抄録
In this report, paddy rice plants cultivated in Wagner's pot and fertilized with ammonium-sulfate containing radioactive sulphur in a very-young-head forming period have been sampled 10 times at various stages of development, then their total amount of sulphur was analyzed by A.O.A.C. method, and also their radioactivities were measured by means of Lauritzen's electroscope. Thus the types of absorption and accumulation of sulphur by rice plant were secured, then the metabolic function was considered from the type of analogy. Results obtained are as follows : 1) Total sulphur in leaves and stalks has a little higher in an early stage of growth showing sbout 0.32% of dry matter. Then the contents decreased gradually to a constant value of 0.23%, which continued until the harvest time. Top-dressing of ammonium sulfate soon resulted in the increase of sulphur concentration of plants. 2) As for the accumulation of sulphur in leaves and stalks per one stump, there exists a maximum point at the head sprouting period. And then this accumulated sulphur decreased almost continually as it moved to the ears which, on the contrary, increased it accordingly, however the concentration of sulphur in ears remains nearly the same. 3) The sulphur in ammonium-sulfate fertilized as a top-dressing was quickly absorbed by plants. After 4 days of top-dressing, the stalks already contained considerable quantity of this sulphur (S-35). The maximum concentration of S-35 in leaf-seathes emerges at about 10 days after. 4) The concentration of S-35 in stalks and leaf-seathes shows a little higher value at the ripening stage. The reason is supposed as follows : As the kernel ripens, sulphur which has been incorporated into organic forms in leaf-blades moves the most at this stage of growth and the sulphur stays and accumulates temporarilly in leaf-seathes and stalks which help for a passage and storage, it is believed. 5) In leaf-seathes, the accumulation of S-35 per one rice stump reaches to a maximum point at about 10 days after top-dressing, and in leaf-blades at about 20 days after. Then the accumulated S-35 decreases owing to the transferance as ears ripen. 6) Although there may be some sulphur compounds including thiamen and biotin which assume some catalitic functions in plants, all the facts above mentioned are available to ascertain the signficance of sulphur in rice plant metabolism, which is found in its function which assume the same type of analogy as that of nitrogen.
