Studies on Protein Content in Rice Grain : I. Variation of protein content between rice varieties and the influences of environmental factors on the protein content

Abstract

In order to clarify protein content variation of the rice varieties and the relation between protein content and environmental factors, some investigations were carried out as follows. To clarify the variation of protein content of rice varieties, 33 varieties of Hokkaido and Tohoku district were planted in the same paddy field for 7 years from 1963 to 1969 and protein content in their rice grains were compared yearly. As to the influences of the environmental factors, rice crops were grown during their ripening stage under high (25-27°C) air temperature, high (30°C) or low (17°C) water temperature, and sunshading, protein content of their rice grains were compared for 2 years of 1968 and 1969. The results are summarized as follows. Protein % in rice grains is respectably differing with rice varieties. In general, earlier ripening varieties tend to show higher % than the later one. Most varieties of Hokkaido belong to the earlier ripening group and showed higher % than most varieties of Tohoku district. In each district, Norin No.20 of Hokkaido and Oirase of Tohoku district were remarkably higher % than the other varieties yearly for 7 years, so it seems that they have somewhat super hereditary natures refering to accumulation of protein. Protein % of the same variety that was planted on the fixed plan differed year by year. This fact shows that protein content is influenced by the weather condition of each year. From the results of some experiments refering to weather environments, it was cleared that protein % of rice grains is increased by high air temperature or high water temperature as well as decreased by low water temperature or sunshading during their ripening stage.