Single and Combined Effects of Cadmium and Zinc on Carrots: Uptake and Bioaccumulation

ABSTRACT

The present study was conducted to evaluate the effects of different concentrations of cadmium (Cd) and zinc (Zn), singly and in combination, on uptake and bioaccumulation of Cd and Zn in Daucus carota L. (carrot) grown under natural field conditions. Carrot plants were treated with two Cd concentrations (10 and 100 μg mL⁻¹), two Zn concentrations (100 and 300 μg mL⁻¹), and two combined concentrations of Cd and Zn (10 + 100 and 100 + 300 μg mL⁻¹) 15 d after seed germination. Treatments were repeated at 10 d intervals up to 90 d of plant age. A control was also kept without a Cd or Zn treatment. Uptake, total accumulation rate (TAR), bioconcentration factor (BCF), primary transport index (PTI), secondary transport index (STI), and accumulation of Cd and Zn in root, stem, and leaf were quantified. The results show that uptake, TAR, and accumulation of Cd and Zn are concentration-dependent phenomena. Highest accumulation of Cd and Zn was found in the root, followed by the stem and then leaves. The results also showed that bioaccumulation of Cd in root, stem, and leaf was greater at the low metal-application rates of Cd and Zn in combination than at the higher rate. This study further showed that interactions of Zn and Cd are dependent on the concentrations of those metals in the soil.

Keywords:

• uptake
• bioconcentration factor
• primary transport index
• secondary transport index
• total accumulation rate
• Cd
• Zn
• bioaccumulation
• Daucus carota

ACKNOWLEDGMENTS

The authors are thankful to Farm Incharge, Institute of Agricultural Sciences, Banaras Hindu University Varanasi for providing field facilities. Rajesh Kumar Sharma is grateful to the U K Department for International Development for its support of the project through a Junior Research Fellowship.