Characterization of Lettuce Plant Growth and Germanium Accumulation Under Various Ge-132 and GeO2 Treatment.

To investigate the effect of inorganic (GeO₂) and organic (Ge-132) germanium on growth from lettuce (Lactuca sativa), we treated various concentrations (0, 10, 25, 50, 100 mg/L for early seedling: 0, 5, 10, 25, 50 mg/L for hydroponically-grown 4 weeks-old plants) with inorganic or organic germanium, respectively. On early seedling growth, all treatments of exogenous inorganic GeO₂ significantly inhibited both root and shoot elongation. In organic Ge-132 treatment, plant growth was not much inhibited at 10 and 25 mg/L and then significant inhibited at 50 and 100 mg/L. On 4 weeks-old hydroponically-grown lettuce, all range of exogenous inorganic GeO₂ significantly inhibited the root and shoot growth, whereas organic Ge (Ge-132) treatment slightly stimulated the plant growth at 5 and 10 mg/L and then significantly inhibited the plant growth at 30 and 50 mg/L. Total Ge contents with organic Ge (Ge-132) treatment were accumulated two times more than those with inorganic Ge treatment at 30 and 50 mg/L, but there was not much different at 5 and 10 mg/L. In addition, Ge was primarily accumulated in the roots with organic Ge treatments, suggesting that organic Ge once taken by the roots was hardly moved to the shoot. In the inorganic treatments, Ge was highly accumulated in the roots at 5 and 10 mg/L treatments, but Ge was accumulated much more in the leaf than in the root at 30 and 50 mg/L treatments. Ge was highly accumulated with follow order in lettuce tissues. (1) In organic Ge treatments (10mg/L), Root hairs (81.3%)> Lateral roots (15.5%)> Stem (1.6%)> Old leaves (1.0%)> Young leaves (0.5%). (2) In inorganic Ge treatments (10mg/L), Root hairs (70.1%)> Lateral roots (16.3%)> Old leaves (7.9%)> Stem (3.3%)> Young leaves (2.3%). [This work was supported by a  grant from ARPC]