Journal Article

Low air humidity increases leaf-specific hydraulic conductance of <i>Arabidopsis thaliana</i> (L.) Heynh (Brassicaceae)

Michal Levin, Jorge Hugo Lemcoff, Shabtai Cohen and Yoram Kapulnik

in Journal of Experimental Botany

Published on behalf of Society for Experimental Biology

Volume 58, issue 13, pages 3711-3718
Published in print October 2007 | ISSN: 0022-0957
Published online October 2007 | e-ISSN: 1460-2431 | DOI: http://dx.doi.org/10.1093/jxb/erm220

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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 (Ψl), 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. Ψl decreased by 0.28 MPa during the first 5 h and then remained stable. During the first hour, leaf-specific K averaged 1.6×10−5 kg MPa−1 m−2 s−1 at high humidity. At low humidity it increased >3-fold to 5.8×10−5 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.

Keywords: Aquaporin; isohydric; leaf conductance; osmotic; water potential; water relations

Journal Article.  6006 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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