Effect of Sudden Salt Stress on Ion Fluxes in Intact Wheat Suspension Cells

Abstract

Although salinity is one of the major problems limiting agricultural production around the world, the underlying mechanisms of high NaCl perception and tolerance are still poorly understood. The effects of different bathing solutions and fusicoccin (FC), a known activator of plasma membrane ATPase, on plasma membrane potential (Em) and net fluxes of Na+, K+and H+were studied in wheat suspension cells (Triticum aestivum) in response to different NaCl treatments. Emof cells in Murashige and Skoog (MS) medium was less negative than in cells exposed to a medium containing 10mM KCl+0.1m M CaCl2(KSM) and to a basic salt medium (BSM), containing 1m M KCl and 0.1m M CaCl2. Multiphasic Na+accumulation in cells was observed, peaking at 13min after addition of 120m M NaCl to MS medium. This time scale was in good agreement with net Na+flux changes measured non-invasively by moving ion-selective microelectrodes (the MIFE system). When 120m M NaCl was added to all media studied, a quick rise of Na+influx was reversed within the first 20min. In both 120 and 20m M NaCl treatments in MS medium, net Na+efflux was observed, indicating that active Na+transporters function in the plant cell response to salt stress. Lower external K+concentrations (KSM and BSM) and FC pre-treatment caused shifts in Na+fluxes towards net influx at 120m M NaCl stress.