[in Japanese]

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The correlations were examined between the growrth angles of crown roots to the soil surface and their diameters in rice plants. 1. A significant correlation was observed between the growth angles and the root diameters, when the whole crown roots of a hill were treated collectively. Namely the thicker roots tended to grow vertically, while the thinner ones horizontally. Thecorrelation coefficient, however, was not always high. The same relationships were found when the crown roots were examined among the upper, the lower or the "P shootunit" roots, respectively. 2. Highly close correlations were found between the growth angles and the root diameters when the crown roots were grouped according to their time of emergence in the vegetative phase of the plants. Their relations, however, fell into different regression lines in accordance with the growing stages of the plants. As to the crown roots emerged after the plants entered into the reproductive phase, no such correlations were found. As a result, it is considered that a possible relation may exist between the geotropism of crown root and their diameters. Further, the geotropism may be affected by the varying quantity of assimilates translocated from the shoot during the growing stages of the plants.

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The lateral branching habit of crown roots was investigated on rice plants grown under different environmental conditions. The crown roots were classified here into the following the three types according to their acropetally decreasing rate of diameter; i. e. the crown roots of the low-(A-type), the intermediate-(B-type) and the high-(C-type)decreasing rates, respectively. Close relations were found between the branching habit and the crown root types mentioned above, irrespective of the differences in the environmental conditions. Namely, the density of laterals on the crown root axes was higher in the C-type roots, decreasing successively in thc B- and the A-type roots, while the length of laterals showed a reverse tendency. Nitrogen application, defoliation and shading, enhanced predominantly the formation of the C-type roots during reproductive phase of the plants. It might be assumed that such environmental conditions may influence on the lateral root formation through modifying the composition of each type of crown roots in the whole root system.

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The positions of initiation and emergence of lateral roots on crown root axes of rice plants were investigated in relation to the diameter of root tip or the elongation rate of each crown root. 1. The root apex-lateral distance (the distance from the root apex to the most newly emerged lateral root) varied remarkably among various crown roots investigated. However, the distance was found to be closely correlated with the diameter of root tip of each crown root and with its elongation rate. 2. As for the root apex-lateral primordium distance (the distance from the root apex to the position of the youngest lateral root primordium), its relation to the crown root growth varied as the stage of elongation of each crown root advanced. Namely, during the early stage of crown root elongation, the distance exhibited a significant positive correlation with elongation rate of the crown root, but not with the diameter of the root rip. 3. On the contrary, in the later stage of crown root elongation, the distance was found to be closely correlated both with elongation rate of the crown root and with its diameter. Therefore, in the later stage of crown root elongation, the higher the elongation rate and the larger the diameter at root tip, the longer become the root apex-lateral primordium distance and also the root apex-lateral distance. Based on the results mentioned above, it was assumed that the position of initiation and emergence of lateral roots on each crown root axis is in a close relation with elongation rate of the crown roots.

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Some properties of the starches contained at culm and endosperm were compared between glutinous (cv. Saitamamochi, cv. S) and non-glutinous (cv. Norin No. 8, cv. N)rice plants of different polyploidy (haploid x to tetrapliod 4 x). The results obtained are summarized as follows: 1. Alkali decomposition values of culm starches varied among polyploids, and they were greater than those of endosperm starches. The glutinous endosperm starches showed a stronger resistance to alkali. 2. Absorption curves of iodine-starch complexes of both culm and endosperm starches varied more or less between cv. N and cv. S and among polyploids. The peaks of absorption curve of culm starches were observed with blue color at 600 to 610 nm wave lengths, except cv. N-4 x which had a peak at a little shorter wavelength. The curves of endosperm starches of cv. N and cv. S had peaks at the shorter wavelengths than those of culm, being near 560 nm with purple color in the former and at 520 to 530 nm with purplish red color in the latter. 3. The absorption curves of iodine-starch complexes obtained from endosperms ripened at different air temperatures were almost similar, but the starch ripened at 35°/30°C (day/night) showed a stronger peak at a shorter wavelength than that at 25°/20°C. 4. X-ray diffraction patterns of endosperm and culm starches gave A type and B type patterns, respectively, and no clear difference was observed among polyploids and between cv. N and cv. S.

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The structural differences of lateral roots in rice plants were investigated in relation to their diameters. 1. Among the lateral roots of any type investigated, whether they were "thick"laterals with further branching ability or "thin" ones with no such ability, the thinner ones tended to diminish their structural complexities quantitatively, i. e. the thickness of cortex, the number of cortical layers, the diameter of the stele, and the number as well as the diameter of vessels decreased, respectively, in proportion to the root diameters. 2. The same relation was found when the structures were examined along an axis of each "thick" lateral root with diameter acropetally decreasing. 3. The apical axial parts of such "thick" lateral roots were found to be closely alike to the "thin" ones both in diameter and in structure, and in these parts no further branching was recognized. Based on these results, it was suggested that there exist a close interrelation among the diameter, the structure and the branching ability of lateral roots, regardless of their types, being " thick" or " thin".

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The ohject of this study is to investigate the effect of planting date on growth and yield of maize for whole-plant silage in the north-marginal area in Japan. Heigenwase, which is an early hybrid, was planted on four dates from mid-May to mid-June over a 4-year period (1976-'79), and some agronomic traits and yields were measured. The results obtained were as fllows: 1. Planting date markedly affected the speed of emergence and silking. As plantlng was delayed, emergence date and silking date were delayed in each year and the days from planting to emergence and from emergence to silking were reduced. Silking was affected by temperature, since efferctive heat-unit accumulation over 6°C from emergence to silking required 735±11°C constantly, regardless of planting dates. 2. As planting was delayed, top mean growth rates during the vegetative growth period were increased and those during the reproductive growth period were decreased in each year. During the reproductive growth period, stover mean growth rates were not affected by planting dates, but ear mean growth rates were obviously the greatest on the earliest planting date in each year. Top mean growth rates during the both vegetative and reproductive growth periods indicated highly positivc correlations (r=0.649, r=0.937) with effective heat-unit accumulation over 10°C. 3. The latest plantings always resulted in the highest stover DM yields, but no distinct stover DM yields advantage occurred with later planting. The earliest plantings led to the highest ear DM yields, total DM yields, TDN yields and percentage DM of whole-plant, and gave a distinct grain maturity advantage. 4. Ear DM yields and total DM yields indicated highly positive correlations (r=0.951, r=0.787) with effective heat-unit accumulation over 10°C during the ear-filling period. Percentage DM of whole-plant indicated a highly positive correlation (r=0.896) with accumulated temperature over 0°C during the ear-filling period. 5. Tpp dry-matter increment during the ear-filling period indicated highly positive correlations with ear DM yield, total DM yield, TDN yield, percentage DM of whole-plant and ear/total ratio. 6. From above results, it was concluded that under severe conditions like Nemuro district, early planting such as mid-May was essential for giving longer and warmer ear-filling period which could lead higher yield and quality for silage maize.

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[in Japanese]

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[in Japanese]

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Although the size and shape of the caryopsis in rice plants are determined by the capacity of the glume, the growth of the caryopsis and the floral glumes may be controlled by different genetic systems and thus they may have different developmental paths. Therefore, in varieties having potentially much longer caryopsis than the glume, the growth of the caryopsis may be affected by the glume leading to abnormal grain formation. One of such abnormal development of caryopsis is "notched" grain which is observcd with variable frequencies in some of the rice varieties. This investigation reveals an account of the mechanism of grain notching and the variation for notched grain frequency in rice. A total of 32 varieties and lines was grown in glasshouse as well as in field to investigate the varietal and environmental variation for the notched grain frequency and also the correlation of notched grain percentage with the unbalance between the length of the caryopsis and the glume. For allowing the caryopsis to grow freely, the top of the glume on one or two panicles in each of the plants was clipped off at two or three days after the anthesis. In the field, glume clipped panicles were protected by parchment paper bags. The length of glume-clipped caryopsis (T1) and untreated one (C1) were measured using ten caryopses randomly taken from each of the 6 plants in glasshouse and 20 plants in the field. T1/C1 ratio was calculated to indicate the degree of unbalance between the potential length of caryopsis (T1) and the longitudinal capacity of glume (C1). One hundred untreated caryopses from each of the plants were exarnined to determine the percentage of notched grain. The percentage was transformed into the degree of angle for the statistical analysis. Correlation between the T1/C1 ratio and the notched grain percentage was also analyzed. Varietal variation ranged from 0 to 90% for notcched grain and from 1.1 to 1.5 for T1/C1 ratio which indicated that the potential length of the caryopsis was 1.1 to 1.5times more than the longitudinal capacity of the glume. From these results, the materials used were classified into three groups: Group A, showing remarkably high, more than 80%, grain notching and high T1/C1 ratio in both the glasshouse and field conditions, group B, showing highly sensitive response of grain notching to the environmental conditions, and group C, showing mostly normal grains with low T1/C1 ratio. The glume-clipped caryopsis did not develop notched grain in all of the materials. Correlation between the glasshouse and field was high for C1 and T1, but it was rather low for notched grain percentage and thc T1/C1 ratio in some varital groups. Highly significant correlation between notched grain percentage and T1/C1 ratio (r=0.94) suggested that unbalance between the length of glume and caryopsis was the primary factor determinig the grain notching. From these studies, it may be concluded that, along with other factors, abnormal growth of the caryopsis restricted by the glume capacity results in notching of the caryopsis.

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It is the purpose of this paper to establish a new method for the measurement of oxydation activity of rice root. After rice root was soaked in ferrous sulfate solution, the oxydation-reduction potential changed quickly. This change may be related to the increases of ferric ion in solution caused by oxydation activity of rice root. Eh-raising process was recorded continuously as shown in Fig. 1. Ageing process of rice root was expressed by the decreases of Eh-raising activity of rice root. Eh-raising activity of rice root of heavy nitrogen application plot decreased as shown in Fig. 4 in this studies. The drainage effect was shown in Fig. 5. Eh-raising activity of continuous paddy plot decreased remarkably at late maturing stage. The effect of pH control of ferrous solution on Eh-raising activity of rice root was shown in Fig. 3. At the unfavourable condition for rice growth as pH 4.4, Eh-raising activity of rice root decreased. From these results, the features of this method were in quick response and continuous recording of oxydation process by root. And the problems on the measuring were errors caused by the contamination of platinum electrode and reference electrode.

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Changes in adenosine tri-phosphate (ATP) content in the embryo, endosperm and bran of kernel were investigated during the development of the rice kernel. ATP content between the ventral and dorsal portions of the rice kernel was also compared. The results are as follows. 1. Embryo: ATP content kept increasing during the whole ripening period, especially the ATP content per dry weight in the embryo was much higher than that in the endosperm. At harvesting time, the ratio of the weight of the embryo to that of the kernel was 6.9%, while the ATP content ratio was 39.3%. 2. Endosperm: ATP content increased during the development and had a peak l4daysafter heading when the translocation of starch to the kerncl was most actively. There after it decreased till harvest and the content at harvest time was very low. 3. Bran: The changes in ATP content were similar to those observed in the endosperm, but the content per dry weight was much higher than that in the endosperm. Also the content per dry weight was 4.7 times as high as that in the endosperm and 2.1 times that in the embryo 7 days after heading. 4. ATP content was always higher in the dcrsal portion of the kernel than in the ventral one over the ripening period. These results abovc mentioned showed that ATP played an important role in ripening of rice kernel.

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Rice plants, cv. Leng Kwang, Nihonbare and Milyang 23, were placed after heading outdoors and at a low temperature (day: 20°C, night: 13°C). The relationship between the changes of ATP content in the kernel and the increase of kernel weight was investigated. The results are as follows. 1. When the plants were placed outdoors, ATP content of the rice kernel increased and the peak was observed l4 days after heading. Thereafter it decreased. On the other hand, at a low temperature the increase in ATP content of the rice kernel was much slower and its peak was observed 21 days after heading. 2. When the plants were placed outdoors, there was a rapid increase in the weight of the kernel 14 days after heading. On the other hand, at a low temperature the increase in the weight of the rice kernel was much slower than that of outdoors and it increased rapidly 21 days after heading. The pattern of increase in kernel weigllt was very similar to that of the changes in ATP content. 3. ATP content in hull was the highest at heading and then decreased. 4. ATP content in the hull of sterile grain was always much lower than that of fertile grains and there was hardly any increase in hull weight during the ripening period.

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[in Japanese]

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The glain growth of rice was found to be highly tolerant to water stress during the poriod of rapid starch seposition, despie of a large reduction in the total dry-matter production. The objective of this study was to examine whether the water stress in the earlier stage of grain growth when the process of cell division and expansion is predominant affects the growth of endosporm as well as final agrain yield per plant. Rice plants (Oryza sativa L. cv. Nipponbare) were grows in 4-liter pots under outdoors conditions. Twenty plants were grown in each pot in which the soil was submerged till ears emerged. All tellers removed as they appeared, only the main culm being kept growing. After the ear emergence, the amount of water applied to 15 pots was reduced for 10 day period inpose the development of defictis in plants (dry treatment 1) Water application was also reduced for another 15 pots between 5 days and 14 days after ear emergence (dry treatment 2). The remaining pots continued to be waterd as before (control). Pots of bith dry treatments were well watered as control after 10 days drying poriod. At intervals during the stress and recovery cycle, the relative water content (RWC) was monitored on the flag leaves between 1300 and 1500 h. During the period between 9 days and 13 days after ear emergence, the measurements of diffusion resistance 9 were taken late in the morning on the flag leaves. The number of spikelets at flowering was noted every day for eavh ear. Plants were harvested at both the being and the end of treatments and at maturity to determani the dry weights of grain, leaf and others. Leaf areas were also determined on these occasions. At the end of dry treatment, the grains which had formed the aleuron, and their dry weight and volume were measured individually. Water deficits, as indicatcd in thc daily trend of RWC, devcloped between 2 days and 10 days after ear emrgence in the plants of dry treatment 1 and between 7 days and 14 days after ear emergence in the plants of dry treatment 2. The renge of RWC in the control was small, between 98 and 100%. Leaf conducatance in plants subjected to desiccation was also reduced, being approximetely 75% of well watered plants. Both RWC and the leaf condutance recovered to same levels as the control plants a days or two after rewatering. Leaf senecence after ear emergence was accelerated in stressed plants, and plants in dry trsament 1 lost green leaves more rapodly than in dry treatment 2. As the flowering of flowring most 1 were subject to wter deficits while they were flowring whereas the watwer stress developed after flowring in the plants of dry treatment 2. Rcduction in both the leaf area and the leaf conductance in stressed plants resulted in less dry matter production than in well watered plants over the period of soil desiccation, but grain growth of the plants, in terms of dry weight, in two dry treatments over this period was not affected at all. Since the dry weight of plant parts other than grain decreased more in stressed plants than in control, the maintenance of grain growth may have resulted from the increased supply of assimilates that had been sttred before anthesis. The result the upper parts of grasins formed the aleuron laver up layer up to 10 days after ear emergence and those of flower of lower parts of ear completed to form it between 10 and 14 days after ear emergence indicates that water deficits developed primarily during the period of repid cell division and expansion in the endosperm of the upper grains of the plants in 1 and in the endosperm of lower grains of plants in dry treatment 2. Thurs, the divison and exapansion of the endosperm cell appeared not to be affected water deficits during its cell development was essentially the same that of control. Since turgor is generally regarded as a primary driving force to control the cell division and expasion, the maintenance of cell division and exapansion may be mediated through the turgor maint

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Two kidney bean cultivars, Taishokintoki (dwarf) and Tokachishirokintoki (determinate, bush) were grown in the equidistant square pattern at five population densities, and dry matter accumulation in plant conlmunities were analyzed. The main results obtained were summarized as follows: 1. Total dry weight was highest at the highest density (44.4 plants/m²), although the difference between 25.0 and 44.4 plants/m² was very little. The maxirnum dry matter production was 641 g/m² and 734 g/m² for Taishokintoki and Tokachishirokintoki, respectively. 2. With increase in population density, dry weight of branches decreased more remarkably than that of main stem, but the ratio of the branch to the main stem was about 1 to 1 at the highest density. 3. CGR and LAI shifted higher with higher densities. NAR which was lower in higher densities, declined with progress of season, but rose temporarily at the middle of July. 4. Relative light intensity at the bottom of the canopy (logarithmic scale) decreased linearly with increasing LAI. The regression value (Ks) was low for Tokachishirokintoki, and the LAI requared for 95% light interception was 2.9 and 4.2 for Taishokintoki and Tokachishirokintoki, respectively. 5. The decrease in NAR with increase in LAI initiated from LAI 0.5. The decreasing rate was high for Taishokintoki with high Ks valuc. 6. LAIopt. and CGRnlax. were higher at stage III (the middle July) with larger solar radiation, compared with stage II and IV. At each stage the value of LAiopt. was high for Tokachishirokintoki, but the varietal difference of CGRmax. was very little. 7. The efficiency of dry matter accumulation per unit photosynthetically-activc radiation (PAR) intercepted (EPAR, dry weight rng/kcal) incrcased gradually up to the middle July and then decreased for Taishokintoki. However, those of Tokachishirokintoki were relatively constant up to the early August. The mean EPAR during the middle growing season (stage II-IV) did not differ between varicties and stages.

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[in Japanese]

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In order to determine the effect of ABA on ozone injury to rice plants, ethylene production, rate of chlorophyll retention and ozone-sensitivity of rice plants pretreated with ABA solution were investigated. The experiments were carried out in pots using rice plants at the 7-8 leaf stage. The results obtained are summarized as follows; 1. Ethylene production by the leaf blades exposed to ozone increased with the increase in the dosage of ozone. 2. Ethylene production was higher in cv. Nihonbare which was more sensitive to ozone than in cv. Tongil. 3. Pre-treatment with ABA solution one hour before ozone treatment reduced ethylene production by the leaf blades exposed to ozone. 4. The rate of chlorophyll retention decreased following injury, but increased remarkably by the pre-treatment with ABA solution. 5. In conclusion, it could be demonstrated that ozone injury of rice plants can be reduced by the pre-treatment with ABA solution.

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Several experiments were carried out to determine the effects of exogenously applied ABA on the water metabolism, and to clarify the endogenous ABA relationships in ozone-sensitivity under different soil water content in rice plants. The rice plants were cultivated in soil with 60, 80, and l00% of maximum water holding capacity and under submerged condition. The results of the experiments were as follows: 1. Ozone injury was reduced with increasing ABA content of which production was increased under water stress conditions. 2. Under water stressed conditions, the rate of water loss was decreased with increasing concentration of ABA applied exogenously. 3. It may be assumed that the ozone-sensitivity is closely related to the stomatal closure caused by the increased ABA content due to water stress.

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In order to determine the effects of nitrogen application on ABA content of rice plants and their ozone-sensitivity, ABA production and ozone injuries were observed under different levels of nitrogen application with two Japonica and two Japonica × Indica type varieties. 1. In all varieties, endogenous ABA content decreased with the increasing level of nitrogen applied, although total nitrogen content increased with the increasing level of nitrogen applied. 2. Ozone injury was found to increasing level of nitrogen applied and to change depending on the varieties. Ozone injury was found to occure seriously with increasing nitrogen content in Jinheung and Nongback, however less pronounced in Tongil and Milyang No. 23. 3. Endogenous ABA content and ozone-sensitivity were related to the nitrogen content in the rice plants.

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