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ENVIRONMENTAL STRESS AND ADAPTATION TO STRESS

Root Plasma Membrane Transporters Controlling K⁺/Na⁺ Homeostasis in Salt-Stressed Barley^1,[C],[W]

School of Agricultural Science (Z.C., T.A.C., S.S.) and School of Mathematics and Physics (I.A.N.), University of Tasmania, Hobart, Tasmania 7001, Australia; Centro Universitario de Investigaciones Biomédicas, Universidad de Colima, Colima 28045, Mexico (I.I.P., I.Z.-J.); Department of Plant Biology, University of Copenhagen, DK–1871 Frederiksberg C, Denmark (A.T.F., M.G.P.); Australian Centre for Plant Functional Genomics, University of Adelaide, Glen Osmond, South Australia 5064, Australia (M.T., D.J.); and Tasmanian Institute of Agricultural Research, University of Tasmania, Kings Meadows, Tasmania 7249, Australia (M.Z.)

Plant salinity tolerance is a polygenic trait with contributions from genetic, developmental, and physiological interactions, in addition to interactions between the plant and its environment. In this study, we show that in salt-tolerant genotypes of barley (Hordeum vulgare), multiple mechanisms are well combined to withstand saline conditions. These mechanisms include: (1) better control of membrane voltage so retaining a more negative membrane potential; (2) intrinsically higher H⁺ pump activity; (3) better ability of root cells to pump Na⁺ from the cytosol to the external medium; and (4) higher sensitivity to supplemental Ca²⁺. At the same time, no significant difference was found between contrasting cultivars in their unidirectional ²²Na⁺ influx or in the density and voltage dependence of depolarization-activated outward-rectifying K⁺ channels. Overall, our results are consistent with the idea of the cytosolic K⁺-to-Na⁺ ratio being a key determinant of plant salinity tolerance, and suggest multiple pathways of controlling that important feature in salt-tolerant plants.

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: Sergey Shabala (sergey.shabala{at}utas.edu.au).

^[C] Some figures in this article are displayed in color online but in black and white in the print edition.

^[W] The online version of this article contains Web-only data.

www.plantphysiol.org/cgi/doi/10.1104/pp.107.110262

^* Corresponding author; e-mail sergey.shabala{at}utas.edu.au.

Received October 1, 2007; accepted October 23, 2007; published October 26, 2007.