[in Japanese]

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Experiment I. The author investigated the influence of the alternate cutting of the primary rachis-branch on the protein content in the brown rice and some agronomic traits using the japonica and the improved semi-dwarf, high-yielding indica varieties. The results are as follows; 1. In all varieties, "the product of the percentage of ripened grains and the weight of 1000 grains" increased by this treatment. In this occasion, the increasing rate was much higher in the improved indica varieties than in the japonica variety. 2. In all varieties, the protein content in brown rice increased by this treatment. Experiment 2. The author compared some agronomic traits between cv. Koganemochi and its mutant whose greatest characteristic was partial sterility. It was very convenient to use this for this research. 1. There was no significant difference in the heading date, the number of panicles per hill, the number of spikelets per panicle, and the culm length between the two. 2. 1000 grains weight of the mutant and the original variety was 23.9 g and 22.0 g, respectively. The percentage of ripened grains was 94.5% in the original variety and 26.8% in the mutant. 3. Grain weight and the ammount of protein content in a grain increased more rapidly after flowering in the mutant than in the original variety. 4. The percentage of the protein content in the brown rice was always higher in the mutant than in the original variety during the ripening period. The percentages of the protein content of the mutant and the original varicty at the time of maturity were 10.56% and 7.33%, respectively. From the results of these experimcnts, it was assumed that the percentage of the protein content in brown rice became higher by the limitting of the number of the ripening grains per panicle under no restriction of dry matter production in rice plant.

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Nitrogenous nutrient is one of the major element to regulate plant growth, however little is known on the plant hormones relationships in the mechanisms of growth regulation with nitrogenous nutrient. Present experiment was conducted to study ethylene relationships in the regulatory mechanism of nitrogenous nutrient in the growth of rice plant. Growth rate, nitrogen content and ethylene evolution in leaves under different nitrogen levels were examined. The results obtained were as follows. 1. The higher the content of nitrogen in leaves and the greater the plant growth, the less was the ethylene evolution in rice leaves. 2. Very clear positive correlation was found between the nitrogen content in the leaves and the growth rate, while high negative correlation was detected between nitrogen content in leaves and ethylene evolution from leaves. 3. Therefore, a fairly close negative correlations were observed between the ethylene evolution from leaves and the rate of growth. Based on those results, it seems probable that the reduced ethylene evolution from leaves under high nitrogen condition may play an important role to explain growth promotion by nitrogen supply in plant.

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[in Japanese]

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Distribution of P, K and Mg on the ventral and dorsal side of the rice kernels was investigated at 8, 16 and 30 days after flowering. The obtained results are as follows; 1. 8 days after flowering 0n the dorsal side: Mg and P were distributed markeeily in the aluerone layer. They were distributed more concentratedly in the pericarp (especially in the vascular bundle) than in the starch cell layer. K was distributed throughout the pericarp, aluerone layer, and vascular bundle and was less concentrated in the starch cell layer than in the pericarp, aluerone layer, and vascular bundle. On the ventral side: The results were almost the same with that on the ventral side. But K was distributed more concentratedly in alueronelayer than that on the dorsal side. 2.16 days after flowering 0n the dorsal side: Mg and P were distributed markcdly in the aluerone layer. Mg in starch cell layer was distributed more conccntratedly than that of 8 days after flowering and was distributed in pericarp, too. P was not almost distributed in pericarp. K was distributed throughout the rice kernel including the starch cell layer. On the ventral side: The results were almost the same with that on the dorsal side. But Mg, P, K, in aluerone layer were distributed more concentratedly than in dorsal-aluerone layer. This tendency was very peculiar in K. 3. 30 days after flowering Both on the two side: P, Mg and K were concentrated in aluerone layer. K (markedly) and Mg were distributed in preicarp, but P was not almost distributed in pericarp.

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In order to obtain basic data on the effective application of artificiallights and colored transparent shelters to plant cultivation, effects of composite lights with a dominant energy in the blue (B), green (G), red (R) and blue and red (BR) on photosynthesis of the following crop plants were investigated: tomato (Lycopersicum esculentum Mill.), sweet pepper (Capsicum annuum L.), strawberry (Fragaria grandiflora Ehrh.), cucumber (Cucumis sativus L.) and squash (Cucurbita moschata Duch.) as vegetable species; and peach (Prunus persica Sieb. et Zucc.), grape (Vitis aestivalis Micahux) and satsuma mandarin (Citrus unshiu Mark.) as fruit tree species. At an irradiance 50 W m^-2 in the waveband 400-700 nm, which gives a rate of about 1/3 of the maximum photosynthesis, the photosynthetic rate relative to white (W) light was generally higher in R, slightly lower in BR and B and clearly lower in G for both species of vegetables and fruit trees. This difference among the light qualities was negligible at irradiances close to the light-saturation point, but extended with decreasing the irradiance. Photosynthetic efficiency, which was expressed in terms of photosynthetic rate at the original slope of light-response curve, was raised with increasing the energy in the red region when the efficiency was shown for unit energy incident (400-700 nm), while the efficiency for unit quanta incident (400-700 nm) was not much different among the light qualities. A possibility of the prcsence of enhancement effect for photosynthesis was found in most of the composite lights, assuming that no enhancement effect is present in G light. The enhanced part, however, did not exceed more than 10 percent even in W light in the average of the species. From the data of the present study and the literature, it was concluded that red light energy is the most important to photosynthesis and that the relative effectiveness of composite lights on photosynthesis can be roughly estimated by means of the sum of the products of the averagc action spectrum by the energy distribution of each light, or by the quantum flux density incident in the waveband 400-700 nm of each light.

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The ultrastructure of small vascular bundles of the 8th leaf blades in rice seedlings was examined with the electron microscope. 1. In the parenchyma sheath cells the chloroplasts have a centrifugal position, whereas the mitochondria have a centripetal position. The phloem is bounded by a single layer of thick-walled parenchyma cells, which differentiate into the mestome sheath cells in the upper leaves. The thick-walled parenchyma cells have the plastids with starch granules, mitochondria and dictyosomes. The suberized lamellae are not detected in the walls of these sheath cells. 2. The protophloem sieve elements and companion cells locatcd abaxially within the vascular bundles show an apparent degeneration in the expanded leaf, but the degeneraion is not observed in the elongating zone of the folded leaf. Thus, the protophloem may degencrate during the leaf emergence and ceases to function after leaf expansion. 3. Late-formcd metaphloem sieve elements are narrow and thickwalled, but the associated companion cells are wider than the sieve elements. The metaphloem sieve elements have the P-type plastids and a small amount of mitochondria and endoplasmic reticulum. The rnetaphloem companion cells contain many mitochondria and endoplasmic reticulum, and often contain osmiophilic globules. Ultrastructural features of the metaphloem parenchyma cells are the same as the companion cells. 4. The distribution of plasmodesmata in transections of the small vascular bundles has been determined. The plasmodesmata occur in the outer and inner tangential walls of the parenchyma sheath cells. The late-formed metaphloem companion cells are connected by numerous plasmodesmata with adjacent parenchyma cells of the metaphloem and metaxylem, and also with the thick-walled parenchyma cells respectively. The companion cell and the sieve element are connected by plasmodcsmata which are branched on the companion cell side. The data support the view that photosynthate moves through a symplastic pathway from mesophyll to the metaphloem sievc elements. The following pathways are suggested.[table]

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Structure of protein bodies in the seeds of 16 species (rice, buckwheat, wheat, Japanese black pine, sesame, Brazil nut, sunflower, water melon, soybean, pea, almond, cashew nut, peanut, hazelnut, walnut and pecan) was studied with semithin sections of aldehyde fixed and GMA embedded tissues. The occurrence of globoid was significantly different among tissues of different species. Globoid size and frequency (number per unit area of section) were estimated to clarify their relationships with total phosphorus content in these tissues. The size and frequency of globoid seems to associated with the difference in phosphorus content. The difference in the appearance of globoid, which is found among various tissues in the seeds or various regions in the tissues suggested the unequal distribution of phosphorus within the seed. In comparison with the seeds of rice, cotton and castor bean in structure of the protein bodies, it was indicated that the difference in protein content in the protein bodies corresponded with the mass of the proteinous regions, that is, protein matrix and crystalloid.

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[in Japanese]

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[in Japanese]

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Investigations have been carried out to determine the lipid content and the fatty acid composition of lowland non-glutinous rice kernel of one line for Sake brewing and three varieties at intervals of 10 days from dough ripening (20 to 25 days before full ripening) to over ripening (35 to 45 days after full ripening). From dough ripening to full ripening, the lipid content and the fatty acid composition varied widely. The lipid content decreased especially until 10 or 15 days before full ripening on dry basis and decreased after increasing until 3 or 15 days before full ripening in 1000 kernels. As to the fatty acid composition, the myristic acid, olelic acid, and linolenic acid content increased and the palmitic acid, stearic acid, and linoleic acid content decreased. After full ripening, the lipid content had a tendency to decrease slightly on dry basis and in 1000 kernels. However, the fatty acid composition was little varied. With respect to each of one line and three varieties, the lipid content on dry basis showed significantly positive correlations with the palmitic acid and linoleic acid content and negative correlation with the oleic acid content. The oleic acid content showed significantly negative correlations with the palmitic acid and linoleic acid content.

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Our primary objectives in this study are to make clear the histological process of transformation of lemma and leafy-organ in proliferated spikelets to the foliage leaf in rice. For this purpose, an X-ray mutant of rice, which was selected from plants two generations after 20 kR X-ray irradiation of dry seed of Japonica cultivar, 'Reimei', was used. In this mutant spikelets are proliferative, changing from Spikelet-type (S-type) to Pistil-type (P-type) to Leafy shoot-type (L-type) as seasons change. Lemmas of S-type proliferation and P-type proliferation were the same on their shapes as normal lemma, but leaf-like organ in the leafy-shoot of L-type proliferation was almost the same as the first leaf on its shape. Leafy-organ above the fifth from the base in the leafy-shoot of L-type proliferation differentiated to blade and sheath. The number of longitudinal veins in this mutant lemmas and leafy-organ was more than that in normal lemma; the number in S-type proliferation was about seven, that in P-type proliferation was seven to nine, and that in L-type proliferation was nine to eleven. Transverse veins were frequently observed in P-type proliferation and L-type proliferation. In the outer surface of S-type lemma, tubercle formation was poorly expressed, and, wart-shaped protuberances and many papillae differentiated in place of the poorlydeveloped tubercles, and, comb-shaped undulations of tangential cell wall in the outer epidermis also was poorly expressed, changing to wave-shaped one as that of the tangential cell wall in the first foliage leaf epidermis. In P-type and L-type proliferations, rows of long-cell and short-cell system differentiated instead of tubercles in their lemma surfaces. In contrast with normal lemma, lemmas and leafy-organs in all of proliferations have cork-silica cell pairs, and those of P-type and L-type proliferations have stomata in their outer surfaces respectively. Leafy-organ of L-type proliferation has lysigenous aerenchyma in its inner tissue. Thus, lemmas of S-type and P-type proliferations, and leafy-organ of L-type one have one of the characters expressed only in foliage leaves. In this study, light microscopic observation on the surface of lemma and leafy-organ of S-type, P-type, and L-type proliferation showed that the epidermal system thereon was transformed to one closely resembling to that of rice leaf surface.

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An investigation was made concerning the influence of nitrogen top-dressing at a later stage of growth on the leaf photosynthetic activity in some newly improved rice varieties of Korea obtained by indica-japonica crossing. The results are as follows: 1. Considerable varietal differences were observed in the apparent photosynthetic activity on leaf area basis determined by oxygen evolution. The Milyang lineage and the Iri lineage showed the highest activity, the other varieties being in the order of Suweon lineage, the japonica (Somewake), and the indica (T-136). The early-maturing varieties showed a tendency to have somewhat higher photosynthetic activity than the later-maturing varieties. 2. Nitrogen content on leaf area basis was lower in the indica-japonica hybrid varieties than in the japonica variety. 3. The nitrogen top-dressing promoted photosynthetic activity in all the varieties, but the degree of response differed from variety to variety. 4. Photosynthetic activity on leaf nitrogen basis also showed varietal differences, regardless of the nitrogen top-dressing. 5. Furthermore, the photosynthesis-promoting effect of increased leaf nitrogen content duc to top-dressing was generally higher in the indica-japonica hybrid varieties than in the Japonica or the indica. 6. By nitrogen top-dressing both NAR and leaf area development were enhanced, leading to increased CGR. This trend was especially clear in the indica-japonica hybrid varicties.

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In order to reconfirm the influence of the producing places especially meteorological conditions upon the chemical components and the disposition structures of starch-cells in the cross section of rice kernels, chemical analyses and observations were made on specimens of the "Koshihikari" variety (the "nanshitsu-mai" type), lowland rice plants cultivated on a standard basis at a lowland rice field attached to the Fukui University as well as those supplied from the lowland rice crop situation experiment stations, Ministry of Agriculture, Forestry and Fisheries of Mito, Chiba, Mie, Miyazaki and Nagaoka for the 4 years between 1975 and l978. It was shown from the above inquiry that some difference in the producing places especially in meteorological conditions serves to produce a difference in the chemical components and the disposition structures of starch-cells in the cross section of rice kernels even on the same variety, that a line of demarcations is to be drawn in this respect, namely in the difference of (P) (Protein-N/Crude starch (each in dry basis %) × 100) and (T) (Soluble-N+Total Sugar (each in dry basis %)), between specimens from soft and hard-textured rice producing areas, that meteorological conditions, especially amount of solar radiation, sunshine hours and air temperature, during each 5 half decades before and after heading stage, exert considerable influences, and that meteorological conditions, especially the sames as above, during 2 or 3 half decades after heading stage, exert great influences upon the disposition structures, while originally it forms the essential characteristic of a rice variety. It was revealed that meteorological conditions have a serious effect-too serious to be ignored after all. Our finding served to point to the identical trend as our reports so far made on other varieties, thus reaffirming the truth of our reports hitherto made.

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The formation of lateral roots in rice plants was examined in relation to the diameter of the crown roots on which they developed. The crown roots were classified into the followilng three types according to their acropetally decreasing rate of diameter; i.e. the crown roots of the low-(A-type), the intermetdiate- (B-type) and the high-(C-type) decreasing rates, respectively. At the lower shoot-units, the A-type roots were mostly common, while towards the upper shoot-units, the proportion of the number of each type roots varied, changing abruptly at about the IX-th shoot-unit, and above it the B-type roots and especially the C-type roots predominated. The time of crown root cmergence on the IX-th shoot-unit coincided with the panicle differentiation stage of the plant. The number oflaterals formed per unit crown root length was more in the C-type roots, decreasing successively in the B- and A-type roots. On the contrary, the length of the laterals showed a reverse tendency, being longer in the A-type roots and decreasing in the order of the B- and C-type roots, respectively. From the result mentioned above, the numerical density of laterals as well as their elongation appeared to be closely related to the changes in diameter of the crown roots ton which they were formed.

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Rice plants develop the fibrous root system which consists of several sets of numerous primary roots initiating from each stem node. There is a definite correlation between leaves and roots in their emergence and development; when the (n) th leaf of a stem is developing, a set of primary roots emerges from the (n-3) th node of the same stem. By using this rooting habit, relations between the growth of roots initiating from the different nodes were investigated with special reference to the nitrogcn movement from shoots to roots. Roots developing during the period of the 9th leaf development were designated as the roots from the 6th node (6th nodal roots) and they were separated from those emerging from the other nodes by tying up into a loose bundle with a fine string of nylon just before the emergence of the 10th leaf. Similarlyr, the roots emerging during the development of the 8th and 10th leaves were separated and designated as the 5th and 7th nodal roots, respectively. For more than 2 weeks prior to the start of experiment, plants were kept in the Kasugai's culture solution containing ¹⁵NH₄⁺ as a tracer. At the beginning of growth of the 6th nodal roots (Day 0 of experiment), plants were transplanted into a culture solution without tracer (CS-plant) or into tap water (W-plant), and the process of growth of the 5th, 6th, and 7th nodal roots was examined for 15 days thereafter. The number of the 6th nodal roots increased 2ts the 9th leaf blade elongated and expanded, then reached maximum at Day 7 when the 7th nodal roots began to emerge. Total length of the 6th nodal roots increased throughout the experimental period. The root length of W-plant exceeded that of CS-plant. The maximum increasing rates of number and of total length of the 6th nodal roots were found during the period from Day 2 to Day 4 and from Day 4 to Day 9, respectively. In a set of the 6th nodal roots, the variation range of root length expanded markedly during the period from Day 4 to Day 7, and the percentage of the primary roots having branches also increased eminently. Dry weight of the 6th nodal roots increased progressively during experimental period in both CS- and W-plant. On the other hand, total nitrogen and ¹⁵N content of the 6th nodal roots increased up to Day 9, then decreased. Absorption of nitrogen from nutrient solution continued for the first 7 days of the experimental period, therefore, the total amount of nitrogen fixed in the CS-plant increased during this period, while the amount was kept constant throughout the experimental period in W-plant. In both CS- and W-plant, however, total nitrogen and ¹⁵N content of the 5th nodal roots ceased to increase on Day 4 when those in the 6th nodal roots began to increase. Similar relation between 6th and 7th nodal roots was found on Day 9 in CS-plant and on Day 11 in W-plant. From these results it is likely to be considered that nitrogen supply from shoot to growing roots terminated at the onset of development of the new set of roots emerging from the nearest upper node. It is conceivable that the growth of nodal roots largely depends upon the nitrogen supplied from shoot rather than upon the nitrogen absorbed from culture solution.

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[in Japanese]

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Photosynthetic activity measured by O₂ evolution and other physiological characteristics such as content of total nitrogen, soluble protein, fraction I protein and chlorophyll (a+b) were investigated in the developing 9th leaf of rice grown under conditions different in air-temperature, light intensity or nitrogen supply. The results obtained are as follows: 1. When the leaf blade emerges out from the preceding leaf sheath, the quantity of fraction I protein increases most rapidly as compared with other leaf constituents. 2. High temperature given during leaf expansion increases photosynthetic activity as well as the content of soluble protein, of fraction I protein and of chlorophyll (a+b). However, high temperature gives no effect on these physiological characteristics after the leaf has attained its final size. 3. Both photosynthetic activity and the content of various leaf constituents increase with increasing nitrogen supplied. Under the same level of nitrogen supply, fraction I protein synthesis is subject to the greatest influence of light intensity, and the transformation from absorbed nitrogen being inhibited by low light intensity. 4. Although considerable amount of total nitrogen and soluble protein are accumulated in the non-emerged part of leaf blade, little amount of fraction I protein is contained with a very low photosynthetic activity. 5. Variation in the photosynthetic activity of a rice leaf during its development (0-12 days after leaf emergence), inducing the effect of environmental conditions, shows the closest curvilinear correlationship with the content of fraction I protein in the leaf, among various leaf constituents. Thus, the content of fraction I protein which is most rapidly synthesized during the leaf development, seems to be the most important limiting factor for the photosynthetic activity of a leaf.

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[in Japanese]

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[in Japanese]

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