Abstract:

The emerged plant Nasturtium officinale R. Br. is a wild vegetable widely distributed in Europe, Asia and North America, and can grow rapidly in nutritious water. In a preliminary study, the cadmium content in shoot of N.of〖KG-*7〗ficinale reached 133.52 mg/kg when the dose of cadmium was 60 mg/kg in soil, exceeding the critical value of a Cdhyperaccumulator (100 mg/kg), indicating that this plant might be a Cdhyperaccumulator. To further the understanding on the cadmium accumulation characteristics of N.of〖KG-*7〗ficinale under various concentrations of cadmium and identify whether this plant is a Cdhyperaccumulator, a pot experiment with cadmium concentration gradient (0, 25, 50, 75, 100 mg/kg) in soil was conducted to study the growth characteristics, the cadmium tolerance and the cadmium accumulation characteristics of N.of〖KG-*7〗ficinale. The results were showed as follows. The cadmium contents in root and shoot of N.of〖KG-*7〗ficinale increased with the increase of cadmium concentration in soil, while the number of branches, the root biomass, the shoot biomass, the chlorophyll SPAD value and the resistance coefficient decreased. The leaves of N.of〖KG-*7〗ficinale appeared yellow when the concentration of cadmium in the soil was greater than 50 mg/kg, and the area of yellow leaf increased with the increasing cadmium concentration in soil, indicating that N.of〖KG-*7〗ficinale had been seriously poisoned by cadmium at these high doses. When the cadmium concentrations in soil were greater than 0 mg/kg, the root/shoot ratio of N.of〖KG-*2/5〗ficinale showed an increasing trend with the increasing concentration of cadmium in soil, indicating that N.of〖KG-*7〗ficinale could increase the proportion of root biomass to enhance the tolerance to cadmium stress. The cadmium content in shoot of N.of〖KG-*7〗ficinale exceeded 100 mg/kg when the dose of cadmium was more than 50 mg/kg in soil, up to the maximum of 214.84 mg/kg (100 mg/kg cadmium in soil). The shoot bioconcentration factor (BCF) of N.of〖KG-*7〗ficinale was greater than 1 and increased with the increase of cadmium concentration in soil. The translocation factor (TF) of N.of〖KG-*7〗ficinale was less than 1 and decreased with the increase of cadmium concentration in soil. The cadmium extraction in root of N.of〖KG-*7〗ficinale was increased with the increase of cadmium concentration in soil. The cadmium extraction in shoot of N.of〖KG-*7〗ficinale was increased when the dose of cadmium was no more than 50 mg/kg in soil, and decreased when the dose of cadmium was more than 50 mg/kg in soil. The amount cadmium extraction of N.of〖KG-*7〗ficinale got the maximum at the dose of 50 mg/kg cadmium in soil, reached 192.23 μg/plant. In field investigation, we found that N.of〖KG-*7〗ficinale had strong tillering ability, easily survived by cutting, and suitable for mowing. Therefore, N.of〖KG-*7〗ficinale is a Cdaccumulator, and could be used to remediate Cdcontaminated less than 50 mg/kg paddy field soil. In addition, N.of〖KG-*7〗ficinale could not be as wild vegetable to eat in cadmium contaminated areas.