Heavy metal accumulation and growth responses in poplar clones Eridano (Populus deltoides x maximowiczii) and I-214 (P. x euramericana) exposed to industrial waste

In this study, the effects of non-hazardous levels of heavy metal (Zn, Cu, Cr and Cd)-enriched organic waste on biomass partitioning and heavy metal accumulation in plant organs in July and October were determined for two poplar clones (Populus deltoides × maximowiczii—clone Eridano and P. × euramericana—clone I-214) commonly used in Italian poplar plantations. Soil amended with the industrial organic waste did not exert any toxic effects on plants. Leaf, stem, root and woody cutting biomasses of treated plants were significantly greater than in the controls in both clones, except for stem biomass at the beginning of October. Leaf area of Eridano and I-124 treated plants was significantly higher than that of control plants, both in July and October, while specific leaf area (SLA) did not show any significant changes due to treatment. Shoot (SMR) and root mass ratios (RMR) were not significantly affected by the treatment in July, while in October plants grown in treated soil showed significant differences in stem and root biomass allocation with respect to controls. Among the four heavy metals (Zn, Cu, Cr and Cd) contained in the industrial organic waste, only Zn, Cu and Cr concentrations in plants differed consistently between clones or soil treatments, while Cd levels were always below the detection limits. Both phytoextraction and phytostabilisation strategies were observed in the two clones studied. The results suggested that only non-hazardous industrial biosolid levels might be environmentally sustainable for poplar plantations.