Variability in salt tolerance of three populations of Hordeum jubatum was determined by analysis of growth parameters and ion relations of plants stressed with Na and Mg salts in solution culture experiments. Two populations from saline meadow habitats (Elstow and Floral) and one from a nonsaline site (University) were salinized with Na2SO4 and MgSO4 at Na:Mg molar ratios of 1:1 and 10:1. Elstow and Floral were more salt tolerant than University. University was more sensitive to the high Mg salt stress (Na:Mg, 1:1) than the high Na salt stress (Na:Mg, 10:1). The leaf area, root dry weight, root to shoot ratio under high Mg salt stress, and the root dry weight under high Na salt stress were significantly less for University plants than for Elstow and Floral plants under equivalent conditions. The greater salt tolerance of the two saline populations was correlated with restriction of Na uptake, more efficient transfer of Ca to young leaves, and the restriction of Mg accumulation in leaf tissue. The results supply evidence for physiologically distinct ecotypes of H. jubatum and indicate that habitat-correlated differences in salt tolerance have evolved in populations of this grass species. Key words: ecotype, Hordeum jubatum, ion balance, magnesium sulphate, salt tolerance, sodium sulphate, soil–plant relations, soil salinity.

Tillers and seedlings of Hordeum jubatum L. from three sites with contrasting salinity regimes in central Saskatchewan, Canada were reciprocally transplanted in order to examine the tolerance of populations of this species to salinity and related habitat factors. Survival, growth and fecundity of the three populations were controlled more by transplant site characteristics than by genetic differences, i.e. differences among populations at a site tended to be smaller than differences among sites. Survival, growth and reproduction of all three populations were best at the non-saline site. The population originating at the non-saline site showed the poorest growth in the two saline habitats, but still had substantial salt tolerance. Fecundity was greatest when the populations were grow at their site of origin.