近年小麦など禾穀類の受粉から受精完了までの所要時間が, 従来いわれていたよりもかなり短いものであることが遂次明らかにされた. そこで受精の前期の過程である花粉発芽・花粉管伸長の様相を, 胚嚢内へ花粉管が入るまでの所要時間との関連において考察した. また花粉発芽・花粉管伸長が温度によっていかに影響されるかを受精所要時間と温度の関係を調べた前報と同様の見地から併せ検討した. 小麦農林26号を用い, 10, 20, 30℃の3段階の温度室で1柱頭あたり200～700粒の花粉を人工受粉し, 柱頭を鏡検した. 一方受粉後短い時間間隔で子房を採取, その胚嚢を鏡検した. 10°区は発芽歩合・伸長率ともに最も劣り, 30°区は20°区に比べて発芽歩合ではやや劣るが発芽した花粉管の伸長率は最も高かった. 受粉後V期(花粉管の伸長がかなり進み空粒になったもの)が初めて現われるまでの呼間は10°=2時間, 20°=1/2時間, 30°=1/4時間であり, 一方受粉後胚嚢内に初めて花粉管が侵入してくるまでの時間は10°=2時間, 20°=1/2時間, 30°=1/4時間であって各温度とも両者の値がよく一致した. このことから小麦では柱頭上に初めて空粒花粉を認め得るころには, 早くも受精に関与する花粉が決定されるものと解釈される. V期が初めて現われたときの花粉数は10°=0.3%(受粉総数の), 20°=1.0%, 30°=0.6%という少数であった. しかもこの時期には柱頭上ではなお大部分の花粉は未発芽またはわずかな花粉管の伸長を示しているにすぎないから, これらが配偶体としては補欠的な役割しか持たないものと考えられよう. これらの結果から小麦の花粉発芽・花粉管伸長においては, 特に受粉後ごく初期の現象が受精に関しては重栗な意義をもち, かつそれが温度によって著しい影響を受けるものであることが明らかになった.

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The effect of seasons, time and plant environments on the rate of oil distillation and the fluctuation of the composition of the essential oil were studied and their structures were biochemically examined. 1) Seasonal Effect: (A) The quantities of oil distillation in each period in different seasons were compared and it was found that in the season of high temperatures, when the rate of oil distillation was high, the .quantity in each period of distillation was generally higher due to the increase of the function of oil secletion in such a season, and especially noted that it was pretty high in after-distillations. (Table 1 & 2, Fig. 1). (B) In fractional distillations the fluctuation of the composition of the essential oil was examined and it was found that the total alcohol %, ester % and ketone % were high in initial distillation and low in after-distillations, but so far as acid number was concerned it was low in initial distillation and high in after distillations (Fig, 2). (C) In the examination of seasonal fluctuations of the composition of the essential oil, the fluctuations of the total alcohol %, ester % and format % were almost equal; that was high in May and June and then became low in the period of high temperatures, when the rate of oil distillation was higher, and again got higher in the months of October and November. The cause of these fluctuations was that the quantity of after-distillations increased during the high temperature season. The fluctuations of free alcohol % and ketone % and acid number were similar and showed an opposite tendency in the composition mentioned above. The cause of this phenomenon was assumed to be that free alcohol and acid increased during the high temperature season due to the decomposition of ester (especially formate) and also due to that ketone % increased by the acidification of alcohol (Fig. 3). 2) Daily Fluctuation: (A) By the examination of the daily fluctuations of oil distillation quantity by period it was found that the increase of the rate of oil distillation was due to the increase in after-distillations. (Table 3, Fig. 4). (B) Between the oil remained in the residuum of distillation in each period (by n. Hexane extraction) and the oil distilled by steam distillation there existed an inverse relation quantitatively. (Fig. 5). (C) In the examination of the daily fluctuations in the composition of the essential oil it was found that the atmospheric temperature and the amount of sunshine had a certain influence on the mutual conversion between ester and free alcohol (Fig. 6). 3) Plant Environments: No significant difference was found in the composition of the essential oil due to the elements and quantity of fertilizers used and the percentage of moisture in the soil. 4) Terpene and Terpene Glucoside: After the hydrolysis by means of NaOH the fractions from steam distillation increased. By this the existence of terpene glucoside could be assumed. By the examination of the seasonal fluctuation of the glucoside it was found that it existed in a high quantity during the period of the high rate of plant growth and low during the period of the low rate of growth (Table 4). From the foregoing statement, as the fluctuating structure in oil distillation, the possibility of the mutual conversion between volatile oil and oil not easily distillable by steam distillation and also that of the mutual conversion between free alcohol and terpene glucoside were conceivable, and the atmospheric temperature and the amount of sunshine were assumed as the possible chief elements influencing such conversions.

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The effect of temperature and day-length on the growth and cold-hardiness of tea plants was studied. The growth temperature showed a close relation on the hardening phenomenon of tea plants, and the higher the temperature the weeker became the plants. Especially when the temperature exceeded 20°C, the plants became very week. Shortday treatment reduced the growth of tea plants in all varieties used, and accelerated the hardening effect of cold temperature.

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(A) The pH value of roots of crops susceptible to soil acidity was decreased when grown in the culture solution of low pH value. (B) Rye, wheat, rape and barley were grown in acidic soil and the separation and identification of organic acids ill each organs were carried out. (1) In the roots of less resisting crops to soil acidity, the content of citric acid was found to be low. (2) And in the leaf-blade of these susceptible crops to acidic soil, the content of citric acid, malic acid, croup 4 (lactic, succinic, α-Ketoglutaric acid) and Gr. 3 (formic, fumaric acid) was found to be higher, but Gr. 5 (trans-aconitic acid et) and Gr. 6 (oxalic, glicolic, cisaconitic acid) were found to be in low concentration.

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チトクローム酸化酵素は呼吸の末端酸化酵素として重要であることはよく知られている. この酵素の作用はCOによって暗黒下で阻害されるが照明によって回復する特徴がある. この光可逆的CO阻害法を用いて水稲根の呼吸における本酵素の関与する程度を知り, また養分吸収がどの程度チトクローム系の呼吸に依存しているかを明らかにするために実験を行ない次の結果を得た. (1) 分けつ期の根ではCOによる呼吸の光可逆的阻害が認められたが, その割合は多い場合でも全呼吸量の約30%であった. (2) 穂孕初期に, 培養液にCOを通泡してチトクローム酸化酵素を阻害した状態で養分吸収を行なわせた結果, 測定した成分の多くは光可逆的に吸収阻害をうけた. その根の光可逆的呼吸の割合は5%以内であったにも拘らず, 光可逆的吸収阻害の全吸収量に対する割合は大きくその順序はK₂O>SiO₂>NH₄-N>H2_Oで, それぞれ約70, 50, 25および0%であった. この順序は既往のH₂Sによる吸収阻害の順序と全く一致した. 以上の結果, チトクロームーチトクローム酸化酵素系の呼吸は養分吸収殊にK₂O, SiO₂の吸収にとって極めて重要であり, H₂Sによる吸収阻害は主にチトクローム酸化酵素の阻害によるものと思われた. 本研究は農林水産技術会議の「土壌と水に関する研究協議会」の中「水稲根の活力診断法に関する研究」の一部である. 研究遂行上指導を頂いた林生理遺伝部長および援助を得た松中昭一技官に感謝する.

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Rice seedlings of various varieties and seedlings grown under different seed-bed conditions were transplanted on the soid of severe reductive state, being applied with starch to the soil. The results were as follows: 1) No parallel relation between the response of top growth and that of root growth was observed among the varieties, namely, a variety is excellent in the root development, in spite of the poor growth of top, and the other is inferior with root growth as well as top growth. However, with the seedlings of different nature but of same variety, the proportional relationship can be observed between the response of top and that of root growth to the reductive soil. 2) The resistance of seedlings of different nature against the reductive state of soil has a close relation to the starch content of the base of stalk, but no similar relation was found among the different varieties. 3) Among the varieties, the resistance, against reductive state, especially response of top growth, seems to be influenced by the oxidative capacity of root.

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The results of experiments carried out from 1950 to 1958 are reported here conclusively. Lowering of rice yield caused by the delayed transplanting, especially when seeding was made very densely on seed-bed, can be explained as follows: 1) Seedlings are grown to too old, 2) shifting of tillering nodes to upwards, and 3) consequently delaying of tillering and heading takes place. Therefore if the sowing is made lately, or sparsely at the normal sowing date on the nursery-bed, and transplanted lately, the yield can be almost as much as those of the standard culture, because these lately transplanted rice plants can carry on rapid growth and heading does not delayed due to the following reasons; 1) As rice plants have good enough space to grow until the time of transplanting, they can produce many healthy tillers from the lower nodes of their stem. 2) Consequently the larger number of tillers and ears are produced. 3) As tillers from the lower part of the stem appears early, the date of heading is also early and which results in heavy grain weight. After late transplanting, the progress of accumulation and translocation of starch, sugars, total carbohydrates or nitrogen compounds in the plants sown lately or sparsely at the normal date of the plots were found practically not different with standard culture plot.

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水稲の晩生種は短日に敏感に感応して幼穂形成をみる極めて鋭敏な植物の一つである. しかし植物の一生を通じて同じ程度の感応度を持っている訳ではなく, 植物エージの若い時代においては短日感応度が低いことは一般に知られている事実である. そこで筆者は極晩生種の瑞豊を用いて短日に感応する能力が植物エージの何時の時期から生ずるものであるか. また植物エージの進行に伴って短日感応度がどのように変化して行くかを知るために二, 三の実験を行なったのである. (I) 1958年に生育初期の短日感応度についてある程度厳密に究明できるような実験を行ない, 第5葉以下というような幼植物時代においても僅かながら短日感応の能力が存在する証拠を見出したのである. (Fig. 1. 参照) (II) 同じく1958年に植物エージの進行とともに短日感応の程度がどのように変化して行くかについて一つの実験を行なった結果, 植物の短日感応程度は植物エージの進行とともに増大して行くものであることを知ったのである. (Fig. 2. 参照) (III) 次に1959年に上述のような植物エージと短日感応度との関係が植物の窒素についての栄養条件によって変化するものかどうかに関して一つの実験を行なった結果, 各段階のエージの植物について, 短日感応度は窒素の多少という栄養条件によってほとんど影響を受けないことが明らかとなった. (Fig. 3. 参照) (IV) 更に1959年に植物エージの進行に伴う短日感応度の増大を植物エージの進行に伴う葉面積の増大ということで説明できないものかと考え, 葉面積と短日感応度との関係を明らかにする目的で, 植物の部分的短日処理に関する一つの実験を行なったのである. その結果, 主茎のみ短日処理して他の分げつを暗黒に保った場合, 主茎のみ残して他の分げつを基部から切除して短日処理した場合, 主茎並びに総ての分げつの葉身部分を切除して短日処理した場合の何れにおいても, 全植物を短日処理した場合と全く同時に幼穂を形成したのである. この結果, 短日を受ける葉面積の大小ということは幼穂形成に無関係であり, 従って, エージの進行に伴う葉面積の増大ということでは短日感応度の増大を説明することはできなかった訳である. (Fig. 4. 参照) なお, この研究は前東京大学農学部教授野口弥吉博士を主任研究者とする総合研究「禾穀類とくに水稲・大小麦の幼穂の分化並ぴに発育に関する生埋生態学的研究」の一部として行なわれたものであり, 野口博士の御指導に対し深甚なる感謝の意を表する次第である.

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The quality of rice kernel in early season cultivation is studied in comparison with that in usual or late season cultivation. In early season cultivation, rice kernels mature in haste and the accumulation of storage matter into the inner parts of kernel is abundant at early stage of maturation, therefore the arrangement of starch cells seems to be somewhat radial on the cross section of kernel. On the other hand, the weak kernels on panicle become frequently into milk-white kernels and chalky kernels on account of an unbalance between demand and supply of storage matter about 10 days after flowering, and some of the other kernels become into partially-chalky kernels and white-belly kernels owing to a tendency. to premature. On the kernels in early season cultivation number of aleurone cells and thickness of bran layer increase and embryos fall off more easily from kernels in process of cleaning, accordingly the cleaning-loss is relatively high as compared with that of the kernels in usual or late season cultivation.

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It is most desirable to prolong the longevity of rice seeds for increasing the certification of seeds as the genetic stocks and improving the efficiency of seed raising. From these standpoints, the authors have been studying on the storage of rice seeds since 1957. In this report, the relation between relative humidity and equilibrium moisture content of seeds was first given. And the longevity of seeds with different moisture contents was reported showing that the seeds with 19-10 % moisture maintained their vitality for over 480 days at 0°C, while the deterioration of vitality occurred in less than 60-430 days for the seeds with 18-8 % moisture at 30°C. As to the drying seeds, hot air drying at 40-60°C was proved to be far more efficient in preparing the dried seeds of 7-4 % moisture than the drying by desiccants such as quick lime or silica gel.

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Though one of the most important points in predicting the yield of rice is to discriminate the non-fertilized grains as early as possible, no reliable method for serving it has hitherto been found. As the results of examining histo-chemically the difference between fertilized and non-fertilized grains, the authors have succeeded in discovering the fact that fertilized trains always begin to accumulate starch in their mesocarps at much earlier stage than the stage at which starch begins, to be accumulated in endosperms, while non-fertilized ones never accumulate starch in any circumstances. Basing upon this fact, the authors established a new method by means of "iodine reaction of starch" which enables one to judge fertilized grains from non-fertilized ones as early as 24 hours after anthesis.

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To make clear the physiological effect of iron on growth and yield of rice plant, a variety, Norin 29, was grown by pot culture under twelve different treatments (table. 1). Two types, of soil, ie, paddy land soil (alluvial) and upland soil (delluvial) were used. To one half of total number of pots (60) containing each of these soils, a definite amount of filter paper was added in order to induce severe reductive state of soil, and to another half no filter paper was added. The former is referred to reductive soil and the latter control soil. Then iron was added in three different levels, 0, 8 and 16 gm. per pot to all of these four groups. thus giving twelve different plots. The results obtained are as follows; (1) The Eh value of soil was found in the order of upland control soil > paddy land control soil > upland reductive soil > paddy land reductive soil. Content of free iron in the soil was just the reverse of the order (fig. 1). (2) Growth (fig. 2) and yield (fig. 3) of the plants were in the same order of upland control soil > paddy land control soil > upland reductive soil. In the plot no. 5 and 6, where iron was applied to paddy land reductive soil, almost all plants were died due to the severe occurrence of "Akagare" (ferrous iron toxity). Lowering of yield due to iron application was more remarkable with the soil of lower Eh value, and the lowering of yield is attributable to the retardation of ripening process and, to less extent, the decrease in panicle numbers. (3) Nitrogen and potassium content (% to dry weight) in plant was rather increased by iron application. This is merely a direct result of growth retardation. But, phosphate content was significantly reduced by iron application, especially when the soil was more reductive (fig. 4). Dry weight of a plant and the total quantity of mineral nutrients absorbed by a plant were determined and expressed in percentage to these of the control plot without iron application as shown in fig. 5. The figure indicates that not only absorption but also translocation of phosphate in plant was retarded by iron application, particularly in the reductive soil. It was observed that absorption of silica and potassium is also influenced by the presence of excessive iron in soil.

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The differentiations of vascular bundles in the leaves, stems and panicles of rice plants were observed, and the differences between the vegetative and reproductive periods were studied. In general, when a leaf primordium covers on the shoot apex, the main vascular strand differentiates at the base of the leaf primordium and grows acropetally and basipetally, but the lateral vascular bundles proceed always acropetally. Each of the primary branches of panicles has a large vascular strand, which has differentiated at the each base of the primary branch primordium, and its differentiating aspect resembles closely to the case of the main vascular strand in the leaf. Then, the large vascular strands in the primary branches of panicles and the main vascular strands in the leaves are presumed to be homogenous tissues. Accordingly, it can be recognized that through the whole growth periods of rice plants, when a protuberance which differentiates on the shoot apex grows to a certain magnitude, a large vascular strand differentiates at the base of the protuberance. Therefore, the differences of patterns of vascular strands between the stem and panicle depend on the different patterns of the protuberances grown on the shoot apices in the vegetative and reproductive periods.

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Taking the weight of fully ripened grain as 100 and converting the weights of grains sampled successively at different ripening stages into percentage-ratios and naming these percentage-ratios as "ripening grades", the authors examined what character of the grains has the highest correlation coefficient between the "ripening grades" using plants treated in various ways and degrees in ripening stages. As the result of it, following characters were pointed out to be capable of practical use, in particular the third one being suggested to be most convenient and promising, in expressing the ripening grades. 1) Specific gravity of a grain. 2) Ratio of a kernel (brown rice) weight to its hull weight of the grain. 3) Proportion of the width of a translucent area to that of the whole area in a transverse section of a kernel.

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Top and root growth and nitrogen content of ryegrass and bigflower vetch in the pure and associated sand culture, fed by nitrogen-free culture solution, were measured periodically. The grass in the association was higher in nitrogen content than that in the pure stand. Especially in the later periods of growth, total nitrogen accumulation in the top parts of the grass in the associated. plots surpassed that of the grass in the pure stand, although the former had only half as many population per pot as the latter. The field experiment, in which several species of legumes are combined with the ryegrass, resulted similarly. And the grass showed the higher nitrogen percentage when the more thriving legumes were associated (significantly correlated). The facts seem to show the cooperative relation of the associated legumes as the underground nitrogen supplier to the grass.

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