Root Plasma Membrane Transporters Controlling K⁺/Na⁺ Homeostasis in Salt-Stressed Barley
2007
(Ian A.)
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.
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