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  • Ecology  (4)
  • root system  (4)
  • 1
    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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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 189 (1997), S. 81-89 
    ISSN: 1573-5036
    Keywords: methodology ; minirhizotron ; model ; root system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In order to help design experiments with minirhizotrons or interpret data from such experiments, a modelling approach is a valuable tool to complement empirical approaches. The general principle of this modelling approach is to calculate and to study the part of a theoretical root system that is intersected by passes through a virtual minirhizotron tube (modelled here as a cylinder). Various outputs can be calculated from this part of the root system, and related to the surrounding root system which is perfectly known, since it has been simulated and stored in a data structure. Therefore, the method involves two levels of modelling that are presented and discussed: the root system architecture of a crop, and the observations that can be achieved with minirhizotron tubes. Illustrations of the method are presented to study the effect of several factors on the rooting depth curves, and to show how images may be calculated to mimic what can actually be viewed from inside the tube. These first results show that the maximum rooting depth curves, as virtually observed in the minirhizotron tube, present large variations and strongly underestimate the maximum rooting depth of the modelled root system (up to 60 cm in average). The underestimation is still more critical when the radius of the tube is lower than 3 cm, and when the tube is close to the vertical (angle lower than 0.2 rad). The use of the 0.9 quantile instead of the average value, for each of the observation dates, leads to a better estimation of the maximum rooting depth.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 164 (1994), S. 155-167 
    ISSN: 1573-5036
    Keywords: axile roots ; maize ; nodal roots ; root length ; root system ; seminal roots ; Zea mays L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The objective of this work was to study elongation curves of maize axile roots throughout their elongation period under field conditions. Relationships between their elongation rate and the extension rate of their branched region were also studied. Maize, early-maturing cultivar Dea, was grown on a deep, barrier-free clay loam (depth 1.80m). Trenches were dug during four periods until after silking and axile roots were excavated. Parameters measured were total length and the lengths of basal and apical unbranched zones. The rank of the bearing phytomer and general data about the carrying plant were also recorded. Results showed that axile roots from lower phytomers had similar elongation rates irrespective of the rank of the carrying phytomer. This elongation rate declined with root age. A monomolecular elongation model was fitted to the experimental data. Elongation was much slower in roots from upper phytomers. A rough linear relationship was found between the elongation rate of axile roots and the length of the apical unbranched zone. This result suggests that laterals appeared on a root segment a constant time after it was formed. Possible mechanisms with may account for the declining elongation rate with root age (increasing distance from aerial parts or adverse environmental conditions in deep soil layers) and variability between individual roots are also discussed.
    Type of Medium: Electronic Resource
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  • 4
    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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  • 5
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    In:  http://aquaticcommons.org/id/eprint/7481 | 424 | 2012-01-01 08:41:28 | 7481 | Centre de Recherches Océanographiques, Côte d'Ivoire
    Publication Date: 2021-07-03
    Description: An estimation of the currents in the Biétri bay is given (tidal currents and currents due to the wind). They are lower than 10 cm.s-1 in the whole lagoon, and near of 5 cm.s-1 in the eastern part. The measures of salinity and tidal observations give the average rate of water renewal, respectively 0.20 and 0.14 d-1 in the central and eastern areas.
    Keywords: Atmospheric Sciences ; Ecology ; Côte d'Ivoire ; Lagune de Biétri ; lagoons ; bathymetry ; currents ; rate of water renewal
    Repository Name: AquaDocs
    Type: article
    Format: application/pdf
    Format: application/pdf
    Format: 13-24
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  • 6
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    In:  http://aquaticcommons.org/id/eprint/8536 | 424 | 2012-03-17 07:59:49 | 8536 | Centre de Recherches Océanographiques, Côte d'Ivoire
    Publication Date: 2021-07-03
    Description: Details are presented of a bacteriological study in Ebrié Lagoon (Abidjan-Côte d'Ivoire) conducted during Oct-Dec 1974. Sampling sites are shown, and estimated and confirmed values for coliforms are given. The significance of the values obtained is briefly discussed, but further important factors, such as meteorological conditions and state of the sea, need clarification before definite conclusions can be made.
    Keywords: Biology ; Ecology ; Environment ; Pollution ; Côte d'Ivoire ; Lagune Ebrié ; lagoons ; bacteria ; microbial contamination
    Repository Name: AquaDocs
    Type: article
    Format: application/pdf
    Format: application/pdf
    Format: 97-101
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  • 7
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    In:  http://aquaticcommons.org/id/eprint/8031 | 424 | 2012-03-09 09:05:22 | 8031 | Centre de Recherches Océanographiques, Côte d'Ivoire
    Publication Date: 2021-06-28
    Description: Outfall at sea of sewage from Abidjan requires information about the die-off of bacteria in the sea. The method of determination is described and validity of data is analysed. These preliminary results point out some features about the choice of methodology.
    Keywords: Biology ; Ecology ; Côte d'Ivoire ; Abidjan ; sewage waters ; bacteria ; die-off
    Repository Name: AquaDocs
    Type: article
    Format: application/pdf
    Format: application/pdf
    Format: 63-80
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  • 8
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    In:  http://aquaticcommons.org/id/eprint/7491 | 424 | 2012-01-01 08:38:01 | 7491 | Centre de Recherches Océanographiques, Côte d'Ivoire
    Publication Date: 2021-07-03
    Description: Total CO2 of brackish water (Ebrié lagoon) is measured with a simple method: degassing and trapping CO2 in NaOh solution, the conductivity of which is a function of the trapped CO2 quantity. A relation CO2 versus salinity is deduced; it is nearly the same as the one deduced from CO2 measurements performed from alkalinity. Dissolved organic C is evaluated with a CHN analyser by evaporating 0.5 ml of acidified sample. Variation coefficient is near 10% for the lagoon values.
    Keywords: Ecology ; Environment ; Côte d'Ivoire ; organic carbon ; brackish water ; data analysis
    Repository Name: AquaDocs
    Type: article
    Format: application/pdf
    Format: application/pdf
    Format: 27-36
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