Metal co-tolerances in the grass Deschampsia cespitosa

Abstract

METAL tolerance in plants growing on metal-contaminated soils around mines1–3, smelters4 and refineries5 have been reported. While metal tolerances in many dicotyledonous species, such as Becium homblei6, Mimulus guttatus7 and Silene cucubalus8, have been found, the emphasis has largely been placed on the study of populations of a limited number of grass species, especially Agrostis tenuis1,2,9–11, Agrostis stolonifera5,12, Festuca ovina3 and Anthoxanthum odoratum13,14. (Adaptive population responses to a number of elements high in soils were recorded for lead, zinc, copper and nickel, reviewed by Antonovics et al.15.) In addition, tolerances to cadmium4 and arsenic16 have been investigated. Jowett17 and Bradshaw et al.11 have postulated that tolerance to more than one element is dependent on the presence of these elements at elevated levels in the soil, that is, tolerance is specific. A few exceptions to this ‘rule’ have been noted, such as the apparent enhancement of nickel tolerance in a zinc-tolerant population of Agrostis tenuis despite the absence of elevated soil nickel11. We present here evidence of the evolution of co-tolerances to copper, nickel and aluminium in a population of Deschampsia cespitosa (L.) Beauv. Also, the occurrence of co-tolerances for lead and zinc, which were not elevated in the soils from which the population was obtained. A limited number of cadmium-tolerant clones were also found in both populations.