Biometrical measurements were made to make clear the change in geometrical structure of rice canopy during the growing season. The results were used to clarify the penetration of direct sun-light into the canopy. The penetration of direct sun-light was calculated from Eq. (1) proposed by Ross and Nilson (1965). The geometrical characteristics of the canopy was found to be a vertical foliage-type at about the heading stage and to change the more horizontal one at about the waxy stage of ripening. The effective leaf area function (G_L (w)) that denotes cosine of the angle between leaf normal and sun direction was determined at each layer within the canopy. The special mean (G^^-_L) of the effective leaf area function was also determined by considering the vertical distribution of leaf area density (f_L(z)) and the effective leaf area function (G_L(w)). Both of G_L(w) and G^^-_L were found to change remarkably with the sun altitude (h₀), showing that the types of change are dependent upon the growth stages of rice crops. The ratio (F_d/F_t) between the partial leaf area index of sun-lit foliage (F_d) and the whole leaf area index (F_t), the ratio (_abF_d/F_d) between the partial leaf area index of foliages receiving light on the reverse side (_abFd) and the sun-lit leaf aera index (F_d), and the extinction coefficient of direct sun-light (k_d) changed by the sun altitude (h₀). The forms of change in these three parameters all depend upon the geometrical characteristics of canopy. It has been pointed out that the vertical foliage-type community is favorable for the photosynthetic activity since the direct sun-light can penetrate into the deeper layer, and that the horizontal foliage-type community is less favorable since the direct sun-light is apt to be absorbed at the upper layers and cannot penetrate into the community so deeply.

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Biometrical measurements of leaf area density (including the surface area of ears and (stems) and spatial distribution of leaves were carried out in a barley field in order to get the data necessary to calculate the penetration of direct solar radiation into the canopy. Similar measurements were also done in potted barley canopies. Sunlit leaf area index and the intensity of direct solar radiation on the foliage surface (leaf, ear and stem) were determined on the basis of the biometrical data and the penetrating rate of direct solar radiation. The following relations proposed by Roos and Nilson (1965) were used to calculate the penetrating rate of direct solar radiation at each depth of the canopy: [numerical formula] and α(w)=α(w)αs(w)αE(w) where αL(w), αs(w), αE(w) and α(w) are the extinction factor due to leaves, the extinction factor due to stems, the extinction factor due to ears and the extinction factor due to whole biomass, respectively, f_L(w'), f_S(w') and f_E(w') are the respective surface area densities of leaves, stems and ears at a depth w', G_L(w') is the effective leaf area function. The vertical distribution of the leaf area density was found te be approximately symmetrical in relation to the half of canopy height at each growing stage. As can be seen in fig. 1, the density of surface area of the ear was twice as large as that of stem. The distribution function of the leaf area in relation to the inclination angle was characterized by the establishment of a sharp peak between 60°and 75°. The distribution function of the leaf area in relation to the azimuth angle was found to be slightly lengthened to the direction perpendicular to the planting row (fig. 1). In the potted barley canopy with sparse density, a peak between 60°and 75°in the leaf area distribution function in relation to the inclination angle became distinctive with growth of crops (see fig. 3). Fig. 4 indicates that the magnitude of the effective leaf area function decreases with increasing sun altitude. This is quite opposite to results of corn fields reported in a previous paper. Values of the effective leaf area function in both the upper and bottom layers of the canopy showed relatively small hourly change, though the values of the middle layer change largely with time (namely sun altitude). This implies that the penetration of direct solar radiation into the canopy is considerably affected by the leaves in middle layer when the sun is high. On the other hand, quite different relatioships between effective leaf area function and sun altitude were observed in the potted barley canopy. The attenuation of direct solar radiation at the low sun altitude was considerable in the upper layer, while the attenuation at the higher sun altitude was considerable in the middle layer (fig. 5). The sun altitude dependence of the mean extinction coefficient for the barley canopy is in good agreement with that for a canopy of leaves with uniform inclination angle of 80°(fig. 6). The percentage of the sunlit area was highest for the ear and that of the stem lowest. The sunlit leaf area index of the barley canopy (F_t=2.8) was about 1.1 when the sun was higher. This was smaller than that obtained in corn field. The sunlit leaf area that is exposed abaxially to direct solar radiation was found to decrease almost linearly with increasing sun altitude except the initial and final parts (fig. 8). Frequency distribution of intensities of direct solar radiation falling on the whole surface was studied to make clear light conditions of each photosynthesizing organ (leaves ears and sheaths) under sunlight. The frequency curves were found to have a weak tendency such that its mode moves toward a weak radiation intensity with increasing sun altitude (fig. 9).

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1. The experiment was carried on the spacing (square of 50, 25, 12.5, 6.25 cm, respectively) combined with or without the restriction of root area (alike to the surface area and its 1/4, 1/16, 1/64) using bottomless frame-work (20cm depth) board plastic materials. The aim of experiment was to clarify the reaction of the plant to the restriction of growing sphere, and special emphasis was laid on the growth and function of root. Results obtained were as follows: 2. Under the condition of denser spacing, the plant increased in number of primary roots per stem, on the other hand, decreased in their weight per unit number. The rot system was distributed shallowly under those conditions. 3. The activity of root, in terms of the capacity to oxidize α-naphthylamine, was depressed either by denser spacing or by stronger restriction of root area. 4. The oxidation-reduction potential of soil in root area was also lowered by denser spacing. 5. The content of mineral nutrients in rice plant was decreased by denser spacing or stronger restriction of root area, especially, that of potassium in either top or root was remarkably decreased by these conditions at later stage of growth. 6. Root of rice plant grown under denser spacing is characterized to distribute shallowly and to be easily depressed in the activity through the deterioration of circumstantial conditions.

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In this experiment. the inoculation of scad into the ligule or the delicate parts inside the uppermost leaf sheath just below the ligule was carried out, using the wheat plants (Variety. Wheat Norin No. 12) which were water-cultured after being pulled out from the field. Only the hyphae, cultured on the potato agar medium, were applied, instead of the conventional method of spore inoculation. The treated plants were at or just after the heading stage. After the inoculation, they were grown in the glass-covered thermostat (23°C) in the room. The clear lesions were observed on the treated parts. From the results of this study, the conclusion was drawn that the hyphae of scab, even without spore, can be successfully applied in the attempt of inoculating the scab into the wheat plants.

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With the aim of controlling the over-growth of rice plants in ill-drained paddy field, a series of experiments has been carried out by using Pentachlorophenol (PCP). The results are summarized as follows: 1) Soil treatment with PCP at the end of effective tillering stage resulted in control of plant height and ineffective tillering. There was a tendency that the more the dosage of PCP, the greater the control of plant growth and ineffective tillering. 2) PCP controlled effectively the growth of such leaves and internodes which were just developing at the time of soil treatment with PCP, and the control was becoming gradually ineffective at the later growing stage. 3) Soil treatment with PCP at the end of effective tillering stage was very effective in controlling the excessive vegetative growth and strengthened the rice plant resistance to lodging, because PCP controlled the elongation of basal internodes and increased breaking resistance of culms. 4) Nitrogen content in rice plant decreased temporarily by soil treatment with PCP, but after the recovery of plant growth it maintained the higher concentration than that in the control.

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Studies were carried out to make clear the effect of soil treatment with PCP on some characters of culms subject to lodging, especially by laying emphasis on the physical properties of culms. Bending moment (M), bending stress (σ), section modulus (Z), and secondery moment of inertia (I) were calculated based on the breaking load, culm diameter, and thickness of culm wall. The results are summarized as follows: 1) Increase of lodging resistance by soil treatment with PCP at the end of its effective tillering stage can be ascribed to the increase of secondary moment of inertia (I) caused by the increase in culm diamerer and in thickness of culm wall. 2) On the other hand, the increase of lodging resistance of rice plant by soil treatment with PCP on about 30th day before heading can be ascribed to the increase of bending moment caused by the increase in bending stress (σ) rather than by the increase in secondery moment of inertia (I). 3) Water content in rice plants and the extent of turgor pressure of culms showed decreases after the soil treatment with PCP.

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In the present investigation, the authors observed the changes caused during the storage in the quality of rough rice grains harvested at the different dates (i. e., August 4, September 5, and November 7). For this purpose, rough rice grains were conditioned at four moisture-content levels: approximately at 16, 18, 22 and 24 % and stored for 30 days at variable temperatures in a barn of wooden construction (room air temperatures: 30.0°C to 28.4°C on August 4; 25.8°C to 17.6°C on September 5; and 15.2°C to 7.5°C on November 7). The results are summarized as follows: 1. The occurrence of deteriorated grain during the storage for 30 days showed an increasing trend in proportion to the earlier harvesting date (higher storage temperature) and higher moisture-content. 2. Viability of embryos (TZ values) tended to decrease more rapidly with longer storage duration, earlier harvesting date and higher moisture-content. 3. In case of grains with less than 17 % moisture-content, grains, irrespective of harvesting dates, could be stored safely for as long as 30 days without any noticeable deterioration in the quality. In case of grains with 18.4∼18.7% moisture-content, grains harvested on August 4 could be stored safely for 20 days and on September 5 and November 7 for 30 days; grains with 20.0∼20.2% moisture-content harvested on August 4 could be stored safely for 7 days and grains harvested on September 5 and November 7 could be stored for 30 days; grains of 21.4∼22.0 % moisture-content could be stored safely for 3 days only in case of grains harvested on August 4, for 10 days in case of grains harvested on September 5, and for as long as 30 days in case of grains harvested on November 7. In case of grains containing 23.4∼24.6% moisture-content, grains harvested on August 4 were impossible to be stored even for one day, but grains harvested on September 5 and on November 7 could be stored safely for one day and for 10 days, respectively.

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Two soybean varieties-Tachisuzunari and Yamabedaizu-were grown under usual field conditions and penetration of radiation through the leaf canopies was investigated with its change in intensity and spectral composition. Photosynthetic response of leaf to light quality was further studied by measuring photosynthetic rate of single leaf under light of blue, green, red and white provided with colored fluorescent lamps. The results obtained were as follows: (1) The intensity of each spectral component of incident radiation decreases at different rates depending on the spectral region as it penetrates through leaf canopy. Infra red radiation penetrates through leaf canopy more than visible part. Of three components in visible part (blue, green, red) the green region penetrates the canopy most. (2) Relation between radiation intensity in leaf canopy and thickness of leaf layer is expressed for each spectral region by the following equation: I_i=I_oie^-KiF where, Ii: intensity of radiation in spectral region i under leaf layer F. Ioi: intensity of incident radiation in spectral region i upon leaf canopy. e: base of natural logarithm. Ki: extinction coefficient of leaf canopy for spectral region i. F: thickness of leaf layer (LAI) cumulated from top surface. Extinction coefficient of Tachisuzunari canopy for blue (390∼490 mμ), green (490∼590 mμ), red (590∼690 mμ), visible region (390∼690 mμ), infra red (690m<) and total radiation (250mμ<) were 0.838, 0.721, 0.894, 0.804, 0.337 and 0.474 respectively. Those of Yamabedaizu canopy are 0.839, 0.668, 0.887, 0.787, 0.388 and 0:525. Extinction coefficient for the light assessed by illuminometer are 0.775 for Tachisuzunari and 0.751 for Yamabedaizu. (3) Spectral composition of radiation changes as the radiation penetrates through leaf canopy because of the uneven extinction of the spectral components. That is, proportion of infra red to total radiation increases whereas that of visible part decreases. Moreover, proportion of green region in visible part increases while that of blue and of red decreases. (4) Photosynthetic rate of single leaf on the basis of equal incident energy varies with the spectral region. Further, the photosynthetic response to light quality differs with kind of leaves. (i) Upper leaves of main stem located at the top of leaf canopy photosynthesize more under red light than under blue light, and under green light in-between. (ii) Lower leaves of main stem located at the bottom of leaf canopy photosynthesize more under red light than under other spectral lights as is observed in the upper leaves of main stem. But their photosynthetic rate under green light is either equal to that under blue light or rather less than the latter, showing a remarkable difference in photosynthetic response from the upper leaves of main stem. (iii) Branch leaves located at the bottom of leaf canopy show a similar photosynthetic response to the lower leaves of main stem, though the relative rates of photosynthesis under green and blue light are higher than those of the latter.

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In the aseptic culture of the stem segments which were cut from the tuber-induced potato plants, these segments started outgrorth of lateral buds soon after inoculating to medium, and formation of tiny new tubers readily succeeded at the end of a certain linear growth period of the lateral shoots. A number of investigators have demonstrated an intimate relationship between nucleic acid metabolism and growth of plant. If the whole nucleic acid complement or some fraction of it in fact controls the initiation of potato tuberization, an inhibition of its synthesis should have some effects on the tuberization of potato. The present experiments were designed to answer the following question: does the tuberization on the aseptic culture of the potato stem segments depend specifically on the synthesis of new nucleic acids and protein ? When the stem segments were cultured on White's nutrient medium supplemented with 8 % of sucrose, an initiation of their tuberization was enhanced by advancing senescence of the mother tubers. Application of 2-thiouracil or 6-azauracil at the beginning of culture resulted to inhibit completely not only the linear growth but the tuberization of the lateral shoots grown from the stem segments. These inhibition could be more or less partially relieved with simultaneous addition of uracil, uridine or orotic acid, except for the case of orotic acid to the azauracil-induced inhibition. While a considerable attenuation of these inhibitory action became gradually to be apparent when the inhibitors were supplied at the advancing stage of culture, the suppression of the tuberization was still complete. On two days before starting the tuberization, no more significant effect on both the growth and tuberization was eventually observed due to the introduction of 6-azauracil. Repressing effect on the tuberization was also caused with chronic or brief treatment of ethionine and its inhibitory activity displayed a tendency to be intensified in proportion to the progressive development of the lateral shoot. Brief incubation with puromycin in the middle of culture period exerted a pronounced detrimental effect on the initiation of tuberization. On the other hand, 5-bromouracil and 6-azathymine produced no appreciable effect on it. In conclusion, the initiation of tuberization on the cultured potato stem segments is greatly accounted for on a basis of the specific RNA and protein which were synthesized in advance of the tuberization, while DNA shythesis did not participate in it. It can be deduced, therefore, that the induction of these synthesis is probably mediated through a certain suitable balance of endogenous growth substances contained in the stem segments.

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印度型は日本型に比し, 胚乳核の増殖・胚乳細胞の増加が速かで澱粉の集積も早い. このことは粒径の生長・粒重の増加に連なり, 成熟速度も急速である. 米の中心部の透明化が始まるとき印度型はすでに完熟時の粒重の30～40%に達しており, 日本型では20～30%, また外観上米の頂部が透明化するとき印度型は80%, 日本型は70%に達している. すなわち, 米の中心部が透明化する頃には印度型の澱粉充実が日本型より遥かに多く, 中心部付近の澱粉填充が密であり, 芯の硬い米になることと関連している. また米粒頂部の透明化後は日本型が澱粉充足が多く米粒周縁部の充実が良好であることを示し, 日本型が外観つやがあり, 搗減りが少ないことと関連する. 印度型は登熟が急速で, 出穂期における葉鞘・稈の澱粉集積が少なく, しかも1穂籾数が多いことは, 1穂内の頴果間に競合がはなはだしく弱勢果が不稔・発育停止・死米・乳白米になりやすく, 印度型の稔実不良の原因をなすものと考えられる.

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Root system formation in rice plant was studied by means of an improved monolith method in relation to soil conditions of seventeen paddy fields of the farmers at Yamagata, Akita, and Gifu prefectures in Japan. It was found in every paddy field that root system formation is greatly affected by the plow-sole in paddy. As to the distribution rate of crown roots into the direct foot-layer of soils, it was proved that the distance from the "center" of the root system (not from the soil surface, × mark in fig. 1) to the plow-sole in paddy soils is a positive factor in deciding it, regardless of such differences as soil texture, variety of rice plant, cultural methods, districts, and etc. In addition to the effect of the plow-sole on the root distribution, the effect of vertical water percolation in paddy soils on it was clarified. When the distance from the "center" of the root system to the plow-sole is the same, root systems at the paddies of very remarkable water percolation (8∼13 cm per day) have the higher distribution rates into the direct foot-layers than those of comparatively low water percolation (0∼5 cm per day). More detailed observations on crown root distribution into three layers of paddy soils (namely, top-, side-, and oblique foot-layer, fig. 1) reveal the following facts: The distribution rate into the top-layer seems to be dominant when the distance from the "center" of the root system to the plow-sole is short (4∼7 cm); and into the side-layer, when it is moderate (10∼12 cm); and then into the oblique foot-layer, when it is long (14∼16 cm). Furthermore, it was found that when vertical water percolation is very remakable (8∼13 cm per day.), crown roots (primary roots) with many secondary roots are densely distributed within a limited region (fig. 4, B₁∼B₄), and when the percolation rate is comparatively low (0∼5 cm per day), long crown roots with few secondary roots are sparsely distributed within a larger region (fig. 4, A₁∼A₅). In future, another investigations should be continued into the mechanism of such effects mentioned above on root distribution, together with phenomenon of geotropism of each crown roots.

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It is well known that "lion tail like roots" are fraquently formed in superficial roots, which develop near soil surface in the period from the initiation of young panicles to heading (fig. 1, S2-S4 and W2-W4). With a view to examine whether water mangement exerts any influence on the formation of this type of roots, several treatments viz. submerged, water percolated while it is kept under submerged condition, drained, alternately submerged and drained, are tried. The results obtained indicate that the submerged rice plant showed the largest extent of the formation. With the percolated as well as the drained, the formation was noticed to some extent. While with the alternately submerged and drained, no formation was found. With an increasing interest to see whether the rate of the formation of roots vary with using various forms of nitrogen, rice plants were grown in three nutrient treatments based on Kasugai's which differ only their nitrogen form viz. ammonium-nitrogen, nitrate-nitrogen and ammonium-nitrogen-nitrate-nitrogen (ammonium nitrogen was cganged to nitrate-nitrogen at the time of the initiation of young panicles). In these experiments it had been observed that the most abundant "lion tail like root" formation usually occurs when ammonium is the source of nitrogen. But no formation was noticed when nitrate supplies the nitrogen. As to the roots grown in the solution (ammonium-nitrogen-nitrate-nitrogen), the formation was recognized to a little extent. As it is well known 4, 12, 18, 17), under alternately submerged and drained soil condition, the form of nitrogen easily changes from ammonium-nitrogen to nitrate-nitrogen. From the results mentioned above, it may be apparent that "lion tail like root" formation has much to do with the form of nitrogen and that it is ammonium-nitrogen which is of importance for its formation.

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Shooting from the root-cuttings have been known in many plant species, and this phenomenon is very important in agriculture with regard to the vegetative propagation of crops and the regeneration of weeds. In this paper some observations on adventitious bud-initiation in root of sweet potato were undertaken to clarify the factors controlling the initiation of adventitious bud. It has been said that adventitious buds initiate in the tissue such as phellogen or parenchyma of cortex from parent root and in a part adjacent to the base of lateral root. In the present observation, the meristem regarded as adventitious bud-primordium was observed only in the cortex of the lateral roots which was surrounded by the cortex tissue of parent root (fig. 1A∼C, fig. 2). Many adventitious buds bearing leaf-primordia were observed in the cortex of parent root, and the vascular system of the adventitious bud connected with that of the lateral root, not of the parent root. From these observations, it is considered that the primordium initiated in lateral root develops to adventitious bud and intrudes into the cortex tissue of the parent root and then grows bigger and bigger which ultimately bears several leaf-primordia (fig. 1). In rare cases, the meristematic cell-aggregate was recognized in the cambium layer of parent root adjacent to the base of lateral root, and this meristem was observed always in a longitudinal row with the lateral root along the parent root (fig. 3A). In a scar, several lateral roots of which vascular system individually connected with that of parent root were found in a longitudinal row along the parent root, and some of them were newly formed ones (fig. 3B, C). Therefore, it seemed that these meristematic cell-aggregates developed to the new lateral roots and not to the adventitious buds. It can be concluded that the meristem in the cortex of lateral root develops to adventitious bud and that of the cambium layer of parent root develops to lateral root. This conclusion differs from the opinion that the meristem initiated in root is "undetermined one", namely it will become that of a root or a shoot. There are a few different opinions about the stage of development of root when an adventitious bud initiates, and it has also been thought that the stage varies with the varieties of sweet potato. In this observation, the adventitious bud-primordium was observed in the juvenile root such as 1 mm in diameter in all the varieties examined (table 1). Therefore, it is confirmed that an adventitious bud generally initiates in the juvenile atage of root development in sweet potato. It was reported that the damage of a lateral root causes the initiation of adventitious bud from the near part to the base of that lateral root. In an experiment where lateral roots were cut off from parent root, no tendency to promote the initiation of adventitious bud by such damage was recognized, however, the promotion of the development of the adventitious bud already initiated was observed slightly (table 2). These findings suggest that the initiation of adventitious bud in sweet potato is caused, by the endogenous factors existing in the root itself.

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サツマイモの根における不定芽分化の要因を究明をるためには, 圃場における根や塊根をとりあつかうより, 培養した根を用いる方が問題が単純化されるので, より好都合であると考えた. このような考えのもとに, 根の培養を試み, また培養根での不定芽分化の検討を行なつた. 1) 従米根の培養に用いられているような, 無機塩類, 糖, ビタミン類などを組成とする簡単な培地では, サツマイモの根の培養は困難であつた. しかし, サツマイモ塊根の抽出物を加えた培地では, 顕著な生長がみられ, 2ヵ月間培養を継続すると10 mmの根端が生長して, 750～1200 mmにもなつた. すなわち, このような培地でサツマイモの根の培養が可能であつた. 2) このようによく生長した培養根について, 側根の基部を組織学的に観察すると, まれではあるが不定芽原基の分化を認めることができた. このことは, 圃場において極めて生育初期の根でも不定芽が分化するという説を裏づけるものである. また培養根によつて, 不定芽分化の要因を検討するための手がかりが得られた.

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Effects of kinetin and other natural substances on chlorophyll retention in rice leaf sections were studied. A leaf section was floated in a petri dish containing a solution of test substance (s) and allowed to stand for 72 hours at 30°C in the dark. It was found that the effect of kinetin on chlorophyll retention in rice leaf sections was more marked in the mature leaf than the young. In this assay, kinetin gave a linear response at concentrations ranging from 0.001 to 0.1 ppm if plotted on a logarithmic scale. Several substances, which were found ordinarily in plant, were tested for their activity of chlorophyll retention in leaf sections. Among those substances tested, a mixture of adenine (100 mg/l) and casein hydrolyzate (1000 mg/l) showed a comparable effect as that of kinetin. Combined effects of kinetin and gibberellic acid (GA₃), and kinetin and indole-3-acetic acid (IAA) were tested. High concentration. of GA₃ stimulated a degradation of chlorophyll. In the presence of GA₃, level of kinetin required for chlorophyll retention increased. Similar results have also been obtained with IAA. It may be assumed that there were antagonistic interaction between kinetin and GA₃, and kinetin and IAA. It was also attempted to isolate kinetin-like substances from roots of rice plant (Oryza sativa. var, Honenwase). Kinetin-like activity was determined by two ways; chlorophyll retention of rice leaf sections and carrot callus growth. The roots extract was held on Dowex 50W H⁺ form at pH 2.5 and eluted with 5N ammonium hydroxide. The eluate was further developed on a filter paper (Toyo, No. 51) using a solvent system of n-butanol-acetic acid-water (12:3:5 v/v). The kinetin-like activity was found at Rf 0.20-0.30, 0.50-0.55, and 0.75-0.80. Substance of Rf 0.50-0.55 was found to be highly active in the chlorophyll retention assay, while substance of Rf 0.75-0.80 was very active in the carrot callus-growth assay. These substances were further fractionated by a column chromatography with Dowex 50W-X8, H⁺ form. When eluted with 2.0N hydrochloric acid, kinetin-like activity was found in fraction Nos. 110∼200. Chromatographic behavior of the fraction 110∼200 seems to be similar to that of factors reported by Rogozinska et al. (1965) and Matubara et al. (1966).

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It was observed that in Helianthus tuberosus L., the phyllotaxy was opposite in early stage and changed to alternate at about 1.5 months before the flowering. From these observation, it was considered that the change of leaf arrangement showed the time of the alternation from vegetative growth to reproductive growth. So, this experiment was carried out to study the relationship between change of phyllotaxy and growth phase. Morphological and histochemical methods were used in these studies and the results were as follows; (1) The change of leaf arrangement occurred at the middle of July. (2) At that time, the shoot apex changed slowly from flat type to dome type. (3) Histochemical change of the nucleic acid (RNA) indicated the change of the growth phase. From these results, it was considered that the change of phyllotaxy was applicable as an indicator of the alternation from vegetative growth to reproductive growth in Helianthus tuberosus L.

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The secondary roots of tobacco seedlings were grown in the water media to which gases of air, oxygen, nitrogen or mixtures of oxygen and nitrogen were bubbled. The results obtained were as follows: 1. The elongation of root was increased in accordance with the root growth. The frequency of cell division in the meristem was most flourishing in the root 2--30 mm in length, on the other hand, the degree of cell elongation was most conspicious in the root elongated beyond 40 mm in length. 2. In the O₂-sufficient water media, many lateral roots developed from all length of the root, whereas in the O₂-deficient media, the development of the laterals were restricted to upper part. 3. The optimum concentration of O₂ for root elongation was around 9 ppm and in such a concentration the elongation persisted for long period, but in the media of 1 ppm the elongation was restricted. 4. In the seedlings grown on the O₂-sufficient water media, cutting off of leaves affected the root elongation, the recorded data on the O₂-deficient media did not show such a response. 5. pre-treatment of the seedling with O₂-deficient media restricted the elongation of root in comparison to the treatment with O₂-sufficient one. The reason would be reduced to the fact that both cell division and cell elongation in the root tip were strongly affected by the influence of O₂.

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In the previous paper, one of writers has suggested that the physiological significance of cortical disintegration in rice roots might be the energy supply to the elongation of the root axis and the lateral root growth. These experiments, using the rice seedlings from 1 to 14 days after bedding were carried out to throw light on the relations among the nitrogen and phosphorus metabolism, the growth of various seedling organs and the cortical disintegration in seminal roots. In 3 days after bedding, the adventitious and lateral roots emerged on the seedling axis. Length of seminal root elongation per day, and initiation and developement of lateral roots were most vigorous in this stage. Increase of the total nitrogen and phosphorous contents in seminal roots carne to the saturation level in 6 and 4 days after bedding respectively. But, after that the elongation of the seminal root went on for 10 days to attain about 50 to 60% of the total langth. This result indicates that the elongation of the seminal roots depend upon the nitrogen and phosphorus derived from aged tissues, after supply of the same to seminal root ceased. While the increase of total nitrogen and phosphorus contents of seminal root cylinder (seminal root cutting off lateral roots) took 3 days after bedding to be saturated and began to decrease later on. These results indicate that the nitrogen and phosphorus contents of the root cylinder might have moved to the lateral roots. The formation of lacunae began 2 days after bedding and developed rapidly till 6 days after bedding. The initiation and developement of lateral roots, closely related to the lacunae emergence and developement, proceeded to keep pace with them. On the other hand, soluble fraction of nitrogen and phosphorus compounds changed remarkably from 1 to 4 days after bedding. SPN meant the cytoplasmic protein nitrogen increased from 1 to 3 days after bedding. Nevertheless the maximum growth rate was found at 3 days after bedding, the increasing rate of SPN at 1 to 2 days was higher than 2 to 3 days after bedding. As the process of the cortical disintegration can be regarded as the catabolic process of cytoplasmic protein, the synthetic process of cytoplasmic protein is superior than that of catabolic one for 1 to 2 days after bedding; both processes are in equibrium for 2 to 3 days after bedding and after that the catabolic one is dominant. In 4 days after bedding, SP containg P compounds decreased, whereas the inorganic phosphorus increased. Generally speaking the decrease of ∼P level shows that in the metabolic pattern synthetic charactor is converted into the catabolic and in the functional pattern, the developmental one into the preservative. This result indicates that these changes of metabolic pattern take place in seminal root at 4 days after bedding. The collective estimation of the physiological significance of the cortical disintegration by these results is tiat this physiological role may be the system of energy supply to elongation of the root axis and lateral root developement. The stage of the changes of the metabolic pattern in seminal root agrees with that of begining of adventitions root growth.

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The translocation of photosynthetically assimilated ¹⁴C from the mesophyll of intact leaf-detached leaf, rooted leaf, and the leaf attached to stem section, was investigated using the technique of spot feeding. Results obtained were summarized as follows: 1) In the intact leaf, it was observed that ¹⁴C was translocated from mesophyll basipetally into the midrib via the veins of 1st order of branching. Little ¹⁴C was detected in the apical part of the midrib and the mesophyll except the part to which ¹⁴CO₂ was supplied. The amount of ¹⁴C in the midrib increased during the period of 15∼30 minutes after ¹⁴CO₂ feeding, then increased slightly, attaining to about 3 % of the total ¹⁴C in the leaf. 2) In the detached leaf, most of the assimilated ¹⁴C remained in the part to which ¹⁴CO₂ was supplied, and very small amount of ¹⁴C was observed in the midrib 180 minutes after ¹⁴CO₂ feeding. 3) In the rooted leaf, ¹⁴C translocated into the roots increased during the period of 30∼60 minutes after ¹⁴CO₂ feeding. About 1.5∼2 % of ¹⁴C was exported from the mesophyll during 60 minutes after ¹⁴CO₂ feeding. 4) In the case of the leaf attached to the stem section, 5 and 10 cm in length, the ¹⁴C moved slowly from the mesophyll, and ¹⁴C-activity in the midrib and in the stem section increased during the period of 120∼180 minutes after ¹⁴CO₂ feeding. On these basis, the relation of source and sinks to the translocation of photosynthetic products were discussed.

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圃場に生育中の作物は太陽エネルギーの一部を反射, 一部を透過, 残部を吸収し, さらに吸収エネルギーの一部を光合成により乾物として固定する。全日射量, 反射量および透過量の全生育期間の連続測定, ならびに生育各期の葉面積(LAI)および乾物重の測定から, 反射率(A), 透過率(k), 吸収率(Ea), 吸収エネルギーに対する乾物生産効率: 利用率(Eu), 投下エネルギーに対する乾物生産効率: 変換率(Ec) (=Ea×Eu)を算出することができる。水稲中生8品種(1967年)および3品種(1968年)についてこれらの量の経過をしらべるとともに, Ecを決定するEaおよびEuと品種の特性との関係を検討して次の結果をえた。1) LAIとAとの関係の品種間差は, 経験式: A=Ap-(Ap-Aw) exp(-K・LAI)により説明できた.(Fig.1)。2) 生育初期～中期にAは急増, kは急減するが, ともに中期以降の増減は少ない。Eaは生育初期に急増以後漸増し, Euは生育とともに低下し, Ecは中期に最高値を示した(Fig.2)。3) 全生育期間の平均値は, A: 17-20%, k: 30-47%, Ea: 37-50%, Eu: 2.81-3.53%, Ec: 1.12-1.71%で, 各効率に有意な品種間差があつた(Table 1)。4) Eaは{LAI×K (吸光係数)}と密接な正の, Euは{K×sla(葉身面積重量比)}と密接な負の相関関係を示した(Table 2)。5) 多収品種は高いLAI, 低いK (直立的な葉), 大きいsla (薄目の葉)という特性を有し, この特性の組合せが光エネルギー利用上有利なことが示された(Table 3)。

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This experiment was conducted to investigate the influences of the deeply placed top-dressing fertilizer and of intermittent irrigation on physiological and ecological characters in rice plant and on rice yield. The treatments consisted of control (plot I), top dressing at deep layer (plot II), and intermittent irrigation plus treatment of plot II (plot III). The results obtained are as follows: 1. The rice yield recorded was 120 percent in plot II and 124 percent in plot m as compared to the control plot. 2. In plot n the plant height was taller then those of control but lodging resistance was greater. This was mainly due to the retarded elongation of lower internode and increased breaking strength of stem. 3. As compared to the plot I, the degree of chlorophyll destruction of leaves was lower in plot II and plot III. The flag leaves in plot III were erect. 4. The α-naphthylamine oxidizing activity of root was most active in plot III, with plot II coming to the next. It is possible, however, that the root activity is closely related with the senescence and inclination of the leaf. 5. The effect of fertilizer applied as a deeply placed top-dressing was different even within one and the same hill. Great differences were shown according to the place of fertilization in the percentage nitrogen content of leaf-blade and in the root activity to oxidize α-naphtylamine. In other words, the nutrients were absorbed by the roots which distributed in deep layer and transferred to the tillers connected with them. 6. The percentage of potash and silicate contents in plant at the heading and harvesting stage were highest in plot III.

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著者らは, 数種の高等植物を用い, 温度, CO₂濃度, 光の強さなどの環境要因の変化が光合成に及ぼす影響について, より総合的に検討し, また, この種間差と葉身の内部形態との関係を明らかにしようとして, 次のような結果を得た。1. CO₂濃度以外の環境条件を一定にした場合のCO₂濃度の変化と光合成の関係すなわち "CO₂カーブ"は種により大きく二つのパターンに分類された. ーつは"CO₂カーブ"の立上りが早く比較的低いCO₂濃度で飽和に達するもので, ほとんどの南方型牧草がこれに属し, 他は対照的に"CO₂カーブ"の立上りが遅く, 比較的高いCO₂濃度で飽和に達するもので, 北方型牧草およびイネなどがこれに属する. 2. 南方型牧草類の"CO2カーブ"の形は P=KP_lmax(CO₂)²/1+K(CO₂)² という式により比較的よく近似できることが示された. 3. 温度に対するみかけの光合成の反応は種により大きく2つのグループにわけられ, 南方型牧草の光合成適温は35℃近辺であつた. これに対し北方型牧草およびイネなどのそれは比較的低くCO₂濃度, 光の強さなどにより大きく変動することが示された. CO₂濃度が300 ppmの場合には一般に南方型牧草より低い値を示し, この値は光の強さによつても変動し, 光が強くなるにつれて, その値は高くなることが示された. 以上の結果に基づき, みかけの光合成の日変化の種による違いについて考察がなされた. 4. 光に対するみかけの光合成の反応は種により大きく2つのタイプに分けられ, 北方型牧草類はCO₂濃度にかかわらず40 klux以上ではほぼ飽和するような"光-光合成カーブ"を示す. 一方南方型牧草類の多くは, CO₂濃度が高くなるほど光によるカーブのパターンの変化が小さくなり, 少なくとも40 kluxでは飽和に達しないような"光-光合成カーブ"を示した. 5. 葉緑維管束鞘(chlorophyllous parenchmatous bundle sheath 以下 CPBSと略記する)の存在とCO₂補償点(CCP)との関係がDowntonらにより明らかにされたが, この点についてさらに多くの植物について検討した結果, CPBSを有する植物は例外なく低いCCPの値を示し, 光合成の主要な環境要因に対する反応の種による違いとCPBSが密接な関係を有することが確認された. 6. CPBSの有無は分類学上の属のレベルで分類可能であつた. イネ科では亜科のレベルでの分類と平行しているが, 例外もみられ, カヤツリグサ科では同一族内の植物であるにもかかわらず, CPBSの存在する種としない種(タマガヤツリ)が認められた. しかし, CPBSの存在と光合成の生理反応の関係は非常に密接であっで, CPBSの存在と光合成の生理反応の関係における例外はみられなかつた. 7. 本実験の範囲では, CPBSを有する植物と有しない植物との2群に明らかに区別ができ, 両者の中間型のものは認められなかつた. 8. ¹⁴CO₂を与え, 光合成を行なわせた後, 一定の時間ごとにアルコールで固定して得られた葉について, ミクロオートラジオグラフィーにより, 光合成産物の集積場所を観察した結果, ¹⁴CO₂を与えて遅くとも5分後にはCPBSのみにアルコール不溶性の光合成産物が蓄積するのが観察された.

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前報において, 種々の環境要因に対する光合成の反応の違いにより, 陸上高等植物は2群に大別されること, またこの差異はChlorophyllous parenchymatous bundle sheath (CPBS)の有無と密接な関係を示すことを確認した. しかし, 2群の間で光合成の反応が異なる原因については十分な検討はなされなかった. 本実験においては, 光呼吸の植物による差異を明らかにすることを目的とし, 互いに光合成の反応のタイプの異なるダリスグラス, トウモロコシおよびイネ, エンバク, イタリアンライグラス, コムギを用いて, 酸素濃度をほぼ零にし, 光呼吸系をおさえた時の光合成の反応を観察した. その結果, 次のことが明らかにされた. 1. 酸素濃度の変化(酸素濃度21←→0%)に対して光合成は瞬間的に反応し, その反応は可逆性が強いことが示された. しかし, イネ, コムギを材料として長時間の測定を行なつた場合に, 酸素濃度を変化させた時の光合成の応答が不安定となる現象をしばしば認めた. これは, 酸素濃度の変化にともない, グリコール酸の代謝に変化をきたした結果, Zelitchにより指摘されたように気孔の開閉が行なわれたためではないかと推論された. 2. CPBSを有し, 光呼吸を示さないとされているダリスグラス, トウモロコシの"CO₂カーブ"も酸素濃度の影響をうけて, わずかながら変化する. 無酸素空気中では通常の空気中と同様, 2次式により近似できるが, ダリスグラスでは2次式の定数Kは一般に小さくなるに対し, トウモロコシでは変化がみられない. P_maxは, いずれにおいても酸素濃度の低下により大きくなることが認められた. 3. CPBSを有しない植物に属するエンバク, コムギ, イネ, イタリアンライグラスの"CO₂カーブ"は酸素濃度により著しい影響をうけ, 一般に酸素濃度が零の場合には, 普通の空気中の場合に比べ, 見かけの光合成が高い値を示した. また, 酸素濃度が零の時の"CO₂カーブ"の形はダリスグラス, トウモロコシの同一条件のものにほぼ類似し, 2次式で近似できる. 4. CPBSを有する植物と有しない植物とで光合成の温度に対する反応が異なる原因も光呼吸系の有無に関係することが推論された. すなわち, 後者は光呼吸系を有し, その反応系が温度に極めて敏感であつたために普通の空気中では前者と異なつた光合成適温を示すが無酸素空気中で光呼吸をおさえた場合には, 両者の光合成適温はほぼ等しくなる. 5. 上述したように無酸素空気中では, CPBSの有無にかかわらず, "CO₂カーブ", みかけの光合成の適温は種間でほぼ等しくなるが, "光-光合成カーブ"には差異が見られた. すなわち, トウモロコシ, ダリスグラスは普通の空気中と同じような"光-光合成カーブ"を示すのに対し, 北方型牧草類の1つであるエンバクでは, 普通の空気中の場合より, 早く飽和に達するような"光-光合成カーブ"を示した. 6. 強光下では, 酸素濃度を低くして光呼吸系をおさえても光合成量の増加は比較的少ないことがエンバクにおいて示された.

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イネ3品種, Te-Tep・湖南〓・短銀坊主の遊離細胞をもちい, 細胞増殖に関する品種間差異, 2, 4-Dの作用, 接種カルス量の影響について研究した. また増殖にともなう細胞の性質と形態の変化, および脂質体顆粒の消長などについても検討した. 40日間の振とう培養によつて, Te-Tepでは10⁶個/ml以上の遊離細胞が得られ, 著しい細胞増殖はカルス接種後25日間見られた. 短銀坊主でも25日程度の間, 著しい細胞増殖が見られ, 40日後には10⁵から10⁶個/ml以上の遊離細胞が得られた. 湖南〓では15日後に3×10⁴から10⁵個/mlに達するのみで, 以後の増殖は見られなかつた. 振とう培養により形成されるイネの遊離細胞は, 単離生細胞(free living cell), 単離死細胞(free dead cell), 集合生細胞(aggregate living cell), 集合死細胞(aggregate dead cell)の4集団に分けることができる. 遊離細胞中における各集団の割合は, 品種間で差異があり, 経時的にも異なる. Te-Tepと短銀坊主では, 単離生細胞のしめる割合が時とともに増大したが, 湖南〓では減少した. イネの細胞増殖に対し, 培養液の2, 4-D濃度が著しい影響を示した. 2, 4-Dは高濃度でTe-Tepと短銀坊主の細胞増殖に寄与するが, 湖南〓ではその影響が明らかでない. また各品種とも単離生細胞の割合は, 高濃度の場合に経時的に増加した. 一般に, 細胞増殖の著しい条件, すなわち品種および2, 4-D濃度に関し細胞数の増加が著しい場合に, 単離生細胞の割合も増大した. 短銀坊主において, 接種カルス量が多いほど, 遊離細胞数は短時日のうちに多くなり, 2週間後には4×10⁵個/mlに達した場合もあつた. しかし40日後の細胞数に関しては, 接種カルス量により著しい差異が見られなかつた. 単離生細胞内に見られる脂質体顆粒の存在は, イネの細胞増殖に関する生長相と関係がある. 細胞増殖が見られなくなつた直後では, 約50%の細胞中に, この顆粒が存在したが, 増殖が見られなくなつてから, しばらくたつた細胞では, その28%にしか顆粒が存在していなかつた. また脂質体顆粒の大きさも, 生長相と関係がある. 培養初期では直径8μ以上の顆粒が1～2%含まれていたが, 終期では1～3.9μの顆粒が90%をしめていた. このように培養期間が長くなると, 顆粒は次第にちいさくなり消失する. 遊離細胞の形態は経時的に変化する. 培養初期には, 短銀坊主に特長的な細長い細胞が見られたが, 終期には楕円形の細胞が多かつた, すなわち培養終期の細胞長は, 初期の64%に減少し, 細胞の幅は110%に増加した.

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1. This experiment was attempted to make clear the growth of the adventitious roots that developted from the hypocotyls, by using nine species of summer legumes as samples. 2. It was observed that the number of the developed adventitious roots (hypocotyl roots) was the same with the number of vascular bundles because of the fact that their primordia were formed by the division of interfacicular parenchyma. 3. The growth of hypocotyl roots of the soybeans for which earthing up was practised on the 25th and the 30th days after sowing was greater than that in those plots for which earthing up was practised on any other dates. 4. The two types were recognized in the secondary growth in thickness of the hypocotyls, and a close relationship was found between the two types of the secondary growth in thickness of the hypocotyls and the development of the hypocotyl roots.

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