  Ion transport is the major determining factor of salinity tolerance in
plants. A simple scheme of a plant cell with ion fluxes provides basic
understanding of ion transport and the corresponding changes of ion
concentrations under salinity. The review describes in detail basic principles
of ion transport for a plant cell, introduces set of transporters essential for
sodium and potassium uptake and efflux, analyses driving forces of ion
transport and compares ion fluxes measured by several techniques. Study of
differences in ion transport between salt tolerant halophytes and
salt-sensitive plants with an emphasis on transport of potassium and sodium via
plasma membranes offers knowledge for increasing salinity tolerance. Effects of
salt stress on ion transport properties of membranes show huge opportunities
for manipulating ion transport. Several attempts to overexpress or knockout ion
transporters for changing salinity tolerance are described. Future perspectives
are questioned with more attention given to potential candidate ion channels
and transporters for altered expression. The potential direction of increasing
salinity tolerance by modifying ion channels and transporters is discussed and
questioned. An alternative approach from synthetic biology is to modify the
existing membrane transport proteins or create new ones with desired properties
for transforming agricultural crops. The approach had not been widely used
earlier and leads also to theoretical and pure scientific aspects of protein
chemistry, structure-function relations of membrane proteins, systems biology
and physiology of stress and ion homeostasis.
