Sodium and chloride ions contribute synergistically to salt toxicity in wheat

The effects of supplying excess mineral salts, involving sodium as a cation and a range of counteranions, including chloride, on the growth and photosynthetic capacity of a salt susceptible bread wheat were studied. Plant performance was much more affected by the NaCl treatment than by the same concentration of either of the two component ions. With the exception of K+, other alkali metal chlorides also greatly inhibit plant growth and the electron flow through photosystem 2. The ranking of toxicity of these cations is Li+>Na+>K+. The synergistic effect of sodium (and other alkali and alkaline earth metals) and chloride shows that neither of these ions alone is responsible for salt stress induced damage.