Abstract
The water relations of growing epicotyl segments of pea (Pisum sativum L.) were studied using the miniaturized pressure probe. For epidermal cells stationary turgor pressures of P=5 to 9 bar and half-times of water exchange of individual cells T 1/2=1 to 27 s were found. The volumetric clastic modulus (ɛ) of epidermal cells varied from 12 to 200 bar and the hydraulic conductivity, Lp=0.2 to 2·10-6 cm s-1 bar-1. For cortical cells P=5 to 11 bar, T 1/2=0.3 to 1 s, Lp=0.4 to 9·10-5 cm s-1 bar-1 and ɛ=6 to 215 bar. The T 1/2 of cortical cells was extremely low and the Lp rather high as compared to other higher plant cells. The T 1/2-values of cortical cells were sometimes observed to change from short to substantially longer values (T 1/2=3 to 20 s). Both short and long pressure relaxations showed all the characteristics of non-artifactual curves. The change is apparently due to an increase in Lp and not ɛ, but the reason for the change in cell permeability to water is not known.
In osmotic exchange experiments on peeled segments using solutions of different solutes, the half-time of osmotic water exchange for the whole segment was approximately 60 s. Water exchange occurred too quickly to be rate controlled by solute diffusion in the wall space. The data suggest that the short T 1/2-values in the cortical cells are the physiologically relevant ones for the intact tissue and that a considerable component of water transport occurs in the cell-to-cell pathway, although unstirred layer effects at the boundary between the segment and solution may influence the measured half-time. Using the theory of Molz and Boyer (1978, Plant Physiol. 62, 423–429), the gradient in water potential necessary to maintain the uptake of water for cell enlargement can be calculated from the measured diffusivities to be approximately 0.2 and 1 bar for growth rates of 1% h-1 and 5% h-1, respectively. Thus, although the T 1/2-values are short and Lp rather high, there may be a significant osmotic disequilibrium in the most rapidly growing tissue and as a consequence the influence of water transport on the growth rate cannot be excluded.
Article PDF
Similar content being viewed by others
Avoid common mistakes on your manuscript.
Abbreviations
- P:
-
turgor pressure
- T 1/2 :
-
half-time of water exchange of individual cell
- Lp:
-
hydraulic conductivity
- ɛ:
-
volumetric elastic modulus
- t 1/2 :
-
average half-time of water exchange of tissue
References
Boyer, J.S. (1968) Relationship of water potential to growth of leaves. Plant Physiol. 43, 1056–1062
Boyer, J.S., Wu, G. (1978) Auxin increases the hydraulic conductivity of auxin-sensitive hypocotyl tissue. Planta 139, 227–237
Cleland, R. (1977) The control of cell enlargement. Symp. Soc. Exp. Biol. 31, 101–116
Cosgrove, D.J. (1981) Rapid suppression of growth by blue light: Occurrence, time course and general characteristics. Plant Physiol. 67, 584–590
Dowler, M.J., Rayle, D.L., Cande, W.T., Ray, P.M., Durand, H., Zenk, M.H. (1974) Auxin does not alter the permeability of pea segments to tritium-labeled water. Plant Physiol. 53, 229–232
Hüsken, D., Steudle, E., Zimmermann, U. (1978) Pressure probe technique for measuring water relations of cells in higher plants. Plant Physiol. 61, 158–163
Kohn, P.G., Dainty, J. (1966) The measurement of permeability to water in disks of storage tissue. J. Exp. Bot. 17, 809–821
Molz, F.J., Ikenberry, E. (1974) Water transport through plant cells and cell walls: Theoretical development. Soil Sci. Soc. Am. Proc. 38, 699–704
Molz, F.J., Boyer, J.S. (1978) Growth-induced water potentials in plant cells and tissues. Plant Physiol. 62, 423–429
Philip, J.R. (1958) Osmosis and diffusion in tissues:Half-times and internal gradients. Plant Physiol. 33, 275–278
Ray, P.M., Ruesink, A.W. (1963) Osmotic behavior of oat coleoptile tissue in relation to growth. J. Gen. Physiol. 47, 83–101
Ray, P.M., Green, P.B., Cleland, R.E. (1972) Role of turgor in plant cell growth. Nature (London) 239, 163–164
Robards, A.W., Clarkson, D.T. (1976) The role of plasmodesmata in the transport of water and nutrients across roots. In: Intercellular communication in plants: Studies in plasmodesmata, pp. 181–203, Gunning, B.E.S., Robards, A.W., eds. Springer Verlag, Berlin Heidelberg New York
Steudle, E., Smith, J.A.C., Lüttge, U. (1980) Water-relation parameters of individual mesophyll cells of the crassulacean acid metabolism plant Kalanchoë daigremontiana. Plant Physiol. 66, 1155–1163
Tomos, A.D., Steudle, E., Zimmermann, U., Schulze, E.-D. (1981) Water relations of leaf epidermal cells of Tradescantia virginiana). Plant Physiol. (in press)
Walker, N.A., Pitman, M.G. (1976) In: Encyclopedia of plant physiology, New Series, Vol. 2 part A, pp. 93–126, Lüttge, U., Pitman, M.G., eds. Springer-Verlag,Berlin Heidelberg New York
Zimmermann, U., Hüsken, D. (1979) Theoretical and experimental exclusion of errors in the determination of the elasticity and water transport parameters of plant cells by the pressure probe technique. Plant Physiol. 64, 18–24
Zimmermann, U., Steudle, E. (1978) Physical aspects of water relations of plant cells.Adv. Bot. Res. 6, 45–117
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Cosgrove, D., Steudle, E. Water relations of growing pea epicotyl segments. Planta 153, 343–350 (1981). https://doi.org/10.1007/BF00384253
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00384253