This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Web of Science (46) Citing Articles via Google Scholar Google Scholar Articles by Läuchli, A. Articles by Epstein, E. Search for Related Content PubMed PubMed Citation Articles by Läuchli, A. Articles by Epstein, E. Agricola Articles by Läuchli, A. Articles by Epstein, E.

Articles

Lateral Transport of Ions into the Xylem of Corn Roots

I. Kinetics and Energetics ¹

^a Department of Soils and Plant Nutrition, University of California, Davis, California 95616

A technique is described for study of the kinetics of lateral transport of ions across single roots of corn, Zea mays, in short term experiments under steady state conditions. The kinetics of chloride transfer to the vessels reflected the kinetics of absorption of chloride by the root cells. Efflux from the root vacuoles contributed to only a small extent to transport of chloride into the exudate. Lateral transport of chloride was inhibited by bromide at chloride concentrations in the ranges of both mechanisms 1 and 2 in a manner implicating competition. The uncoupler carbonylcyanide m-chlorophenylhydrazone used at 1 µM caused transfer of chloride to cease almost immediately at both low and high concentrations of chloride. Oligomycin depressed transport of chloride to the vessels within 10 to 15 minutes after application at 2 micrograms per milliliter. Inhibition by oligomycin was 75% at 0.5 mM chloride and 55% at 5 mM.

It is concluded that lateral transport of chloride across corn roots is mediated by the dual mechanisms of ion absorption which reside in the plasmalemma. Transfer of chloride is inhibited by bromide and depends upon ATP as energy source. Chloride moves from the plasmalemma, the site of carriermediated absorption, to the xylem vessels by way of the symplasm. There is no evidence in these experiments that lateral transport of chloride in corn roots is governed by diffusion at any concentrations of chloride used in these experiments.

¹ Supported by a travel grant from the American-Swiss Foundation for Scientific Exchange to the senior author, and a grant from the Office of Saline Water, United States Department of the Interior, to the junior author. A preliminary report of this investigation was presented at the XI International Botanical Congress in Seattle, Wash., August 25, 1969. The method used in the exudation experiments has also been briefly described in a previous paper on the absorption and translocation of potassium and rubidium (21).

This article has been cited by other articles:

				F. Ma and C. A. Peterson Frequencies of plasmodesmata in Allium cepa L. roots: implications for solute transport pathways J. Exp. Bot., May 1, 2001; 52(358): 1051 - 1061. [Abstract] [Full Text] [PDF]