Metal tolerance, accumulation and translocation in poplar and willow clones treated with cadmium in hydroponics

To evaluate the phytoremediation capabilityof some poplar and willow clones a hydroponicscreening for cadmium tolerance, accumulation andtranslocation was performed. Rooted cuttings wereexposed for 3 weeks to 50 ?M cadmium sulphatein a growth chamber and morpho-physiologicalparameters and cadmium content distribution invarious parts of the plant were evaluated. Total leafarea and root characteristics in clones and specieswere affected by cadmium treatment in differentways. Poplar clones showed a remarkable variabilitywhereas willow clones were observed to be morehomogeneous in cadmium accumulation and distribution.This behaviour was further confirmed by thecalculation of the bio-concentration factor (BCF) andthe translocation factor (Tf). Mean values of all theclones of the two Salicaceae species showed thatwillows had a far greater ability to tolerate cadmiumthan poplars, as indicated by the tolerance index (Ti),calculated on the dry weight of roots and shoots ofplants. As far as the mean values of Tf was concerned,the capacity of willows to translocate was double thatof poplars. On the contrary, the mean values of totalBCF in poplar clones was far higher with respect tothose in willows. The implications of these results inthe selection of Salicaceae clones for phytoremediationpurposes were discussed.