Abstract
The effect of oxygen on the trans-root potential (TRP) of excised roots in Plantago media L. and P. maritima L. was investigated. Two distinct reactions were found. In some experiments (type A roots) the reaction of TRP to anoxia was bi-phasic, and this reaction fits well into a model, assuming the presence of two spatially separated proton pump sites in the roots: one at the plasmalemma of epidermal and cortical cells and the other at the symplast/xylem interface. The two pumps work in opposite directions. In other experiments (type B roots) no hyperpolarization as a response to anoxia at the inner symplast membrane was observed. There is evidence that the inner pump is also present in these roots, but only in an inactive or electroneutral state. It is concluded that O2-deficiency prevails more often in the central part of the root than in epidermal and cortical cells, when roots are brought gradually under anoxia. This causes the pump located at the symplast/xylem interface to be inhibited more quickly than the other at decreasing O2-concentrations in the bathing solution.
Similar content being viewed by others
Abbreviations
- CCCP:
-
carbonyl cyanide m-chlorophenylhydrazone
- E1 :
-
membrane potential of epidermal and cortical cells, a summation of ED1, a diffusion potential, and EHYP1, a hyperpolarization produced by an electrogenic pump
- E2 :
-
membrane potential of xylemparenchyma cells, a summation of ED2, a diffusion potential, and EHYP2, a hyperpolarization produced by an electrogenic pump
- ED :
-
diffusion potential measured as TRP under anaerobic conditions
- EK :
-
Nernst potential of K+
- e.m.f.:
-
electromotive force
- Jx :
-
flow rate of xylem sap
- PD:
-
electrical potential difference
- p.m.f.:
-
proton motive force
- pO2 :
-
oxygen concentration, at air saturation it is 21%
- TRP20 :
-
trans-root electrical potential difference, the summation of the potential difference across cortex and stele, the suffix refers to the oxygen concentration in the bathing solution
References
Ansari, A.Q., Bowling, D.J.F. (1972) The effect of water and salt fluxes on the trans-root potential in Helianthus annuus. J. Exp. Bot. 23, 641–650
Behl, R., Jeschke, W.D. (1981) Influence of abscisic acid on unidirectional fluxes and intracellular compartmentation of K+ and Na+ in excised barley root segments. Physiol. Plant. 53, 95–100
Bowling, D.J.F., Ansari, A.Q. (1972) Control of sodium transport in sunflower roots. J. Exp. Bot. 23, 241–246
Brouwer, R. (1956) Water uptake from water and salt solutions. Acta Bot. Neerl. 3, 268–276
Davis, R.F., Higinbotham, N. (1969) Effect of external cations and respiratory inhibitors on electrical potential of the xylem exudate of excised corn roots. Plant Physiol 44, 1383–1392
Dunlop, J., Bowling, D.J.F. (1971) The movement of ions to the xylem exudate of maize roots. III. The location of the electrical and electro-chemical potential differences between the exudate and the medium. J. Exp. Bot. 22, 453–464
Erdei, L., Kuiper, P.J.C. (1979) The effect of salinity on growth, cation content, Na+-uptake and translocation in salt-sensitive and salt-tolerant Plantago species. Physiol. Plant. 47, 95–99
Fiscus, E.L., Kramer, P.J. (1970) Radial movement of oxygen in plant roots. Plant Physiol. 45, 667–669
Graham, R.D., Bowling, D.J.F. (1977) Effect of the shoot on the trans-membrane potentials of root cortical cells of sunflower. J. Exp. Bot. 28, 886–893
Hanson, J.B. (1978) Application of the chemiosmotic hypothesis to ion transport across the root. Plant Physiol. 62, 402–405
Jeschke, W.D. (1980) Roots: cation selectivity and compartmentation, involvement of protons and regulation. In: Plant membrane transport: current conceptual issues, pp. 17–29, Spanswick, R.M., Lucas, W.J., Dainty, J., eds. Elsevier, Amsterdam
Keltjens, W.G. (1978) Factors affecting absorption and transport of potassium in maize roots. Ph. D. thesis, Agricultural State University, Wageningen, The Netherlands
Kennedy, C.D. (1979) The effect of applied suctions and 2,4-dichlorophenoxy-acetic acid on water and salt efflux from the cut ends of excised maize roots. J. Exp. Bot. 30, 275–289
Kuiper, F., Kuiper, P.J.C. (1974) Permeability and self-induction as factors in water transport through bean roots. Physiol. Plant. 31, 159–162
Lopushinsky, W. (1964) Effect of water movement on ion movement into the xylem of tomato roots. Plant Physiol. 39, 494–502
Lüttge, U., Higinbotham, N. (1979) Transport in plants, pp. 323–336, Springer, Berlin Heidelberg New York
Okamoto, H., Ichino, K., Katou, K. (1978) Radial electrogenic activity in the stem of Vigna sesquipedalis: involvement of spatially separate pumps. Plant Cell Environ. 1, 279–284
Pitman, M.G. (1971) Uptake and transport of ions in barley seedlings. I. Estimation of chloride fluxes in cells of excised roots. Aust. J. Biol. Sci. 24, 407–421
Pitman, M.G. (1977) Ion transport into the xylem. Annu. Rev. Plant Physiol. 28, 71–88
Poole, J.R. (1978) Energy coupling for membrane transport. Annu. Rev. Plant Physiol. 29, 437–461
Shone, M.G.T. (1968) Electrochemical relations in the transfer of ions to the xylem sap of maize roots. J. Exp. Bot. 19, 468–485
Shone, M.G.T. (1969) Origins of the electrical potential difference between the xylem sap of maize roots and the external solution. J. Exp. Bot. 20, 698–716
Spanswick, R.M. (1981) Electrogenic ion pumps. Annu. Rev. Plant Physiol. 32, 267–289
Wildes, R.A., Pitman, M.G., Schaeffer, N. (1976) Inhibition of ion uptake by cycloheximide. Planta 128, 35–40
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
de Boer, A.H., Prins, H.B.A. & Zanstra, P.E. Bi-phasic composition of trans-root electrical potential in roots of Plantago species: involvement of spatially separated electrogenic pumps. Planta 157, 259–266 (1983). https://doi.org/10.1007/BF00405191
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00405191