caa a22 4500 397521936 CHVBK 20180308164635.0 cr unu---uuuuu 161202e199502 xx s 000 0 eng 10.1093/jxb/46.2.199 doi (NATIONALLICENCE)oxford-10.1093/jxb/46.2.199 Reversible closing of water channels in Chara internodes provides evidence for a composite transport model of the plasma membrane [Elektronische Daten] [Tobias Henzler, Ernst Steudle] Treatment of internodal cells of Chara corallina with the water channel blocker HgCl2 caused a decrease of the hydraulic conductivity of the membrane (Lp) by a factor of three to four. In the presence of (practically) non-permeating solutes such as sugars or salts, the osmotic responses were similar to those found in controls, i.e. reflection coefficients (σs) were close to unity. However, when treating the internodes with osmotic solutions of rapidly permeating lipophilic substances such as low molecular weight alcohols or acetone, the picture of biphasic pressure relaxations due to the exchange of both water and solutes changed considerably. In the presence of HgCl2, reflection coefficients were substantially reduced and even became negative for some solutes (anomalous osmosis). Different from reflection coefficients, permeability coefficients (Ps)remained constant upon treatment. When using heavy water (HDO) as a small hydrophilic solute which should cross the membrane largely via water channels, results were different: the reflection coefficient of HDO increased and permeability decreased. Treating the cells with 5 mM 2-mercaptoethanol to remove the mercury from transport proteins (water channels) reversed changes in Lp and σs. The results disagree with conventional membrane models, which imply a homogeneous membrane. They are readily explained by a composite model of the membrane in which proteinaceous arrays with specific water channels are arranged in parallel with lipid arrays. The latter account for most of the permeability of the small organic test solutes used and are not affected by the channel blocker. From the data, detailed information is obtained about transport properties of the arrays (water channels). © Oxford University Press Research Papers nationallicence Anomalous osmosis nationallicence Chara nationallicence composite membrane nationallicence hydraulic conductivity nationallicence permeability coefficient nationallicence reflection coefficient nationallicence water channels nationallicence Henzler Tobias Lehrstuhl Pflanzenökologie, Universitä;t Bayreuth, D-95440 Bayreuth, Germany aut Steudle Ernst Lehrstuhl Pflanzenökologie, Universitä;t Bayreuth, D-95440 Bayreuth, Germany aut Journal of Experimental Botany Oxford University Press 46/2(1995-02), 199-209 0022-0957 46:2<199 1995 46 exbotj https://doi.org/10.1093/jxb/46.2.199 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1093/jxb/46.2.199 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Henzler Tobias Lehrstuhl Pflanzenökologie, Universitä;t Bayreuth, D-95440 Bayreuth, Germany aut NATIONALLICENCE 700 1- Steudle Ernst Lehrstuhl Pflanzenökologie, Universitä;t Bayreuth, D-95440 Bayreuth, Germany aut NATIONALLICENCE 773 0- Journal of Experimental Botany Oxford University Press 46/2(1995-02), 199-209 0022-0957 46:2<199 1995 46 exbotj Metadata rights reserved CC BY-NC-4.0 http://creativecommons.org/licenses/by-nc/4.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-oxford