腹白米に関する研究 : 第3報 登熟期の環境条件が腹白米発現におよぼす影響

抄録

These studies in series were devoted to clarify the characteristics of white belly kernel which had an opaque part at the ventral portion of its endosperm. In this experiment, leaf cutting, branch trimming, shading and temperature treatments at various stages were conducted to manifest the effects of ripening conditions on the occurrence of white belly kernel. The experimental materials used were Norin-8 and Kinmaze of Japonica type variety and Kosen and Te-Tep of Indica type variety. The following results were obtained. 1. By leaf cutting treatments, the occurrence of white belly and ill ripening kernels was enhanced, but that of perfect kernels was reduced. The appearance of white belly kernels was more frequently occurred by the elimination of both a flag and a subjacent leaf than by the elimination of only a flag leaf. 2. Branch trimming treatments made the occurrence of white belly and ill ripening kernels decrease and made the occurrence of perfect kernels increase. 3. Decrease in the occurrence of white belly and ill ripening kernels and increase in the occurrence of perfect kernels were brought about by nitrogen top-dressing treatments. Nitrogen top-dressing treatments were more effective for the occurrence of white belly kernels in lower branches than that in upper branches. The occurrence of white belly kernels was reduced by increasing contents of top-dressing treat-ments (from O to 1.2g N/pot). 4. Shading treatments at the early ripening stages were effective for the reduction of the occurrence of white belly and ill ripening kernels. Although shading treatments at the latter stages enhanced the occurrence of white belly and ill ripening kernels. 5. The occurrence of white belly and ill ripening kernels was stimulated by high temperature treatments, whereas that of white belly and ill ripening kernels was reduced by low temperature treatments. The occurrence of white belly kernels tended to pararell with that of ill ripening kernels, which had different opaque parts in their endosperm tissues. The occurrence of white belly kernels decreased when rice grains were sufficiently supplied with nutrition and the duration of ripening was prolonged, while the insufficient supbly of nutrition to rice grains and the reduction of ripening period stimulated the occurrence of white belly kernels. From these results, it might be appeared that the occurrence of white belly kernels was mainly influenced by the durability of ripening activity or kernels in the latter stages, i.e., 20 to 30 days after flowering