著者

長戸 一雄 河野 恭広

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.32, no.2, pp.181-189, 1963

被引用文献数

6

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The studies reported here were undertaken to explore the relations among hardness distribution, the three dimensions of kernel and structure of endosperm tissue with reference to varietal differences of grain texture. 1. Hardness ratio. Hardness distribution of rice kernel is represented by hardness distribution along the dorsiventral line and the lateral line crossing at the central point on the cross section of kernel as reported previously. However, it is more concise and convenient to be indicated by the ratio of hardness of the middle point to that of the central point (Hardness ratio). On the cross section of the kernel of which hardness ratio is less than 1.0, the central core is hardest and hardness becomes smaller toward the peripheral region, and distinct difference can not be found between the hardness of dorsiventral line and that of lateral line. (fig. 1 Century Patna and Zenith) On the section of which hardness ratio is more 1.0, hardness is largest on the middle region and becomes smaller toward the central core and the peripheral region, moreover the dorsiventral region is softer than other region (fig. 1 Asahi, Cody and Yamadanishiki). It is assumed that the former is the characteristic of Indica and the latter characterizes Japonica. 2. Relation between hardness ratio and length-breadth ratio of rice variety. Negative correlation is found between hardness ratio and length-breadth ratio. Regression lines are Y=-0.036X+1.042 and Y=-0.303X+1.603, in Indica and Japonica varieties respectively, neverthless, some Japonica varieties of which hardness ratios are more than 1.18 distribute fairly apart from Japonica line and their length-breadth ratios are 1.7 or thereabout (fig. 2). 3. Relation between length-breadth ratio and thickness-breadth ratio. Generally speaking, positive correlation is recognized between length-breadth ratio and thickness-breadth ratio, but this correlation is scarcely applicable to Japonica varieties (Fig. 3). 4. Relation between hardness ratio and thickness-breadth ratio. There is negative correlation between hardness ratio and thickness-breadth ratio in Indica varieties, yet this correlation is ambiguous in Japonica varieties as well as the relation between length-breadth ratio and thickness-breadth ratio (fig. 4). 5. Structure of endosperm tissue on the cross section. Shapes of the cross sections of kernels vary from round to spindle-shaped according to the thickness-breadth ratios and correspond roughly to hardness ratios as above mentioned (Fig. 5). (1) Cells of the central core. Cells of the central core of A-group (hardness ratio approximately 0.93) are somewhat isodiametric and arranged radially, while those of E-group (hardness ratio approximately 1.20) are uneven and markedly flattened and arrangement of them is disordered. Shapes and arrangement of cells of other groups show intermediate figures between A-and B-groups according to the hardness of central core of each variety. Shapes and arrangement of cells of central core may be affected by the density of strarch in cells, therefore they are correlated with the hardness of central core (fig. 1). (2) Cells along the dorsiventral line. Cells along dorsiventral line are not much different from thme of other region in A-group, but those of E-group are extremely flattened along the dorsiventral direction and arrangement of them is disordered, and those of C-and D-groups are flattened to the extent according to the hardness of dorsiventral line. In Japonica varieties (C, D-and E-groups) starch accumulation in cells of several layers along the dorsiventral line is slightly or markedly insufficient, for this reason, these cells are nattened and arrangement of them is disordered by the oppression of surrounding cells. This characterisic of endosperm structure may be the making of the facts that the kernels of E-group become often white-cored during development and dry kernels of Japonica especially of E-group make frequently dorsiventral

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