A new morphogenetic model on the most suitable leaf-internode unit anddevelopmental stage for controlling plant types in rice cultivation[Japanese]

摘要

In any theory on rice cultivation, methods for controlling the plant type form the core. An analysis identified the most suitable leaf-internode unit for targeting to control the plant type and the appropriate stage to do this. The growth of the shoot is determined by the units, consisting of an internode and the leaf connected to that lower node. The leaf with the largest increase in elongation rate after top-dressing is not the elongating young leaf, but the leaf primordium positioned above that leaf. Therefore the most effective control of the plant type is achieved by targeting the particular unit that is in the differentiation stage. This model could explain the following. (1) Contrary to Matsushima's theory, a decrease in nitrogen absorption results in shortening the upper lamina without affecting the Lower internodes. (2) Excessive fertilization in the early growth period results in spindly growth of the lower internodes. Therefore if the nitrogen absorption declines from the middle period, the lower internodes and lamina show excessive growth, but the upper internodes and lamina stay short, as in the "akiochi" type. (3) If the fertilization levels in the early growth period are kept low and topdressing is applied in the middle growth period, a plant type with a reverse triangle shape caused by well-developed upper internodes and lamina in contrast to short lower internodes is formed.