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Inhibition of Water Channels by HgCl2 in Intact
Wheat Root Cells1
Wen-Hao Zhang* and
Stephen D. Tyerman
School of Biological Sciences, The Flinders University of South
Australia, G.P.O. Box 2100, Adelaide 5001, Australia
To assess the extent of water flow
through channels in the membranes of intact higher plant cells, the
effects of HgCl2 on hydraulic conductivity
(LP) of wheat (Triticum
aestivum L.) root cells were investigated using a pressure
probe. The LP of root cells was reduced by
75% in the presence of 100 µM HgCl2. The K+-channel blocker tetraethylammonium had no effect on the
LP at concentrations that normally block
K+ channels. HgCl2 rapidly depolarized the
membrane potential (Vm) of the root cells.
The dose-response relationship of inhibition of
LP and depolarization of
Vm were not significantly different, with
half-maximal inhibition occurring at 4.6 and 7.8 µM,
respectively. The inhibition of LP and the
depolarization of Vm caused by
HgCl2 were partially reversed by -mercaptoethanol. The
inhibition of LP by HgCl2 was
similar in magnitude to that caused by hypoxia, and the addition of
HgCl2 to hypoxia-treated cells did not result in further
inhibition. We compared the LP of intact
cells with that predicted from a model of cortical cells incorporating
water flow across both the plasma membrane and the tonoplast using
measured values of water permeability from isolated membranes, and
found that HgCl2 has other effects in addition to the
direct inhibition of water channels.
1
This study was supported in part by the
Australian Research Council.
*
Corresponding author; e-mail Wenhao.Zhang{at}flinders.edu.au; fax
618-8201-3015.
Plant Physiol. (1999) 120: 849-858
Copyright Clearance Center: 0032-0889/99/120//10
© 1999 American Society of Plant Physiologists
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