[in Japanese]

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A cross between Brimful from Nepal (a scented variety with high protein) and Nippon bare (a Japanese rice variety) was carried out in 1977 and F₂-F₅ plants were grown from 1978 to 1982. The present experiment was conducted for getting the informations on breeding of rice variety with high protein. The results obtained are summarized as follows : Grain protein content in F₂ and F₃ plants showed wide and continuous distributions. Mean of F₂ plants was located between P₁ (high protein parent) and P₂ (low protein parent) and slightly lower than the mid parent (Figs. 1, 2). The narrow sense heritability of protein content based on the variance and co-variance of F₂ and F₃ plants was O.588. As concerns protein content and agronomic characters, result of F₅ plants did not show significant correlation except one line (Table 8). These results indicated that it was possible to select promising lines having high protein property and desirable agronomic characters. As compared with F₃ and F₄ generations, F₅ was high in mean value of protein content and also decreased in the genetic variance of protein one (Tables 1, 2, 7). High protein property showed the tendency of being bred in true in F₅ generation. As for amino acid contents in F₄ and F₅, there were significant differences among the lines in three amino acids per dry weight basis, not per protein basis, and the lines were far better in the trait than Nippon bare (Tables 4, 9). Significant correlation was observed between protein content and lysine and threonine per dry weight in F₄ and F₅ plants (Tables 5, 10). The promising lines which have high protein property and also relatively good agronomic characters were selected based on thc measured results in F₅ plants (Table 11).

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Dependence of seed yield on sink capacity and matter supply from the source was examined in individual pods of rape plants (Brassica napus L., cv. Norin No. 16) grown in a field. The effects of matter supply from the source were examined grading light intensity by shading treatments in the ripening period. The effects of sink capacity were analyzed based on the individual variation of seed number that occurred naturaly in a pod. Seed yield and sink capacity were expressed as those based on unit surface area of pod and termed "relative seed yield" and "relative sink capacity" respectively. Aspects of variation in relative sink capacity in the "pod layer" were also examined. The results obtained are summarized as follows: 1. Under natural light (no shading), relative seed yield increased linearly with relative sink capacity, suggesting that seed yield was determined by sink capacity of pod. Under lower light intensities (72% and 44% of natural light), relative seed yield increased with relative sink capacity only in the case where the latter was small. Above a critical point, the increase in relative sink capacity did not result in an increase of relative seed yield any more, showing that seed yield was determined by matter supply from the source in this situation. The critical point of the relative sink capacity lowered with decreasing light intensity (Fig. 1). 2. Relative seed yield increased with light intensity, the rate of increment was larger at the larger relative sink capacity (Fig. 2). 3. Since pods located at higher levels of the pod layer are exposed to strong light, it is desirable that the relative sink capacities of those pods are large. However, the acutual vertical distribution of relative sink capacity in a pod layer wes just the opposite to this (Figs. 3 and 4). 4. There was a fairly close positive correlation between percentage of seed-setting and relative sink capacity. Thus, improving seed-setting in pods at higher levels of the pod layer was considered to be effective for increasing seed yield (Fig. 5).

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Using rape plants (Brassica napus L., cv. Norin No.16), the following two experiments were conducted. In Exp. I, leaf cutting (cutting of all leaves) and leaf shading (80% of natural condition) were carried out at various stages during the period from the beginning of flowering to near maturity. In Exp. II, just after the end of the flowering period, pod thinning (25 and 50% of non-treated plant), leaf cutting (cutting of all leaves) and shading (whole plant, 50% of natural condition) were carried out. From the data obtained, times and factors for determination of yield components were examined mainly from the view point of assimilate supply. The results are summarized as follows : 1. Number of pods per plant kept increasing upto the end of the flowering period and then decreased rapidly due to abortion of young pods located at upper positions of inflorescences. The abortion ceased a week after the end of the flowering period and pod number kept a constant level thereafter (Fig. 1). 2. Number of pods decreased significantly by shading and cutting of leaves conducted at and before the middle of the flowering period. However, the treatments carried out later than that stage did not show such an effect. From this fact, it was suggested that the development of individual pods had been potentially decided at the end of the flowering period (Taable 1). 3. Number of seeds per pod was significantly affected by shading and cutting of leaves carried out at and earlier than the end of the flowering period and was not affected so by later ones (Table 1). 4. Dry weight per seed was affected significantly by the treatments carried out at and earlier than a week after the end of the flowering period (Table 1). 5. From the above-mentioned results, it was concluded that final magnitude of yield components was fixed in the order of number of pods per plant, number of seeds per pod and dry weight per seed . 6. Number of pods per plant decreased by shading and cutting of leaves at early stages in the flowering period. The extent of decrease in pod number that resulted from a treatment, corresponded to the decrease in dry matter production of plant due to the treatment. Since there wils no substantial difference in the relationships between dry matter production of plant and pod number in the both treatments, pod number was considered to be determined by assimilate supply (Table 1, Fig. 2). 7. The effects of whole plant shading and leaf cutting on number of seeds per pod were quite different. The shading affected little or only slightly seed number though the treatment resulted in considerable reduction in dry matter production of plant per pod. Pod thinning (without leaf cutting) resulted in a large increase in dry matter production of plant per pod, nevertheless it did not bring about an increase in seed number. Contrastingly, leaf cutting caused a large reduction in the seed number even when dry matter production of plant per pod was similar to that for control. From these facts, it was considered that the process of seed set was regulated rather by some unknown substances from leaves than assimilate (Table 2, Fig. 3). 8. Dry weight per seed was changed by pod thinning, leaf cutting and whole plant shading closely correlating with dry matter production of plant per seed. From this, it was shown that dry weight per seed was primarily determined by assimilate supply (Table 2, Fig.4). 9. Percentage of oil in seed was changed by treatments and increased with increasse in dry matter production of plant per seed. The contents of protein and other constituents without oil and protein (most of these are considered to be polysaccharides) decreased with increase in dry matter production of plant per seed with a much larger rate in the latter. Since energy cost for biosynthesis is oil > protein > polysaccharides, it was suggested that the higher the energy cost for biosynthesis of a substance, the synthesis is acceralated at the higher rate as assim

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[in Japanese]

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1. An experiment was designed to investigate the effect of cutting frequency on the change of components in the alfalfa swards. Cv. Moapa (early, quick regrowth after cutting, erect type) and cv. Vernal (late, slow regrowth after cutting, prostrate type) were grown in pure and mixed swards at a density of 100 plants/m². Two cutting schedules, 4 and 6 cuts per year, were imposed on these swards. Yield and plant number per unit area were examined at each cutting time. 2. Percentage of Vernal in the yield of the mixed swards decreased as cutting schedules advanced. The rate of decrease was greater in the 6-cut sward than in the 4-cut sward (Fig. 1). 3. Plant numbers per unit area reduced as the cutting schedules advanced both in the pure and mixed swards. The rate of reduction was much higher in the case of 6 cuts than in the case of 4 cuts (Fig. 2). 4. The reduction in plant numbers in the mixed swards was mainly due to the reduction of the plants of Vernal (Fig. 2). The surviving rate of Vernal in the mixed swards was lower than that in the pure swards, and the surviving rate of Moapa in the mixed swards was higher than in the pure swards (Fig. 3). 5. The yield of individual plant of Moapa in the mixed swards was greater than that of Vernal at every cutting time (Figs. 4 and 5). 6. It was inferred from these results that an alfalfa sward would eventually shift to a sward in which late type plants were less in number than in the original sward, and that the shift would probably be accelerated by increased cutting frequency.

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[in Japanese]

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[in Japanese]

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[in Japanese]

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Leaves and/or bracts of safflower plants were removed at the first flowering stage of the head of the main stem, for the purpose of obtaining information as to the contribution of leaves and bracts to seed yield and yield components, i.e. number of seeds per head and 100-seed-weight, during maturity. The results are summarized as follows : 1. The area of bracts is only 5% of the total area of leaves and bracts in the main stem, but it reaches about 50% in the branches. The ratio in the whole plant was about 14% (Table 1). 2. At the maturity, stems, leaves and heads accounted for about 25%, 15% and 60% of the total dry weight, respectively. Removal of leaves and/or bracts decreased the dry weight of heads, especially that of the branches, more remarkably than the dry weight of stems or leaves (Table 2). 3. Removal of leaves or leaves and bracts decreased the seed yield through the reduction of both the number of seeds and 100-seed-weight. Removal of leaves or leaves and bracts affected the seed yield and number of seeds of the head of the branches more remarkably than those of the main stem, and affected 1OO-seed-weight similarly in the head of the main stem and in the head of the branches (Tables 3, 4). 4. All leaves and bracts contributed to the seed yield of the plant by about 70%. When all leaves and bracts were removed, seed yield of 1.3 g was gained. This seed yield was presumably contributed by the stored photosynthates and the current photosynthates during maturity by the other green parts such as the surface of the stem and head. All leaves and bracts contributed similarly, by about 45%, to the number of seeds and 100-seed-weight (Table 5). 5. The contribution of all leaves to the seed yield was as large as 56% when the bracts were present, and much larger, i.e. about 69%, when the bracts were removed. The contribution of all leaves to the number of seeds and 100-seed-weight was 37% and 28%, respectively, when the bracts were present (Table 5). 6. The leaves of the main stem contributed to the seed yield of the plant by about 40%. The contribution of the leaves of the main stem to seed yield, the number of seeds and 100-seed-weight of the plant was larger than that of the branch leaves. The leaves of the main stem contributed not only to the seed yield of the main stem itself but also to that of the branches. Similarly, the leaves of the branches contributed to both the seed yield of the main stem and that of the branches (Table 5). 7. The contribution of bracts to seed yield was rather small, about 8%, when the leaves were not removed, but it was very large, about 35%, when the leaves were removed (Table 5). The contribution of the bracts to 100-seed-weight when the leaves were removed was especially large. It is suggested, therefore, that the bracts have an ability to substitute for leaves in the ripening of seeds.

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