Effect of sudden salt stress on ion fluxes in intact wheat suspension cells

Although salinity is one of the major problems limiting agricultural produc tion around the world, the underlying mechanisms of high NaCl perception an d tolerance are still poorly understood. The effects of different bathing s olutions and fusicoccin (FC), a known activator of plasma membrane ATPase, on plasma membrane potential (E-m) and net fluxes of Na+, K+ and H+ were st udied in wheat suspension cells (Triticum aestivum) in response to differen t NaCl treatments. E-m of cells in Murashige and Skoog (MS) medium was less negative than in cells exposed to a medium containing 10 mM KCl + 0.1 mM C aCl2 (KSM) and to a basic salt medium (BSM), containing 1 mM KCl and 0.1 mM CaCl2. Multiphasic Na+ accumulation in cells was observed, peaking at 13 m in after addition of 120 mM NaCl to MS medium. This time scale was in good agreement with net Na+ flux changes measured non-invasively by moving ion-s elective microelectrodes (the MIFE system). When 120 mM NaCl was added to a ll media studied, a quick rise of Na+ influx was reversed within the first 20 min. In both 120 and 20 mM 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 BS M) and FC pre-treatment caused shifts in Na+ fluxes towards net influx at 1 20 mM NaCl stress. (C) 2000 Annals of Botany Company.