A multielement analysis of Cu induced changes in the mineral profiles of Cu sensitive and tolerant populations of Silene paradoxa L.

This work investigates the Cu induced changes in element profiles in contrasting ecotypes of Silene para- doxa L. A metallicolous copper tolerant population and a non-metallicolous sensitive population were grown in hydroponics and exposed to different CuSO4 treatments. Shoot and root concentrations of Ca, Cu, Fe, K, Mg, Mn, Mo, Na, P, S and Zn were evaluated through ICP-OES. Results indicated that increasing the environmental Cu concentration had a population dependent effect on element profiles, shoot-to-root ratios and correlations among the elements. Generally, in the tolerant population Cu treatment induced a higher element accumulation in roots and had minimal effects on the shoot element profile, thus resulting in a progressively decreasing shoot-to-root ratio for each element. In the sensitive population element concentrations in root and shoot were much more affected and without a consistent trend. Copper treatment also affected the correlations between the elements, both in roots and shoots of the two populations, but more so in the sensitive population than in the tolerant one. Thus, Cu exposure strongly disturbed element homeostasis in the sensitive population, but barely or not in the tolerant one, probably mainly due to a higher capacity to maintain proper root functioning under Cu exposure in the latter. Differences in element profiles were also observed in the absence of toxic Cu exposure. These differences may reflect divergent population-specific adaptations to differential nutrient availability levels prevailing in the populations’ natural environments. There is no evidence of inherent side-effects of the Cu tolerance mechanism operating in the tolerant population.