GERMANIUM ACCUMULATION AND TOXICITY IN BARLEY

The accumulation of germanium (Ge) by barley (Hordeum vulgare cv. 'Ari vat') grown at various Ge and pH levels was investigated because Ge is an industrially important metal and bioaccumulation of Ge is a potent ially useful means of concentrating this trace metal. Six-day-old barl ey seedlings were grown in perlite and nutrient solution adjusted to a pH of 4.5, 6.0, or 7.5 supplemented with 20, 40, 60, or 80 mu M Ge fo r seven days. The plants were divided into roots and shoots after harv esting; the dry weight and Ge content of the individual organs were me asured, as was the peroxidase activity in the distal 1 cm of the prima ry leaves. Barley seedlings accumulated Ge in the roots and shoots; th e shoots accumulated Ge linearly as medium Ge concentration increased. The dry weight of the organs was not affected, although necrosis was observed in the primary leaves of the seedlings treated with Ge concen trations greater than 20 mu M. Peroxidase activity in the primary leav es also increased as the Ge levels in the medium increased which indic ated that elevated levels of Ge stimulated leaf senescence. These resu lts demonstrate that barley plants can take up Ge and suggest that Ge is not toxic at the levels that might occur in areas where Ge is norma lly mined.