著者

長戸 一雄 江幡 守衛 石川 雅士

出版者

日本作物學會

巻号頁・発行日

vol.41, no.4, pp.472-479, 1972 (Released:2011-03-04)

著者

長戸 一雄 江幡 守衛

出版者

日本作物学会

雑誌

日本作物學會紀事 (ISSN:00111848)

巻号頁・発行日

vol.34, no.1, pp.59-66, 1965-09-14

被引用文献数

20

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With the purpose of making clear the effects of temperature on the development and the quality of kernels, rice plants of seven varieties, representing a wide range in adaptability to high temperatures, were subjected to temperatures of 23° and 30℃. at various stages of ripening. (Table 1) The results are summarized as follows. 1) Effect on ripening period, High temperatures throughout the ripening period accelerate the starch accumulation into kernel and the kernel development during the early period of ripening, but depress them in the late period. As a result, the length of ripening period is remarkably shortened and the weight of matured kernel is somewhat reduced. (Fig. 1, 2) However, the extent of reduction in length of ripening period and kernel weight are varied with varieties and more in the varieties seemed to be less adaptable to high temprature. 2) Effect on the dorso-ventral ratio. The ventral radius which grows in the early period of ripening is lengthened and the dorsal radius which grows until the late period is shortened by high temperature, with the consequence that the ratio of the dorsal radius to the ventral radius (dorso-ventral ratio) is lessened. (Fig. 3) The variations of dorso-ventral ratios caused by high temperature are greater in the varieties assumed to be less adaptable to high temperature than in the more adaptable varieties. Accordingly, the rates of variations in dorso-ventral ratios will be able to indicate the varietal differences in adaptability to high temperature. (Table 2) 3) Effect on the occurence of white-ridge kernels. When the growth of cells and the starch accumulation in the dorsal region of kernel are depressed by high temperature, the accumulation of starch into the outermost layers of starch cells along the dorsal ridge becomes markedly insufficient and these layers remain as opaque with the result that the dorsal ridge of the kernel is white colour in external look. Therefore, occurence of white-ridge kernels is closely connected with the decrease of dorso-ventral ratio and is abundant in less adaptable varieties of which dorso-ventral ratios greatly decrease by high temperature. (Fig. 4) The results of measurement of Vickers hardness indicating the density of starch accumulation show that the white-ridge kernel is softer than the normal kernel, especially, on the outer part of basal and dorsal regions of kernel. (Fig. 6) Then, the milling-loss is markedly more in white-ridge kernels owing to the softness of the outer part of kernel as well as the increase of thickness of bran. (Table 4, 5) 4) Effect on the occurence of basal-white kernel. Under high temperature, in the inferior kernels on a panicle, starch becomes insufficient to fill up starch cells on the outermost part of basal region on account of depression of starch accumulation in the late period of ripening, and the basal part becomes opaque and white colour in appearance. Then, the basal-white kernels occur numerously in the inferior kernels of lees adaptable varities by high temperature. (Fig. 5, 9) Therefore, the basal-white kernel is soft on the outer part of basal region as shown in Fig. 6, then the milling-loss increases as compared with the normal kernel. (Table 5) 5) Effect on the occurence of milky white kernel. The milky white kernel is milky white in external appearance owing to the opaque part at the central or middle region on the cross-section of kernel and becomes "chalky rice" by milling. (Fig. 7) This kernel nccurs in such a case that the accumulation of starch into the kernel is transitorily checked for a few days during ripening. When ripening of kernel is hastened by high temperature, competition for absorption of nutrients occurs among the kernels on a panicle, then the superior kernels continuously absorb nutrients and become to normal kernels, whereas, the inferior kernels can scaresely absorb for a few days and some of them cease their growth and the others resume absorption according as the

著者

玉置 雅彦 江幡 守衛 田代 亨 石川 雅士

出版者

日本作物学会

雑誌

日本作物學會紀事 (ISSN:00111848)

巻号頁・発行日

vol.58, no.4, pp.653-658, 1989-12-05

被引用文献数

3

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穂揃期窒素追肥ならびに登熟温度が米質に及ぼす影響について, 米飯のテクスチャー, タンパク質, アミロース, 結合脂質 (fat-by-hydrolysis) 含有率の点から検討した。窒素追肥により, 白米タンパク質含有率は増加した。米飯のテクスチャーのうち, そしゃく性値は, タンパク質含有率の増加にともない増加した。粘着性および食味指数値は, タンパク質含有率が8.5%のときに最も高くなった。アミロースおよび結合脂質含有率は, タンパク質含有率と関係が見られなかった。以上から, アミロースおよび結合脂質含有率の変化が小さいときには, 米飯のテクスチャーは, タンパク質, 特に難溶性タンパク質に強く影響されることが示唆された。一方登熟温度処理により, うるち米は低温ではそしゃく性値が顕著に大きく, 粘着性および食味指数値は顕著に小さくなった。もち米では, これらの傾向はみられなかった。アミロースおよび結合脂質含有率は, うるち米では低温ほど高まったが, もち米では変化が見られなかった。タンパク質含有率は, うるち米, もち米とも低温では減少した。登熟温度がうるち米米飯のテクスチャーに及ぼす影響は, アミロースおよび結合脂質含有率の変化によるものであり, タンパク質含有率には影響されなかった。しかしながら, もち米米飯のテクスチャーは, 登熟温度に影響されなかった。