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  • 1
    Electronic Resource
    Electronic Resource
    The root surface phosphatases ofEriophorum vaginatum: Effects of temperature, pH, substrate concentration and inorganic phosphorus (1988)
    Springer
    Plant and soil 105 (1988), S. 3-10 
    Details
    ISSN: 1573-5036
    Keywords: arctic ; Eriophorum ; pH ; phosphatases ; phosphorus ; PNPPase ; root enzymes ; temperature ; tundra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Eriophorum vaginatum L. subsp.spissum (Fern.) Hult., a dominant plant in arctic tundra ecosystems, has acid phosphatase activity evenly distributed along its root surface from the root tip to a distance at least 16 cm from the tip. These root surface phosphatases have optimal activity from pH 3.5 to 4.0; mean soil pH for soil samples collected with roots was 3.69. Apparent energy of activation and Q10 values (14.0 kcal mol−1 and 2.2, respectively) do not provide evidence for temperature acclimation, but substantial phosphatase activity was measured at 1°C. Kinetic parameters determined for this root surface phosphatase were as follows: Km=9.23 mM, Vmax=1.61×10−3 μmoles mm−2h−1. The presence of inorganic phosphorus in the assay medium did not inhibit root surface phosphatase activity except at very high concentrations (100 mM); even then, only slight inhibition was detected (7 to 19%). A comparison of hydrolysis rates with inorganic phosphate assimilation rates measured forE. vaginatum indicates that organic phosphate hydrolysis may occur at approximately one third the rate of inorganic phosphate absorption. Calculations show that inorganic phosphate produced by root surface phosphatase activity may satisfy 65% of the annual phosphate demand ofE. vaginatum. Since arctic tundra soils are typically higher in dissolved organic phosphorus compounds than in inorganic phosphate, root surface phosphatase activity may make a considerable contribution to the phosphate nutrition of this widespread and abundant arctic plant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02371136
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  • 2
    Electronic Resource
    Electronic Resource
    Carbon and nitrogen dynamics along the decay continuum: Plant litter to soil organic matter (1989)
    Springer
    Plant and soil 115 (1989), S. 189-198 
    Details
    ISSN: 1573-5036
    Keywords: carbon ; cellulose ; decomposition ; δ13C ; δ15N ; lignin ; nitrogen ; stable isotopes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Decay processes in an ecosystem can be thought of as a continuum beginning with the input of plant litter and leading to the formation of soil organic matter. As an example of this continuum, we review a 77-month study of the decay of red pine (Pinus resinosa Ait.) needle litter. We tracked the changes in C chemistry and the N pool in red pine (Pinus resinosa Ait.) needle litter during the 77-month period using standard chemical techniques and stable isotope, analyses of C and N. Mass loss is best described by a two-phase model: an initial phase of constant mass loss and a phase of very slow loss dominated by degradation of ‘lignocellulose’ (acid soluble sugars plus acid insoluble C compounds). As the decaying litter enters the second phase, the ratio of lignin to lignin and cellulose (the lignocellulose index, LCI) approaches 0.7. Thereafter, the LCI increases only slightly throughout the decay continuum indicating that acid insoluble materials (‘lignin’) dominate decay in the latter part of the continuum. Nitrogen dynamics are also best described by a two-phase model: a phase of N net immobilization followed by a phase of N net mineralization. Small changes in C and N isotopic composition were observed during litter decay. Larger changes were observed with depth in the soil profile. An understanding of factors that control ‘lignin’ degradation is key to predicting the patterns of mass loss and N dynamics late in decay. The hypothesis that labile C is needed for ‘lignin’ degradation must be evaluated and the sources of this C must be identified. Also, the hypothesis that the availability of inorganic N slows ‘lignin’ decay must be evaluated in soil systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02202587
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  • 3
    Electronic Resource
    Electronic Resource
    Exoenzyme accumulation in epilithic biofilms (1991)
    Springer
    Hydrobiologia 222 (1991), S. 29-37 
    Details
    ISSN: 1573-5117
    Keywords: biofilm ; epilithon ; exoenzyme activity ; community structure ; stream ecology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Although exoenzyme accumulation is often proposed as an explanation for the high metabolic activity of biofilms, little is known about the abundance, distribution and turnover rates of exoenzymes within these communities. To assess accumulation, epilithic biofilm samples were collected from a fourth-order boreal river and homogenized. The resulting particles were fractionated by size and each fraction was assayed for nine exoenzyme activities, chlorophyll, and ATP. In general, carbohydrase activities were not correlated with microbial biomass indicators; the largest pool of activity was in the aqueous phase (〈 0.2 µm). Phenol oxidase, peroxidase, and phosphatase activities were largely particle-bound and often correlated with microbial biomass distribution. It was concluded that the epilithic biofilm matrix was effective at accumulating carbohydrase activity and that this accumulation may partially account for the metabolic resistance of epilithic biofilms to dissolved organic matter fluctuations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00017497
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    Paper (German National Licenses)
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