3.1 Heavy metal levels and morphology of S. cataractae from the
field
The concentrations of Cd and Cu in soils (total levels) differed
significantly across sites (χ² = 0.64, p <
2.2e-16 and χ² = 4.36, p <
2.2e-16 for Cd and Cu respectively; Figure 1). Site 2
(in the center of the mine) showed the highest concentrations of Cu,
followed by sites 1 (edge) and 3 (center), and ultimately 4 (edge). For
Cd, site 3 showed the highest concentration followed by sites 2, 1 and 4
(which did not differ from each other). Total levels of Cd and Cu inS. cataractae also differed among populations (χ² = 3.00,
p<0.0001 and χ² = 1.28, p<0.001 for Cd and Cu
respectively), however, the differences found in plants did not reflect
the same pattern as found in soils. Total and relative Cu were highest
in Sc3 and did not differ significantly among the other three
populations (Fig. 1B and 1C). Total Cd was lowest in Sc1 and did not
differ significantly among the other three populations (Fig. 1D). The
relative levels of Cd in plant tissue, however, did not show significant
differences among populations (χ² = 0.02, p=0.615; Fig. 1F).
The morphological measurements performed on the field samples revealed
that plants from the center of the mine (Sc2, Sc3) were smaller than
those from the edges (Sc1, Sc4) for all traits studied except leaf width
in Sc2 (χ² = 24.80, p < 2.2e-16 for plant
length; χ² = 2.75, p < 2.2e-16 for leaf
length; χ² = 3.39, p < 2.2e-16 for leaf
width; Fig. 1G to I).