Screening for different cadmium allocation in plant organs of poplar and salix clones.

The release of heavy metals and organic pollutants in the environment, by natural and human activities, has caused a diffuse contamination of the biosfere. In the last years phytoextraction has shown great potential as an alternative technique for the removal of this contamination. Several studies have been performed on plants that show high capability to accumulate heavy metals. These species usually known as hyperaccumulators are characterised for small size and low growing that result in a limitation of the effective extraction capacity on surfacebasis. In this context, forest trees present some characteristics that can be useful for phytoremediation purposes such as fast growing, extended root system, high biomass production and low impact on food-chain. In particular, it has been proposed that clones of poplar and willow, even if considered hypoaccumulators, used in a short rotation coppice cultivation (SRC), which allows an enhanced biomass production, could overcome the effective extraction limitation. One of the major constraint regards the low root to shoot translocation of heavy metals in these species. Hence, enhancing metal allocation in the harvestable parts of the plants is an important goal for the utilization of these species in a phytoremediation strategies. The aim of this study was to evaluate the capability to accumulate and translocate cadmium of different genotypes of poplar and willow. Cuttings of Populus x euramericana, Populus deltoides, Populus x interamericana, Populus nigra, Populus alba and Salix clones were grown in hydroponic culture system in a controlled environment. After a rooting stage, cuttings were exposed to a 50 ?M cadmium solution for three weeks. During this period growth analysis, gas-exchange and chlorophyll fluorescence measurements were carried out. At the end of the treatment cuttings were collected, weight, separated in roots, stem and leaves and processed for cadmium determination. Preliminary results showed that among clones a different cadmium allocation in the analysed organs occurred. In particular some clones accumulated this metal in roots (~75% of total cadmium accumulated), stem (~20%) and leaves (~5%), while another set of clones showed a distribution of metal only between roots and stem. These latter clones evidenced a less damage to the photosynthetic apparatus.