Efficiency of Zn phytoextraction, biomass yield and formation of low-molecular-weight organic acids in S × rubens – a hydroponic experiment

Abstract

The aim of the study was to estimate Zn phytoextraction and changes in biomass of S × rubens growing in modified Knop's solution with different levels of Zn addition (0.5, 1.0, 2.5 and 5.0 mM). Obtained results were correlated with secretion of selected low-molecular-weight organic acids (LMWOAs) in the rhizosphere, roots and leaves. An increase in Zn concentration in Knop's solution resulted in Zn accumulation in roots, shoots and leaves. The highest accumulation was observed for plants growing in 5 mM Zn, at concentration levels 4741.36 ± 98.66, 1227.31 ± 16.57 and 2241.65 ± 34.90 mg kg−1 DW in roots, shoots and leaves, respectively. The bioaccumulation factor and the translocation factor for plants growing in 0.5, 1.0 and 2.5 mM Zn clearly indicate that this Salix taxon is an effective Zn accumulator. The general reduction of Salix biomass with an increase in Zn concentration in the solution was observed. In the rhizosphere, the total LMWOA concentration was almost 0.93 µmol kg−1 DM for control (Zn free) plants, while for 5.0 mM of Zn it was 4.9 µmol kg−1 DM. Increasing concentrations of acids were observed in roots (1.34 for the control and 5.57 µmol kg−1 DM for plants treated with 2.5 mM of Zn).