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  K+ transport properties of K+ channels in the plasma membrane of Vicia faba guard cells.

Schröder, J. (1988). K+ transport properties of K+ channels in the plasma membrane of Vicia faba guard cells. The Journal of General Physiology, 92(5), 667-683. doi:10.1085/jgp.92.5.667.

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Item Permalink: http://hdl.handle.net/11858/00-001M-0000-002D-3B9C-0 Version Permalink: http://hdl.handle.net/11858/00-001M-0000-002D-3B9E-C
Genre: Journal Article

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Schröder, J.1, Author              
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1Department of Membrane Biophysics, MPI for biophysical chemistry, Max Planck Society, ou_578579              

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 Abstract: Electrical properties of the plasma membrane of guard cell protoplasts isolated from stomates of Vicia faba leaves were studied by application of the whole-cell configuration of the patch-clamp technique. The two types of K+ currents that have recently been identified in guard cells may allow efflux of K+ during stomatal closing, and uptake of K+ during stomatal opening (Schroeder et al., 1987). A detailed characterization of ion transport properties of the inward-rectifying (IK+,in) and the outward-rectifying (IK+,out) K+ conductance is presented here. The permeability ratios of IK+,in and IK+,out currents for K+ over monovalent alkali metal ions were determined. The resulting permeability sequences (PK+ greater than PRb+ greater than PNa+ greater than PLi+ much greater than PCs+) corresponded closely to the ion specificity of guard cell movements in V. faba. Neither K+ currents exhibited significant inactivation when K+ channels were activated for prolonged periods (greater than 10 min). The absence of inactivation may permit long durations of K+ fluxes, which occur during guard cell movements. Activation potentials of inward K+ currents were not shifted when external K+ concentrations were changed. This differs strongly from the behavior of inward-rectifying K+ channels in animal tissue. Blue light and fusicoccin induce hyperpolarization by stimulation of an electrogenic pump. From slow-whole-cell recordings it was concluded that electrogenic pumps require cytoplasmic substrates for full activation and that the magnitude of the pump current is sufficient to drive K+ uptake through IK+,in channels. First, direct evidence was gained for the hypothesis that IK+,in channels are a molecular pathway for K+ accumulation by the finding that IK+,in was blocked by Al3+ ions, which are known to inhibit stomatal opening but not closing. The results presented in this study strongly support a prominent role for IK+,in and IK+,out channels in K+ transport across the plasma membrane of guard cells.

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Language(s): eng - English
 Dates: 1988-11
 Publication Status: Published in print
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 Rev. Method: Peer
 Identifiers: DOI: 10.1085/jgp.92.5.667
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Title: The Journal of General Physiology
Source Genre: Journal
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Pages: - Volume / Issue: 92 (5) Sequence Number: - Start / End Page: 667 - 683 Identifier: -