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  • 1
    Electronic Resource
    Electronic Resource
    The significance of ectomycorrhizal fungi for sulfur nutrition of trees (1999)
    Springer
    Plant and soil 215 (1999), S. 115-122 
    Details
    ISSN: 1573-5036
    Keywords: allocation ; beech ; cysteine ; Fagus sylvatica ; glutathione ; Laccaria laccata ; methionine ; mycorrhization ; oak ; phloem ; Quercus robur ; sulfate ; sulfur ; uptake ; xylem ; xylem loading
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Sulfur nutrition of plants is largely determined by sulfate uptake of the roots, the allocation of sulfate to the sites of sulfate reduction and assimilation, the reduction of sulfate to sulfide and its assimilation into reduced sulfur-containing amino acids and peptides, and the allocation of reduced sulfur to growing tissues that are unable to fulfill their own demand for reduced sulfur in growth and development. Association of the roots of pedunculate oak (Quercus robur L.) and beech (Fagus sylvatica L.) trees with ectomycorrhizal fungi seems to interact with these processes of sulfur nutrition in different ways, but the result of these interactions is dependent on both the plant and the fungal partners. Mycorrhizal colonisation of the roots can alter the response of sulfate uptake to sulfate availability in the soil and enhances xylem loading and, hence, xylem transport of sulfate to the leaves. As a consequence, sulfate reduction in the leaves may increase. Simultaneously, sulfate reduction in the roots seems to be stimulated by ectomycorrhizal association. Increased sulfate reduction in the leaves of mycorrhizal trees can result in enhanced phloem transport of reduced sulfur from the leaves to the roots. Different from herbaceous plants, enhanced phloem allocation of reduced sulfur does not negatively affect sulfate uptake by the roots of trees. These interactions between mycorrhizal association and the processes involved in sulfur nutrition are required to provide sufficient amounts of reduced sulfur for increased protein synthesis that is used for the enhanced growth of trees frequently observed in response to ectomycorrhizal association.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004459523021
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  • 2
    Electronic Resource
    Electronic Resource
    Consequences of N Deposition to Forest Ecosystems - Recent Results and Future Research Needs (1999)
    Springer
    Water, air & soil pollution 116 (1999), S. 47-64 
    Details
    ISSN: 1573-2932
    Keywords: nitrate ; ammonium ; uptake ; regulation ; nitrogen oxides ; ammonia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Wet and dry deposition of atmospheric nitrogen (N) compounds into forest ecosystems and their effect on physical, chemical and microbial processes in the soil has attracted considerable attention for many years. Still the consequences of atmospheric N deposition on N metabolism of trees and its interaction with soil microbial processes has only recently been studied. Atmospheric N deposited to the leaves is thought to enter the general N metabolism of the leaves, but the processes involved, the interaction with different metabolic pathways, and the connection between injury by atmospheric N and its metabolic conversion are largely unknown. Laboratory and field experiments have shown that N of atmospheric NO2 and NH3, deposited to the leaves of trees, is subject to long-distance transport in the phloem to the roots. This allocation can result in considerable decline of N uptake by the roots. Apparently, the flux of N from the soil into the roots can be down-regulated to an extent that equals N influx into the leaves. This down-regulation is not mediated by generally enhanced amino-N contents, but by elevated levels of particular amino acids. Field experiments confirm these results from laboratory studies: Nitrate (NO3) uptake by the roots of trees at a field sites exposed to high loads of atmospheric N is negligible, provided concentrations of Gln in the roots are high. At the ecosystem level, consequences of reduced N uptake by the roots of trees exposed to high loads of atmospheric N are (1) an increased availability of N for soil microbial processes, (2) enhanced emission of gaseous N-oxides from the soil, and (3) elevated leaching of NO3 into the ground water. How recent forest management practices aimed at transforming uniform monocultures to more structured species-rich forests will interact with these processes remains to be seen. Possible implications of these forest management practices on N metabolism in trees and N conversion in the soil are discussed particularly in relation to atmospheric N deposition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005257500023
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