Phytoremediation of Zn: Identify the Diverging Resistance, Uptake and Biomass Production Behaviours of Poplar Clones Under High Zinc Stress

Abstract

A dose–response study was performed in four commercial clones, Baldo (Populus deltoides), Jean Pourtet (Populus nigra), I-214 (Populus x euramericana) and Villafranca (Populus alba), to investigate the best performing species in terms of metal content and high metal resistance (absence of symptoms) useful in biomass production on contaminated water/land by zinc. Zinc (1 μM as control and 1 mM) was applied for 4 weeks in a hydroponic system. Clone Villafranca was the least damaged, while the most sensitive was clone I-214. The highest zinc concentration in all different parts of plants analysed was recorded in Villafranca > I-214 > Baldo > Jean Pourtet. The higher translocation factor was seen in Baldo, the lowest in Villafranca. Analyses of leaf damage showed a reduction on Chl a in young leaves (96 %) in I-214 stressed plants, whereas in Villafranca, Chl a was about double compared to the control. Regarding other photosynthetic pigments, violaxanthin was significantly correlated to zinc concentration in old leaves. The responses of clones to zinc (Zn) stress were specific: Villafranca was the most resistant, while I-214 showed the highest biomass production under Zn excess. Since these two clones have useful and complementary traits for uptake and detoxification while maintaining high biomass production under Zn excess, they are interesting candidates for understanding the key resistance mechanisms.