Abstract
Accumulation of Cl- by excised barley roots, as of K+, approaches a maximum level at which the ion influx and efflux rates become equal. The rate of Cl- influx at this equilibrium is close to the initial rate while the efflux rate increases with time from zero to equality with influx. The Cl- fluxes are independent of simultaneous exchange flux of the cations, but depend on the nature and concentration of the salt solutions from which they originate. The Cl- content at equilibrium, however, is largely independent of the external concentrations. The approach to equilibrium reflects the presence of the cation. Cl- flux equilibrium is attained more rapidly in KCl than in CsCl or CaCl2. This is presumably an effect of much slower distribution of Cs+ and Ca++ than of K+ within the roots. Accumulated Cs+ appears to form a barrier to ion movement primarily within the outermost cells, thereby reducing influx and ultimately efflux rates of both Cl- and cations. Slow internal mixing and considerable self-exchange of the incoming ions suggest internal transport over a series of steps which can become rate-limiting to the accumulation of ions in roots.
Full Text
The Full Text of this article is available as a PDF (967.3 KB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Bange G. G., Overstreet R. Some Observations on Absorption of Cesium by Excised Barley Roots. Plant Physiol. 1960 Sep;35(5):605–608. doi: 10.1104/pp.35.5.605. [DOI] [PMC free article] [PubMed] [Google Scholar]
- ETHERTON B., HIGINBOTHAM N. Transmembrane potential measurements of cells of higher plants as related to salt uptake. Science. 1960 Feb 12;131(3398):409–410. doi: 10.1126/science.131.3398.409. [DOI] [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]
- Laties G. G., Budd K. THE DEVELOPMENT OF DIFFERENTIAL PERMEABILITY IN ISOLATED STELES OF CORN ROOTS. Proc Natl Acad Sci U S A. 1964 Aug;52(2):462–469. doi: 10.1073/pnas.52.2.462. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Prevot P., Steward F. C. SALIENT FEATURES OF THE ROOT SYSTEM RELATIVE TO THE PROBLEM OF SALT ABSORPTION. Plant Physiol. 1936 Jul;11(3):509–534. doi: 10.1104/pp.11.3.509. [DOI] [PMC free article] [PubMed] [Google Scholar]
- SEVERINGHAUS J. W., BRADLEY A. F. Electrodes for blood pO2 and pCO2 determination. J Appl Physiol. 1958 Nov;13(3):515–520. doi: 10.1152/jappl.1958.13.3.515. [DOI] [PubMed] [Google Scholar]
- VENKATESWARLU P., ARMSTRONG W. D., SINGER L. ABSORPTION OF FLUORIDE AND CHLORIDE BY BARLEY ROOTS. Plant Physiol. 1965 Mar;40:255–261. doi: 10.1104/pp.40.2.255. [DOI] [PMC free article] [PubMed] [Google Scholar]