Athyrium wardii
(Hook.) is a promising herbaceous
plant species for phytostabilization of cadmium
(Cd)-contaminated sites with large biomass and fast growth
rate. However, little information is available on its tolerance
mechanisms toward Cd. To further understand the
mechanisms involved in Cd migration, accumulation and
detoxification, the present study investigated subcellular
distribution and chemical forms of Cd in the mining ecotypes
and corresponding non-mining ecotypes of
A. wardii
via greenhouse pot experiment. Subcellular fractionation of
Cd-containing tissues demonstrated that the majority of the
element was mainly located in soluble fraction in cell
walls. This indicated that both the vacuoles and cell walls
might be evolved the Cd tolerance mechanisms to protect
metabolically active cellular compartments from toxic Cd
concentrations. Meanwhile, Cd taken up by the plant
existed in different chemical forms. Results showed that
the majority of Cd in plant was in undissolved Cd–phosphate
complexes (extracted by 2 % CH
3COOH), followed
by water-soluble Cd–organic acid complexes, Cd(H
2PO
4)
2,
pectates and protein form (extracted by deionized water
and 1 M NaCl), whereas only small amount of Cd in roots
was in inorganic form (extracted by 80 % ethanol), which
suggests low capacity to be transported to aboveground
tissues. It could be suggested that Cd integrated with
undissolved Cd–phosphate complexes in cell wall or
compartmentalization in vacuole might be responsible for
the adaptation of the mining ecotypes of
A. wardii to Cd
stress.