I study electrical properties of membranes surrounding living plant cells. Many life processes involve moving ions in and out of the cell. Potential difference (p.d.) across the membrane can be measured and controlled. The ionic currents flowing through a multitude of specific transport systems (constituted by protein molecules imbedded in the lipid bilayer) show characteristic p.d. dependencies. Such current-voltage (I/V) curves allow isolation, characterisation and modelling of different transporters. Work has been done on the electrogenic proton pump, K+ channels, H+/OH- channels, Cl- channels, the action potential, amine uniport and Cl-/2H+ symport. My new project investigates the role of some of these transporters play in the cell response to varying salinity of the outside medium. The experiments are performed on giant-celled algae Characeae (single cells are up to 1 mm in diameter and several cm in length), which allow extensive manipulation, such as perfusion of the cell contents with artificial solutions, removal of vacuole or permeabilization of the outer cell membrane. The patch clamp technique is also employed to measure single channel currents in the inner cell membrane, the tonoplast.