日本作物学会紀事
Online ISSN : 1349-0990
Print ISSN : 0011-1848
ISSN-L : 0011-1848
34 巻, 1 号
選択された号の論文の12件中1~12を表示しています
  • 杉本 勝男
    1965 年 34 巻 1 号 p. 1-5
    発行日: 1965/09/14
    公開日: 2008/02/14
    ジャーナル フリー
    This investigation was carried out at Bukit Merah Padi Experiment Station in malaya 1962 to 1963 under Colombo Plan. The results are summarized as follows. 1. The process of elongation of the organs showed a S-shaped curve (Fig. 1). The peak date of the principal elongation period was the mid-point of the mentioned S-shaped curve. The beginning or end date of the principal elongation period was subjected to the time when certain organs elongated and reached to 10 % or 90 % of final length. The peak date of the principal elongation period of related organs took place nearly about the same time as indicated below, (B0 : S1 : N2), (B1 : S2 : N8), (B2 : S3 : N4) and (B3 : S4 : N5) (See Tab. 1). The indicatin to each separate organs is explained in Fig. 2. All the numberings begin from the topmost part of plant descending to the base. Immediately after the peak date of the principal elongation period of leaf blades or sheaths, started the beginning date of the principal elongation period of the next upper organs and after the former reached the end date of its principal elongation period, started the peak date of the principal elongation period of the latter (Tab. 1, 3). 2. The changes in dry weight of organs also showed a S-shaped curve ( Fig. 3). The inter-relation among the different organs in respect of the changes in dry weight was more or less similar to that of the elongation process of organs (Tab. 1). 3. When the velocity of the elongation of a certain organ reached its maximum, the increase in dry weight was about to begin. When the increased dry weight reached its maximum, the elongation was about to terminate (Tab. 4-a, b). The elongation and increase in dry weight of organs continued to be systematic from the lower to the upper organs. 4. When the increase in the dry weight of panicle was great during the panicle pregnancy stage, there was naturally a reduction in the dry weight increase of the other organs. As soon as the formation of the panicle was about to be complete, N1 and N0 showed a marked increase in dry weight. After the fertilization there was a remarkable increase in dry weight of the panicle. As long as the increase in dry weight of the panicle was conspicuous, there was a decrease in the weight of sheaths and internodes. The decrease was slightly marked in Pe Bi Fun than Radin China 4. From then on, there was a slightly decline in the increasing tendency of dry weight of the panicle and also a halt in the decrease of the weight of sheaths and internodes. During about 5 days just after heading, the increasing weight of the panicle was small. This can reasonably be attributed to the effect probably caused by the enhanced consumption due to the respiration at the time of flowering and fertilization. 5. The peak date of the principal elongation period of each organs mentioned above were presumed. However, the full matured length or weight of certain organs varied with nutritional and environmental conditions. The above mentioned result on the regularity of elongation process and changes in dry matter was similar to that of Japonica rice plant. And it can be benificially used in the morphological and physiological diagnolosis of Indica rice plant.
  • 杉本 勝男
    1965 年 34 巻 1 号 p. 6-13
    発行日: 1965/09/14
    公開日: 2008/02/14
    ジャーナル フリー
    The author carried out an experiment on rice cultivation from 1962 to 1964 at Bukit Merah Padi Experiment Station in double cropping areas of Malaya. The results of main experiment are summarized as follows. 1. Changes of the growth phase of top and root (Fig. 1 and 2) Radin China 4, a medium-term variety in main season, and Pe Bi Fun and B. M. 5, both short-term varieties in off season, were cultivated under non-fertilized, fertilized and furnace-slag-applied conditions. It was seen that the stage of fertile-tiller-formation came about 30 to 35 days after the rice transplantation and the stage of maximum number of tillers was 40 to 42 days after transplantation in all plots tested. The soil in B. Merah was under a heavily reduced condition, showing Eh values of between-100 and 50 mV during the paddy season. The rate of dry weight increase of the root became gradually greater after transplantation and reached to its max. around the spikelet differentiation stage. The maximum index of rooting ability was seen concurrently just after or 10 days after transplantation. Following this, there was a gradual decrease throughout the stage. The index of rooting ability was extremely low after the spikelet differentiation stage. 2. The influence of pruning of spikelets on percentage of ripened grains (Fig. 3) The percentage of ripened grains in control hills was 81 to 91 in the non-fertilized plot and 76 to 88 in both the fertilized and furnace slag plots for four seasons. It was noticed that there was not much a difference in the percentage of ripened grains when the primary rachis were cut off at 1/3 or 1/2 to decrease the spikelet. The percentage of ripened grains in the pruned hills was 89 to 96 %. The non-pruned hills, except for the non-fertilized plot, produced imperfect grains amounting to 12 to 24 %. The reason for this can be attributed to rather excessive number of spikelets in each panicle. 3. Morphological observation of lodged hills and changes of index of lodging (Fig. 4 and 5) It was seen that N3 or N4 internode was longer and much thinner in the lodged hills. This was the main cause for breaking. Measurement of the moment (plant height × fresh weight of plant) and breaking strength of N4 and N3 was measured after heading. According to Dr. SEKO in Japan, if the index of lodging (moment / breaking strength × 100) is bigger than 200, lodging is very likely to occur. The index of lodging showed its maximum value at the maturing stage in all plots. It was seen that the fertilized plot was greater in the moment and less in the breaking strength compared with non-fertilized plot. The reading of the index of lodging was 240 to 300 in the fertilized plot. Thus the fertilized hills showed to be weak to lodging. From the above investigation, it can be said that the varieties in Malaya have a greater tendency for lodging. 4. Experiment on fertilizer response of 7 varieties (Fig. 6) It was found that heavy fertilizing in most cases brought about an increase in the yield, especially when the maturation period was longer in a fertile field. But in a poor field, like B. Lima, Mayang Ebos 80 and Subang Intan 16 gave a better yield than the varieties having a relatively longer maturation period. It can be stated that Sigadis, M. Ebos 80 and S. Intan 117 have a high fertilizer response. 5. Experiment on the amount of nitrogen and its application time (Fig. 7 and 8) It was generally presumed that suitable amount of nitrogen to increase the yield would be 0.34 to 0.68 kg per are in the main season and 0.34 kg in the off season respectively. This might be attributed to the difference in the maturation period of the varieties used. It was also found that top-dressing at the stage of spikelet differentiation or reduction division was most effective in the main season while in the off season the effective time of the application could not be determined. [the rest omitted]
  • 田崎 順郎
    1965 年 34 巻 1 号 p. 14-19
    発行日: 1965/09/14
    公開日: 2008/02/14
    ジャーナル フリー
    1. The classification of Adzukibean varieties based on responses to daylength was carried out and several characteristics of the varieties with regard to these responses were studied. 2. The early varieties were apperared to have less sensitivity to short-day and the late varieties were showed to have great sensitivity. The order arranged in series, from the early to the late of varieties, coinsided with the order of sensitivity to daylength among all varieties in Adzukibeans. 3. M 2 group, intermediate variety, is an unstable group which is very sensible to the effect of daylengh and temperature, and its flowering date is especially liable to vary by the different temperature from year to Year. 4. The grade of sensitivity to daylength among varieties in every region showed the latitudinal adaptation. While in comparison with Manturian and Hokkaido ecotypes, the former showed slightly greater than the latter for the sensitivity to short-day. This difference may be due to the determinate and indeterminate plant type. The early varieties distributed in the southern region have the greater sensitivity to short-day than the early varieties in the southern region have the greatest sensitivity to short-day. 5. Under the stronger level of short-day, the threshold of temperature to flowering showed no difference among varieties, but under long-day treatments, the threshold of temperature to flowering gradually increased according to the degree of lateness of the varieties. This may be due to the varietal difference for responses to photoperiod influenced by temperature. 6. The grade of sensitivity to short-day was decided by the difference of flowering dates between short- and long-day treatments. The flowering date showed no difference at the short-day plot. Therefor, the different sensitivity to daylength among varieties was appeared by the difference of the delay of flowering under long-day plot. In this test, the experiment was taken place under the natural condition of seasonal temperature. So, the delayed varieties received the different temperature on subsequent growth to flowering in comparison with the earlier varieties which have already finished their flowering. Under different conditions, we cannot compare the characteristics of the varieties. But in this experiment the thresholds of temperature on flowering from early to late among varieties, were just arranged in the order of the seasonal increase of temperature. From the reason above, when we want to test the relative order of sensitivity to daylength, it may be possible to use the changing temperature under seasonal condition. 7. The order of the grade of earliness and the sensitivity to daylength among varieties, coinsided with each other. This shows that the selection by the long photoperiod on the summer solstice in Central Japan and the test of 16h30m long-day plot under natural temperature, have the seame effectiveness each other. Then, the test of the earliness may substitute for a practical method of the test of the sensitivity to daylength.
  • 田崎 順郎, 本間 久
    1965 年 34 巻 1 号 p. 20-24
    発行日: 1965/09/14
    公開日: 2008/02/14
    ジャーナル フリー
    1. The natural temperatures between two different latitudinal regions or between two altitudinal regions combined with the natural daylength at the regions of low temperature on each, were used for the means of the test on the sensitivity to temperature. 2. The sesitivity to temperature among varieties is adapted to the latitudinal relation, i. e. the early varieties distributed in the north with the dull sensitivity to short-day have the greater sensitivity to temperature while the late varieties in the south with the greater sensitivity to short-day have the smaller sensitivity to temperature. The Japanese ecotype is more or less sensible to temperature than the Continental ecotype. The late varieties need high threshold of temperature to flowering, but they have low sensitivity to temperature. 3. Many arguments have appeared for the varietal difference of the response to temperature influenced in photoperiodism on the soybean. Some workers have shown that the late varieties in the south with high sensitivity to short-day have high sensitivity to temperature than the early varieties in the north with low sensitivity to short-day. In comparison with the fact mentioned above, the relation among varieties may be possibly reverse. To make this confusion clear, studies were conducted for this problem. As a result, for the means of obtaining the different temperature to test, it is not adequate to plant on different seasons, or to use the glass house for the field condition on legume. The different two temperature conditions derived from the altitudinal regions show the most suitable method for clarifying the difference among varieties on the sensitivity to temperature.
  • 松島 省三, 田中 孝幸, 星野 孝文
    1965 年 34 巻 1 号 p. 25-29
    発行日: 1965/09/14
    公開日: 2008/02/14
    ジャーナル フリー
    The prime necessity to increase the grain-yield of rice is to increase the number of spikelets per unit area, whereas with an increase in number of spikelets the rice plants are very liable to grow excessively and luxuriously and the percentage of ripened grains easily goes down in general. Considering therefore that an increase of the percentage of ripened grains under luxurious growth conditions is most important for maximizing yield, the authors made an experiment to clarify the relation between the morphological characteristics and the percentage of ripened grains under luxurious growth conditions. By heavily fertilizing the rice plants which planted in the early season, and at various growth stages, moreover, by top-dressing some of them with ammonium sulphate, and on the contrary, by restricting the absorption of nutrients on some of them, the authors succeeded in obtaining various kinds of rice plants differing in morphological characteristics in receiving light. After classifying the rice plants into five groups according to the number of spikelets per unit area, the authors investigated the relation between the morphological characteristics and the percentage of ripened grains, obtaining the following results. (1) The percentage of ripened grains was negatively correlated with each length of the flag-leaf (uppermost)-blade, second (penultimate) leaf-blade and third leaf-blade, and with the sum of length of the flag-leaf-blade and second leaf-blade and also that of the flag-leaf-blade, second leaf-blade and third leaf-blade. Among these characters the sum of length of the flag-leaf-blade and the second leaf-blade showed the highest correlation to the percentage of ripened grains. (cf. Fig. 5). (2) The percentage of ripened grains was also negatively correlated with each curvedness of the leaf-blabe of the flag-leaf, second-leaf and third leaf, and with the sum of curvedness of the flag-leaf and second leaf, and that of the flag-leaf, second-leaf, and third leaf. Among these characters the sum of curvedness of the leaf-blade of the flag-leaf and the second-leaf showed the highest correlation to the percentage of ripened grains. (cf. Fig. 8) By the curvedness of the leaf-blade is meant the quotient which is given by dividing the actual length (the arc) of a leaf-blade by the distance (the chord) between its auricle and the top of its curved leaf-blade. (3) The percentage of ripened grains was also negatively correlated with each angle of the stem to the flag-leaf as well as the second leaf, and also with the sum of these two angles. In partiqular, the sum of these two angles showed the strongest correlation to the percentage of ripened grains. (cf. Fig. 13) (4) In any cases above mentioned the second leaf-blade showed the closest relation to the percentage of ripened grains. It was pointed out, therefore, that for forecasting or diagnosing the percentage of ripened grains stress should be laid on the morphological characteristics of the second (penultimate) leaf-blade.
  • 熊野 誠一, 藤瀬 一馬
    1965 年 34 巻 1 号 p. 30-34
    発行日: 1965/09/14
    公開日: 2008/02/14
    ジャーナル フリー
    With the purpose of finding some clue as to the physiological mechanism of tuberous roots formation, the studies were set about roots respiration by the use of Warburg's manometer. Following results were obtained. 1. Oxygen uptake of roots at varying pH of buffer solution from 4.2 to 7.6 showed a little change, but optimal region was found at pH 6-7. 2. It was found that the temperature coefficient (Q10) of oxygen uptake by tuber disks in air was 3-4 at temperature from 21 to 32°C. This was larger than the Q10 of fiberous roots or intact tuber. Both the Q10 of tuber disks and fiberous roots decreased in water compared with the Q10 in air. 3. Oxygen uptake of the roots in water markedly decreased, though CO2 output was less changeable compared with the respiration in air. Rate of decreasing of O2 uptake in water was different among kinds of roots, small diameter, large diameter and tuberous. The O2 uptake of roots in water decreased considerably by removing of lateral roots. 4. Oxygen uptake of roots in gas phase increased with O2 concentration up to 20 per cent. O2 uptake of roots in water increased in proportion to O2 concentration of gas phase in Warburgvessel over 20 per cent., however, there was difference of increased rate between the large diameter roots and small diameter roots. 5. Oxyge uptake of tuber disks increased in inverse proportion to the thickness of disk from 500 μ to 3000 μ. Respiratory rate of disks with the thickness of 500 μ was more than three times compared with that of an equivalent masks of intact tuber. 6. Respiratory rate of roots decreased rapidly until about 30 days from planting and decreased gradually thereafter. Respiratory rate of fiberous roots increased from the base toward the tip of roots both in water and in air. But, there was difference of respiration rate in water among parts of tuberous root, joint, flesh and tail. 7. Respiratory rate of tuber disks was promoted by 2, 4-dinitrophenol (2.5 × 10-5 Mol) and inhibited by potassium cyanide (10-4 Mol) and monoiodoacetic acid (10-3 Mol) though the effects of these on fiberous roots were little. It was supposed that such difference in respiration may be due to the qualitative difference between tuber disks and fiberous roots.
  • 熊野 誠一, 藤瀬 一馬
    1965 年 34 巻 1 号 p. 35-39
    発行日: 1965/09/14
    公開日: 2008/02/14
    ジャーナル フリー
    To make clear the influence of environmental conditions on tuberous roots formation of sweet potato, roots were divided into the part of nutrient absorption and the part of tuberous root formation as shown in Fig. 1 and various environmental conditions, such as temperature (high and low), aeration (aerobic pearlite and non-aerobic pearlite by filled up with water) and light (roots were exposured to sunlight and roots were intercepted from light by black cover), were given only to the part of tuberous root formation. The results obtained may be summarized as follows: 1. The aerobic condition was more favorable for tuber formation than the other favorable conditions, i. e. low temperature, high temperature and non-exposure. The non-aerobic condition and the exposure to sunlight were unfavorable for tuber formation. 2. The meristematic activity of primary cambium was high and degree of lignification of stele cells was small in the roots cultured under the favorable conditions, while the contrary phenomena were observed in the unfavorable conditions. These results were in almost agreement with those of Togari, except the fact that cambium activity of the roots under the low temperature condition rather decreased compared with that under the high temperature one. 3. The concentrations of N, P2O5, K2O and reducing sugar in the roots on 23 days from planting were lower under the aerobic or the high temperature than those cultured under the non-aerobic or the low temperature condition, though the concentration of starch was higher under the former. It was conceivable that cell division and starch synthesis in roots were remarkably feeble under the non-aerobic condition and the exposure to sunlight. 4. High positive correlations were recognized between the respiratory rate and the concentrations of three major nutrient elements and reducing sugar in roots on 23 days from planting, while starch showed negative correlation to respiratory rate throughout various environmental conditions except the non-aerobic condition. Moreover, it was noticed that the effects of dinitrophenol and monoiodoacetic acid on the respiration of roots under the non-aerobic condition differed from those under the other conditions. 5. There was the intimate relation between net assimilation rate and dry-weight of tuber throughout all experimental conditions. It is assumed that tuber bulking has beneficial effect on the net assimilation rate.
  • 角田 公正, 和田 純二, 佐藤 亮一
    1965 年 34 巻 1 号 p. 40-43
    発行日: 1965/09/14
    公開日: 2008/02/14
    ジャーナル フリー
    In regard to rice plants differing in the variety, cultural condition and growth year, investigations were carried out to clarify the variation among hills as well as among panicles in the degree of sterile damage caused by the low temperature during the formation and development of young panicles, and further to determine a necessary number of samples required to estimate an average sterility percentage of a given field on the basis of the latest statistics. Results obtained may be summarized as follows ; 1. There was an inversely proportional relation observed between the sterility degree of a whole field and the coefficient of variation (c.v.) of sterility index (sin-1√(percent. of sterile grains)) among hills. And the regression equation holding true between the above two and another equation representing the relation between a necessary number of samples and the coefficient of variation of an item to be investigated made it possible to calculate the number of hills to be sampled in a given field according to the degree of damage, the level of significance and the precision of investigation. 2. The c.v. of the sterility index among panicles in a hill showed a tendency to decrease while the sterile damage of the whole field increased, but it did not fall below 20 % at the lowest. In the case of a hill being regarded as an investigation unit, therefore, it will be necessary, from a statistical viewpoint, to investigate the strility percentage of all the panicles in a hill. 3. Percentage of sterile grains of a panicle having the largest number of spikelets in a hill seemed to be lower than that of the whole hill when the damage was comparatively heavy, while higher when it was comparatively small. 4. The c.v. of the sterility index among panicles sample at random from the field did not fall below 20 % in any case. It was considered to be necessary therefore to sample more than 60 panicles to estimate an average sterility perceatage of a given field with a significance of 95 % and a precision of 5 %.
  • 角田 公正, 和田 純二, 佐藤 亮一
    1965 年 34 巻 1 号 p. 44-46
    発行日: 1965/09/14
    公開日: 2008/02/14
    ジャーナル フリー
    With rice plants differing in the variety, cultural condition and growth year as materials, the authors investigated the distribution of sterile grains in a panicle caused by the low temperature in the developmental stage of young panicles and also cleared the relation between the frequency of occurrence of distribution types classified into six groups as shown in Table 1 and the sterile damage degree or the heading stage of the panicles investigated. 1. The sterility percentage of primary rachis-branches was found to be higher, in general, than that of secondary rachis-branches except for cases where damages were much smaller. 2. The frequency of occurrence of each distribution type was found closely related to the degree of sterile damage of the whole field as well as to the heading stage of panicles investigated: the distribution types in which sterile grains appeared more in the upper part of a panicle than in the middle and lower ones, namely, type I and II, were higher in the frequency in the case of heavier damage mainly due to earlier heading, while the types in which sterile grains appeared more in the lower part of a panicle, namely, type V and VI, were higher in the frequency in the case of smaller damage mainly due to later heading. 3. The cause of above phenomena is not known yet. It is presumed however from the past studies that they have a relationship, both direct and indirect, to two factors, namely, the developmental process of young panicles occurring in the period of an abnormal fall of the temperature and the difference in the order of differentiation and development among spikelets in a panicle.
  • 西川 欣一
    1965 年 34 巻 1 号 p. 47-51
    発行日: 1965/09/14
    公開日: 2008/02/14
    ジャーナル フリー
    The experiment was performed from 1962 through 1963 to clarify the effects the N, P and K fertilization level would have on the growth and yield of alfalfa. In this experiment in which pots were used, 4 plots (nil (0), low (1), control (2) and high (3) plots) were provided for each of N, P and K supplied. The plants were cut 10 times in al during the test period, namely, 4 times in the first year of experiment and 6 times in its second year. The results obtained are summarized as follows: (1) The effect on the plant height was especially remarkable in the case of N and P fertilization level, and was less evident when K fertilization level was applied. The influence of P was evident in the first year, and the plant height was especially small in the P0 plot. On the other hand, remarkable effects of N were observed with regard to the plants subjected to 1st and 2nd cuts in the second year. As a matter of fact, the plant height was smaller in the N 0 plot, and this effect was particularly evident in the N3 plot to which a relatively large amount of N was supplied. (2) The number of plant stems increased as the number of cuts went up. The effect in question was most evident in the case of N fertilization level, and P fertilization level and K fertilization level followed in that order. The number of stems increased with the rise of the amount of N supplied, and so this tendency was most eviden in the N3 plot. With regard to the effect observed in the P fertilization level plots, the number of stems decreased in the P 0 plot, and no remarkable difference was observed among the stem numbers in the P1, P2 and P3 plots. With the increase in the amount of K supplied, the number of stems tended to go up bit by bit, but the difference among the stem numbers of the different levels was not significant. (3) The hay yield was most severely influenced by the amount of P supplied, and the yield in the P 0 plot was lowest of all the 12 plots. The effect of N on the hay yield was noticeable in the first year but in the second year, no significant difference was observed between the yields in question so far as N fertilization level was concerned. In contrast, K fertilization level had no effect on the hay yield in the first year, but had noticeable effects in the second year. (4) In view of the dry matter producing rate in forced draught oven at 70°C, the amount of dry matter produced did not necessarily decrease even during the high-temperature period.
  • 西川 欣一
    1965 年 34 巻 1 号 p. 52-58
    発行日: 1965/09/14
    公開日: 2008/02/14
    ジャーナル フリー
    This experiment was conducted to study the growth conditions of alfalfa free from the cutting treatment, as well as the changes taking place in the content of three essential nutrient elements in the course of its growth. The main results obtained were as follows: (1) The plant height, the number of nodes and the number of stems reached their maximum at the stage of full bloom, whereas the root diameter continued to increase almost rectilinearly until the experiment came to an end. (2) Both the leafiness and the T/R ratio decreased with the growth of the plant. The T/R ratio, in particular, began to decrease drastically at the start of the tap-root growing stage due to the sudden increase in the weight of the roots. (3) With regard to the distribution of oven dry weight among various organs of the plant, the roots occupied the greater part of the weight in question, accounting for more than 50 per cent of the total weight after the flowering time. The oven dry weight of the stem part increased by degrees with the growth of the plant (from 21 to 31 per cent), whereas that of the leaves gradually decreased (from 50 to 11 per cent). The oven dry weight of the flowers occupied only 2 per cent of the total weight, constituting a very small part in the weight distribution. (4) As to the hay producing rate dried in a forced draught oven at 70°C, both the tops and the roots attained the highest rate during the period from the stage of buds to that of early bloom. (5) The percentage of N, P and K contained in the plant body was relatively high in the early stage of growth, and tended to decrease with the growth of the plant. The percentage of N contained was the highest in the leaves, and the flowers, the roots and the stems followed in that order. In fact, the leaves were found to contain twice as much amount of N as that of the stems. On the other hand, the percentage of K contained was the highest in the leaves, and the stems, flowers and roots followed in that order. (6) The absolute amount of N, P and K absorbed in the plant body differed greatly accrding to the change in the dry matter weight. The amount in question gradually increased with the growth of the plant. The maximum amount differed depending on the essential nutrient elements and the variety of the organs, although it began to deccease at a certain period of time. (7) The greater part of N contained in the plant distributed over the leaves at the early stage of growth, but later, 50 per cent of the N content were concentrated in the roots. The percentage in regard to P was similar to that of N, but, in the stage of ripe pod, about 60 per cent of the entire P content gathered in the roots, exceeding the corresponding value of N. The greater part part of K distributed in the upper part of the plants, particularly in the stem.
  • 長戸 一雄, 江幡 守衛
    1965 年 34 巻 1 号 p. 59-66
    発行日: 1965/09/14
    公開日: 2008/02/14
    ジャーナル フリー
    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°C. 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. [the rest omitted]
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