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  • Articles  (2)
  • Water potential  (2)
  • Springer  (2)
  • American Geophysical Union
  • Blackwell Publishing Ltd
  • 1
    Electronic Resource
    Electronic Resource
    Influence of rocks on soil temperature, soil water potential, and rooting patterns for desert succulents (1992)
    Springer
    Oecologia 92 (1992), S. 90-96 
    Details
    ISSN: 1432-1939
    Keywords: Agave ; Cactus ; Root morphology ; Sonoran Desert ; Water potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary At a site in the Sonoran Desert, subterranean rocks and exposed boulders affected soil water potential as well as root morphology and distribution. For Agave deserti, the number of lateral roots per unit length of main root was 11 times higher under rocks and six times higher alongside rocks than in rock-free regions. Total root length per unit soil volume for Echinocereus engelmannii averaged 3-fold higher within 1 cm of boulders than 5 cm away, where the soil was drier. The total length of lateral roots per unit length of main root for Ferocactus acanthodes was 4.2 m m−1 under rocks but only 0.8 m m−1 in rock-free regions. The number of lateral roots per unit length of main root for Opuntia acanthocarpa was 7-fold higher alongside rocks than in rock-free regions and even higher under rocks. For transplanted and watered A. deserti, the number of new main roots produced per 1–2 month interval averaged 13 for five plants on the north side of boulders, 8 on the south side, 11 for five plants with half of their roots under rocks, 2 for those with half of their roots over rocks, and 3 for the control plants without rocks. Laboratory experiments showed that the soil water potential under rocks for 10 and 30 mm waterings stayed above −0.5 MPa for 13 and 19 d longer, respectively, than for regions away from rocks. The shortwave absorptance of granitic rocks from the field site was 0.82, the thermal conductivity coefficient was 1.50 W m−1 °C−1, and the volumetric heat capacity was 1.75 MJ m−3 °C−1. Field measurements indicated that 5-cm-thick buried rocks decreased the diel variation in soil temperatures on their undersurface by only 0.4° C compared with soil. Thus, the primary influence of rocks at the field site on root proliferation and branching for the four species was apparently caused by influences on soil water content.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317267
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  • 2
    Electronic Resource
    Electronic Resource
    Water relations and mucopolysaccharide increases for a winter hardy cactus during acclimation to subzero temperatures (1991)
    Springer
    Oecologia 88 (1991), S. 340-346 
    Details
    ISSN: 1432-1939
    Keywords: Extracellular ice ; Freezing tolerance ; Opuntia humifusa ; Osmotic pressure ; Water potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Thickness, relative water content (RWC), osmotic pressure, water potential isotherms, and mucopolysaccharide content were measured for the photosynthetic chlorenchyma and the water-storage parenchyma of the winter hardy cactus, Opuntia humifusa, after shifting from day/night air temperatures of 25° C/15° C to 5° C/−5° C. After 14 d at 5° C/−5° C, the average fraction of water contained in the symplast decreased from 0.92 to 0.78, the water potential of saturated (fully hydrated) tissue was essentially unchanged, but the osmotic pressure of saturated tissue decreased (by 0.15 MPa for the chlorenchyma and 0.12 MPa for the water-storage parenchyma). After 7 weeks at 5° C/−5° C, tissue thickness was reduced by 61% for the chlorenchyma and 65% for the water-storage parenchyma, and the RWC decreased by 42% and 68%, respectively; these changes contributed to an osmotic pressure increase of 0.55 MPa for the chlorenchyma and 0.34 MPa for the water-storage parenchyma. During the 7 week acclimation to low temperature, mucopolysaccharide increased by 114% for the chlorenchyma and by 89% for the water-storage parenchyma. The water potential of the extracted mucopolysaccharide was relatively constant for an RWC between 1.00 and 0.30, decreasing abruptly below 0.30. Changes in water relations parameters and in mucopolysaccharide content during low-temperature acclimation may reduce water efflux from the cells, and thus reduce damage due to rapid dehydration during extracellular freezing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317576
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