Water relations of turgor recovery and restiffening of wilted cabbage leaves in the absence of water uptake.
A novel phenomenon in which wilted cabbage leaves appeared to regain positive turgor pressures without additional water uptake has been previously reported (J Levitt [1986] Plant Physiol 82: 147-153). These experiments were replicated and the biophysical nature of turgor recovery characterized. Leaf water potential and its components were assayed in hydrated, wilted, and desiccated leaves which appeared to regain turgor after wilting. The hypotheses that turgor recovery was due to an increased volumetric elastic modulus (epsilon), or alternatively the result of solute redistribution were tested. Quantitative evidence that turgor recovery occurs in excised leaves was found. Leaf turgor pressure in hydrated leaves ( approximately 0.6 megapascal) decreased to zero upon wilting. After continued desiccation, turgor pressure returned to approximately 0.3 megapascal even though leaf relative water content declined. The epsilon of hydrated leaves was large and there was no evidence of an increased epsilon in the turgor-recovered leaves. Solute mobilization occurred during desiccation. The apoplastic osmotic potential decreased from -0.15 to -0.44 megapascal in hydrated and turgor-recovered leaves, respectively, and solutes were transported from the lamina to the midrib tissue. Solute redistribution coupled with the high epsilon may have resulted in localized turgor recovery in specific cells in the desiccated leaves.
Weisz
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U.S. Department of Agriculture, Agricultural Research Service, University of Florida, Gainesville, Florida 32611.
Randall
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Sinclair
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