Salt sensitivity in wheat : a case for specific ion toxicity.

Two selected lines of bread wheat, Triticum aestivum L., differing in their relative salt resistance, were grown in isosmotic solutions of different ionic compositions to investigate sensitivity to specific ions. Growth rates and ion accumulation were determined. The salt composition of the various solutions had little effect on the growth of the salt-resistant line, but significantly affected that of the salt-sensitive line. Specifically, solutions containing high Na(+) concentrations were more toxic than those containing high Cl(-) concentrations or high concentrations of nutrient ions. There were few differences in ion accumulation between lines in a given treatment, although the sensitive line tended to accumulate more Na(+) than the tolerant line in the salt treatments with high Na(+) concentrations. The overall results provide evidence that there is a definite specific ion effect which is related to salt sensitivity in wheat. It is suggested that superior compartmentation of toxic ions, principally Na(+), may be a mechanism of salt resistance in this case.