Journal Article

Light response of hydraulic conductance in bur oak (<i>Quercus macrocarpa</i>) leaves

Mihaela C. Voicu, Janusz J. Zwiazek and Melvin T. Tyree

in Tree Physiology

Volume 28, issue 7, pages 1007-1015
Published in print July 2008 | ISSN: 0829-318X
Published online July 2008 | e-ISSN: 1758-4469 | DOI: http://dx.doi.org/10.1093/treephys/28.7.1007
Light response of hydraulic conductance in bur oak (Quercus macrocarpa) leaves

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A four- to seven-fold enhancement of leaf hydraulic conductance by light has been reported in three temperate tree species. The enhancement occurs in the liquid-flow pathway between the petiole and the site of water evaporation. The enhancement occurs within 1 h, and dissipates in darkness over a period of 1 to 10 h depending on species. Here we report light-induced enhancement of leaf hydraulic conductance in a fourth species, bur oak (Quercus macrocarpa Michx.), the dependence of the effect on light flux and color, its absence in leaves of seedlings, and the impact on the response of leaf vein severance and several metabolic inhibitors. The light response of leaf hydraulic conductance approached saturation at a photosynthetic photon flux of 150 μmol m−2 s−1. Hydraulic enhancement was greater in response to blue and green light than to visible radiation of longer wavelengths, although at the same irradiance, the response to white light was greater than to light of any single color. Atrazine (a photosystem II inhibitor), fusicoccin (which stimulates plasma membrane-bound H+-ATPase) and HgCl2 (an aquaporin blocker) reduced the light response of leaf lamina hydraulic conductance. When 2-mercaptoethanol was added following mercury treatment, the light response was totally suppressed. Our results are consistent with the notion that the effect of light on leaf lamina hydraulic conductance is controlled by factors acting outside the leaf veins, possibly through light-induced changes in membrane permeability of either mesophyll or bundle sheath cells, or both.

Keywords: 2-mercaptoethanol; aquaporins; atrazine; fusicoccin; gas exchange; HgCl2; irradiance; leaf lamina hydraulic conductance; sodium fluoride; stomatal conductance

Journal Article.  0 words. 

Subjects: Plant Sciences and Forestry

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