Research output: Contribution to Journal/Magazine › Journal article › peer-review
<mark>Journal publication date</mark> | 03/1997 |
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<mark>Journal</mark> | Journal of Experimental Botany |
Volume | 48 |
Number of pages | 10 |
Pages (from-to) | 431-440 |
Publication Status | Published |
<mark>Original language</mark> | English |
Event | Annual Meeting of the Society-for-Experimental-Biology - LANCASTER, United Kingdom Duration: 24/03/1996 → 29/03/1996 |
Conference | Annual Meeting of the Society-for-Experimental-Biology |
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Country/Territory | United Kingdom |
Period | 24/03/96 → 29/03/96 |
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.