XVI International Botanical Congess

Vibrating ion-selective microelectrodes were used to measure kinetics of H+, K+, Cl-, Ca2+, and Na+ in response to NaCl and mannitol treatment in root and leaf tissues. Activation of the electrogenic H+-pump was the most pronounced effect of the salt stress. Similar hyperosmotic treatment, but with mannitol only slightly modified net H+ fluxes indicating high specificity of stress perception. Significant Na+ and Cl- uptake was evident only within the first 5-7 min of NaCl treatment, followed by the net efflux of these ions. Responses of K+ transporters were also stress-specific, varying from increased net K+ efflux (NaCl treatment) to net K+ influx (mannitol treatment). High Ca2+ concentration prevented H+-pump activation by NaCl which might explain amelioration of salt tolerance by Ca2+.