Bioaccumulation of 60Co2+ ions in tobacco plants

Tobacco has previously been used in investigations of metals and radionuclide uptake. This study presents determination of bioaccumulation and translocation of 60Co2+ ions in tobacco plants (Nicotiana tabacum L.) grown in Hoagland’s nutrient solution. Cobalt concentration in tobacco plants increased with increasing concentration in nutrient solution. Bioaccumulation from the initial concentration C0 = 0.96 μM Co reached 90% after 7 day cultivation. Only small amounts of Co accumulated in roots, up to 2 - 4 % were removable from roots by washing with 0.1 M CoCl2, indicating that this portion of Co is bound to the root surface in ion-exchangeable form. Tobacco roots retained approximately 2/3 of accumulated cobalt and 1/3 was transported to shoots. Autoradiography revealed that 60Co was preferentially localized in younger leaves. Prolongation of cultivation time did not change the [Co]roots : [Co]shoots ratio significantly. Relationships between growth rate, transpiration rate, uptake and distribution of cobalt in plant tissue are discussed.