Studies on the systems and controlling factors in translocation and destribution of absorbed nitrogen in gramineous crops.

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To clarify the controlling factors in absorption and translocation of nitrogen in rice plant, the distribution of nitrogen was researched by using ^<15>N fertilizer. The destribution of absorbed nitrogen was varied with the leaf positions and the inside and outside half-leaves in rice plant. The reasons of the fact that the nitrogen contents of an outside half-leaf was higher than that of an inside half-leaf were considered that the width of outside half-leaf was narrower, the volume of nodal roots on an outside half-leaf was larger, and the nitrogenabsorbed by outside nodal roots was translocated only to outside half-leaves and could not retranslocate directly to another side. The aitrogen contents showed a high positive correlation with the leaf color intensity. The most stable leaf spots in leaf color intensity were at the center of lateral sides of a midrib of leaf blade on uppermost fully expanded second leaf. In wheat plant, the defferences in leaf color between outside and inside half-leaf were not recognized. The degrees of variation in leaf color intensity on leaf positions in wheat plant and corn plant were larger than that of rice plant, but, basic tendency of variation in leaf color intensity in leaf positions corresponded to that of rice plant. The effects of legumes incorporated as green manures, sunn hemp and peanut, was examined for nitrogen contribution to the succeeding wheat. Total nitrogen content was higher in peanut compared with sunn hemp. The contribution percentage of nitrogen accumlated by each legume to total nitrogen of the succeeding wheat was 11.2% on the peanut plot and 9.4% on the sunn hemp plot. Peanut crop contribated more nitrogen to the succeeding wheat compared with sunn hemp.