Abstract
A study was made on the absorption and translocation of 1-14C-naphthyl N-methylcarbamate (NAC) by the rice plant at 1, 3, 7, and 14 days after soil treatment. Suspension of 416 micro grams of NAC toxicant was applied to different layers of each pot containing 500 grams of dry soil. Four methods were used to apply insecticide to the soil: (a) deep placement, (b) application to whole soil, (c) shallow placement, and (d) application to surface water. Just after the application of insecticide, rice seedlings were transplanted on treated soils which were held under flooded condition. The radioassay of extracts from plants, surface water, and soils was made by a Geiger-Muller counter, and the metabolites in the extracts were separated by the paper chromatography.
The results obtained were summarized as follows:
1. The detected amounts of radioactive materials per unit weight of the plant by application (c) and (d) were larger than the others, but decreased rapidly at the end of 14 days after treatment.
2. The amount of uptake of radioactive materials by the rice plant was associated with the radioactivity present in the surface water. This trend was particularly evident in the case of the leaf blade. It seemed that the radioactive materials dissolved in surface water were absorbed into the tissues through the lower part of leaf sheath and translocated to the leaf blade, probably along the stream of plant. sap. However, the detected amount of radioactive materials from the plant had but little association when the radioactivity of the surface water was only a trace or none, and that some portion of radioactive materials in the plant may have been due to what was absorbed through the root.
3. Recoveries of radioactive materials from the soils applied by (b) and (d) methods, some 50 days later experiment, were respectively 105.0 and 36.3 per cent of the theoretical, which include the absorbed amount by the rice plant.
