Oecologia

, Volume 88, Issue 3, pp 340–346

Water relations and mucopolysaccharide increases for a winter hardy cactus during acclimation to subzero temperatures

  • Michael E. Loik
  • Park S. Nobel
Original Papers

DOI: 10.1007/BF00317576

Cite this article as:
Loik, M.E. & Nobel, P.S. Oecologia (1991) 88: 340. doi:10.1007/BF00317576

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.

Key words

Extracellular ice Freezing tolerance Opuntia humifusa Osmotic pressure Water potential 

Copyright information

© Springer-Verlag 1991

Authors and Affiliations

  • Michael E. Loik
    • 1
    • 2
  • Park S. Nobel
    • 1
    • 2
  1. 1.Department of BiologyUniversity of CaliforniaLos AngelesUSA
  2. 2.Laboratory of Biomedical and Environmental SciencesUniversity of CaliforniaLos AngelesUSA