PLANT PHYSIOLOGY , Vol 110, Issue 4 1309-1316, Copyright © 1996 by American Society of Plant Biologists
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WHOLE PLANT, ENVIRONMENTAL, AND STRESS PHYSIOLOGY |
A Study of the Stationary Volumetric Elastic Modulus during Dehydration and Rehydration of Stems of Pea Seedlings
R. Murphy and JKE. Ortega
Department of Mechanical Engineering, Bioengineering Laboratory, University of Colorado at Denver, Campus Box 112, P.O. Box 173364, Denver, Colorado 80217-3364
The relationship between cortical-cell turgor pressure (P) and tissue water
mass (W) was determined for stem segments of pea (Pisum sativum L.)
seedlings subjected to hydration and dehydration. This allowed a test for
elastic hysteresis in the cortical cells. The P-W curves for dehydration
and hydration were not coincident. In some experiments, the P-W curves
exhibited a "roll-off" at high P, similar to the "plateau effect" sometimes
observed in pressure-chamber studies. When hydration was followed by a 4-h
dehydration, the tissue water mass (W0) at minimum turgor was reduced. This
might reflect a reduction in apoplastic water mass and/or a contraction of
the symplast during dehydration. Neglecting the decrease in W0 leads to
underestimates of the stationary volumetric elastic modulus
([epsilon]stat). The result of an analysis that assumes W0 was constant
during hydration suggests that there was no significant difference in
[epsilon]stat between dehydration and hydration and, hence, no significant
elastic hysteresis. However, a 16-h dehydration increased [epsilon]stat;
this might be a response to water stress.
