JXB Advance Access published online on November 22, 2006
Journal of Experimental Botany, doi:10.1093/jxb/erl203
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1 Division of Biological Sciences, University of Paisley, Paisley, PA1 2BE, Scotland, UK
* To whom correspondence should be addressed. A pressure probe technique and an osmotic swelling assay were used to compare water transport properties between growing and non-growing tissues of leaf three of barley. The epidermis was analysed in planta by pressure probe, whereas (predominantly) mesophyll protoplasts were analysed by osmotic swelling. Hydraulic conductivity (Lp) and, by implication, water permeability (Pf) of epidermal cells was 31% higher in the leaf elongation zone (Lp=0.5±0.2 µm s-1 MPa-1; Pf=65±25 µm s-1; means ±SD of n=17 cells) than in the, non-growing, emerged leaf zone (Lp=0.4±0.1 µm s-1 MPa-1; Pf=50±15 µm s-1; n=24; P <0.05). Similarly, water permeability of mesophyll protoplasts was by 55% higher in the elongation compared with emerged leaf zone (Pf=13±1 µm s-1 compared with 8±1 µm s-1; n=57 and 36 protoplasts, respectively; P <0.01). Within the leaf elongation zone, a small population of larger-sized protoplasts could be distinguished. These protoplasts, which originated most likely from parenchymateous bundle sheath or midrib parenchyma cells, had a three-fold higher water permeability (P <0.001) as mesophyll protoplasts. The effect on Lp and Pf of known aquaporin inhibitors was tested with the pressure probe (Au+, Ag+, Hg2+, phloretin) and the osmotic swelling assay (phloretin). Only phloretin, when applied to protoplasts in the swelling assay caused an average decrease in Pf, but the effect varied between isolations. Technical approaches and cell-type and growth-specific differences in water transport properties are discussed.
Received April 10, 2006
Revised September 6, 2006
Accepted September 19, 2006
RESEARCH PAPER
Water permeability differs between growing and non-growing barley leaf tissues
Vadim Volkov 1, Charles Hachez 2, Menachem Moshelion 3, Xavier Draye 4, François Chaumont 2, and Wieland Fricke 5 *
2 Unité de Biochimie Physiologique, Institut des Sciences de la Vie, Université catholique de Louvain, Croix du Sud 5-15, B-1348 Louvain-la-Neuve, Belgium
3 The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, Faculty of Agricultural, Food & Environmental Quality Science, The Hebrew University of Jerusalem, Rehovot, 76100 Israel
4 Unité d'écophysiologie et amélioration végétale, Université catholique de Louvain, Croix du Sud 1-10, B-1348 Louvain-la-Neuve, Belgium
5 Division of Biological Sciences, University of Paisley, Paisley, PA1 2BE, Scotland, UK; UCD School of Biology and Environmental Science, University College Dublin, Belfield, Dublin 4, Ireland
Wieland Fricke, E-mail: wieland02fricke{at}yahoo.co.uk
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