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  • 1
    Electronic Resource
    Electronic Resource
    Nitrogen-15 partitioning within a three generation tiller sequence of the bunchgrass Schizachyrium scoparium: response to selective defoliation (1987)
    Springer
    Oecologia 74 (1987), S. 330-334 
    Details
    ISSN: 1432-1939
    Keywords: 15N partitioning ; Herbivory ; Grass ; Schizachyrium scoparium ; Nitrogen allocation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Nitrogen partitioning among three generations of tillers within the bunchgrass Schizachyrium scoparium var. frequens was investigated in a controlled environment as a potential mechanism of herbivory tolerance. Nitrogen-15 was transported from the labelled primary tiller generation to both shoots and roots of nondefoliated secondary and tertiary tiller generations within 24 h. Partial defoliation increased shoot nitrogen concentration of secondary and tertiary generation tillers by 110 and 120%, respectively, 24 h following defoliation. Shoot nitrogen concentration was preferentially increased by partial defoliation of tertiary generation tillers throughout the 120 h experimental period, but diminished to concentrations comparable to nondefoliated tillers within shoots of the secondary generation at 72 h. In contrast to nitrogen concentration, the total amount of nitrogen imported by secondary and tertiary generation tillers decreased 62 and 73%, respectively, 24 h following partial defoliation and did not attain values comparable to respective nondefoliated tillers. Consequently, preferential nitrogen concentration occurred in response to partial tiller defoliation without an increase in total nitrogen import based on the reduction in the total nitrogen requirement per tiller generation associated with defoliation. Estimates of both the total amount of nitrogen import and nitrogen concentration are necessary to accurately interpret the dynamics of intertiller nitrogen allocation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00378925
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  • 2
    Electronic Resource
    Electronic Resource
    Leaf carbon isotope discrimination and vegetative responses of Dryas octopetala to temperature and water manipulations in a High Arctic polar semi-desert, Svalbard (1993)
    Springer
    Oecologia 95 (1993), S. 463-469 
    Details
    ISSN: 1432-1939
    Keywords: Arctic physiological ecology ; Carbon isotope discrimination ; Climate change ; Water-use efficiency ; Polar semi-desert
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Integrative ecophysiological and vegetative responses of Dryas octopetala were measured in response to field perturbations of temperature, precipitation and their interactions in a polar semi-desert in Svalbard, Norway (79°N, 12°E). Leaf carbon isotope discrimination (Δ), total leaf nitrogen concentration and leaf development were determined for photosynthetic leaves collected during the last week of August 1991, after one season of manipulations. Individual leaf weight and the total mass of leaf tissue were significantly lower when water was added, irrespective of temperature regime. Leaf carbon isotope discrimination and estimated long-term c i/c avalues (the ratio of CO2 concentration in leaf intercellular spaces to that in the atmosphere) were significantly higher under all three field manipulation treatments, and Δ was significantly reduced when Dryas was grown under drought conditions in a related greenhouse study. Nitrogen concentrations of plants from the field experiment were significantly lower under warmed conditions regardless of water regime. Our results indicate that changes in environmental conditions in high arctic settings will result in alterations of Dryas leaf gas exchange, as expressed by increases in carbon isotope discrimination, which may be accompanied by shifts in leaf nitrogen content and leaf biomass.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317428
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