1956 Volume 26 Issue 10 Pages 413-418
The author distinguished three stages in the growth of rice plat, viz., the 1st stage is from the germination to the ear forming, the 2nd stage is from the ear forming to the flworing and the 3rd stage is after flowering. Three stages of growth are chiefly connected with the function of leaves 3/0〜5/0,6/0〜9/0 and 10/0〜12/0 respectively. To make clear the physiological bases of these characteristic functions of leaves, the characteristics of nitrogen metabolism of these leaves are studied first. The present report embodies results of these studies. The following results were obtained from them. 1) The total amount of nitrogen in each leaf increases accompanying with the growth of that leaf, and, after reaching to the maximum value, it decreases. The time when the maximum nitrogen accumulation in a leaf is attained, comes in sequence from lower leaf to upper leaf as indicated in Fig. 4. Periods between the peak of the curve of the nitrogen fluxion of one leaf and that of the next leaf are not constant. Specifically, in leaves 3/0〜5/0 the periods are almost the same; in 6/0〜9/0 nitrogen begins to accumulate from lower leaves first, then to upper ones, but it does not outflow from these leaves until earforming stage. Then the nitrogen in all leaves decreases at the same time and nitrogen accumulates in spikelet and stem simultaneously; in leaves 10/0〜12/0 nitrogen begins to accumulate from lower leaves to upper ones. After the flowering stage nitrogen in these leaves begins to flow out and accumulates in ear synchronously. 2) Translocation quotients of nitrogen (as shown in Table 3) differ by the position of the leaf, In the case 3/0〜5/0 it shows about 50%, in the case of 6/0〜9/0 it shows 70%, and in the case of 10/0〜12/0 it reaches to 75%. 3) In the 1st stage of growth, the nitrogen contents of leaves at upper position are higher than that of lower ones, but in the 2nd stage of growth, nitrogen contents of leaves at any position are almost the same. 4) Leaves 3/0〜5/0 have characteristic connection to tillering. As far as the nitrogen metabolism is concerned, it is not reasonable to consider that a tiller at any position becomes independent receiving its nitrogen supply from the stored in the leaf at the same position. But substances assimilated by a leaf accelerate nitrogen absorption and the nitrogen thus absorbed goes up to the tiller at the same position.
