As shown by TF data (Table 2), Pb was the most translocated element
(average TF value of 0.80), followed by Zn and Cu (average TF values of
0.41 and 0.38, respectively). Average BCF of shoots and roots were in
the following decreasing order: Zn N Cu N Pb. BCF values of roots were
higher than for shoots. BCF and TF were calculated to evaluate the ability
of the plant to accumulate metal in the tissues from soils and transfer
them from roots to shoots, respectively. The fact that TF and BCF values
were low (b1) suggests that alfalfa was unable to extract significant
amounts of metals from the soil and translocate them to the shoots. As
a result this species could be rather used for phytostabilization purposes
than for phytoextraction, which would not be feasible in a reasonable
frame-time (Robinson et al., 2015). Moreover, both TF and BCF values
were generally lower in bioaugmented treatment. These results seem
to be consistent with Lebeau et al. (2008), who reviewed several
experiments of phytoextraction-assisted bioaugmentation with bacteria
and found that PGPR always decrease TF, while BCF vary irrespective of
bioaugmentation.