The uptake of strontium-90 and calcium by lowland and upland rice from soil, and their distribution in the plants

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Abstract
The authors previously investigated, using samples produced in the 1956–1957 period, the radioactive contamination of soils and crops caused by A- and H-bomb tests (1), and clarified that, when the quantity of calcium is taken as the standard, the degree of Sr-90 contamination is unusually high in the grains of rice and wheat (see Note below). With regard to the routes of Sr-90 contamillation into plants, we can assume two ways : one is the uptake via roots from soil (2), and the other is the direct sticking of radioactive fallout to the visible parts of plants and resultant direct absorption. The question of which of these two routes plays a key role, depends the kinds of plants, portions in plants, and the property of radioactive fallout. Qualitatively, the contamination route via root plays a greater role in the case of calcium rich plants, and the reverse is the case with such farm products as the grains of rice and wheat, which contain extremely low amount of calcium.