Abstract
Potassium ion and Na+ influx and efflux rates into and from excised barley roots are compared with the maximum capacity of accumulation. Potassium ion and Na+ influx and efflux involve a cation exchange that is independent of simultaneous exchange of the accompanying anion. These exchange fluxes depend on the concentration and cation composition of the solutions from which they originate. Selective differences between K+ and Na+ fluxes are sufficient to account for a cationic distribution within the roots that differs markedly from that of the external solution and that persists for extended time periods. The accumulation maximum is a cation exchange equilibrium with the cation influx and efflux rates approaching equality. The equilibrium level is independent of the individual cation fluxes and the external solution concentration. It is a finite quantity which appears to be determined by the internal anion concentration including accumulated as well as endogenous anions.
Full Text
The Full Text of this article is available as a PDF (885.3 KB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- COTLOVE E., TRANTHAM H. V., BOWMAN R. L. An instrument and method for automatic, rapid, accurate, and sensitive titration of chloride in biologic samples. J Lab Clin Med. 1958 Mar;51(3):461–468. [PubMed] [Google Scholar]
- Epstein E., Hagen C. E. A KINETIC STUDY OF THE ABSORPTION OF ALKALI CATIONS BY BARLEY ROOTS. Plant Physiol. 1952 Jul;27(3):457–474. doi: 10.1104/pp.27.3.457. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Epstein E., Rains D. W., Elzam O. E. RESOLUTION OF DUAL MECHANISMS OF POTASSIUM ABSORPTION BY BARLEY ROOTS. Proc Natl Acad Sci U S A. 1963 May;49(5):684–692. doi: 10.1073/pnas.49.5.684. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Epstein E., Rains D. W., Schmid W. E. Course of Cation Absorption by Plant Tissue. Science. 1962 Jun 22;136(3521):1051–1052. doi: 10.1126/science.136.3521.1051. [DOI] [PubMed] [Google Scholar]
- Fried M., Noggle J. C. Multiple Site Uptake of Individual Cations by Roots as Affected by Hydrogen Ion. Plant Physiol. 1958 Mar;33(2):139–144. doi: 10.1104/pp.33.2.139. [DOI] [PMC free article] [PubMed] [Google Scholar]
- HODGKIN A. L., KEYNES R. D. The potassium permeability of a giant nerve fibre. J Physiol. 1955 Apr 28;128(1):61–88. doi: 10.1113/jphysiol.1955.sp005291. [DOI] [PMC free article] [PubMed] [Google Scholar]
- JACKSON P. C., ADAMS H. R. Cation-anion balance during potassium and sodium absorption by barley roots. J Gen Physiol. 1963 Jan;46:369–386. doi: 10.1085/jgp.46.3.369. [DOI] [PMC free article] [PubMed] [Google Scholar]