抄録
The rice plant was cultured in nutrient solutions which have various degrees of the phosphorus concentration (from 0 to 200 p.p.m. P_2O_5) and the following results were obtained. (1) The maximum yield of the rice plant is obtained at the concentration of 20 p.p.m.P_2O_5 in the culture solution. (2) The phosphorus content of the rice plant increases according to the increasing phosphorus concentration in the culture solution. And this tendency is most remarkable at theleaf and stem and less at the root and the least at the ear. 3) There exists the marked interrelationship between the yield and the phosphorus content of the rice plant. Judging from this interrelationship, three stages are distinguished in the condition of the rice plant. Namely, 1st step : in the case of low concentration (under 5 p.p.m. P_2O_5), both the yield and the phosphorus content of the plant increase with the increasing phosphorus concentration in the culture solution. This step may be called "the deficiency stage". 2nd step : in the case of optimum concentration (5-20 p.p.m. P_2O_5), the yield of the plant increases with the icreasing phosphorus concentration in the culture solution, but the phosphorus content in the plant remains comparatively constant. This step may be called "the normal stage". 3rd step : in the case of high concentration (above 20 p.p.m. P_2O_5), the yield of the plant decreases with the increasing phosphorus concentration in the culture solution, but the phosphorus content of the plant increases. This step may be called "the excess stage". (4) The maximum absorption of phosphrus by the rice plant appears when the phosphorus concentration in the culture solution is 150p p.m. P_2O_5. (5) The phosphorus content of the rice plant increases according to the increasing concentration of phosphorus in the culture solution. The increase of phosphorus in the ear is attributed to the increase of phytin in the case of 0-100 p.p.m. P_2O_5 in the culture solution, while in the case of above 100p.p.m.P_2O_5,it is attributed to the increase of inorganic phosphorus. But in the leaf and stem, and the root, it is attributed only to the increase of inorganic phosphorus.
