Analysis of Yield-Determining Process and Its Application to Yield Prediction and Culture Improvement of Lowland Rice : LXVI. Studies on the method for controlling the length of a given leaf-blade, sheath and inter-node in rice plants.

摘要

Subjecting the rice plants to nitrogen-depletion treatments, nitrogen top-dressing treatments and root-pruning treatments at different growth stages, the authors examined the effects of the treatments on the lengths of leaf-blade, sheath and inter-node born on each node by comparing the lengths with those of non-treatments, succeeded in establishing a method for controlling their lengths. 1. Increasing the supply of nitrogen is quite effective for lengthening each leaf-blade, sheath and inter-node, while decreasing the supply is most important for shortening them. 2. There is found a definite e synchronous growth among leaf-blades, sheaths and inter-nodes, i. e., taking B1, B2, B3, B4………as the 1st (upper-most), 2nd 3rd and 4th leaf-blade from above and taking S1, S2, S3, S4………as 1st (upper-most), 2nd, 3rd and 4th sheath from above and taking No, N1, N2, N3………as the upper-most (between the neck-node of a ear and the node of an upper-most leaf), 2nd, 3rd, 4th inter-node from above, B1 grows simultaneously with S2 and N3, and B2 grows simultaneously with S3 and N4, and B3 with S4 and N5, and so forth. Therefore, if B1 is lengthened, or shortened, S2 and N3 are also lengthened or shortened synchronously, and if B2 is lengthened or shortened, S3 and N4 are also lengthened or shortened synchronously. Thus, there are synchronously growing leaf-blades, sheaths and inter-nodes in the growth of rice plants, and so each leaf-blade grows synchronously with its own corresponding sheath and inter-node. 3. When one wants to shorten a given leaf-blade (for instance B3), one has to restrict the nitrogen supply (by cutting roots or other methods) at or just before the time when the top of that leaf-blade (B3) begins to appear from the immediate lower sheath (S4), and when one wants to lengthen a given leaf-blade (B3), one ought to top-dress nitrogen at the time when the top of the previous leaf-blade (B4) begins to appear from the immediate lower leaf-sheath (S5). When one wants to shorten a given sheath (for instance S4), one has to reduce thc nitrogen supply at or just before the time when the top of B3 start to appear from the immediate lower sheath (S4). 4. By microscopic and anatomical observations the most susceptible developmental stage of a leaf-blade has been found to be the stage II in fig. 3. The stage II is just after the time at which the sheath of a leaf has been differentiated and the sheath as well as the blade are growing most vigorously.