For the purpose of finding the influence of root-cutting and no aeration treatment to roots at flowering stage on the content of nicotine in the whole leaves, experiments were conducted by using several varieties of water-cultured and field-grown tobacco. The results obtained were as follows. 1. According to the data of water-culture experiment, nicotine concentration in the leaves of Hicks and MC subjected to no aeration treatment was lower than that in the root-cut tobacco. On the other hand, the whole leaves of non-topping tobacco contained lower quantity of nicotine than those of the topped tobacco subjected to no aeration and root -cutting. 2. In Hicks variety, a close relationship was observed between the respiratory rate of whole roots and concentration and content of nicotine in the whole leaves. In MC variety, the correlation between the respiratory rate of whole roots and nicotine concentration was significant. 3. According to the data of field experiment, concentration and content of nicotine in the whole leaves of high nicotine varieties from which the adventitious roots originated from stalk base had been cut off tended to increase by lower topping, and tended to decrease by higher and non-topping. In low nicotine varieties, effect of cutting adventitious roots was not so remarkable as high nicotine varieties.

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We studied with respect to changes in chlorophyll content and chlorophyll retention of leaf segments accroding to the growth of various leaf blades in rice plant. The results obtained may be summarized as follows : (1) Leaf blades can be classified into two groups in patterns of changes in chlorophyll content of leaves, namely, the first group of leaves grown in vegetative stage and the second group of leaves grown in reproductive stage. The first group of leaves showed higher chlorophyll content and shorter living day of leaves than that of the second group of leaves. (2) Except for reduction division stage and heading stage, the chlorophyll a/b ratio of various leaves was about three through the growth stage. Remarkable increase of the chlorophyll a/b ratio was seen at reduction division stage and just after heading stage. (3) There was high significant correlation between the chlorophyll content and the nitrogen content. The first group of leaves showed an increase in chlorophyll content with a decrease of nitrogen content according to growth. (4) Changes in chlorophyll retention of leaf segments of the first group of leaves differed from that of the second group of leaves. The former's chlorophyll retention declined rapidly as growth advanced, but the latter's declined slowly showing a oscillation.

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During the ripening stage of rice plant, the interrelationship of leaf senescence index proposed by the authors and root activities among the varieties of rice plant examined was studied with respect to chlorophyll content in leaf blades. The results indicate that the close correlation was found between root activities and leaf senescence index during ripening stage. Therefore, it is suggested that the leaf senescence index may be practically applied to diagnostic evaluation for root activities during ripening stage.

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It has been clarified that the rates of apparent photosynthesis in C₃ plant such as rice and wheat, which evolve a large quantity of carbon dioxide in the light, become higher as the oxygen concentration in the air decreases. However, the drastic change in oxygen concentration from 21 per cent to a few per cent may inhibit some of the physiological functions of plant which have adapted to the present atmosphere. The present experiment was conducted to evaluate the effect of low oxygen concentration for a long period on dry matter production and growth of rice plant. The plant was kept in the assimilation chamber in both control and low oxygen plots. The plant in low oxygen plot was treated with the air containing 3 per cent oxygen and the plant in control plot was aerated with ordinary outdoor air. The gas treatment was conducted only in the daytime for 20 days from the heading stage to the milky dough stage. The following results were obtained. 1. The increased weight of dry matter during the treated period was significantly higher in the low oxygen plot than in the control. This increase was mainly due to the reduced photorespiration rate in low oxygen concentration. 2. The space between tillers was extremely expanded after 20 hours from the begining of low oxygen treatment. 3. When the rice plant was exposed to low oxygen concentration at flowering time, remarkable sterility occurred. Such phenomenon was also observed when only the panicle was kept in low oxygen concentration. Thus, the sterility observed here seems to be caused, not by the translocated substances from the leaf and stem, but by the direct damage of low oxygen to fertilization. 4. The grain fertility of Cyperus microiria Steudel, on the other hand, was hardly affected by oxygen concentration of 3 per cent at which the rice plant showed remarkable sterility. This fact suggests that the influence of low oxygen on fertility of plant differs with species. 5. It follows from these findings that the lowering of oxygen in the air is effective in increasing the dry matter production of rice plant, while deteriorate the physiological functions relating to fertility and growth.

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Effect of amount and fertilized period of nitrogen, amount of phosphate, top dressing of potassium and amount of calcium silicate on fat content in rice kernel was observed. Results were summarized as follows: Nitrogen heavily fertilized, especially at ripening period, fat content in rice kernel decreased remarkably. Effect of amount of phosphate, potassium and calcium silicate on fat content was not recognized clearly. Above-mentioned effect of nitrogen was connected to percentage of total nitrogen in leaves at heading date, protein content in rice kernel and percentage of full ripened grain. In these studies, correlation coefficient and partial correlation between fat content (X₁) and above factors were calculated and obtained results were as follows: In relation to percentage of total nitrogen content in leaves at heading date (X₂) r₁₂=-0.9066^***, r_12.4=-0.7355^*, r_12.3=-0.5670^ns In relation to protein content in rice kernel (X₃) r₁₃=-0.8649^**, r_13.4=-0.7636^*, r_13.2=-0.1971^ns In relation to percentage of full ripened grain (X₄) (except No. 8 plot) r₁₄=0.8634^**, r_14.3=0.7609^*, r_14.2=0.5862^ns

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Some varieties of floating and non-floating rice plants were grown under submerged condition by raising water level at a slow rate of 3 cm per day for 23 days followed by a rapid rate of 11 cm for 12 days. Growth and carbohydrate of the floating and non-floating rice were compared to those in ordinary condition. The results obtained were as follows: 1. Total internode length, leaf number and plant height tended to increase under submerged condition and the response was more striking in the floating rice. 2. Dry matter of the non-floating rice decreased associated with growth under submerged condition when the rate of raising water level was rapid, but that of the floating rice increased even at the rapid rate. 3. Under ordinary condition, the contents and concentrations of reducing and non-reducing sugars (especially of the former) were larger, but the concentration of crude starch was lower in the floating rice than in the non-floating rice respectively. In the floating rice, the content of reducing sugar become larger under submerged condition when the rate of raising water level was slow, and remained the similar value when the rate was rapid as compared to that in ordinary condition. In the non-floating rice the content of reducing sugar was markedly reduced under submerged condition when the rate was rapid. 4. The contents and concentrations of non-reducing sugar and crude starch decreased under submerged condition, but the rate of decrease was lower in the floating rice than in the non-floating rice. These results may suggest that the larger increase in total internode length of the floating rice under submerged condition is closely related to the increase in reducing sugar content within plant.

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In one experiment, several varieties of floating and non-floating rice plants were grown under submerged condition by raising water level as described in previous report. Total-, protein-, total soluble-, and amide plus ammonia-nitrogen of the floating and non-floating rice plants were compared with those under ordinary condition. In another experiment, Co. 64 and Norin No. 22, the floating and non-floating rice plant respectively, were grown under submerged condition by raising water level and then lowering it. The various fractions of nitrogenous compounds of the leaf blade, leaf sheath and internode grown under submerged condition were compared with those under ordinary condition. The results obtained were as follows: 1. Under ordinary condition, there were no significant differences in the contents of total-, protein-, and amid plus ammonia-nitrogen between the non-floating and floating rice, but the content of total soluble-nitrogen was slightly higher in the floating rice, while concentrations of total-, protein-, and total soluble-nitrogen were higher in the non-floating rice. 2. The content of protein-nitrogen of the non-floating rice was decreased, but that of the floating one was increased under submerged condition. Concentration of protein-nitrogen decreased in both types of plant by submerging treatment. 3. Both content and concentration of total soluble-nitrogen in the non-floating rice was increased under submerged condition, while those of the floating rice showed no appreciable change. 4. The content of amide plus ammonia-nitrogen was increased markedly under submerged condition in both the non-floating and floating rice, especially in the former. Amide plus ammonia-nitrogen concentration of the non-floating rice was increased more markedly as compared to that of the floating rice. 5. The nitrogenous compounds of the leaf sheath and internode were more affected by submerging treatment than that of leaf blade. The ratios of total soluble-nitrogen or amide plus ammonia-nitrogen to protein-nitrogen became larger under submerged condition in the non-floating rice, while the change of the ratios remained narrow in the floating rice. These results may show that the floating rice maintains the normal nitrogen metabolism under both ordinary and submerged condition.

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生育時期および生育条件による水稲農林29号の酸性酢酸エチル分画における内生ジベレリン活性の変化をしらべた. 茎葉中のジベレリン含量はおおむね生体100g当り0.1～0.4μgの間にあり, 最高分けつ期の約15～20日前頃に最大に達し, 以後9月初めの出穂期にむかつて漸減した. 穂のジベレリン含量は出穂の数日後に著しい急増を示し生体100g当り約0.5μgに達したのち急激に減少した. 遮光や高温処理のように生長量を増加させる処理を加えるとジベレリン含量は増加し, 窒素欠乏処理のような生長を減退させるような処理によりジベレリン含量は減少した. また, 乾燥種子にはジベレリン活性は検出されないが, 吸水4日目頃より活性があらわれ, 次の4日間に活性は著しく増大した. これらのことから, 水稲の生育に内生ジベレリンが重要な役割をはたしているものと推定される.

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To clarify the role of main stem in the establishment of canopy of the individual peanut plant, seasonal change of 2 indices of main stem growth rate (elongation rate, cm/day, abbreviated to SER and leaf emergence rate, 1vs./day, LER) and their difference between infraspecific two varietal groups were studied, using the data dealt in previous paper (MAEDA, 1968). Thirty one, mainly tropical, varieties, of which taxonomic positions were known and divided by the author (MAEDA, 1964), were sown monthly from April to August (table 1 and fig. 1). Results obtained and discussions are as follows : 1. Number of leaves and length of main stem at harvest were larger significantly (p<0.01) in varietal group E (v.g.E) than those of varietal group P (v.g.P) in all of plots (table 2). 2. From the behavior of SER and LER in the 1st growth period (mean air temperature: ca. 19°C) and in the 2nd growth period (ca. 22°C) in April-sow. plot (fig. 2), it was considered that such a range of temperature affected slightly against the leaf emergence and development of epicotyl primordia which hnd differentiated in the dormant embryo, but it was inhibitory against the new differentiation in epicotyl apex which follows the former. Thus, the "lag-phase" in main stem growth had been observed in April-sow. plot disappeared in later sowing plots, and the number of leaves emerged during the 1st growth period of each of the plots increased with the delay of sowing time (table 3). 3. SER and LER in both varietal groups showed highly positive correlation to the mean air temperature in the 1st growth period of each of plots (during ca. 20 days after germination) respectively (fig.3, A), contrary, the lower correlations were obtained for all of growth periods (v.g. E: 0.564^**, v.g. P: 0.325^n.s.). 4. And the values of regression coefficients between SER and LER of the 1st growth period differed significantly (p<0.001) with those of later growth periods in each of the plots (fig. 3, B). These facts may suggest that the degree of influence of the air temperature upon the SER and LER differs with growth stages. 5. It was considered that the advantage in the morphological differentiation of the embryo) in dormant seed in v.g. P, compared with v.g. E (MAEDA, 1972) is a reason for the higher SER and LER in the 1st growth period of April∼June-sow. plots in v.g. P than v.g. E (figs. 2 and 3, A). 6. By the difference in the pattern of seasonal change, and lower values and earlier decline of both rates in v.g. P, having much branches' apices than v.g. E, having fewer ones, the action of growth competetion between main stem apex and apices of the branches, as the another internal factor affecting SER and LER, was supposed. That is, it may be said that the severer physiological stress upon the main stem apex in v.g. P caused by such a competetion seemed to be a reason for the earlier decline of growth, and subsequently, of the shortness in length and fewness in the number of leaves of main stem in this varietal group, comparing with the v.g. E, having longer main stem with much leaves, and of which growth continues until later. The fact shown by SOEJIMA et al. (1967) that the main stem of the peanut of a Virginia tybe variety, of which all of branches were excised artificially, continued its elongation until about twice as tall as the control plants, also may support the above-mentioned opinions.

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As reported in the previous papers, ^{8, 16)} the nitrogen top-dressing at the full heading stage increases the carbon assimilation rate after heading, the resistance to lodging as a result of starch accumulation in the culm base, and consequently the percentage of ripened grains as well as the yield, and furthermore, it also increases the nitrogen content in kernels. Therefore, the authors tried some experiments to clarify the effects of the nitrogen top- dressing at the full heading stage on the taste quality of kernels (evaluated by sensory test), on the inspection grade of brown rice, and on the content of ⁴⁵Ca and ³²P in rice plants. Results are summarized as follows: 1) As the nitrogen content in kernels increases, the taste quality of kernels evaluated by the sensory test tends to decrease. However, it is quite noticeable that the taste quality of samples of kernels differs with different varieties and different cultural methods even in cases in which the nitrogen contents in the samples are almost equal with one another. Accordingly, selecting the variety to be used and improving methods, such as top-dressing, one will be able to increase the nitrogen content in kernels without decreasing the taste quality of kernels. 2) From the results of a factorial experiment which consists of calcium and phosphorus applied at the transplanting time as a basal dressing, the nitrogen top-dressing at the full heading stage and the transplanting time, it is clearly recognized that the nitrogen top-dressing at the full heading stage increases both the percentage of ripened grains and the inspection grade of brown rice, and that the inspection grade goes up with an increase in the percentage of ripened grains. 3) The number of grains per square meter being equal with one another, the percentage of ripened grains increases with an increase in the number of grains on primary rachis branches against total number of grains on panicles. 4) From a tracer experiment, it is revealed that the amount of ³²P and that of ⁴⁵Ca which are accumulated in brown rice increases 80% and more than two times, respectively, by the nitrogen top-dressing at the full heading stage. 5) It seems that the nitrogen top-dressing at the full heading stage affects the nitrogen content in brown rice through the nitrogen content in rice plants, especially through leaf blades at the heading stage.

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光質に対する植物反応の研究には多くの場合単色光が用いられるが, 植物の正常な生育を保証するに足る十分な強度をもつ種々な光質の光を得るには, 単色光よりも白色光から特定の波長帯を除去した混合色光を用いる方が有利である. 本研究は, 水稲の育苗時における自然光の選択的利用に関する基礎的知見を得るため, 人工白色光から種々の波長帯を除去した光に対する生育反応を調査した. 実験はグロース・キャビネット内で行ない, 光処理条件の異なる3実験を実施した. 実験1は紫外部除去(-UV), 紫青部除去(-VB), 青緑部除去(-BG)および橙赤部除去(-OR)とし, 植物面での照射エネルギーは33,000 erg cm^-2 sec^-1とした. 実験2は-VB, -BG, -GY (緑黄部除去), -YO (黄橙部除去)および-ORで180,000erg cm^-2 sec^-1とし, 実験3は実験2とほぼ対応する波長帯を約1/2除去し200,000erg cm^-2 sec^-1に調整した. 3実験ともそれぞれ等エネルギーの白色光標準区(W)を設けた. 水稲農林25号を土耕栽培し, 日長15時間, 昼夜変温下で光処理を行ない, 播種後14日目または22日目に生育反応を比較した. 草丈, 葉鞘長および葉身長は, 等エネルギーの白色光と比較して-VB, -BG区で明らかに増大し, -YO, -OR区でむしろ抑制された. この傾向は照射エネルギー強度および波長帯除去程度の多少にかかわらず認められた. これに対して, 葉身幅および葉身傾斜角度は長波長帯除去によつて増大し, ことに葉身角度は-YOおよび-ORで著しく大となつた. 照射光中の青色光域(B, 400-500nm)に対する赤色光域(R, 600-700nm)のエネルギー比(R/B比)と生育反応の関係を検討した結果, 草丈, 葉長などの伸長生長はR/B比とともに2次曲線的に増大し, ことに葉鞘長でその変化の幅が大きかつたが, 葉身角度は伸長生長と反対の曲線を示した. 葉身の葉緑素含量は伸長生長を促進した-VB区で概して低かつた. また, 葉緑素含量に対する紫外線吸収物質の割合は光質によつて変化し, 紫外部除去光で増大するとともにR/B比の増加にともなつて増大した. 乾物重は, 帯域の除去がほぼ完全な-YOおよび-OR区で明らかに低かつたが, 白色光よりも乾物生産に効果の高い光質は実験によつて異なつていた. 実験1では-UVと-BG区で著しく効果が大であつたが, 実験2では-VB区, 実験3では-YO区で若干増加したに過ぎなかつた. 乾物重は葉面積が大きい区で高く, 両者の間に密接な関係がみられたが, 葉身への乾物の分配率はむしろ植物の全乾物重の増加とともに減少することが実験2で認められた. 以上から, R/B比の大きい光の照射によつて, 草丈ことに葉鞘長が長くその割に乾物重の大きい苗が容易に得られることが明らかになつた.

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In order to evaluate the influence of light intensity on the growth of leaf and root in sugar beet varieties, six varieties grown in the field were subjected to shading treatment by cheesecloth at three growing stages (early, middle, and late) as shown in Fig. 1. The results obtained were as follows : 1) The shading at early and middle growing stages brought about the increase in length of leaf, blade and petiole, but the decrease in blade width. These facts suggested that the shading caused the elongation of leaf, which was quite similar to the phenomenon as was often the case with the dense planting. 2) Since root length expressed the length of the noticeable thickened part of the tap root, the larger root length was regarded as the prosperous thickening growth of the lower part of root. The root diameter in individual beet representing the largest diameter of a root will be the yardstick of the thickening growth of the upper part of root. The shading treatments at early and middle growing stages suppressed the thickening growth of the whole root, and the influences of shading were more conspicuous at the lower part of root. However, the interruption of the treatments promoted the thickening growth of this part, and consequently at the end of season the root shape of the treated plant did not show any marked difference as compared with the control. 3) The shading treatment at the early growing stage caused the suppression of the increase in weight of root and leaf, and especially root weight decreased remarkably. After the interruption of the shading, leaf weight was promptly recovered at middle growing stage and it became larger than that of control. These inclinations were marked in varieties such as AJ 4 and Tsukisappu (errect plant type). The shading at middle growing stage caused the increase in leaf weight, but the differences of the increase due to the plant types were not oflserved. 4) The yield type varieties in which leaf weight showed the marked increase by the shading treatment had the lower sugar content at the end of season than that of control. 5) The shading at the late growing stage caused the decrease in sugar content. But the influences on the sugar type varieties (Hon-Iku No. 401 and AJ 4) were not so conspicuous. 6) It was pointed out that the residual effects of the shading such as over-luxuriant growth of leaf and the decline in photosynthetic capacity in shade leaf produced by shading hindered the growth of root.

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With forage turnip (variety: Shimofusakabu) cultivated in the different amount of fertilizer application and different intrarow spacing as materials, the effects of random plant-missing treatment on the yield was investigated. 1. The yield per plant increased by the missing trestment. The increasing rate of the yield inclined to be higher in root than in top and also in dense spacing than in sparse spacing. k. Coefficient of variation (c.v.) of the yield among plants which showed as a rule higher value than other crops, was increased by the treatment. In this case the change of the c.v. was influenced directly by two factors accompanied with the treatment, i.e. the nonuniformalizing the intrarow spacing and the doubling the mean intrarow spacing, and the increasing degrees of c.v. caused by the former factor exceeded the decreasing degrees of c.v. caused by the latter factor. 3. Though the missing plant increased the yield of the neighboring ones, the increasing rate of yield, namely, the compensative ability for missing plant was seemed relatively low, and even the continuous missing of plants hardly rose the increasing rates of the yield in neighboring plants. 4. The yield per unit ares was always decreased both in top and root by the same two factors accompanied with the treatment as alresdy seen in the change of the c.v. of the yield, and the doubling the intrarow spacing exert a greater influence on the yield in comparison with the nonuniformalizing the intrarow spacing under the sparse spacing condition, while under the dense spacing condition those two factors reduced the yield to similar extent.

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The distribution of absorbed nitrogen derived from basal and top-dressed fertilizer was investigated by tracing ¹⁵N. In the basally fertilized plots, at rooting stage, nitrogen derived from fertilizer was distributed apparently more in leaf sheaths than in laminae, and in the top-dressed plots, it was distributed apparently more in leaf sheaths than in laminae just after top-dressing, because there were new growing organs in leaf sheaths. The nitrogen derived from fertilizer in rice plants translocated gradually from sheaths to laminae with emergence of new laeves. So, it could be assumed that a large amount of absorbed nitrogen distributed in new growing organs. At the later growth stage the rice plants were top-dressed, it took the less number of days to accumulate the maximum amount of nitrogen in the laminae. Nitrogen applied at the ear emergence was firstly found in leaf sheaths, culms and laminae, and it translocated to ears with the progress of ripening. At maturity, nearly 70 percent of absorbed top-dressing nitrogen was found in the ear. At the earlier growth stage of rice plants fertilizer was applied, the higher ratio of tagged nitrogen in the laminae to that of the whole plant was there at the ear emergence, and the lower ratio of tagged nitrogen in the cars to that of the whole plant was there at maturilty.

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The fate of basal nitrogen enriched with ¹⁵N was investigated in the paddy field under the various cultural conditions. Rice plants were transplanted at three different times, early May, late May and mid June, and were grown under two doses of basal nitrogen, 70 kg/ha and 150 kg/ha with 28 hills/m² of plant density. Furthermore, shading plots and high plant density plots, 56 hills/m² were established in case of transplanting at late May. Soil ammonium nitrogen derived from fertilizer disappeared by the end of June, in the plots transplanted at the early and late May, except the shaded plots. It disappeared by the mid July in the plots transplanted at the mid June. The rate of decrease of soil ammonium nitrogen derived from basal fertilizer was accelerated by dense planting and was decreased by the shading treatment. In all the plots, rice plants absorbed the basal nitrogen only the period when the ammonium nitrogen derived from the basal fertilizer stayed in plowed layer as previously reported. The recovery of basal nitrogen by rice plant was nearly 30 percent in all the treatments, in spite of absorption process and absorbing period being very different in each experimental plot. It was assumed that the percentage recovery and duration of absorption by plant was controlled by the absorbing rate of rice plant and the rate of denitrification in plowed layer.

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The role of seed size playing in the early growth of corn seedlings was studied in relation to the sub-sequent dry matter production by the spaced plant experiment. Thirty-five varieties were used to investigate varietal difference and in three varieties of them, seeds were classified to five groups according to the weight. Measurements were made of: (1) Maximum weight of young seedlings cultivated in dark incubator. (2) Effect of seed size on early seedling growth under field condition. The results obtained are as follows : 1. Heavy seeds formed heavier young seedlings and leaves expanded in proportion to weight of seedlings in dark. Heavy seeds required more days to attain the maximum seedling weight. 2. Also under field condition, seedlings from heavy seeds grew better than those from light seeds, until, at least 40 days after sowing. 3. Above results suggest that, the heavier the seed, the greater the initial photosynthetic area elaborated, and hence the greater the absolute dry weight increase during the early part of the vegetative phase.

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タイ国の乾期後半, 4, 5月頃は最も気温が高くなり, 日最高気温が35°～36℃あるいはそれ以上の日が多い. 近年タイ国においても, IR8などに似た, 非感光性の新しい交雑種がさかんに育成されつつある. これらの品種のなかには, この乾期高温時に開花すると, 多くの空籾を生ずるものがある. 著しい場合には, 空籾率が数十パーセントに達することがある. そこで, 1970年に, 同国でこの問題を研究して, つぎのことを明らかにした. 1) 受精した籾には必ず澱粉の蓄積がみられるというが, 肉眼で判別した空籾の大部分は, ヨード反応を示さず, 不受精籾とみられた. 2) 4～5月にわたつて出穂するように, 12の品種を数回作付して, 空籾生成程度を調べた. その結果, 空籾率が30%を超えるものから, 通常値とみられる10%以下のものまで, その発生程度に顕著な品種間差異が認められた. 3) この間の気温と発生程度との関係, 開花期における高温処理, また国内各地の実態調査などから, 開花時における高温が, 空籾の異常発生の主たる誘因の1つであろうと推定された. すなわち, 開花時に, 日最高気温が34,5℃以上の高温の日が続くと, 受精障害がおこるものと考えられる.

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イネ品種短銀坊主の種子から生じたカルスを, 液体培地中で振とう培養し, 遊離細胞を形成させた. この遊離細胞を新鮮培地に移して, 継代培養をおこなつた. 継代培養によるイネ遊離細胞の増殖経過と, 細胞の性質との関係を調べた. 39回の継代培養実験中14回の実験で, 細胞の増殖が見られた. 細胞増殖の著しい場合には, 脂質体顆粒を含む生細胞の割合が多い. また, 染色しないで観察できる細胞核を含む生細胞の割合も多い. 新鮮培地に移してから10～20日後液体培地中に, カルスの小片が肉眼で見えるようになる. 細胞増殖が見られないときもカルス形成は観察されるが, 細胞増殖の著しいときに, カルスの生体重の増加も著しい. 細胞増殖の見られる場合には, Feulgen反応によつてよく染まる細胞核をもつ細胞の割合が多くなる. 以上の結果から, 液体培地に継代培養したときのイネ遊離細胞の増殖と, 細胞の性質との関係について考察した.

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In some cases of direct sowing culture (direct seeding culture of paddy rice on upland field) in the Kanto district, there is observed a year by year decrease in yield. The purpose of this experiment is to clarify the reasons for this decrease. In the previous paper, the cause of this problem has been reported with reference to the movement of inorganic nitrogen in the soil. In this paper the cause related to phosphorus nutrition is described. Two kinds of paddy soil were chosen, one was alluvial which is rich in available phosphorus and the other was diluvial which is not so rich as the former. In the case of direct sowing culture, the experimental plots were divided by the number of years and the amount of phospsorus applications. Especially the difference between direct sowing and transplanting culture, caused by phosphorus applications, was examined. The results are presented as follows: 1. Direct sowing culture in diluvial paddy soil. The content of available phosphorus in the soil and of the phosphorus in the rice plants in diluvial soil were lower than those in alluvial soil. Heavy phosphorus application gave the remarkable good effect to the growth and yield of rice in diluvial soil. It was observed that the growth and yield of rice tend to be retard year by year by continuous direct sowing culture under different levels of phosphorus application. However, the tendency was not so much remarkable in heavy phosphorus application plots. 2. Transplanting culture in diluvial paddy soil. The effect of heavy phosphorus application on the growth and yield of rice plant was less in the transplanting culture than in the direct sowing one. It was attributed to the difference of phosphorus absorption between transplanting and direct sowing culture. 3. Direct sowing culture in alluvial paddy soil. The incrcased levels of phosphorus applications were not effective to the growth and yield of rice plant in this soil due to the high content of available phosphorus which was sufficient for the growth. 4. From the above facts it could be concluded that the decrease of yield in the continuous direct sowing culture caused by the shortage of phosphorus absorption could be recognized only in such soils that were low in available phosphorus content. This yield decrease could be lightened to some degree by increasing the amount of phosphorus application. On the contrary, in alluvial paddy soil which was high in available phosphorus (most part of paddy field in Japan is occupied by this soil), such decrease could not be found, even under continuous direct sowing culture.

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Diurnal stomatal behaviors were studied in three leaves (an upper immature, a middle immature, and a lower mature leaves) of a potted tobacco plant under green house condition using recording porometers, during three days. The effect of soil moisture stress (pF) upon stomatal behavior was also examined. 1. Every morning, pre-dawn opening was observed evidently in the upper and middle immature leaves, but hardly seen in the lower mature leaf (fig. 1). 2. The stomatal opening markedly increased in every leaf with increasing light intensity after sunrise even under high soil moisture stress (fig. 1). 3. The time of peak in the stomatal opening appeared earlier as the leaf became older. In the case of the immature leaf, the same phenomenon was seen under highest pF condition (table 1). These peaks showed sharped shape by the shortening of their width (opening period) due to the occurrence of remarkable midday closure (fig. 1). 4. The lower mature leaf showed severe midday closure of stomata at high light intensity even under mild soil moisture stress pF 3.10, but the upper immature leaf scarcely showed midday closure. 5. Soil moisture stress increment promoted the development of midday closure in depth and length in every leaf, especialy in the upper and middle immature leaves (table 2). 6. Averaged stomatal opening and opening period decreased with increasing leaf age and soil moisture stress (fig. 2). This resulted from that the leaf water deficit was produced by internal (leaf age) and external (pF) conditions, and that such deficit caused the midday closure and the suppression of reopening of tobacco stomata (table 2). 7. Marked difference was found between forenoon stomatal opening curve and afternoon stomatal closing curve within the middle and lower leaves. 8. The notable photoactive opening (including hydropassive opening) after sunrise and remarkable midday closure (hydroactive closing) under strong solar radiation occurred simultaneously in the tobacco stomata in three leaves. Such synchronism suggests that these both stomatal behaviors were associated with the variation of xylem hydraulic tension.

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キシュウスズメノヒエは, わが国南部に自生する野草で, 北限は関東北部といわれており, 最近, その生長量の盛んなことと飼料価の高いことなどから水田の飼料作物として注目されるようになつた. 沖縄, 奄美大島, 鹿児島および福岡に自生しているシュウスズメノヒエを材料として, 15, 20, 25, 30および33℃に調節されたガラス室内での生長をRGR, NARおよびRLGRで比較した. その結果, 各系統は, それぞれの採集地の温度に適応した生長を示すことがわかつた. なお, この差異にはNARよりもRLGRが大きく作用していることも明らかになつた.

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