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Article Addendum
Step by Step: Deciphering Ion Transport in the Root Xylem Parenchyma
Barbara Köhler
volume 2 | issue 4
july/august 2007Pages: 303 - 305
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Proton pumps produce electrical potential differences and differences in pH across the plasma membrane of cells which drive secondary ion transport through sym- and antiporters. We used the patch-clamp technique to characterize an H+-pump in the xylem parenchyma of barley roots. This cell type is of special interest with respect to xylem loading. Since it has been an ongoing debate whether xylem loading is a passive or an active process, the functional characterization of the H+-pump is of major interest in the context of previous work on ion channels through which passive salt efflux into the xylem vessels could occur. Cell-type specific features like its Ca2+ dependence were determined, that are important to interpret its physiological role and eventually to model xylem loading. We conclude that the electrogenic pump in the xylem parenchyma does not participate directly in the transfer of KCl and KNO3 to the xylem but, in combination with short-circuiting conductances, plays a crucial role in controlling xylem unloading and loading through modulation of the voltage difference across the plasma membrane. Here, our recent results on the H+ pump are put in a larger context and open questions are highlighted.
Authors
Barbara Köhler
Universität Potsdam, Potsdam-Golm, Germany
We now provide open access to journal articles published online for one year or more. This article may be downloaded at the following link:
Download PDF If the document does not open, please right-click on the link (control-click on a Macintosh) and select the option to save the file to disk.