Thallium Uptake and Translocation in Barley and Sunflower Grown in Hydroponic Conditions

Thallium (Tl) is highly toxic to humans compared with other heavy metals and metalloids, but the risk of its bioaccumulation has not been adequately considered. Thus, Tl uptake and translocation in barley and sunflower under hydroponics with the applications of diethylene triamine pentaacetic acid (DTPA) and citric acid were investigated. Thallium concentrations in roots of both the plants were higher than those in the shoots. Translocation index (TLI) of Tl in barley decreased from 14.9 to 10.0% with increasing Tl treatments in barley, but it increased from 5.9 to 7.5% in sunflower. The concentration of Tl in the barley tissues increased with DTPA applications, but it decreased with citric acid treatments. In contrast, Tl in the sunflower tissues decreased with DTPA treatments, while it increased with the applications of citric acid. However, Tl concentrations in the tissues of both plants were not significantly different between the two concentrations (5.0 and 30 mg/kg) of DTPA and citric acid applications.