心白米に関する研究 : 第1報 心白米の発生

抄録

White-core rice kernel which has an opaque part in the center of grain, has long been appreciated by brewers in Japan. In order to find out the mechanism of white-core occurrence authors have made some experiments over two years with two rice varieties Hyogo-Omachi (1956, 57) and Hattan-Jugo (1957). White-core grain percent was high in the grains of vigorous position on the ear. And the grain weight of the kernels with white core was bigger than normal kernels of the same position. Results of an investigation on grain size revealed that white-core grains were significantly longer and wider than normal grains, indicating a vigorousity in primary seed growth. Partial cutting of panicle in early stages of seed development markedly increased the percentages of white-core grain. Five-day shading treatments around heading time resulted in considerable decreases of white core percent. Nitrogen dressing around the same period was revealed to be contributive to increased percentage of white-core grains. The results of these experiments led to a conclusion that favorable conditions to the primary seed growth accelerated white core forming in the grains resulting in the delaying of secondary growth of kernels and in the consequent insufficiency of starch filling in a flatish tissue around the center of young kernel. An once-ill-filled tissue seemed to remain opaque and inactive in the course of maturity in disregard of the progress of transparency in the outer tissues.