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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 86 (1991), S. 81-87 
    ISSN: 1432-1939
    Keywords: Competition ; Hemiparasitism ; Host selectivity ; Rhinanthus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Rhinanthus minor (Yellow-rattle) was grown in replacement series mixtures with Lolium perenne and Trifolium repens. The hemiparasitic interaction resulted in Relative Yield Totals (the sum of the yields in mixture relative to those in monoculture) considerably above 2. The hemiparasite caused a greater decrease in the yield of the legume and also performed better on the legume, indicating that T. repens was a better host for R. minor than L. perenne under the experimental conditions. When L. perenne and T. repens were grown in binary mixture with or without R. minor the hemiparasite affected considerably the competitive relationship between the two species by selectively parasitizing the legume. The effect of R. minor on competition between the two species was, however, dependent upon the nutrient status of the soil: the higher the level of soil nitrogen the fewer haustorial connections were made with T. repens and the less was the depression in its yield. In another series of experiments in which Festuca rubra, Holcus lanatus and L. perenne were grown in various binary mixtures with or without R. minor it was also shown that the yield of a preferred host was depressed to the advantage of a non-preferred host. It is suggested that the mediation of competition by the hemiparasite provides a mechanism by which it might affect the structure and diversity of plant communities.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 78 (1989), S. 401-406 
    ISSN: 1432-1939
    Keywords: Rhinanthus ; Hemiparasitism ; Host selectivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Rhinanthus minor (Yellow-rattle) is a widespread hemiparasitic plant of grassland habitats throughout Britain. Association analysis of the dune vegetation at Holme-next-the-Sea in eastern England revealed only two potential host plants through positive association. In contrast direct examination of the root systems revealed haustorial connections with 20 host species. The number of species parasitized by one plant ranged from one to seven. Data from another four sites in Britain and one in central Europe indicate that the natural host range of R. minor encompasses at least 50 species from 18 families with 22% in the Leguminosae and 30% in the Gramineae. Comparison of the number of haustorial connections made to each species with the abundance of roots in the soil shows that R. minor is a highly selective parasite, but that the selectivity is not consistent between populations or between plants from different parts of the same population. The reasons for host selectivity are discussed.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Acta applicandae mathematicae 7 (1986), S. 113-135 
    ISSN: 1572-9036
    Keywords: 70B15 ; Mechanism ; algebraic curve ; real elliptic curve ; Morse Theory ; Segre quartic surface
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract The paper seeks to elucidate the geometry of a simple engineering mechanism, comprising four bars smoothly jointed together to form a movable quadrilateral with one fixed side. The configurations of this mechanism correspond to the points of an elliptic curve, to which is associated interesting geometry and Morse theory. By appropriate projection, this curve yields the 2-parameter family of plane curves described by points rigidly attached to the side of the quadrilateral opposite the fixed side: the geometry of the general projection is related to the configuration of lines on a Segre quartic surface.
    Type of Medium: Electronic Resource
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