The perennial plant Armeria maritima ssp. halleri, growing on the copp
er-rich soil of a medieval mine dump, tolerates high heavy metal (HM)
concentrations and accumulates e.g. 2000 (leaves) to 4000 (roots) time
s more copper in comparison to plants growing under normal conditions.
For copper, as an example, the mechanisms of the HM-tolerance are dis
cussed. The HM-tolerance of Armeria is the result of morphological dif
ferentiations and biochemical alterations. As measured by EDX analysis
a great part of the copper in roots and leaves is retained in vacuole
s of idioblasts (<<tannin cells>>) containing homogeneous or flaky pre
cipitates of osmiophilic material. In the homogeneous precipitates, hi
gh copper concentrations can be measured. EELS spectra revealed that t
he copper in these vacuoles is chelated by polyhydroxy phenolic compou
nds. Moreover, a complex mixture of phenolic compounds from leaves and
roots of Armeria can be separated by HPLC. Copper ions reaching the v
ascular bundle are translocated via the transpiration stream into the
leaves and are excreted partly by salt glands on both leaf surfaces. C
rystals on the surface of the leaves contain besides P, S, Cl, K and C
a large amounts of Cu and to a smaller extent Zn, Ni, Fe and Mn. A sig
nificant part of the copper in roots and leaves is found to be localiz
ed in cell walls, in the cytoplasm, in the stroma of the plastids and
in the chromatin of the nuclei. In these compartments the copper is bo
und preferentially to proteins, as determined by EELS. Obviously, the
copper in the cytoplasm represents a stress situation for the cell, re
sulting in an expression of heat stress proteins (HSP).