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Summary

Populations of Agrostis tenuis can be found growing on a variety of different mine workings in conditions of metal contamination toxic to most higher plants. Samples of such populations together with samples of populations taken from ordinary pastures were tested for tolerance to high concentrations of copper, nickel, lead and zinc by measuring the effect of these metals on the rooting of tillers. The soils in which the populations were originally growing were analysed for each of the four metals and the tolerances of the populations have been related to the levels of the metals in the soils.

In general, the mine populations show remarkable tolerance to the particular metals present in high quantities in the soils of their original habitats: the pasture populations do not show this tolerance. The tolerance is specific, for, except in the case of zinc and nickel, tolerance to one metal is not accompanied by tolerance to any other. There must, therefore, be three specific tolerances in the one species. Individual tolerances can however occur together and this can be related to the occurrence of the two metals together in toxic quantities in the soil.

The tolerances must be genetically controlled but the physiological mechanism involved is not clear. A number of other species were also shown to have populations tolerant to high levels of zinc.