JXB Advance Access published online on October 10, 2007
Journal of Experimental Botany, doi:10.1093/jxb/erm220
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© 2007 The Author(s).
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
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RESEARCH PAPER |
Low air humidity increases leaf-specific hydraulic conductance of Arabidopsis thaliana (L.) Heynh (Brassicaceae)
1Institute of Field and Garden Crops, The Volcani Center, Bet Dagan 50250, Israel
2Institute of Soil, Water and Environmental Sciences, The Volcani Center, Bet Dagan 50250, Israel
To whom correspondence should be addressed. E-mail: vwshep{at}volcani.agri.gov.il
The typical isohydric plant response to low relative humidity involves stomatal closure, followed by long-term responses like adjustment of shoot-to-root ratios. Little information is available on the early responses of the root system to exposure of shoots to low humidity, nor is it clear to what extent responses of Arabidopsis thaliana conform to the isohydric model. In this study, A. thaliana plants grown hydroponically at high humidity were exposed to two constant relative humidities, 17% and 77%, while the root system remained in aerated nutrient solution. Leaf conductance (gs), transpiration, water potential (
l), osmotic potential, and whole plant hydraulic conductance (K) were determined for the following time intervals: 0–10, 10–20, and 20–40 min, and 0–5, 5–10, and 24–29 h. At low relative humidity, no change in gs was detected. l decreased by 0.28 MPa during the first 5 h and then remained stable. During the first hour, leaf-specific K averaged 1.6x10–5 kg MPa–1 m–2 s–1 at high humidity. At low humidity it increased >3-fold to 5.8x10–5 kg MPa–1 m–2 s–1. Similar significant differences in K were observed during all time periods. Low concentration mercury amendments in the hydroponic solution (5 µM and 10 µM HgCl2) had no discernible influence, but pre-exposure to 50 µM HgCl2 reduced K differences between humidity treatments. As HgCl2 is known to be a potent inhibitor of aquaporin function, this suggests that aquaporins may have played a role in the fast hydraulic response of plants transferred to low humidity. The rapid hydraulic response and the influence of mercury raise the possibility that an alternative response to atmospheric dryness is increased K modulated by aquaporins.
Key words: Aquaporin, isohydric, leaf conductance, osmotic, water potential, water relations
* Both to be considered as first authors.
Received 21 June 2007; Revised 15 August 2007 Accepted 22 August 2007
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