Effect of cadmium on growth, micronutrient concentration, and δ-aminolevulinic acid dehydratase and acid phosphatase activities in plants of Pfaffia glomerata

Pfaffia glomerata (Spreng.) Pedersen plantlets were grown under different cadmium (Cd) concentrations (0, 20, 40, 60 and 80 μM) in a hydroponic system during 7 d. Plant growth, micronutrient, chlorophyll and carotenoid concentrations, as well as δ-aminolevulinic acid dehydratase (ALA-D; E.C.4.2.1.24) and acid phosphatase (AP; E.C.3.1.3.2) activities were analysed. Cadmium concentration in both shoots and roots increased with increasing external Cd levels. Metal concentration in roots were on average 12-fold higher than in shoot tissues. Root length was unaffected by Cd treatments. In contrast, dry weight of both shoot and roots increased significantly after exposure to 20 and 40 μM Cd. Additionally, shoot and total plant dry weight were only reduced in plants exposed to 80 μM Cd. In contrast, root dry weight decreased significantly after exposure with Cd concentrations above 40 μM. A micronutrientand organdependent response to Cd toxicity was observed. Zinc and Cu concentrations in both, shoot and roots did not alter due to exposure to Cd. Cadmium stress reduced Mn uptake but not its translocation within the plant. A synergistic effect of Cd on Fe concentration in root at 20 μM and 80 μM Cd levels was observed. The activity of AP, and especially that of ALA-D, was reduced with increasing Cd levels. At these Cd levels, the chlorophyll concentration was also reduced. There was a positive correlation between concentrations of carotenoids and chlorophylls. Our results indicate that P. glomerata seems to have some degree of Cd tolerance.