A patch clamp study of Na+ transport in maize roots

Roberts, Stephen K. and Tester, Mark (1997) A patch clamp study of Na+ transport in maize roots. Journal of Experimental Botany, 48. pp. 431-440. ISSN 0022-0957

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The mechanisms mediating Na+ transport in higher plant roots were investigated by applying the patch clamp technique to protoplasts isolated from the cortex and stele of maize roots. In the cortex, permeation of Na+ through a time-dependent K+-selective inward rectifier was negligible. Instead, Na+ influx into maize roots probably occurs via an instantaneously-activating current. This current was partially inhibited by extracellular Ca2+, but was insensitive to extracellular TEA(+), Cs+ and TTX. In outside-out patches, a plasma membrane ion channel was found which mediated an inward Na+ current which, at least in part, underlies the whole-cell instantaneously-activating current, the unitary conductance of this channel was 15 pS in 102:121 mM Na+ (outside:cytosol). Channel gating was voltage-independent and distinct from that observed for the inwardly rectifying Kf-selective channel in the same cell type. Increasing extracellular Ca2+ from 0.1 to 1 mM reduced the open probability and unitary conductance of this channel. In 102 mM a(+):123 mM K+ (outside:cytosol) a P-Na: P-K of 2.1 was calculated. It is suggested that the plasma membrane Na+-permeable channel identified in the cortex of maize roots represents a pathway for low affinity Na+ uptake by intact maize roots. In the stele, permeation of Na+ through outwardly rectifying K+ channels was found to be negligible and the channels are thus unlikely to be involved in the transport of Na+ from the root symplasm.

Item Type: Journal Article
Journal or Publication Title: Journal of Experimental Botany
Uncontrolled Keywords: /dk/atira/pure/subjectarea/asjc/1300/1314
Departments: Faculty of Health and Medicine > Biomedical & Life Sciences
ID Code: 72399
Deposited By: ep_importer_pure
Deposited On: 09 Jan 2015 17:01
Refereed?: Yes
Published?: Published
Last Modified: 03 Dec 2019 03:44
URI: https://eprints.lancs.ac.uk/id/eprint/72399

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