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231223s1997 xx |||||o 00| ||eng c |
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|a 10.1093/jxb/48.Special_Issue.481
|2 doi
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|a pubmed24n0684.xml
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|a (NLM)21245226
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|a DE-627
|b ger
|c DE-627
|e rakwb
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| 041 |
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|a eng
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| 100 |
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|a Amtmann, A
|e verfasserin
|4 aut
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|a Multiple inward channels provide flexibility in Na+/K+ discrimination at the plasma membrane of barley suspension culture cells
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|c 1997
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|a Text
|b txt
|2 rdacontent
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|a ƒaComputermedien
|b c
|2 rdamedia
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|a ƒa Online-Ressource
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|2 rdacarrier
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|a Date Completed 02.10.2012
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|a Date Revised 19.01.2011
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|a published: Print
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|a Citation Status PubMed-not-MEDLINE
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|a Ion transport across the plasma membrane of suspension-culture cells derived from immature barley embryos has been studied in low (15 mM KCl) and high (additional 150 mM NaCl) salt conditions to understand how plants discriminate between K(+) and Na(+) during ion uptake. In both media about 50% of the cells exhibited resting potentials more negative than any of the passive diffusion potentials. In whole-cell patch clamp experiments membrane hyperpolarization activated large inward currents. Whilst the instantaneous current components did not discriminate between K(+) and Na(+), the time-dependent current, I(in), was selective for K(+) over Na(+). Further analysis of I(in) revealed the following properties: double exponential current activation (time-constants 0.03 s and 0.3 s, half activation potential - 171 mV); no inactivation; complete block by Ba(2+) (30 mM in 100 mM KCl) and part block by TEA(+) (maximum 50% with 20 mM); dependence on millimolar concentrations of cytoplasmic ATP; no block by external or cytoplasmic Na(+). The selectivity sequences K(+) ≫ Rb(+) > NH(+)(4) > Na(+) ≫ Cl(-) and K(+) ≫ NH(+)(4) > Na(+) > Rb(+) were determined from measurements of reversal potentials and relative steady-state currents respectively. P(Na):P(K) was 0.07 ± 0.02 (from reversal potentials) and I(Na):I(K) was 0.17 + 0.05 (from relative currents). A high variance among the observed permeability ratios suggested that several channels with different ion-selectivities contributed to the time-dependent whole-cell currents. In single channel experiments, several inward channels with distinct properties were found. The major channels were (i) a voltage-gated, K(+)-selective channel (12 pS), (ii) an ATP-activated non-selective cation channel (7 pS) and (iii) an inward-rectifying anion-channel (150 pS, all unitary conductances given for 100 mM KCI). No significant differences were found in whole-cell currents or single-channel characteristics between cells that had been adapted to a high-salt growth-medium (150 mM NaCl) and non-adapted cells. The idea that differential regulation of plasma membrane ion channels gives rise to a physiological flexibility, allowing the cells to control Na(+) uptake under varying external conditions, is discussed
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|a Journal Article
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|a Laurie, S
|e verfasserin
|4 aut
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|a Leigh, R
|e verfasserin
|4 aut
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| 700 |
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|a Sanders, D
|e verfasserin
|4 aut
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| 773 |
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|i Enthalten in
|t Journal of experimental botany
|d 1985
|g 48 Spec No(1997) vom: 15. März, Seite 481-97
|w (DE-627)NLM098182706
|x 1460-2431
|7 nnns
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| 773 |
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|g volume:48 Spec No
|g year:1997
|g day:15
|g month:03
|g pages:481-97
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| 856 |
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|u http://dx.doi.org/10.1093/jxb/48.Special_Issue.481
|3 Volltext
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