Accumulation and Toxicity of Germanium in Cucumber under Different Types of Germaniums

The effects of germanium dioxide (GeO ₂) and 2-carboxyethyl germanium sesquioxide (Ge-132) treatments on cucumber (Cucumis sativus L.) growth and Ge accumulation and toxicity were investigated. Accumulated Ge contents in plant treated with GeO ₂ were two times greater than that in plants treated with Ge-132. Germanium accumulated primarily in the shoots in the GeO ₂ treatments and in the roots in the Ge-132 treatments. In contrast GeO ₂ was easily transported from roots to shoots. In cucumber fruit, the range of Ge content in both the GeO ₂ and Ge-132 treatments was in the order of stalk > rind > pulp > seeds, suggesting that Ge accumulation was based on distance from xylem. Silicon (Si) content significantly decreased as GeO ₂ concentration increased, but there was no difference in Si content in the Ge-132 treatment. Therefore, plant growth and Ge accumulation are affected differently by GeO ₂ and Ge-132 treatments, based partly on treatment concentrations.