Copper resistance in Silene armeria ecotypes: Does co-tolerance play a role?

Abstract

Silene armeria can be found both on soils without ion toxicity problems and heavy metal-rich sites. Among the latter ecotypes adapted to serpentine soils and ecotypes that perform well on Cu mine spoils have been described. In this study the influence of high Cu concentrations on growth and mineral nutrition of three ecotypes of S. armeria (ecotype Cadriano from agricultural soil, ecotype Prinzera from a serpentine site, and ecotype Vigonzano from Cu mine spoil) was investigated in order to evaluate the degree of Cu resistance in these ecotypes. Plants growing in nutrient solutions with Cu concentrations ranging from 0.1 (control) to 20 µM Cu displayed different Cu resistance: Cadriano < Prinzera < Vigonzano. Cu analysis in tissues suggests that the better performance of Prinzera than of Cadriano was due to more efficient Cu exclusion by the serpentine ecotype. The ecotype from the mine spoils seems to owe its high degree of Cu resistance to both, efficient restriction of uptake and tolerance of higher tissue Cu concentrations. The Cu resistance in the serpentine ecotype may not be due to co-tolerance of Cu (not present in excess in the soil of origin) and Co, Ni or Cr (high availability at the original site) but caused by efficient Cu exclusion, a property that may be related to the ability of the serpentine ecotype to handle unfavourable Mg/Ca concentrations.