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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, U.K. and Cambridge, USA : Blackwell Science Ltd
    Plant pathology 49 (2000), S. 0 
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The effect of epidemics of Mycosphaerella pinodes on crop growth, radiation interception efficiency (RIE) and radiation use efficiency (RUE) was studied in field conditions and the growth of diseased crop was modelled. Natural epidemics were simulated in field plots by dispersion on the ground of barley grains colonized by the fungus. Growth and leaf area index (LAI) were measured in healthy and diseased plots during the growth season. Epidemics affected crop growth mainly by decreasing RUE, with a slight decrease in RIE. This was probably due to the strong effect of M. pinodes on leaf photosynthesis and the lateness of Mycosphaerella blight epidemics on spring pea, which became serious when the canopy was already formed, thus decreasing RIE only by accelerating the senescence of leaves. The data were used to evaluate the performance of a crop growth model for diseased pea crops. The model comprised the decrease in photosynthesis rate in the leaves, the vertical gradient of disease intensity and the differences in photosynthetic function of the various layers of the canopy. This model, validated over 2 years in the field, accurately simulated the crop growth in diseased plots. Thus the decrease in RUE may be accounted for solely by photosynthesis losses in diseased leaves. This simple model may be used for disease management, defining damage thresholds for chemical application and criteria for tolerant variety selection.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The effects of Ascochyta blight (caused by Mycosphaerella pinodes) on the net photosynthetic rate of glasshouse-grown dried pea were studied on foliar discs and whole plants in pots showing different disease intensities, assessed visually using a disease scale (scores 0 to 5) or by an estimation of the fraction of leaf area with necrosis using an image analyser. The photosynthetic rate of foliar discs was measured using a leaf disc electrode; for plants it was assessed by CO2 exchange rate measurements in a closed chamber. A reduction in the net photosynthetic rate of diseased plants was correlated with an increase in disease score. A 53–56% reduction was found in foliar discs with a mean disease score of 3. On whole plants, mean scores of 3.5 and 4.0 were associated with reductions of 36% and 98% respectively. The disease also induced a decrease in the photosynthetic efficiency of the non-necrotic leaf area. The photosynthetic rate was zero when 30–40% of foliar area was necrotic on foliar discs and on whole plants. A function was derived from the foliar disc data that described the dependence of photosynthetic rate on the fraction of leaf area without necrosis. The model is discussed with reference to data obtained from entire plants and other pathosystems.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Advances in Space Research 4 (1984), S. 13-18 
    ISSN: 0273-1177
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Advances in Space Research 4 (1984), S. 61-68 
    ISSN: 0273-1177
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-5036
    Keywords: biological nitrogen fixation ; supernodulation ; nitrate-tolerance ; symbiosis ; leaf-less
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Pisum sativum L. is known for high seed and protein yields but also for.yield instability. Because legumes utilize two sources of nitrogen (atmospheric N2 fixed in nodules and assimilation of soil mineral N), studies on their nitrogen nutrition is more complex than in other plants. In this work, pea symbiotic mutants (with no nodules at all ([Nod-]), with inefficient nodules ([Nod+Fix-]) or showing an hypernodulating and a ‘nitrate-tolerant symbiosis’ character ([Nod++Nts]), their semi-leafless isogenic homologues and the parental control line cv Frisson were fertilized with three levels of mineral nitrogen (0, 25 or 50 g N m-2) to generate a range of mineral nitrogen regimes in the same genetic background. Impact of the source and level of nitrogen nutrition was measured on reproductive development, growth, nitrogen accumulation and seed yield. It was shown that a N deficiency induced flowering termination. It also led to a large decrease in the number of seeds produced and the amount of N accumulated in forage and in seeds, when little effect was observed on the progression rates of reproductive stages along the stem. The single seed weight and the amount of dry matter accumulated in forage neither responded strongly to N deficiency. The source of nitrogen was shown to be of little importance to yield but the application of about 50 g N m-2 was necessary to reach the yield of the control cv Frisson when exclusive assimilation was ensuring the N requirements of the plant. Despite the fact that the nitrate-tolerant and hypernodulating mutant P64 used in this study did not yield as well as the parent cv Frisson, it is proposed that [Nod++Nts] characters could act as a yield regulating factor.
    Type of Medium: Electronic Resource
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