EFFECTS OF HIGH COPPER CONCENTRATIONS ON BIOMASS ALLOCATION, METAL BIOCONCENTRATION AND TOLERANCE ABILITY IN THE POPLAR CLONE "MONVISO"

Poplar plants exposed to high Cu concentrations highlighted a good metal tolerance, expressed as tolerance index (Ti) calculated on a whole plant basis (Table 1). A lower tolerance was observed in plants exposed to the highest Cu concentration (T2). Nevertheless, the Ti value of T2 plants allows to define this poplar clone as tolerant, according to Lux et al. (2004). A notable tolerance to Cu in poplar was previously put in evidence (Borghi et al. 2008), even if a large genotype variability is reported (Castiglione et al. 2009). In this work, Cu exposure modified the biomass allocation among organs (Table 1). Results showed that plants allocated more than 50% of the dry mass in the leaves followed by stem and roots. In particular, the highest value of leaf mass ratio was found in T2 plants whereas T1 plants showed a significant increase of biomass allocation in the roots. In table 2, data regarding the bioconcentration ability (BCF) and the translocation factor (Tf) are reported. In control conditions, poplar plants concentrate Cu at the same extent in the root and in the aerial part, as a result of the physiological processes involving such micronutrient. Under increasing Cu concentrations, a strong reduction of BCF was observed in the aerial part, especially in T2 plants. A decrease of BCF in the roots was observed as a consequence of the Cu enhancement in the medium. According to previous studies on the metal translocation capacity in poplar plants (Zacchini et al. 2009), clone "Monviso" showed a very low Tf under high Cu concentrations.