Abstract
Water potential, osmotic potential and turgor measurements obtained by using a cell pressure probe together with a nanoliter osmometer were compared with measurements obtained with an isopiestic psychrometer. Both types of measurements were conducted in the mature region of Tradescantia virginiana L. leaves under non-transpiring conditions in the dark, and gave similar values of all potentials. This finding indicates that the pressure probe and the osmometer provide accurate measurements of turgor, osmotic potentials and water potentials. Because the pressure probe does not require long equilibration times and can measure turgor of single cells in intact plants, the pressure probe together with the osmometer was used to determine in-situ cell water potentials, osmotic potentials and turgor of epidermal and mesophyll cells of transpiring leaves as functions of stomatal aperture and xylem water potential. When the xylem water potential was-0.1 MPa, the stomatal aperture was at its maximum, but turgor of both epidermal and mesophyll cells was relatively low. As the xylem water potential decreased, the stomatal aperture became gradually smaller, whereas turgor of both epidermal and mesophyll cells first increased and afterward decreased. Water potentials of the mesophyll cells were always lower than those of the epidermal cells. These findings indicate that evaporation of water is mainly occurring from mesophyll cells and that peristomatal transpiration could be less important than it has been proposed previously, although peristomatal transpiration may be directly related to regulation of turgor in the guard cells.
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References
Boyer, J.S. (1966) Isopiestic technique: Measurement of accurate leaf water potentials. Science 154, 1459–1460
Boyer, J.S. (1967) Leaf water potentials measured with a pressure chamber. Plant Physiol. 42,133–137
Boyer, J.s. (1969) Measurement of the water status of plants. Annu. Rev. Plant Physiol. 20, 351–364
Boyer, J.S. (1985) Water transport. Annu. Rev. Plant Physiol. 36, 473–516
Boyer, J.S., Knipling, E.B. (1965) Isopiestic technique for measuring leaf water potentials with a thermocouple psychrometer. Proc. Natl. Acad. Sci. USA 54, 1044–1051
Boyer, J.S., Potter, J.R. (1973) Chloroplast reponse to low leaf water potentials. I. Role of turgor. Plant Physiol. 51, 989–992
Cowan, I.R. (1977) Stomatal behaviour and environment. Adv. Bot. Res. 4, 117–228
Dainty, J. (1963) Water relations of plant cells. Adv. Bot. Res. 1, 279–326
Frensch, J., Schulze, E.-D. (1988) The effect humidity and light on cellular water relations and diffusion conductance of leaves of Tradescantia virginiana L. Planta 173, 554–562
Hüsken, D., Steudle, E., Zimmermann, U. (1978) Pressure probe technique for measuring water relations of cells in higher plants. Plant Physiol. 61, 158–163
Maercker, U. (1965) Zur Kenntnis der Transpiration der Schließzellen. Protoplasma 60, 61–78
Maier-Maercker, U. (1979) “Peristomatal transpiration” and stomatal movement: A controversial view. I. Additional proof of peristomatal transpiration by hygrophotography and a comprehensive discussion in the light of recent results. Z. Pflanzenphysiol. 91, 25–43
Maier-Maercker, U. (1983) The role of peristomatal transpiration in the mechanism of stomatal movement. Plant Cell Environ. 6, 369–380
Meidner, H. (1975) Water supply, evaporation, and vapour diffusion in leaves. J. Exp. Bot. 26, 666–673
Meidner, H. (1976) Vapour loss through stomatal pores with the mesophyll tissue excluded. J. Exp. Bot. 27, 172–174
Neter, J., Wasserman, W., Kutner, N.H. (1983) Applied linear regression models, pp. 147–158, Richard D. Irwin, Homewood, Illinois, USA
Nonami, H., Boyer, J.B., Steudle, E. (1987) Pressure probe and isopiestic psychrometer measure similar turgor. Plant Physiol. 83, 592–595
Rand, H.H. (1977) Gaseous diffusion in the leaf interior. Trans. Am. Soc. Agr. Eng. 20, 701–704
Scholander, P.F., Hammel, H.T., Bradstreet, E.D., Hemmingsen, E.A. (1965) Sap pressure in vascular plants. Science 148, 339–346
Schulze, E.-D. (1986) Carbon dioxide and water vapor exchange in response to drought in the atmosphere and in the soil. Annu. Rev. Plant Physiol. 37, 247–274
Shackel, K.A. (1987) Direct measurement of turgor and osmotic potential in individual epidermal cells: Independent confirmation of leaf water potential as determined by in situ psychrometry. Plant Physiol. 83, 719–722
Shackel, K.A., Brinckmann, E. (1985) In situ measurement of epidermal cell turgor, leaf water potential and gas exchange in Tradescantia virginiana (L.). Plant Physiol. 78, 66–70
Tomos, A.D., Steudle, E., Zimmermann, U., Schulze, E.-D. (1981) Water relations of leaf epidermal cells of Tradescantia virginiana. Plant Physiol. 68, 1135–1143
Tyree, M.T., Yianoulis, P. (1980) The site of water evaporation from sub-stomatal cavities, liquid path resistances and hydroactive stomatal closure. Ann. Bot. 46, 175–193
Zimmermann, U., Steudle E. (1978) Physical aspects of water relations of plant cells. Adv. Bot. Res. 6, 45–117
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Nonami, H., Schulze, ED. Cell water potential, osmotic potential, and turgor in the epidermis and mesophyll of transpiring leaves. Planta 177, 35–46 (1989). https://doi.org/10.1007/BF00392152
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DOI: https://doi.org/10.1007/BF00392152