Effects of thallium in soil on the growth and thallium content of komatsuna (Brassica campestris L.)

摘要

Since Tl is toxic for various organisms including humans and brassicas have a high concentration of Tl, the uptake of Tl by komatsuna from soil was investigated in pot experiments for 28 days. Tl was added at 0 (control), 5, 10 and 20 mg/kg DW to soil which contained 0.448 mg Tl/kg dry weight (DW). Chlorosis was only observed on the leaves of the 20 mg/kg DW plot. Fresh weight yield of the shoot was nearly the same in 0, 5 and 10 mg/kg DW plots and decreased by 51% in the 20 mg/kg DW plot. DW yieldof the shoot in the 20 mg/kg plot was only 43% of the control plot. Tl content was 0.38 mg/kg DW in the shoots of the control plot, and increased markedly by the addition of Tl. The shoots in the 20 mg/kg DW plot contained 163 mg Tl/kg DW. Some 96-99% of the absorbed Tl was translocated to the shoots. Concentration factors (ratio between the content of the element in plant tissue and its content in soil, calculated on a dry weight basis) in the 0, 5, 10 and 20 mg/kg DW plots were 0.8, 4.8, 5.7 and 8.0,respectively. Tl content of the shoots in the control plot was 0.028 mg/kg FW, which is about one-fourth of the maximum Tl content allowed in food regulated in Germany (0.1 mg/kg FW). When Tl content in the shoots was about 150 mg/kg DW, the dry weightyield of the shoots decreased by 50%.