Using ²⁰³Hg-labeled organo-mercury disinfectants, the study on the behavior of mercury in rice plants was carried out, and the following results were obtained;
1. ²⁰³Hg-phenylmercuric acetate penetrated quickly into the tissues of rice plants on any stages after the application of the disinfectant, and was translocated especially to newly developing parts of the plants. As for the rice plants at heading stage, radioactive mercury was finally accumulated in the rice grains, when the water emulsion of ²⁰³Hg-phenylmercuric acetate was applied either by injection into the tissues of leaf sheath or by dipping of leaf blade.
2. When the rice leaves were infected with the blast disease, radioactive mercury which was absorbed from roots as an aqueous solution of ²⁰³Hg-phenylmercuric acetate, was accumulated in the tissues surrounding the infected lesion of the leaves. Feature of mercury penetration into leaf tissues was different with disinfectant formulations, and among emulsion, wettable and dust formulations, the penetration of mercury in dust formulation which was less phytotoxic to rice leaves, was most gentle.
3. ²⁰³Hg-labeled phenylmercuric acetate, phenylmercuric chloride, phenylmercuric dinaphthylmethane disulfonate, N-phenylmercuric p-toluenesulfonanilide, N-ethylmercuric p-toluenesulfonanilide or methoxyethylmercuric chloride, was applied to the rice plants on either tillering stage or flowering stage, and mercury content in rice grains after harvest was estimated. In refining process of rice grains, mercury content was lowered as following order; husk, raw rice and polished rice. Mercury content of polished rice from the rice applied with 50ppm solution of the organo-mercury disinfectants was mostly less than 0.1 ppm in the application on tillering stage, and was in ranges of 0.146ppm to 0.528 ppm in the application on flowering stage. Since the polished rice occupied the greater portion in weight of rice grains, the absolute amount of mercury was much in polished rice as compared with that in husk and bran. The younger of rice plant stage was applied with the organo-mercury disinfectants, the lower of mercury content in rice grains was found.