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WHOLE PLANT AND ECOPHYSIOLOGY

Drought and Abscisic Acid Effects on Aquaporin Content Translate into Changes in Hydraulic Conductivity and Leaf Growth Rate: A Trans-Scale Approach^1,[W],[OA]

INRA, UMR 759 Laboratoire d'Ecophysiologie des Plantes sous Stress Environnementaux, F–34060 Montpellier, France (B.P., T.S., F.T.); Institut des Sciences de la Vie, Université catholique de Louvain, B–1348 Louvain-la-Neuve, Belgium (C.H., F.C.); and Biogemma Auvergne, ZI du Brézet, F–63028, Clermont-Ferrand, France (E.R.)

The effects of abscisic acid (ABA) on aquaporin content, root hydraulic conductivity (Lp_r), whole plant hydraulic conductance, and leaf growth are controversial. We addressed these effects via a combination of experiments at different scales of plant organization and tested their consistency via a model. We analyzed under moderate water deficit a series of transformed maize (Zea mays) lines, one sense and three antisense, affected in NCED (for 9-cis-epoxycarotenoid dioxygenase) gene expression and that differed in the concentration of ABA in the xylem sap. In roots, the mRNA expression of most aquaporin PIP (for plasma membrane intrinsic protein) genes was increased in sense plants and decreased in antisense plants. The same pattern was observed for the protein contents of four PIPs. This resulted in more than 6-fold differences between lines in Lp_r under both hydrostatic and osmotic gradients of water potential. This effect was probably due to differences in aquaporin activity, because it was nearly abolished by a hydrogen peroxide treatment, which blocks the water channel activity of aquaporins. The hydraulic conductance of intact whole plants was affected in the same way when measured either in steady-state conditions or via the rate of recovery of leaf water potential after rewatering. The recoveries of leaf water potential and elongation upon rehydration differed between lines and were accounted for by the experimentally measured Lp_r in a model of water transfer. Overall, these results suggest that ABA has long-lasting effects on plant hydraulic properties via aquaporin activity, which contributes to the maintenance of a favorable plant water status.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: François Tardieu (tardieu{at}supagro.inra.fr).

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www.plantphysiol.org/cgi/doi/10.1104/pp.108.130682

^* Corresponding author; e-mail tardieu{at}supagro.inra.fr.

Received October 1, 2008; accepted February 6, 2009; published February 11, 2009.

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