests increases butterfly abundance and diversity     

James L. Hanula  Scott Horn 《Forest Ecology and Management》2011,262(4):674-680

Invasive plants are one of the greatest threats to endangered insect species and a major threat to Lepidoptera in eastern North America. We investigated the effects of the invasive shrub Chinese privet (Ligustrum sinense) and two methods (mulching or hand-felling) of removing it from riparian forests on butterfly communities and compared them to untreated, heavily invaded control plots and to “desired future condition” forests that never had extensive privet cover. Privet mulching resulted in nearly twice as many butterflies as privet felling and both treatments had more butterflies two years after privet removal than untreated control plots. Butterfly communities on control plots differed from those on the two treatments and the desired future condition forests. A number of forest characteristics were evaluated but only herbaceous plant cover (excluding privet) was positively correlated with butterfly abundance, diversity and evenness. The Carolina satyr, Hermeuptychia sosybius, was the best indicator of forests where privet had never invaded. Removing Chinese privet from riparian forests in the southeastern United States greatly improved forest habitats for butterflies and evidence suggests that butterfly communities in other temperate forests could benefit from removal of extensive shrub layers dominated by a single species.  相似文献   

Changes in penetration resistance of Ultisols from southern China as affected by shearing     

B. Zhang  R. Horn  T. Baumgartl   《Soil & Tillage Research》2001,57(4):193-202

Shear stresses and soil properties modified due to stress play an important role during formation of seals in a series of rainfall events and during tillage. The objectives of the study were to evaluate the effects of the penetrometer geometry on the penetration resistance as affected by shearing under different initial soil conditions and to use the information on soil strength to elucidate shearing process. Nine homogenous air-dried soils (<2 mm) were sprayed and stored so as to obtain equilibrium soil water contents. The moist soils were sheared by horizontal displacement of layers of soil particles/aggregates in between hands in one direction. The soil cores were prepared with comparable bulk density before the measurement of maximum penetration resistance (P_max) with a small flat tip and a cone tip penetrometers. At a wide range from 0.05 to 6.2 MPa, P_max was linearly correlated between the small flat tip and the cone tip penetrometers. The conversion ratio was higher under the saturation condition irrespective of the shearing effect. The penetrometer with the small flat tip was more sensitive for the weak soils. Shearing generally increased P_max in most cases, but it decreased P_max for some sandy soils under both saturated and unsaturated conditions and for a clayey soil under the saturated condition. The soil consisting of swelling clay exerted a decrease in P_max. Rearrangement and/or sliding of particles/aggregates and increase in soil suction during shearing were attributed to the increase in P_max. Increase in porosity due to the aggregation during shearing was ascribed to the decrease in P_max. In addition, it was shown that agricultural cultivation resulted in a reduction in soil strength.  相似文献   

Rheological‐stiffness analysis of K+‐treated and CaCO3‐rich soils     

Wibke Markgraf  Rainer Horn 《植物养料与土壤学杂志》2006,169(3):411-419

Rheological methods are applied whenever flow behavior of substances needs to be investigated on a particle‐to‐particle scale executed by a parallel‐plate rheometer. Under oscillation, mechanical effects due to trafficking or vibrations caused by agricultural and forest machinery can be simulated by conducting amplitude‐sweep tests. Hooke's law of elasticity, Newton's law for ideal fluids (viscosity), Mohr‐Coulomb's equation, and, finally, Bingham's yielding are well‐known relationships and parameters in the field of rheology. This paper aims to introduce rheometry as a suitable method to determine the mechanical behavior of salt‐affected soils when subjected to external stresses. Potassium‐treated loamy sand from Halle and loamy silt from Kassel, both sites located in Germany, as well as loess from Israel, saturated with NaCl solutions in several concentrations were analyzed. From the stress‐strain–relationship parameters like the storage modulus G′ and the loss modulus G″, yield stress τ_y and the linear viscoelastic (LVE)–deformation range including the deformation limit γ_L, i.e., the transition from an elastic to a viscous state, were determined and calculated, respectively. With respect to salt effects, amplitude‐sweep tests on originally CaCO₃‐rich Avdat Loess show an increasing stability if saturated with higher NaCl concentrations. Comparable tests with K⁺‐rich substrates from Halle and Kassel evinced similar tendencies including the phenomenon of a critical K⁺ content, which becomes more obvious in case of the drained (–60h Pa) loamy‐silt samples from Kassel. Nevertheless, a higher microstructural stability is given in both substrates from Halle and Kassel, affected by different water contents, in general, which influence the exchange and availability of cations. The results verify that oscillatory tests are applicable for retracing salt‐induced effects, beside those ones, which are influenced by texture, current water content, and/or further chemical parameters.  相似文献   

Räumliche Spannungsmessungen mit dem Stress State Transducer (SST) in ungesättigten aggregierten Böden - theoretische Betrachtungen und erste Ergebnisse     

Rainer Horn  Clarence  Johnson  Harald Semmel  Robert Schafer  Matthias Lebert 《植物养料与土壤学杂志》1992,155(4):269-274

Stress measurements in undisturbed unsaturated soils with a Stress State Transducer (SST) - theory and first results A method to quantify the spatial stress distribution will be introduced and first results will be discussed. This method allows the detailed analysis of principal and shear stresses as well as the determination of the direction angle of principal stresses and the octahedral shear stress angle. The described Stress State Transducer (SST) is composed of six single strain gage sensors that enable the accurate and reproducable recording of stresses in six directions in a wide load range. Their data form the base for calculation of spatial stress distribution. Some first results show that in a luvisol derived from loess wheeling at a wheel load of 4.0 Mg induces high shear stresses in a depth of 30 cm. This probably causes plastic soil deformation.  相似文献   

Primer-directed enzymatic amplification of DNA with a thermostable DNA polymerase   总被引：2172，自引：0，他引：2172  

R K Saiki  D H Gelfand  S Stoffel  S J Scharf  R Higuchi  G T Horn  K B Mullis  H A Erlich 《Science (New York, N.Y.)》1988,239(4839):487-491

A thermostable DNA polymerase was used in an in vitro DNA amplification procedure, the polymerase chain reaction. The enzyme, isolated from Thermus aquaticus, greatly simplifies the procedure and, by enabling the amplification reaction to be performed at higher temperatures, significantly improves the specificity, yield, sensitivity, and length of products that can be amplified. Single-copy genomic sequences were amplified by a factor of more than 10 million with very high specificity, and DNA segments up to 2000 base pairs were readily amplified. In addition, the method was used to amplify and detect a target DNA molecule present only once in a sample of 10(5) cells.  相似文献   

Imprinting: lasting effects on uracil incorporation into chick brain   总被引：4，自引：0，他引：4  

P P Bateson  S P Rose  G Horn 《Science (New York, N.Y.)》1973,181(99):576-578

On the first day after hatching, domestic chicks were trained for 20, 60, 120, or 240 minutes with an imprinting stimulus. On the second day, they were all retrained for 60 minutes. The greater the chicks' experience on the first day, the lower the rate of incorporation of tritiated uracil into macromolecules in the anterior part of the forebrain roof on the second day. Such effects were not found in other brain regions, nor in any brain region of chicks that received similar treatment on the first day but were not retrained on the second.  相似文献   

Rutile-bearing refractory eclogites: missing link between continents and depleted mantle   总被引：9，自引：0，他引：9  

Rudnick RL  Barth M  Horn I  McDonough WF 《Science (New York, N.Y.)》2000,287(5451):278-281

A mass imbalance exists in Earth for Nb, Ta, and possibly Ti: continental crust and depleted mantle both have subchondritic Nb/Ta, Nb/La, and Ti/Zr, which requires the existence of an additional reservoir with superchondritic ratios, such as refractory eclogite produced by slab melting. Trace element compositions of minerals in xenolithic eclogites derived from cratonic lithospheric mantle show that rutile dominates the budget of Nb and Ta in the eclogites and imparts a superchondritic Nb/Ta, Nb/La, and Ti/Zr to the whole rocks. About 1 to 6 percent by weight of eclogite is required to solve the mass imbalance in the silicate Earth, and this reservoir must have an Nb concentration >/= 2 parts per million, Nb/La >/= 1.2, and Nb/Ta between 19 and 37-values that overlap those of the xenolithic eclogites. As the mass of eclogite in the continental lithosphere is significantly lower than this, much of this material may reside in the lower mantle, perhaps as deep as the core-mantle boundary.  相似文献