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  • Artikel  (3)
  • Convective boundary layer  (1)
  • Dinoflagellates  (1)
  • Zea mays L.  (1)
  • Springer  (3)
  • American Institute of Physics (AIP)
  • 2000-2004
  • 1995-1999  (3)
  • 1990-1994
  • 1960-1964
  • 1998  (2)
  • 1996  (1)
  • Geologie und Paläontologie  (2)
  • Physik  (1)
  • Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft  (1)
Publikationsart
  • Artikel  (3)
Verlag/Herausgeber
  • Springer  (3)
  • American Institute of Physics (AIP)
Erscheinungszeitraum
  • 2000-2004
  • 1995-1999  (3)
  • 1990-1994
  • 1960-1964
Jahr
  • 1998  (2)
  • 1996  (1)
  • 1994  (2)
Thema
  • Geologie und Paläontologie  (2)
  • Physik  (1)
  • Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft  (1)
  • Biologie  (1)
  • 1
    ISSN: 1432-0975
    Schlagwort(e): Key words Coral ; Sea anemone ; Dinoflagellates ; Symbiosis ; Eutrophication
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract  Symbiotic dinoflagellates are abundant in the endoderm cells of tropical marine anthozoans, but the cell-specific density (CSD) of symbionts has not yet been investigated. In this study we used mechanical and enzymatic methods of maceration, and staining with substrate-specific fluorochromes, to observe a large number of individual host cells from 33 species of tropical anthozoans collected in Florida, Hawaii and Jamaica or cultured in Monaco. In the majority of species, most of the host cells contained a single algal cell (singlet). Host cells with two or more (up to six) algae were much less abundant. The average CSD for the 33 species was 1.54±0.30 (range 1.11 to 2.19). Singlets arranged in a monolayer can account for the areal density of algae observed in many anthozoans. The dinoflagellates occupy most of the interior of macerated host cells, leaving the host cytoplasm and cell membrane as a thin outer layer, often unresolvable by light microscopy. This spatial arrangement may favor diffusion and transport of CO2, bicarbonate ions, and nutrients from the environment to the algae. The effect of nutrient enrichment on CSD was determined by exposing eleven species to chronically elevated levels of ammonium-N. After four weeks all species exhibited a dramatic increase in algal mitotic index and CSD. The potential consequences of environmentally induced increases in CSD in tropical anthozoans are discussed in terms of the decreased cell-specific photosynthesis (CO2 limitation) and decreased rates of calcification observed in other studies.
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 2
    ISSN: 1573-1472
    Schlagwort(e): Turbulence ; Convective boundary layer ; Clear air radar observations ; Coherent organizations ; Radar-aircraft joint observations
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The scientific objective of the TRAC experiment (Turbulence Radar Aircraft Cells) was to investigate the respective roles played by small-scale turbulence and coherent structures in the vertical transfer within the atmospheric boundary layer (ABL). Field research held in June 1993 in France was based on coupled aircraft and Doppler radar measurements. The results discussed here are mainly focused on the evaluation of the performance of the radar in the 3D description of the clear air ABL, which was the technical goal of TRAC. During the experiment, the radar was able to provide continuous and coherent echo fields over a range of several tens of kilometres, extending up to about 3 km. Good agreement was obtained in the ABL between the radar-derived turbulent quantities and airborne measurements. As depicted by the reflectivity fields, coherent organizations were found to be a common feature of the eleven ABL cases analyzed. These organizations evolved during the day between a banded structure and a cellular pattern. A very weak correlation was found between the reflectivity field and the atmospheric parameters measured by the aircraft. However, in terms of characteristic scale, the reflectivity field appeared to be strongly related to the water vapour field. The inhomogeneity induced by the coherent circulations questions the representativity of one-dimensional sampling of these 3D fields and suggests the need to adapt the traditional statistical approach of the ABL.
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 3
    ISSN: 1573-5036
    Schlagwort(e): maize ; root growth model ; root mapping ; root spatial distribution ; root system ; Zea mays L.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: 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.
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
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