Heavy metals tolerance in an invasive weed (Fallopia japonica) under different levels of soils contamination.
In order to assess the tolerance of the highly invasive weed Fallopia japonica to heavy metals, a greenhouse experiment was conducted in which this plant was cultivated in control soil and in the soils polluted by different levels of Cd, Cr, Cu, Pb and Zn. The content of heavy metals in soil did not eliminate the F. japonica rhizome's capacity to regenerate. However, at the beginning of the experiment, the presence of some metal doses: Cd (100, 200 mg.kg-1), Pb (200 mg.kg-1) and Zn (300 mg.kg-1) delayed the rhizome regeneration compared to the control plants. In the soils contaminated with any level of Cr or Pb, shoots grew with similar vigour to the control plants. Only the high doses of Cd (100, 200 mg.kg-1), Cu (300 mg.kg-1) and Zn (300 mg.kg-1) significantly delayed the plants' growth. The morphological features of F. japonica from the soils polluted with Cr and Pb were not significantly different from the control plants. Among the tested heavy metals that had the greatest impact on the morphology of F. japonica were Cd (100, 200 mg.kg-1), Cu (300 mg.kg-1) and Zn (300 mg.kg-1). A chemical analysis indicated that this weed accumulated large quantities of metals when cultivated in the contaminated soil. Particular attention was paid to its relatively high Cd uptake. In the variant where a dose of 100 mg Cd.kg-1 was applied, the plants (aboveground part) accumulated more than 630 times the amount of cadmium found in the control. The abilities of F. japonica to regenerate from rhizome fragments, to grow and develop under the stress conditions created by heavy metals, and to take up metals are evidence that this plant is characterised by metal tolerance.