Journal Article

Onion Root Water Transport Sensitive to Water Channel andK<sup>+</sup> ChannelInhibitors

Masashi Tazawa, Emi Sutou and Mineo Shibasaka

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 42, issue 1, pages 28-36
Published in print January 2001 | ISSN: 0032-0781
Published online January 2001 | e-ISSN: 1471-9053 | DOI:
Onion Root Water Transport Sensitive to Water Channel andK+ ChannelInhibitors

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  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry


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Transroot osmotic water flux (Jos) and radial hydraulic conductivity (Lpr) in onion roots were greatly increased by three means; infiltration of roots by pressurization, repetition of osmosis and chilling at 5°C. Jos was strongly reduced by the water channel inhibitor HgCl2 (91%) and the K+ channel inhibitor nonyltriethylammonium (C9, 75%), which actually made the membrane potential of root cells less sensitive to K+. C9 decreased the rate of turgor reduction induced by sorbitol solution to the same extent as HgCl2. Thus, C9 is assumed to decrease the hydraulic conductivity (Lp) of the plasma membrane by blocking water channels, although possible inhibition of the plasmodesmata of the root symplast by C9 cannot be excluded. Onion roots transported water from the tip to the base in the absence of the osmotic gradient. This non-osmotic water flux (Jnos) was equivalent to Jos induced by 0.029 M sorbitol. Jnos increased when Jos was increased by repetition of osmosis and decreased when Jos was decreased by either HgCl2 or by C9. The correlation between Jnos and Jos suggests that non-osmotic water transport occurs via the same pathways as those for osmotic water transport.

Keywords: Key words: Hydraulic conductivity — K+ channel inhibitor — Membrane potential — Non-osmotic water transport — Onion roots — Water channel inhibitor.; Abbreviations: APW, artificial pond water; C9, nonyltriethylammonium; Em, membrane potential; Jnos, transroot non-osmotic water flux; Jos, transroot osmotic water flux; Lp, cell hydraulic conductivity; Lpr, transroot hydraulic conductivity; TEA, tetraethylammonium.

Journal Article.  6535 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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