Protein Contents of Developing and Mature Rice Grain

Abstract

1. As a percentage of dry weight, the total nitrogen content of brown rice decreased notably after flowering on account of a rapid accumulation of carbohydrate in grain and showed minimum value at 20 days after flowering, then increased slightly until maturity. (fig. 1, 2, 3) Albumin and globulin contents decreased slowly toward maturity and prolamin content did not show a notable change during maturation. Glutelin content showed a similar change to that of total nitrogen content. 2. The amounts of albumin and globulin per grain increased during the former period and showed a slight decrease during the latter period of maturation. The amount of prolamin increased during the former period and did not change during the latter period. The amount of glutelin per grain showed a rapid increase during 28 days after flowering and increased slowly until maturity after that. The change of glutelin represented that of total nitrogen. (fig. 5) 3. The middle portion of brown rice was fractionated into bran, outer part and inner part as shown in fig. 6 and the weight of them were 9, 43 and 49% of the whole middle portion, respectively. Glutelin content was highest in the outer part and lowest in the inner part. Albumin, globulin and prolamin contents were highest in bran and lowest in the inner part. The total nitrogen content was highest in bran. (table 3) 4. The nitrogen contents in leaf-sheath and culm of rice plant during ripening period had a positive effect upon the nitrogen contents of brown and milled rice. The top-dressing of nitrogen at heading stage and the shading treatment during ripening raised the nitrogen content of rice plant. Consequently, the nitrogen contents of brown and milled rice were increased notably by these treatment. (fig. 7, table 6) 5. The small grains had higher protein content than the larger grains of same variety and the former had lower degree of milling than the latter. This relationship was also observed between the upland-cultured rice grains and the lowland-cultured rice grains. Probably, the high-protein grains are harder than the low-protein grains. (table 7)