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  • Articles  (5)
  • Articles: DFG German National Licenses  (5)
  • Springer  (3)
  • American Institute of Physics (AIP)  (2)
  • 2000-2004
  • 1995-1999  (4)
  • 1990-1994  (1)
  • 1960-1964
  • 1996  (4)
  • 1993  (1)
  • Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition  (3)
  • Physics  (2)
  • Geosciences
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  • Articles  (5)
Source
  • Articles: DFG German National Licenses  (5)
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  • 2000-2004
  • 1995-1999  (4)
  • 1990-1994  (1)
  • 1960-1964
Year
Topic
  • Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition  (3)
  • Physics  (2)
  • Geosciences
  • Biology  (4)
  • Medicine  (1)
  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 1128-1135 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Raman spectroscopy is used to investigate strong band bending at the interface in semi-insulating substrates of ZnSe/GaAs heterostructures grown at high epitaxy rates. Direct evidence is given of the enhancement of polar modes strength, on the substrate side, by the electric field of the space-charge zone associated with Fermi-level pinning. The latter is qualitatively analyzed by following band flattening under illumination through the evolution of interfacial coupled LO-phonon–plasmon modes. Corresponding Raman line shapes are discussed within the phenomenological approach of D. H. Hon and W. L. Faust [Appl. Phys. 1, 241 (1973)]. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 3236-3237 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-5036
    Keywords: maize ; root growth model ; root mapping ; root spatial distribution ; root system ; Zea mays L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Most existing water and nutrient uptake models are based on the assumption that roots are evenly distributed in the soil volume. This assumption is not realistic for field conditions, and significantly alters water or nutrient uptake calculations. Therefore, development of models of root system growth that account for the spatial distribution of roots is necessary. The objective of this work was to test a three dimensional architectural model of the maize root system by comparing simulated horizontal root maps with observed root maps obtained from the field. The model was built using the current knowledge on maize root system morphogenesis and parameters obtained under field conditions. Simulated root maps (0.45 × 0.75 m) of horizontal cross sections at 3 depths and 3 dates were obtained by using the model for a plant population. Actual root maps were obtained in a deep, barrier-free clay-loamy soil by digging pits, preparing selected horizontal planes and recording root contacts on plastic sheets. Results showed that both the number of cross-sections of axile roots, and their spatial distribution characterized with the R-index value of Clark and Evans (1954), were correctly accounted for by the model at all dates and depths. The number of cross-sections of laterals was also correctly predicted. However, laterals were more clustered around axile roots on simulated root maps than on observed root maps. Although slight discrepancies appeared between simulated and observed root maps in this respect, it was concluded that the model correctly accounted for the general colonization pattern of the soil volume by roots under a maize crop.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-5087
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Water deficit is one of the most common environmental limitations of crop productivity by affecting growth through alterations in metabolism and gene expression. The mechanisms involved in drought perception and signal transduction pathways are poorly understood. The participation of the plant hormone abscisic acid (ABA) has been well established. ABA levels increase when there are changes in the environment that result in cellular dehydration. Different approaches have been taken to understanding the molecular responses to desiccation and how ABA regulates gene expression. Recent efforts have identified particular topics of importance in the dissection of the signal transduction pathway which are summarized as follows: physiological approaches: identification of signalling molecules. Genetic approaches: the use of mutants, and Molecular approaches: promoter analysis.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-5036
    Keywords: architecture ; model ; root map ; root profile ; root system ; soil bulk density
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Differences between observed and simulated vertical root maps were studied in an attempt to evaluate the predictive ability of a simulation model of root system architecture under field conditions on mature plants, and to identify avenues for improvement. Some methodological problems associated with root mapping in the field are considered with a sensitivity analysis. Comparisons were made on a maize crop (early maturing hybrid F1 cultivar ‘Dea’) 15 days after silking. Four vertical root maps, perpendicular to the row and midway between two successive plants, were observed. Simulated root maps for different locations along the row showed essentially the same pattern, attesting of an approximately two-dimensional distribution of the roots in such a crop. Simulation of the intesection of roots with thin layers (thickness from 0 to 20 mm) instead of a perfect plane allowed us to assess effects due to the roughness of actual trench walls, and possible artefacts in the observation of root intersections. The simulated root profiles were very sensitive to this thickness, especially in the 0–5 mm range, in both average values, and overall shape. Actual data were close to the 3 mm thick simulations. This value seems plausible under our field conditions. Differences between simulated and actual root maps were shown to be mostly accounted for by the variations in soil bulk density. Thus, this environmental parameter appears as the most important one to include into the model for improving its predictions.
    Type of Medium: Electronic Resource
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