Cadmium Uptake and Growth Responses of Seven Urban Flowering Plants: Hyperaccumulator or Bioindicator?

The application of flowering plants is the basis of urban forest construction. A newly-found flowering hyperaccumulator is crucial for remediating urban contaminated soil sustainably by cadmium (Cd). This study evaluated growth responses, Cd uptake and bioaccumulation characteristics of seven urban flowering plants. Based on growth responses of these plants, Calendula officinalis L. showed high tolerance to at least 100 mg kg −1 Cd, in terms of significant increase in biomass and with no obvious changes in height. After 60 d exposure to 100 mg kg −1 Cd, the accumulated Cd in shoots of the plant reached 279.51 ± 13.67 μg g −1 DW, which is above the critical value defined for a hyperaccumulator (100 μg g −1 DW for Cd). Meanwhile, the plant could accumulate Cd to as much as 926.68 ± 29.11 μg g −1 DW in root and 1206.19 ± 23.06 μg g −1 DW in plant, and had higher Cd uptake and bioaccumulation values. According to these traits, it is shown that Calendula officinalis L. can become a potential Cd-hyperaccumulator for phytoremediation. By contrast, Dianthus caryophyllus L. is very sensitive to Cd stress in terms of significantly decreased biomass, height and Cd uptake, indicating the plant is considered as a Cd-bioindicator.