2.5.2 Relative Cd and Cu content in moss
We mounted freeze-dried samples from each population and treatment on
aluminum stubs with double sticky carbon disks (SEM-carbon foils, PELCO
Tabs TM Carbon Conductive Tabs, Double Coated) and
then carbon coated them with a 10-20 nm carbon layer (Leica EM MED 020)
to prevent surface charge. We carried out all measurements with scanning
electron microscope JEOL JSM-IT300 (SEM) in combination with energy
dispersive X-ray microanalysis (EDX) for elemental analyses by SDD
(silicon drift detector) and software TEAM V.4.3, operating at 20 kV. We
used the following acquisition conditions: 35º take off angle, a 30 s
live time, and a ∼30% dead time. For S. cataractae , we selected
6 plants per population and treatment (including field samples, in which
only the leaves could be measured), and performed 4 measurements per
plant: two on two different leaves, and two on the stem (n=12
measurements for each of the structures, except for Sc1 in which n = 6
for stems). For C. purpureus protonema, we performed a total of
n=10 measurements per population and treatment. Relative concentrations
are expressed as weight percent (i.e. weight of the element of
interest divided by the weight of all elements present in the sample).