The cytosolic Na :K ratio does not explain salinity-induced growth impairment in barley: A dual-tracer study using 42K and 24Na

Abstract

It has long been believed that maintenance of low Na+ : K + ratios in the cytosol of plant cells is critical to the plant's ability to tolerate salinity stress. Direct measurements of such ratios, however, have been few. Here we apply the non-invasive technique of compartmental analysis, using the short-lived radiotracers 42K + and 22Na+, in intact seedlings of barley (Hordeum vulgare L.), to evaluate unidirectional plasma membrane fluxes and cytosolic concentrations of K+ and Na+ in root tissues, under eight nutritional conditions varying in levels of salinity and K + supply. We show that Na+ : K+ ratios in the cytosol of root cells adjust significantly across the conditions tested, and tha..