The balance between grass and clover in mixed sward is highly susceptible to environmental change. Many studies have shown that a sward can become grass-dominant or clover-dominant according to the nutrient status or grazing management imposed on it. In this paper seasonal and yearly changes of botanical composition in mixed sward of orchard grass and ladino clover grown under different treatments in cutting height and amount of nitrogen application, are presented. 1. In all results so far obtained by the author, the percentages of grass are tend to decrease as time passes. It is found that the kind of treatment affects on decreasing rate of grass percentage. Low cut treatment accelerates decreasing rate and high cut treatment makes it slow. Seasonal maximum in grass percentage is found in spring, and then it decreases rapidly through summer to autumn. 2. Yield decrease in grass and yield increase in clover in progress of year are due in part at least to decrease of stem number density in grass and increase of stolon number density in clover progress of year. 3. Spring high yield in grass is due to its high stem number density and plant height. Summer low yield is due to sudden decreasing in stem number density and autumn low yield is due to low stem number density and plant height. 4. Spring high yield in clover is due to its high stolon number density, and summer decrease of yield is in parallel with decrease of stolon number density. It is likely that autumn increase of yield is due to increase of new developed stolon number. 5. By cutting at a high level, yield of grass increases but that of clover decreases. Those are attributed to increase of grass stem number density and the consequent shading of clover, i.e. to decrease of stolon number density. 6. Application of nitrogen gives increased yields of grass and decreased yields of clover especially in spring. In any seasons, much more yields of clover are found in the plots without nitrogen. 7. The responses of clover in pure stand to treatment in height of cutting and nitrogen application are quite different from those in mixed sward. On the other hand, in case of grass, differences to treatment between pure stand and mixed sward are not so much, however the decreasing rates of hill number density in mixed sward are rather faster than those in pure stand. It is likely to be concluded that various aspects of responses found in pure stand are not applicable to phenomena which take place in mixed sward.

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Experiments were carried out to reveal the differences of rainfall interception due to the canopy of various tobacco varieties. Four varieties, Burley 21 (conical plant with standing leaves), Mito 3 (conical plant with drooping leaves), Bright Yellow (conical plant with intermediate leaf type) and Enshu (cylindrical plant with intermediate leaf type) were selected for this study. The rainfall run down along the stipules and stalks was measured by using catchment basins each of which with a funnel shaped collar attached to the stalk by paraffin. Canopy penetration under tobacco plant was measured by means of gutters made of vinyl chloride, 10cm wide and 1m long, which had been arranged on the ground over whole width of inter row spacing. Soil moisture was determined by a tension meter. 1) The amount of ground rainfall which fell to the center of the interspace was different by varieties and largest amount was found in the field of Mito 3. 2) More than twice as much precipitation falls in the center of the interspace than in the adjacent parts of the row space. 3) A part of the rainfall was conducted to the ground along the stipules and the stalks. This amount, which varied by varieties as that had been observed in the ground rainfall, was the largest in the field of Burley 21. 4) The soil moisture in the inter row spacing of the field on which Mito 3 is grown has a tendency to be lower than that in the field of Burley 21. 5) Thus the distribution of ground rainfall was influenced by the character of vegetative canopy and appeared to contribute to the specific growth of plant.

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1) タバコのオゾン障害についての研究を行なうため, 光(23Klx), 温度(5゜～35℃)および相対湿度(55～75%)の制御のできるオゾン処理装置を試作した. 処理チャンバー(80×90×100cm)内においてわずかな環境条件のばらつきがみられたが, 実験遂行上大きな支障となるものではなかつた. 2) オゾン処理により圃場で観察されたと同じような病斑症状が発生した. 3) Bel-W3では20pphm×h, H-2では30pphm×hで病斑が現れた. 両品種ともオゾンdose (pphm×h)と病斑の発生程度とはかならずしも比例的でなかった. すなわちdoseが同一の場合, 短時間で高濃度で処理した方が長時間で低濃度で処理するよりも障害が大で, またdoseが前者より後者の方が大なる時でさえ, 短時間高濃度の方が障害が大となる傾向がみられた. また同一doseの場合, 低濃度で何回にも分けて処理するよりも, 高濃度で処理回数を少なくした方が障害の発生ほ大となった. 4) 1～2時間の短時間処理ならば, 切断葉でも着生葉と同様にオゾン反応をみる実験に供することができた.

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制御環境下のオゾン処理装置を用い, タバコのオゾン障害の発生におよぼす温度の影響について調べた. その結果, 1) 23℃恒温下で生育させたタバコは, 13℃恒温下のものよりオゾン感受性が大であった. また明期温度よりも暗期温度が感受性に大きく影響した. 2) オゾン処理時の温度を13゜～32℃の間で変えて調べたところ, 処理時の温度と障害の発生程度との間に負の相関がみられた. 3) 病斑の発生および病斑の進行は高温条件(23℃)で促されたが, 障害の発生程度および発生葉数は低温(13℃)条件下にあったものが大であった. 4) 以上の結果から低温, とくにオキシダント遭遇後の低温がタバコの生理的斑点病の発生と関係が深いことが示唆された.

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Investigations have been carried out to determine the influence of soil moisture, i.e. pF:0, 1.5, 2.2 and 2.7, after young panicle formation stage on the protein, fat and ash contents in lowland brown rice of two varieties. The results indicated that all the components were influenced by the soil moisture conditions. According as the soil moisture decreased, the protein content increased and the ash content decreased. On the other hand, the fat content increased slightly after decreasing from pF 0 to 1.5. With respect to the effects of soil moisture upon the components, the largest was on the ash and the second was on the protein.

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間けつ光下での大豆個葉の同化速度を測り, 光化学活性と暗反応活性との相対関係の品種間差および飽和光下同化速度と光化学活性との関係を調べた. また暗反応活性と飽和光下同化速度との関係を推定した. その結果次に示す諸点が明らかにされた. 1. 連続飽和光下での同化速度品種間順位は, Harosoy>ワセコガネ>シロメユタカ>しなのめじろ>農林1号>YL-2-1であった. この順位は前報の順位とほぼ一致した. 2. クロロフィル突然変異系統のYL-2-1では, 光化学活性/暗反応活性の比が正常品種に比して明らかに小さかった. 3. 正常品種では両活性の相対関係の品種間差はほとんど認められなかった. すなわち, 光化学活性の高い品種は, 概してその暗反応活性もまた高い傾向があるものと推定された. 4. 光化学活性の指標の一つとして測定したmaximum flash yieldと飽和光下同化速度との間に正の相関関係が認められた. この結果は, 光化学活性の指標の一つとして, クロロプラストのHill活性を測定した前報の結果と一致した. 5. 暗反応活性と飽和光下速度との間にも正の相関関係があることが推定された.

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大豆15品種の初生葉を用いて, 同化速度と面積生体重, 同乾物重, 単位面積当り葉肉容積等との関係を検討し次の結果を得た. 1. 面積生体重, 同乾物重, 単位面積当り葉肉容積, 乾物率等の形質と同化速度との間には相関関係が認められなかった. 2. 単位面積当り葉肉容積と面積生体重との間にはきわめて密接な正の相関関係が認められた. 単位面積当り葉肉容積Y(μ³/μ²)と面積生体重X(g/dm²)との間には, 実験1ではY=89.55X+7.80, 実験2ではY=92.7X+5.01の回帰式が得られた. 3. 面積乾物重は, 単位面積当り葉肉容積および面積生体重との間には相関が認められず, 乾物率との間に正の相関が認められた.

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The effect of subculture and temperature on shoot differentiation of rice callus was examined. The callus tissues were cultured in the medium containing kinetin. Starch granules and other cell constituents of the callus were observed in their green regions. While rooting capacity in Te-Tep remained in long term callus cultures over 15th passage, any shooting was not obtained in Aichi asahi cultures over 9th passage. Variation in temperature condition was effective in callus growth, but not in shoot differentiation. Starch granules were stained purple or reddish purple colour with Lugol's solution. In addition, large granules of dark purple colour were observed in green regions of callus tissues in kinetin medium. Disappearance of the starch granules were observed in the tissues in gibberellin medium after 9 days culture. A technique was investigated for epon-sections of rice callus tissues. Some staining methods of azure II·methylene blue, fuchsine-methylene blue, hematoxylin-safranin and toluidine blue were used. Nuclei, nucleoli, osmiophilic granules and cell walls were observed in the green region. Especially, morphological characteristics were revealed in chloroplasts, starch granules and amyloplasts.

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福井県九頭竜川上流の真名川流域に昭和36年ごろから止葉に赤枯れ症状が発生し, 登熟に悪影響がみられた. このため昭和42年より本症の防止対策と発生機作について現地試験, 調査分析を実施した. 1. この症状は登熟期に止葉の先端から赤褐色に枯れ第2葉におよんだ. 発生は出穂後高温の続く年に著しく, 収量構成要素のうち登熟歩合や千粒重など, 後期に決定される形質への影響が大きい. 2. 罹病稲の止葉から2,000～5,000ppmの高いマンガン含量が分析されたが, 逆に, 窒素, 珪酸, 鉄等の含量が少なく, 稲体の養分バランスの指標とされるFe/Mn比が著しく低くなり, 結局マンガン過剰による体内の代謝異常にもとづく, 生理病と認められた. 3. この症状は主として, 透水の良い乾田に発生しており, マンガン含量は高いが, その他の養分は相対的に低く土壌肥沃度が低いため, マンガンと鉄, 珪酸などとの拮抗作用から稲体養分の不均衡を招きやすい傾向があった. 4. このことが誘因となって, 登熟期の秋落ち症状を呈するような場合に発生することが, 葉鞘のヨードデンプン反応の結果からうかがわれた.

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前報において水稲の止葉が, 登熟期に赤褐色に枯れる症状の原因はマンガン過剰とその他の無機成分の欠乏, とくにFe/Mn比の低いことにともなう生理病と推定された. この傾向は従来の赤枯病と著しく異なることが明らかとなったので, その品種間抵抗性と施肥法による防止対策を検討した. 1. この発生は早生のみに認められ, 中晩生には発生は認められないが, 早生の中でもとくに7月26～30日に出穂するものに多発の傾向が認められた. 2. 明らかな品種間差が認められ, 現地の主要品種であるホウネンワセはもっとも抵抗力が弱く, フジミノリはもっとも強く, いずれの年次においてもほとんど発生を認めなかった. 3. このような品種間差は, 従来報告されている赤枯れ病とはまったく異なる傾向を示したが, その原因は体内の鉄含量に由来すると推定された. 4. 晩期追肥・深層追肥などの施肥法による防止効果はかなり高く, このことは登熟期に体内窒素含量が高く維持されているためで, 緩効性肥料などの使用によっても, ほぼ同様な効果が得られた. このように窒素の効果が高いことも, この症状が赤枯れやブロンジングと異なる特徴である.

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水稲の登熟期に止葉が赤褐色に枯れ上る, いわゆる止葉枯れ症は砂質・礫質からなる乾田に発生し, 土壌中のマンガンが他の養分に比して活性に働くことに由来するものと推定されたので深耕・生石灰等の土壌改良による防止対策を検討した. 1. 土壌改良をはかることがもっとも有効であった. 2. 客土・深耕等による地力の増強をはかることにより, 登熟期においても稲体養分が高く維持されて, 止葉枯れの発生はほとんどみられず高い効果が得られた. 3. グリーソ・アッシュ, ベントナイト, 平炉滓および珪酸石灰等も有効であったが, とくに生石灰の施用が有効であった. 4. これは稲体の珪酸や石灰の含量が高くなることによって, 健全化することと同時に同化作用および転流作用が促進される. さらに土壌中においてもマンガン等の過剰養分に対する拮抗作用等の効果によるものと推定された. 5. これらの土壌改良剤の効果は止葉枯れ抵抗性の弱い品種ほど有効であった. 6. 以上の結果を総括して, 止葉枯れ症の発生は, 第2図にみられるような発生機作によるものと推定された.

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1) Experiment-I was conducted to examine the effects of a high level of nitrogen (N) application with several fertilizers, including slowly available N as a farmyard manure, rape seed cake, fish meal, IB and CDU on the growth and yield of soybeans subjected to low temperature, at 15°C, day and night under the natural light condition of a glasshouse in the phytotron for 15 days (L-1) or 30 days (L-2), from a few days before the onset of the flowering of the controls grown in a glasshouse, similar to the natural condition. In addition to an indeterminate type of American variety which was mostly used, its isogenic line, genetically alike in characters other than inability of nodulation, was referred to measuring the effects of nitrogenous fertilizers on growth and yield. The results will be described with nodulating plants unless otherwise indicated. Based on the flowers developed under 15°C during the sensitive stages to low temperature and their corresponding controls, seed yield and yield components of each fertilizer plot were compared with the L-2 and control condition for measuring the direct effect of low temperature injury. The major sources of decrease in seed yield were the decrease in the pod number, or pod setting rate, and the fertile seed percentage, but the statistical difference among fertilizers was only obtained in the pod number, or the pod setting rate. The rate of damage caused by the low temperature treatment was least at the farmyard manure and greatest at the CDU plot. In the total seed weight produced through the flowering period, the farmyard manure plot was the highest in both the two low temperature treatments and the control. All of the other four slowly available N fertilizers tested were also superior to both the high and standard level of ammonium sulfate. The weights of leaves and stems at maturity were the highest at the farmyard manure plot and all of the fertilizers tested showed similar trend to the seed yield. The nonnodulating line markedly responded to N fertilization in growth and yield, but the trend of response to fertilizers was in contrast to that of the nodulating line. Compared with the high level of ammonium sulfate plots, the plots slowly available N including the farmyard manure produced about 30% less in dry matter weight. The excellence of the farmyard manure for growth and yield was only shown in the nodulated plants in which no significant depression of N fixation was observed through plant development in spite of the high rate of N contained 2) Experiment-II was conducted to confirm the results of experiment-I and to examine the effects of the application of humates or oat straw, combined with the nitrogenous fertilizers, on the plants, when subjected to low temperature for 15 days, from the onset of flowering (L-4), five days before (L-3), or after (L-5) the onset of flowering of the controls, grown under the natural condition. The variety used is a representative of the determinate type in Hokkaido. The farmyard manure again exhibited stable and high seed weight over three different stages of low temperature treatments and the control. The plot, combined with 80% of N from slowly available N as CDU and 20% from ammonium sulfate, with or without the addition of humate or oat straw, showed as significantly high as farmyard manure in the seed yield, compared with the plots of high and standard levels of ammonium sulfate. Despite the increase in the 100-seed weight, the addition of humate, and or oat straw indicated no increase in the seed weight because of the depression of vegetative growth and the tendency of decrease in the flower number. [the rest omitted]

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In this study, the elongation of plumules grown from seeds which were pre-treated at high temperature through soils after germination was examined. Materials used were two paddy rice cultivars in japonica type and two rice varieties in indica type. High temperature pre-treatment of seeds before sowing was conducted as follows: After immersion at 25°C for 20 hours, the seeds were treated at 40°C for 8 days. Seeding depth was 6cm, soil moisture content about 20% and cultural temperature about 20°C. The following results were obtained. 1. In paddy rice plants injaponica type, the numbers of days from seeding to emergence time of plumules was shorter in the lot of high temperature pre-treatment of seeds than the untreated lot. However, no significant difference between the lots of high temperature pre-treatment of seeds and immersing seeds (25°C for 20 hours) was observed. 2. Though the mesocotyl of plumules grown from seeds pre-treated at high temperature in japonica type was as same long as that of untreated plumules in indica type, the growth of the plumules of the former was less slow than those in the latter. This was due to the difference of the speed of mesocotyl elongation between the plumules of the japonica and indica types. Moreover, multiplication of the parenchyma cells in mesocotyl was more active in the latter than in the former.

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This investigation was carried out to determine the effect of ethylene in soil on growth of tomato and soybean plants. These plants were grown by fog culture system and the roots were exposed to 1 to 10 ppm of ethylene for a week. The results obtained are summarized as follows: 1. When roots were exposed to ethylene, the root elongation was greatly inhibited but the dry weight of roots increased in both tomato and soybean plants. 2. Shoot growth in tomato plants was inhibited when roots were exposed to ethylene. In soybean the dry weight of shoots increased with 1 to 10 ppm ethylene application to roots and stem elongation was promoted when roots were exposed to 1 ppm of ethylene. 3. Ethylene application caused a brownish discoloration of the roots. The root apices were swollen and curled. Ethylene also stimulated development of root hairs in tomato and secondary branched roots in soybean. 4. When roots were exposed to ethylene, the oxidizing activity of α-naphthylamine by roots decreased significantly in tomato, but showed a marked increase in soybean. 5. These results suggest that the low concentration of ethylene in the soil atmosphere affected the development and growth of roots as well as the growth of shoots in field.

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This investigation was conducted on rice seedlings to elucidate the plant growth-regulating properties of 3-hydroxy-5-methyl isoxazole which is an effective fungicide against the damping-off organism of rice seedlings. The results obtained are summarized as follows: 1) The promotion of root growth by 3-hydroxy-5-methyl isoxazole was assumed to be mediated by its metabolite (N-β-glucoside) in plants. 2) The formation and development of lateral roots and root hairs were accelerated in the early seedling stage. The root growth was vigorously promoted by 3-hydroxy-5-methyl isoxazole in the later seedling stage. 3) The rooting ability and root activity (oxidizing or reducing activity of roots) were enhanced by 3-hydroxy-5-methyl isoxazole.

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In the previous paper, the authors estimated that the effect of the nitrogen depletion treatment on the further growth might vary according to the growth potency (e.g., growth amount such as the dry weight of plants or the number of tillers) at the starting time of the treatment and the length of the treatment. From the same point of view as in the previous paper, furthermore, the authors tried some experiments to clarify the effect of the growth potency at the starting time (70 in leaf number index) of the nitrogen restriction treatment and the nitrogen concentration of nutritional solution during the treatment on the further growth of rice plants. Achieving this purpose, the rice plants with different amount of growth at LNI 70, raised by the different amount of nitrogen supply under gravel culture, were supplied with different levels of nitrogen solution during the period of the middle growth stage (70-90 in LNI). The following results were obtained: 1. The lower the nitrogen concentration of the nutritional solution during the treatment, the less in the dry weight, the total activity of ³²P in rice plants and the amount of oxygen consumed by roots, at the expiry of the treatment. 2. Under an identical nitrogen concentration during the treatment, the smaller the growth amount at LNI 70 was, the greater the decrease was found in the dry weight, total activity of ³²P and the amount of oxygen consumed by roots, respectively. And the longer in the length of the treatment, the higher effect of growth retardation was obtained. 3. Judging from the amount of <32>P uptake and the oxygen consumed by roots, in the plants fed with 30 ppm of nitrogen before the treatment, conspicuous effects of the treatment on the plant growth appeared in 2 weeks after the starting time of the treatment, and the rice plants seemed to be able to recover from the growth retardation by the treatment in the case of 3 week-treatment. And also in the plants fed with 60 ppm of nitrogen before the treatment, the effect of the treatment was detected in 3 weeks after the starting time of the treatment and the rice plants seemed to be able to recover from the growth retardation even in 4 week-non-nitrogen treatment. 4. Compairing with the ratio of the growth amount of the plants fed with 0, 5 and 10 ppm of nitrogen during the treatment against that of control (which was supplied with 60 ppm of nitrogen before the treatment and 30 ppm during the treatment, abbr. 60-30 ppm), the indices of the growth amount of 60-0 ppm and 30-10 ppm showed nearly identical values, at 10 day nourishment with 30 ppm of nitrogen solution after 3 week-treatment. 5. Examining the effect of the nitrogen restriction treatment on the growth of rice plants, it is necessary to consider the following 3 factors; the growth amount at the starting time of the treatment, the nitrogen concentration of nutritional solution during the treatment and the length of the treatment period.

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Some morphological observations were carried out on the proliferations in the mutant spikelets induced by X-ray irradiation in Oryza sativa L. var. Reimei. X-ray was irradiated on seeds at the dosage of 20 kR. in 1966, followed by sowing in soil. Spikelets which were used for observation had been sampled in the year from 1968 to 1972. Results which have been obtained were as follows; 1) One or more spikelet-like organs were found in the spikelet. 2) One or more leafy-shoots which have been composed of many leaf-like glumes were found in the spilelet, the tips of which had (a) one or more spikelet-like organs, (b) incomplete ovary, (c) stigma-like intermediate organs having no ovarian structure, or (d) vegetative shoot having no reproductive organ. There were general tendencies in those spikelets having proliferations mentioned above, such as (1) rudimentary glume had no change, (2) lemma and palea had many veins in themselves exhibiting slender forms, (3) the position of spikelet-like organs to differentiate was above that of palea where reproductive organs differentiated usually, and no reproductive organ was found in that place. It was considered that these spikelet-like organs or leafy shoots were the typical proliferations, and those proliferations would have been induced just before the time of differentiation of reproductive organs on the apical meristem of spikelet primordium, and that those proliferations might be initiated as the result of the supression of transformation of apical meristem from vegetative stage to reproductive stage in a narrow sense. Judging from the results and considerations mentioned above, it was presumed that the apical meristem of the spikelet primordium which was going to differentiate proliferation maintained relatively larger size and more differentiated organization than those of the control at the time when stamen primordia differentiated. Some discussions were undertaken on the physiological and genetical background of the development of the proliferations.

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The present study was undertaken to determine the fundamental structure of the proliferations common to the "Spikelet-type" having spikelet-like organ(s) in it and the "Leafy-shoot-type" having leafy shoot composed of a number of leafy glumes alternately, and to determine the type of proliferations by the analysis of positional relation between rachilla and the proliferative axis. Results obtained were as follows; 1) The number of empty glumes was increased generally, followed by the increase of the veins in them. 2) Both lower and upper lemma, the latter was corresponding to palea due to its position, had a variety of axillary organs in their axillae, and the frequency of their organ differentiation was increased acropetally. 3) In the half number of the S-type proliferation, the form of the shoot apex was vegetative, showing the transformation into the L-type one. 4) The organs had a 1/2 phyllotaxis in both S-type and L-type proliferations. 5) The L-type proliferation had spikelet-like organs similar to the S-type one at the basal portion of the S-type one. 6) Adventitious roots were recognized at the basal portion of proliferated spikelets and leafy-shoots. As mentioned above, the type of proliferations found in this experiment was recognized to be "diaphysis" which was induced by the apical growth of the shoot apex of rachilla, judging from that the phyllotaxis were the same both in the rachilla and proliferative axis, and the proliferative axis were situated on the extention line of the rachilla and corresponded to the main axis as seen from the upper lemma position. The proliferative structure common to the S-type and the L-type were, therefore, as follows: 1) development of the proliferative axis by apical growth of rachilla differentiating more spikelet-like organs than usual, 2) spikelet-organs were differentiated on the tip of the proliferative axis, 3) their organs were arranged with a 1/2 phyllotaxis from rachilla to the proliferative axis consistently. The proliferation of this experiment, therefore, was grasped as a process of the vegetativation caused by the development of rachilla, and the L-type proliferation was seemed to be a transformed type of the S-type of which the shoot apex continued to differentiate vegetative glumes indefinitely. From the point of the morphogenesis of spikelets, those proliferations were considered to be results of a conversion of growth stage from the differentiation-stage of glumes into that of rachis or spikelet just before the time of differentiation of stamen or pistil. Some discussions were given of the development of the proliferative-body into an independent plantlet, and the signicance of the initiation of adventitious roots.

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Developmental analyses were investigated on the occurrence of the abnormal spikelets caused by low temperature about 14-18°C using rice cultivars "Sachikaze" and "Rikuu 132". The various morphogenetic abnormalities of spikelets were induced by the low temperature when they were treated at the stage of their primordial differentiation, from 3 to 2 weeks before heading time. The increments of florets in a spikelet were observed frequently in the panicles which were treated at the earlier stage of their development and on the other hand the increments of floral organs in a spikelet were observed frequently in the panicles which were treated at the later stage of their development. Since the increments of florets and floral organs had also been clarified to be induced by gibberellin treatment, it was considered that the level of gibberellin-like substances is enhanced in the meristematic regions of spikelet primordia by low temperature and they brought about different influences in the morphogenesis of spikelets depending upon the developmental stages when they were set under low temperature conditions.

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Several observations were made regarding leaf and tiller arrangement and on the relationship between this arrangement and the overlapping of leaf sheath margins. The following results were obtained. When examined from the side of the even numbered leaves in the main stem the first leaves of the primary tillers were found to emerge either to the left or to the right of the line joining the midrib of odd numberred and even numbered leaves of the main stem (fig. 1, 2). The ratio of these two types of the first leaf emergence was about the same. The first leaves of n group tillers (n represents secondary, tertiary or higher tillers) emerge in direction of (n-2) group tillers when looked along the line joining midrib of odd numbered and even numbered leaves of the (n-1) parent tiller. The prophyll has a narrow margin and a broader one. The first leaf of the tiller enclosed by the prophyll emerged in the direction of the narrow margin of the prophyll. The two margins of the leaf sheath are found to be overlapping according to an orderly pattern. The first leaf of the tiller emerged from the direction of the overlapped margin of the leaf sheath sustending the tiller (fig. 1, 2). Occasionally it was observed that the emergence of the first leaves in some tillers and overlapping of margins of some of the leaf sheath occurred independently of the above mentioned orderly patterns. The n group tillers have twisted so that their first leaves move closer to the (n-1) group parent stem. When a large number of such tillers emerged from a single parent stem, they got themselves placed in an are, their first leaves orienting innerside (fig.3). These orderly arrangement of leaves and tillers in the rice plant will be useful in identifying various, tillers and in finding the correct number of leaves in those tillers.

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In the previous paper, a hypothesis (Model N), interpreting the morphological nature of the normal spikelet in rice plant, was proposed. And it was postulated that the main vascular bundle in the axis of the normal spikelet consists of two kinds; that of spikelet axis (rachilla) and that of floret one, and their connective point presents in the axis between upper empty glume and palea. In this paper, the course of vascular bundle of the normal spikelet is traced with serial-microtome sections. The main vascular bundle extends to lateral direction in the level just above the abcission layer (Plate 1-1∼3) and forms a ring (Plate 2-1), that is, a vascular cylinder. As shown in Plate 1, it is clear at higher level that the main vascular bundle has a large gap (arrow symbols in Plate 1) between the both bases of midrib trace of lemma and palea (a and o in Plate 1). And the main vascular bundle forms a solid column from the gap to the base of pistil. To research the detail of the vascular course around the gap is an important problem. The trace of midrib of lemma (a in Plate 2-2) detaches itself from the vascular cylinder at the ventral side, forming an incomplete gap on this cylinder (Plate 2-1∼3). The half tissue of the vascular cylinder containing left and right parts of the leaf trace "a", increases in the thickness at the ventral side and two lateral leaf traces diverge into the latero-ventral position from the both parts (b and c in Plate 2-3). These traces connect with each lateral veins of lemma. Subsequently the both parts of the vascular cylinder join together inside of the cylinder and synchronously detach themselves from the dorsal arc of the cylinder (Plate 2-4∼5). In this way, the main vascular bundle of solid column type is composed at the ventral side, namely at the axil of lemma (vfa in Plate 2-6, 7). And this main vascular bundle diverges the traces into the flower organs; palea, lodicules, stamens and pistil (see Plate 1). However, it does not always occur in palea as follows. The dorsal arc of the vascular cylinder divides into four fragments after the divergence of a trace (c₂ in Plate 2-5, 7), forming a gap, into upper empty glume. Two fragments of outer side (m and n) supply a trace to each marginal veins of lemma. Two remnants (w and z) join again each other as shown in Plate 2-8, and connect with the midrib of palea (o in Plate 2-11). Therefore, the midrib of palea, not producing any gaps, is classified into two kinds according to its origin (one; "o" in Plate 1, the other; "o" in Plate 2). The main vascular connection between "cylinder" and "solid column" is observed at the nordal region, where axillary axis (floret axis) branches out from main axis (spikelet axis), as shown in other grass spikelets, for example, Triticum and Bromus. The vascular system between the main vascular bundle of solid column type and traces of the flower organs resembles to that of floret in other grass spikelets, except that the traces of palea does not always diverges from the main vascular bundle of solid column type. Moreover it seems that these vascular courses in the normal spikelet are quite alike an unilacunar type as usually seen in many dicots. The conclusion obtained from these comparative anatomical aspects is that the main vascular bundle of solid column type at axil of lemma is considered to be a branch trace in connection with the vascular cylinder. In other words, the vascular cylinder and its branch trace are correspond to the main vascular bundle of spikelet axis and that of floret one, respectively. It can be said that our conclusion does not contradict with the hypothesis (Matuba, 1971) shown previously. Such anatomical analysis leads us to a conclusion that the axis in the normal spikelet consists of two kinds; spikelet axis and floret one, in spite of the external appearance as same as single axis. [the rest omitted]

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This study was conducted to clarify the dry matter production of grain sorghum and growing behavior with relation to planting rate and amount of fertilizer in order to obtain high grain yield. The hybrid variety, GS76Y was seeded on May 24 in 1972. The dry weight of each organ of plant was measured at intervals about 2 weeks apart ranging from the early stages of growth to ripening time. Irrigation was applied at half bloom stage. The results obtained were as follows; 1. The maximum rate of dry matter production was 42 g per m² of field per day with the high planting density and heavy manuring plot during 14 days near heading date. In this period, mean daily solar radiation was 502 cal per cm² of field and mean daily temparature was 28.4°C. 2. The mean maximum value of net assimilation rate in heavy manuring plots and in light manuring plots were 17.7 and 14.2 g per m² of leaf area per day, respectively. The value of net assimilation rate was high at the early stages of plant growth and decreased with grow. 3. Grain yield was significantly varied with the planting density. The highest grain yield per are was 82 kg on the basis of dry matter. lt was obtained at planting densities of 25 and 40 plants per m² of field on heavy manuring plots. 4. Total dry matter produced in ripening period ranged from 62 to 81 kg per are and was equivalent to above 90 percent of grain yield. 5. Dry matter production was depended largely upon leaf area before heading, and net assimilation rate after heading. The value of net assimilation rate during the ripening period decreased with higher leaf area index. However, in case 4 and beyond that of leaf area index, net assimilation rate was increased as the percent of nitrogen content of leaf blade, namely, there was positive correlation between net assimilation rate and percent of nitrogen content of leaf blade in the ripening period. 6. It was recognized that the number of grains per unit field was closely related to the amount of nitrogen absorption of top at heading date. The amount of nitrogen, phosphorus, and potassium absorption at ripening time were in the range of 17.8 to 25.1, 3 to 4 and 26 to 34 kg per 10 are, respectively.

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