PLANT PHYSIOLOGY , Vol 111, Issue 2 597-603, Copyright © 1996 by American Society of Plant Biologists
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WHOLE PLANT, ENVIRONMENTAL, AND STRESS PHYSIOLOGY |
Freezing Characteristics of Rigid Plant Tissues (Development of Cell Tension during Extracellular Freezing)
C. B. Rajashekar and M. J. Burke
Division of Horticulture, Kansas State University, Manhattan, Kansas 66506 (C.B.R.)
The freezing characteristics and development of cell tension during
extracellular freezing were examined in supercooling stem tissues of
riverbank grapes (Vitis riparia) and cold-hardened leaves of live oak
(Quercus virginiana) and mountain cranberry (Vaccinium vitis-idaea).
Dormant stem xylem and pith tissues of river-bank grapes were resistant to
freeze-induced dehydration above the homogeneous nucleation temperature,
and they developed cell tension reaching a maximum of 27 MPa. Similarly,
extracellular freezing induced cell tension in the leaves of live oak and
mountain cranberry. Maximum cell tension in the leaves of live oak was 16.8
MPa and 8.3 MPa in the leaves of mountain cranberry. Following peak
tensions in the leaves, a decline in the pressure was observed with
progressive freezing. The results suggest that resistance to cell
deformation during extracellular freezing due to cell-wall rigidity can
lead to reduced cell dehydration and increased cell tension. A relationship
to predict freezing behavior in plant tissues based on cell rigidity is
presented. Based on cell-water relations and ice nucleation rates,
cell-wall rigidity has been shown to effect the freezing characteristics of
plant tissues, including freeze-induced dehydration, supercooling, and
homogeneous nucleation temperatures.
