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  • 1980-1984  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Relations between water content, potential and permeability in stems of conifers (1982)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 5 (1982), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. The influence of sapwood water content on the conductivity of sapwood to water was measured on stem sections of Pinus contorta. A reduction in relative water content from 100 to 90% caused permeability to fall to about 10% of the saturated value.Pressure–volume curves of branchwood and stem sapwood of Pinus contorta and Picea sitchensis have been analysed to definè the tissue capacitance and the time constant and resistance for water movement between stored water and the functional xylem as functions of tissue water potential. Three phases in water loss were discernible. In the initial phase at high water potentials (〉 –0.5 MPa), the capacitance was large, the time constant long and the resistance to flow large in comparison with intermediate water potentials (−0.5 to −1.5 MPa). At still lower water potentials (−1.5 to −3.0 MPa), the time constant and resistance declined still further but the capacitance had a tendency to increase again, especially in the stemwood of Sitka spruce. Typical values in the second phase were for the time constant 5 s, for the resistance 4 × 10−13 N s m−5 and for the capacitance (change in relative water content per unit change in potential) 1×10−11 m3 Pa−1. These parameters define the availability of stored water and are being used in a dynamic model of water transport in trees.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1365-3040.ep11572656
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    A method for measuring radial differences in water content of intact tree stems by attenuation of gamma radiation (1983)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 6 (1983), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. A technique is described for the nondestructive measurement of water content variations in the stems of trees.The density of intact tree stems in the forest was estimated using attenuation of gamma radiation. Water content was calculated after subsequent derivation of the volume fraction of solid matrix.A radial sequence of such measurements was obtained by measuring a sequence of chords, and assuming homogeneity within concentric tori. Analysis of the source of errors showed that the system was a close approximation of an ideal, rigid-geometry, mono-energetic source/detector system, with basic precision dependent on the quantity of gamma radiation measured. Correlation coefficients between the gamma-attenuation technique and subsequent gravimetric estimates of water content for two field experiments reported here were 0.882 and 0.938.The technique was shown to be capable of describing the radial and diurnal variation in water content at two heights in the stem of a 20-year-old tree of Pinus contorta.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1365-3040.ep11587650
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    A new method of measuring water potential in tree stems by water injection (1981)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 4 (1981), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. A new method of measuring xylem water potential in the stems of trees is described. The flow rate of water injected into the xylem at two or more known pressures is measured. The xylem water potential is derived either graphically from the relationship between flow rate and applied pressure, or from the solution of simultaneous flow equations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1365-3040.ep11604670
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    Paper (German National Licenses)
    Fulltext
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