Responses of Populus × euramericana (P. deltoides × P. nigra) clone Adda to increasing copper concentrations

We investigated the effect of high copper (Cu) concentrations on poplar woody cuttings (Populus × euramericana) clone Adda in order to estimate the degree of metal tolerance. Metal accumulation was also investigated to determine where and to what extent Cu is stored within the plant. Plant responses to Cu were determined comparing biomass growth and photosynthetic potential measured at concentrations of 0.4 (control), 20, 100, 500 and 1000 μM of Cu supplied with Hoagland's solution in an aerated hydroponic system. Results obtained in this study show that increasing levels of Cu resulted in a general reduction of plant growth at concentrations equal or higher than 100 μM. At these concentrations of Cu, reductions of chlorophyll contents and photosynthetic parameters were also observed. The metal was mainly accumulated in the root system at all Cu levels. Since no significant differences were noticed in growth and photosynthesis between control plants and those treated with 20 μM of Cu, we conclude that Adda clone was able to tolerate quite high concentration of Cu and we propose it as a good candidate for screening Cu tolerance in the field.