Abstract
Water-relation parameters of leaf mesophyll cells of the CAM plant Kalanchoë daigremontiana have been determined directly in cells of tissue slices using the pressure-probe technique. Turgor pressures measured in cells of the second to fourth layer from the cut surface showed an average of 1.82 ± 0.62 bar (mean ± sd; n = 157 cells). This was lower than expected from measurements of the osmotic pressure of the cell sap. The half-time (T1/2) for water-flux equilibration of individual cells was 2.5 to 8.8 seconds. This is the fastest T1/2 found so far for higher-plant cells. The calculated values of the hydraulic conductivity were in the range of 0.20 to 1.6 × 10−5 centimeters second−1 bar−1, with an average of (0.69 ± 0.46) × 10−5 centimeters second−1 bar−1 (mean ± sd; n = 8 cells). The T1/2 values of water exchange of individual cells are consistent with the overall rates of water-flux equilibration measured for tissue slices.
The volumetric elastic moduli (∈) of individual cells were in the range 13 to 128 bar for turgor pressures between 0.0 and 3.4 bar; the average ∈ value was 42.4 ± 27.7 bar (mean ± sd; n = 21 cells). This ∈ value is similar to that observed for other higher-plant cells.
The water-storage capacity of individual cells, calculated as Cc = V/(∈ + πi) (where V = cell volume and πi = internal osmotic pressure) was 9.1 × 10−9 cubic centimeters bar−1 per cell, and the capacity for the tissue was 2.2 × 10−2 cubic centimeters bar−1 gram−1 fresh weight. The significance of the water-relation parameters determined at the cellular level is discussed in terms of the water relations of whole leaves and the high water-use efficiency characteristic of CAM plants.
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- Hanscom Z., Ting I. P. Responses of succulents to plant water stress. Plant Physiol. 1978 Mar;61(3):327–330. doi: 10.1104/pp.61.3.327. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Hüsken D., Steudle E., Zimmermann U. Pressure probe technique for measuring water relations of cells in higher plants. Plant Physiol. 1978 Feb;61(2):158–163. doi: 10.1104/pp.61.2.158. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Lüttge U., Ball E., Greenway H. Effects of Water and Turgor Potential on Malate Efflux from Leaf Slices of Kalanchoë daigremontiana. Plant Physiol. 1977 Oct;60(4):521–523. doi: 10.1104/pp.60.4.521. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Lüttge U., Kluge M., Ball E. Effects of osmotic gradients on vacuolar malic Acid storage: a basic principle in oscillatory behavior of crassulacean Acid metabolism. Plant Physiol. 1975 Nov;56(5):613–616. doi: 10.1104/pp.56.5.613. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Nobel P. S. Water Relations and Photosynthesis of a Desert CAM Plant, Agave deserti. Plant Physiol. 1976 Oct;58(4):576–582. doi: 10.1104/pp.58.4.576. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Philip J. R. Osmosis and Diffusion in Tissue: Half-times and Internal Gradients. Plant Physiol. 1958 Jul;33(4):275–278. doi: 10.1104/pp.33.4.275. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Steudle E., Zimmermann U. Effect of turgor pressure and cell size on the wall elasticity of plant cells. Plant Physiol. 1977 Feb;59(2):285–289. doi: 10.1104/pp.59.2.285. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Steudle E., Zimmermann U. Hydraulische Leitfähigkeit von Valonia utricularis. Z Naturforsch B. 1971 Dec;26(12):1302–1311. [PubMed] [Google Scholar]
- Szarek S. R., Johnson H. B., Ting I. P. Drought Adaptation in Opuntia basilaris: Significance of Recycling Carbon through Crassulacean Acid Metabolism. Plant Physiol. 1973 Dec;52(6):539–541. doi: 10.1104/pp.52.6.539. [DOI] [PMC free article] [PubMed] [Google Scholar]