Does the polluted environment modify responses to metal pollution? A case study of two Cistus species and the excess of copper and lead

Abstract

Populations of Cistus ladanifer L. and C. salviifolius L. from an abandoned mine area in Riotinto (SW Spain) and unpolluted control site were examined to test tolerance to Cu and Pb. Metal tolerance was tested in hydroponic experiments with different Cu (1, 25 and 100 μM Cu) and Pb (0, 100 μM Pb) concentrations. A germination test was also carried out to investigate possible differences between populations. Additionally some physiological and chemical parameters were analyzed in plants from Cu experiment. The results revealed different responses to high Cu and Pb between both species as well as between sites. The populations of C. salviifolius from the polluted site performed better in the medium with 25 μM Cu than the population from the unpolluted site indicating an adaptative Cu tolerance. However, no differences in Cu tolerance were found for the populations of C. ladanifer. Interestingly, the opposite result was found for Pb indicating that C. ladanifer has an adaptative tolerance to Pb. Copper content was higher in roots than in leaves (mean value of 2881 mg kg−1 in C. ladanifer and 4006 mg kg−1 in C. salviifolius treated with 100 μM Cu) and an the high levels of proline and asparagine should be involved in C. salviifolius Cu tolerance. Germination percentage in C. salviifolius was greater in seeds from population of unpolluted sites (mean values of 89.3%).