The main aims of the present investigations are (1) to determine the assimilation rates of ¹⁴CO₂ of the organs consisting the rice ear, i.e. hulled grain, hull, abortive grain and rachis-branch (including rachis and pedicel), and then (2) to determine the redistribution of ¹⁴C-assimilates among those organs after a given time. Plants from 10 to 14 days after ear emergence were used through the present experiments. ¹⁴CO₂ gas was applied to the materials in following two ways; one is to the ear, and another to the shoot. The materials were harvested immediately after one hour exposure to ¹⁴CO₂ for (1) experiment and at one week after exposure to ¹⁴CO₂ gas for (2) experiment. When ¹⁴CO₂ gas was applied to the ear, assimilation rates of ¹⁴CO₂, i.e. ¹⁴C/mg dry weight/hr and ¹⁴C/1OO spikelets/hr were high in the rachis-branch, while were very low and/or almost negligible in the hulled grain and the hull. The translocation rate of ¹⁴C-assimilates to the hulled grain was most rapid for one hour following one hour exposure to ¹⁴CO₂ gas, and became slow thereafter. The translocation of ¹⁴C-assimilates to the hulled grain, however, seems to continue for five to seven hours after exposure to ¹⁴CO₂ gas. For one week following exposure to ¹⁴CO₂ gas, the hulled grain functioned as a greedy "sink" organ of ¹⁴C-assimilates, while the rachis-branch and the abortive grain as a rich and a poor "source" orga'n of ¹⁴C-assimilates, respectively. On the other hand, the hull worked as a "source" organ in some cases, but in others. Each of "sink" and "source" capacities of the hull, however, was very small compared to the hulled grain and the rachis-branch. The assimilation rate of ¹⁴CO₂ of the rachis-branch, ¹⁴C/100 spikelets/hr tended to be higher in varieties which was heavier in dry weight of the rachis-branch per 100 spikelets. Tsuno, et al. (1975) showed that net ear photosynthesis correlated positively with chlorophyll content of the ear. Therefore, the basic benefit of heavy dry weight of the rachis-branch may be to associate with the dense thickness and the anatomy having relatively high proportion of photosynthetic components. It is interesting that the varieties showing high assimilation rate of ¹⁴C/ 100 spike1ets/hr tended to be also high in ¹⁴C/mg dry weight/hr. When ¹⁴CO₂ gas was applied to the shoot, the assimilation rates of ¹⁴CO₂ of leaf blade and sheath were the highest in flag leaf. The assimilation rate of ¹⁴CO₂ of the rachis-branch, ¹⁴C/mg dry weight/hr was similar to it of the flag leaf sheath and from one-half to one fourth of the flag leaf blade. The rachis-branch worked as only one "source" organ of ¹⁴C-assimilates in the ear, while others as "sink" organs. The proportion fixed by the ear out of the total amount of ¹⁴C-assimilates, however, was 4%, and it fixed by the rachis-branch 3%.

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It has been known that the rice mesocotyl elongates in dark and wet condition. As the seedlings for mechanical transplanting, the elongation of mesocotyl is unfavourable because of the anxiety to grow in disheveled or of the risk to be injured at the transplanting. Indica rice varicties are apt to elongate more than japonica ones. So, in the present experiment, we surveyed the way to retard the mesocotyl growth in indica varieties using IBP, a fungicide for rice blast and other diseases, as a plant growth regulator. Exp. 1 The seeds of Oryza sativa L. cv. Hatishail (indica, aman type), Kele (indica, aus type) and Salak (javanica, tjereh type) were used as materials. Seeds were sterilized and placed on culture medium containing 0, 2.5, 5, 10, 20, 40, 80 or 160 ppm IBP in a test tube, and incubated in darkness for 12 days at 32°C. Length of mesocotyls of Hatishail, Salak and Kele were 113 mm, 76 mm and 66 mm rcspectively. However, the mesocotyl elongation of these varieties was markedly retarded with the increase of concentrations of IBP. Shoot length was incrcased by IBP application at 2.5-80 ppm. Exp. 2 Three varieties culturcd in southern district of China, belonging to the indica, shen type, were tested under the same conditions described as those in Exp. 1. These varieties had longer mesocotyls, but lesser extent than those in Exp. 1, and the mesocotyl growth was also depressed by IBP application followed by an increase of shoot growth. Exp. 3 Eight varieties cultured in Korra (senen indica × japonica type varieties and one japonica variety) were tested under the same conditions except that the IBP concentration was set at 0 or 20 ppm, as that of Exp. 1. Mesocotyl length of indica × japonica type varieties were varied from maximum 32.0 mm to minimum 2.1 mm whereas that of japonica type variety was 4.8 mm. IBP depressed the mesocotyl elongation and stimulated the shot growth likely to the above experiments. Exp. 4 According to a routine procedure of raising seedlings for mechanical transplanting, seeds were soaked in water or 10 ppm IBP solution for 4 days at 6°C, then allowed to germinate for 22 hours at 32°C. Germinated seed were sowm in nursery bed soil in box, and incubated in darkness at 32°C. After the plumule emergence, the boxes were transfered into a dim light chamber for 2 days at 25°C. Under thes conditions, the mesocotyl elongation of indica type varieties was less than those cultured in vitro experiments as in Exps. 1-3. However, in British Hondulas Creole the mesocotyl length was depressed as to only 1 mm by IBP, in comparison to about 6mm of water control. The inhibitory effect of IBP on mesocotyl growth was varied with variety. The present paper suggests that the mesocotyl elongation can be retarded by the IBP application in almost all indica varieties, but more experiments are needed to use IBP as a growth retardant, particularly in the practical use.

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Using phytotrons with natural light, several day air-temperatures (night air-temperatures were 5°C lower than the respective day air-temperatures) were combined with the three soil-temperatures as shown in Table 5, to investigate the combined effects of air-and soil-temperatures on the growth and tuber production of the potato plants. The first treatment was given from juvenile to tuber formation stages for 23 days and the second treatment during bulking stage for 30 days. The results are summarized as follows : 1. The plant height was greatest at 24°C air-temperature (mean daily temperature; 21.5°C) combined with 30° soil-temperature; i.e. 24°-30°. Before tuberization occurred, the dry weight of whole plant almost parallelled plant height in response to various temperatures. Tuberization occurred most quickly at 24°-24°, being followed by 17°-17°. Under 30° air-temperature (mean daily temperature; 27°) tuberization was inhibited but slightly occurred when soil-temperature was lowered. At bulking stage, 17° air-temperature (mean daily temperature; 14.5°) was most favorable for tuber growth, and tuber yield was highest at 17°-17°, being followed by 24°-24°. 2. The dry matter and nitrogen distribution in leaf before tuberization were increased with decrease of air-temperature reaching more than 50% of whole plant. At bulking stage, however, they decreased at all organs except tubers with decrease of air-temperature due to their higher distributions at tubers. Under these situations, dry matter, total available carbohydrate (TAC) and total nitrogen or crude protein (CP) distributions at stem markedly decreased. 3. Leaf/stem in terms of dry matter and nitrogen accumulations increased with decrease of temperature, and tended to increase at soil-temperatures that promoted tuber growth. 4. Nitrogen concentrations and soluble-N/protein-N in leaf at bulking stage tended to decrease, while TAC concentrations, TAC/CP increased with decrase of air-temperatures. Stem and roots showed the almost similar responses. It was observed that soluble-N/protein-N in stem was especially higher as compared to other organs. In stem, CP concentrations were high under high air-temperature and low at the soil temperatures favorable for tuber growth, while TAC concentrations, sugar/starch, and TAC/CP increased with decrease of air-temperature, the latter being distinctly high at soil temperatures favorable for tuber growth. 5. The thickness of leaf blade and the length of palisade cells increased, while the pallisade cell density decreased with decrease of air-temperature. 6. RGR had a strong positive correlation with NAR, both being higher at the conditions favorable for tuber growth with a higher distribution of dry matter to it. NAR showed a positive correlation with length and volume of pallisade cell, but a negative correlation with its density, and showed positive correlations with root efficiency. 7. In the temperature regimes of this experiment, tuber yield showed a negative correlation with the mean air-soil temperatures (air+soil/2 temperatures), and the highest yield was obtained at 24°-24°, 17°-17°, sllowing a possibility that soil temperature too should change diurnally. It was suggested that the temperature conditions most favorable for tuber growth increased the matter in tubers, root efficiencies, NAR and leaf/stem ratio, resulting in the highest dry matter production of whole plant.

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To hasten the growth of tea plant in the replanting field, the effectiveness of layer-mixing plowing before planting and the effectiveness of irrigation and compost application after planting was investigated at the diluvial soil of Makinohara hill, Shizuoka prefecture in l969-1974. The growth of young plant was hastened by the irrigation and supply of compost in the soil. But the soil improvement by the layer-mixing plowing was not so effective during 5-6 years after planting. The reasons for the above facts may be as follows: (1) Although physical property of soil was improved by the layer-lnixing plowing, there still remained an impermeable layer consisted of coagulated gravels in a deeper zone. It was found later that root development was further improved when this impermeable layer was broken. (2) However, the growth of aerial part was not affected by the layer-lnixing plowing except on the breakdown of impermeable layer. This is becausc the chcmical fertility of soil was decreased by its being mixed with deep soillayer. Therefore, the soil amendment materials must be applied in combination with the improvement of physical property of soil by the breakdown of impermeable layer. Also the root growth by the irrigation was more affected when this impermeable layer wvas broken.

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根粒菌を接種した大豆(品種コガネダイズ)を生育全期間にわたって¹⁵N硝酸塩を含む培養液で水耕栽培し,培地から吸収したNと根粒のN固定活動に由来するNが,大豆の生長にそれぞれどのように貢献しているかを調べた. 根粒のN固定活動は栄養生長とともに活発となり,1日当たりのN固定量は稔実初期に最高に達した. この時期までに植物体内に蓄積したNについてみると,培地由来のものとN固定に由来するものがほぼ等しい割合で存在していたが,その後N固定作用は稔実の進行とともに急激に衰えたのに対し,培地からのN吸収は引きつづき活発に行われ,その結果成熟期の全Nに占める固定Nの割合は26%に低下した. Nの全蓄積量中種子に移行した割合を,固定Nと培地由来Nについて個別的にみると,前者72%,後者75%となり,双方とも種子生産に効率よく用いられていることがわかった. しかし両者の間にはアラントインへのとりこみに大きな差がみられ,アラントイン態Nの源泉は主として固定Nであると考えられた.

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Relations of photosynthetic and respiratory activities of rachis-branch including rachis and pedicel, husk and hulled grain with their nitrogen content were examined. The age of ear used for measurements was the same as in a previous report (SASAHARA, 1981). Changes in ear respiration with ear temperature were determined on four indica, three japonica and four large grain varieties. Ear temperature increased at the rate of 2 or greater for a temperature coefficient, 〓₁₀ in the range of ear tempcrature from 20 to 30°C, but became smaller than 2 for 〓₁₀ in some varieties above 30°C of ear temperature. The different response of ear respiration to the high ear temperature seems due to varietal difference in ear physiology. Both the increasing rate of car respiration and its value at the different ear tempcrature showed some varietal variations. Measurements of ear photosynthesis and respiration on 23 cultivars were made in about 50 days from August 6 for an extremely early maturing variety, Ishikarishiroge to September 21 for an extemely late maturing one, Yamahoshi. During the measurement period, outdoor temperature changed and influenced ear temperature in an assimilation chamber irradiated, changed 33 to 40°C on an average, but in darkness was kept at 19°C. Temperature of the ingoing air at the entrance of an assimilation chamber correlated negatively with the temperature difference between temperature of the ingoing air and ear temperature in an irradiated chamber, while the temperature difference correlated positively with ear temperature. Thus, the high temperature difference seems to have been caused by the low temperature of ingoing air and the high temperature of ears due to exposure to the former, i.e. ears of some varieties incrcased its temperature against the low temperature of ingoing air. Such increase of ear temperature seems to reflect changes in some physiological activities of ear with transfer from the outdoor of low temperature to the warm condition irradiated. Each of the temperature difference, temperature of the ingoing air and ear temperature, however, showed no significant correlation at least with net ear photosynthesis. Therefore, those three temperature factors appears to have no effect on varietal difference of net ear photosynthesis. Nitrogen content of the rachis-branch including rachis and pedicel correlated positively with net ear photosynthesis and ear respiration (r=0.477 and 0.449, respectively, and each is significant at 5% level). Nitrogen content of the husk showed no significant correlation with net ear photosynthesis, but positively with ear respiration (r=0.447, significant at 5% level). Nitrogen content of the hulled grain showed no correlation with net ear photosynthesis and ear respiration. In the previous report (SASAHARA, 1981), the rachis-branch was regarded as one of the most important organs in ear photosynthesis, i.e. almost all ¹⁴C-assimilates in the rice ear were fixed by the rachis-branch and negligiblely by the husk and the hulled grain. The present results coincide well with the previous report. Besides, the correlation of nitrogen content of the rachis-branch to ear respiration may show that the rachis-branch functioned actively for translocation of the assimilates from other organs to the ear, and it is interesting that nitrogen content of the husk showed a correlation with ear respiration. In case of the hulled grain, the storage protcin in the grain might have obscured the fraction active for respiration.

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作物の葉身傾斜角や葉面方向は光合成の受光態勢と関連して,物質生産にとり重要な要因である. そこで茶葉の葉面方向に及ばす青色光および澄-赤色光の効果について検討した. 1) 白色光から500nm以下を除去した照明下(-VB光)あるいは暗黒下に置かれた1年生幼木に,さらに横から第1図に示す青色光,赤色光および-VB光を照射した. 葉はその葉面方向により90度ずつに分類し,光源の方向をbとすると,青色光で照射した場合に,光源の方向に向く葉がふえbの割合が増加した. -VB光でも多少のbの割合の増加は見られたが,赤色光は効果を示さなかった. 2) この青色光に対する茶葉の反応は照射光の強度と照射時間に比例して増加したが,最大の反応を起こすためには,少なくとも15Wm^-2以上の光強度で48時間以上の照射が必要であった. 3) 一方,この反応は-VB光で可逆的に阻害されたが,青色光を12日以上照射することにより,反応は不可逆的となり,葉面方向はほとんど変化しなかった. 阻害反応に対する反応スペクトル(560～680nm)をみたところ,600nmにひとつのピークを示すことがわかった. これらより,青色光および橙一赤色光の光強度を変えることによって茶葉の葉面方向を制御しうる可能性がある.

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第9葉抽出期の水稲の第8葉身(成熟葉)または第5葉身(古葉)を,¹⁵Nで標識した0.2%尿素溶液に浸潰し吸収させ,7日後の植物体各部分への¹⁵Nの分布状態を調べた. 第5,8葉身から吸収された¹⁵Nの一部は¹⁵N供与葉中に,他は生長の活発な新葉(第9,第10葉),分げつ,新根(第6,第7節根)ヘ転流し,それぞれTCA不溶態窒素画分にとり込まれた. これとは対照的に供与葉より下位の葉への¹⁵Nの転流は不活発であった. 供与葉から転流した¹⁵Nの根への分配割合は,培養液中に窒素が存在しない条件下(-N区)において,第8葉(約27%)よりも第5葉(約47%)で明らかに高かった. 培養中に窒素が存在する条件(8ppm,+N区)でも,第8葉から転流した¹⁵Nのうち約25%が根ヘ分配され,培地中の窒素の有無は葉から根への窒素の転流割合にほとんど影響を与えなかった. 実験期間中の-N, +N両区の水稲体各部分の窒素含量の増減から,この期間中に生長した新葉ならびに新根へそれぞれとり込まれた窒素のうち,根から新たに吸収された窒素と植物体中の他の部分から転流した窒素の割合を推定した. その結果,新葉と新根における他の部分から転流してきた窒素(再転流窒素)の割合は,それぞれ約46～52%と約59%であった. 以上の結果より,とくに根の生長に必要な窒素のかなりの部分が地上部から供給されており,成熟葉ならびに古葉が新根への窒素供給器官として重要な役割を果していると推論した.

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大豆個体群の葉群の上層に位置する葉身,葉柄を開花始以降の数時期にテープで支持して直立させ,子実生産に及ぼす影響を異なる栽培条件下で2ケ年間検討した. 1. 処理によって葉群の空間配置は大きく変化し,畦間では葉群の下層まで光がよく透過し,その結果密植,狭畦条件では粒数が増加して無処理区に比べ最高11%増収した. 2. 処理効果の発現にはLAIが大きく関与しており,草型処理区ではLAIの増加に対する収量増加の割合が高く,LAIが大きくなるほど無処理区との収量差は拡大した. 3. 2ヶ年の比較から処理効果の発現には日射量も関与したものと思われ,日射量の少ない年次で処理効果が大きかった. 4. 処理時期では,LAIが大きくなり葉群の相互遮へいが激しくなる開花姶から4週間の処理で効果が大きかった. この時期の処理によるCGRの増加はLAIよりもNARの増加に依存し,増加した乾物は莢への分配率を高めて着芙数を増し,一部は非同化部に蓄積された. 蓄積された同化産物は後子実に移行して一莢粒数の増加に寄与したものと推察された.

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イネカルスにおける茎葉および幼苗の形成率を,従来の方法に比較し,数倍高める方法,すなわち二段階培養法を開発した. 前培養と最終培養において各種の植物ホルモン作用を検討した結果,前培養にアブサイシン酸,最終培養にカイネチンを用いた組み合わせの二段階培養が,茎葉および幼苗の形成を最も著しく促進した. これらの植物ホルモンとイネカルスにおける器官形成との関連性について議論した. カルスからの茎葉形成が困難な他の作物に対する二段階培養法の適用は,これらの作物における幼苗の作出にも有望と思われる.

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Ultrastructure of the large vascular bundles in expanded and folded leaves of rice plants were observed by an electron microscope, and the results were compared with those of the small vascular bundles previously reported. 1. The large bundles have more developed mestome sheath than the small bundles. The suberized lamellae occur in the outer and inner tangential walls of the mestome sheath cells, but are absent in the middle portion of the radial walls. The lamella occurs between primary and secondary walls of the mestome sheath cells. 2. The protophloem sieve elements and companion cells located abaxially within the large bundles, mature in the elongating zone of the folded leat and begin to degenerate before emergence of the leaf. So far as the same portion of the leaf is concerned, the maturation and degeneration of the protophloem in large bundles are earlier than those in the small bundles. 3. In the border region between phloem and xylem of the large bundles, the parenchyma cells of metaphloem and metaxylem, and the cells of mestome sheath are interconnected by numerous plasmodesmata. According to this observations, the following symplastic pathways for photosynthate are suggested. [figure] 4. The large bundles have many metaxylem parenchyma cells, in which abundant mitochondria and endoplasmic reticulum are contained. The function of the metaxylem parenchyma cells in absorption and transfer of solutes is discussed.

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グレインソルガム穀粒に含まれるタンニン成分は鳥害の軽減に有効であるが,家蓄の嗜好率や消化率にも関係している. そこで,グレインソルガムの鳥害抵抗性品種11F₁品種および非鳥害抵抗性品種28F₁品種を約200km離れた2ヶ所(ExpcrimentとPlains)に同一品種が異なる登熟期間をもつように栽培し(Exp-1:Exp-2,Plains-1:Plains-2),異なる栽培地と登熟期における鳥害程度とタンニン含量の変異と,それらの間の相互関係を調査して,次のような結果を得た. 鳥害抵抗性品種はRS700(Rating値で0.7)を除き,全く鳥害を受けなかった. しかし,非鳥害抵抗性品種はRating値で0(無被害)から約9(鳥害程度81～90%)の鳥害を受けた. 非鳥害抵抗性品種の鳥害程度と粒色との間には一定の関係は認められなかった. しかし,鳥害程度と開花期との間にはExP-1(r=-0.784)とExp-2(r=-0.576)では負の,Plains-1では有意な正の相関関係(r=0.466)が認められた. これは試験区周辺における鳥の餌になる作物の多少と関係が深いと推察される. 鳥害程度の栽培環境間の比較では,Plains-1とExp-1(r=-0.507),Plains-1とExp-2(r=-0.610)との間にはともに負の有意な相関関係が認められた. しかし,ExP-1とExP-2との間には正の有意な相関関係が認められた(r=0.717). 品種と栽培地との交互作用は1%水準で有意であった. 非鳥害抵抗性品種には白粒から褐色粒までの変異があり,そのタンニン含量は0.2～0%であった. 鳥害抵抗性品種は2.1%から7.8%のタンニンを含み,タンニン含量は栽培環境によって異なりPlains-1>Exp-1>Exp-2=Plains-2の順位であった. 品種と栽培環境との交互作用は有意であった. タンニン含量の栽培環境間比較では,Exp-1とExp-2(r=0.760),Plains-1とExp-2(r=0.601)との間には正の相関関係が認められた. しかし,Exp-1とPlains-1(r=0.506),Plains-1とPlains-2(r=-0.334)との間には有意な関係は認められなかった. 以上の結果から,鳥害圧が小さいと考えられる地域ではタンニンを含んだ鳥害抵抗性品種を栽培するならば鳥害はかなり軽減できるといえよう. また,ある栽培環境条件下において,高度な鳥害抵抗性や高タンニン含量を示した品種が他の条件下でも同じように高度な抵抗性や高タンニン含量を示すとは限らないと推察された.

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As for rice cultivation in cool region of Japan, it is very important to get heading date within a period which could avoid both destructive damage and inhibition of ripenning caused by cool air temperature. In order to evaluate more safe plan for mechanical rice cultivation in Hokkaido, the quantitative effect of changeable natural air temperature on the growth of rice plant was investigated by the method of accumlated heat unit in effective degrees. The results are as followes. 1) Effective aero-heat unit (θ) was given to each classfied air temperature into 2°C. This was introduced from the relation between each temperature (Ti) and days for increase by 0.2 leaf age in rice plant at Ti (Di). This relation was obtained experimentally by measuring elongation of 8th leaves with 3 rice varieties, "Kitakogane", "Kitahikari" and "Matsumae" in the air temperature controlled growth chamber. 2) Concerning 9 varieties of 8 cropping seasons transplanted young seedlings, 3 index namely days (ΣD), sumed total of diurnal mean temperature (ΣT) and accumlated aero-heat unit in effective degrees (Σθ) from transplanting to heading were calculated. Coeffcients of variance of Σθ among 8 cropping seasons was considerably smaller than that of ΣT and ΣD. 3) Same tendency was also obtained in different years, localities and cropping seasons in Hokkaido districts. Therefore, Σθ could be considered as an useful thermal index to estimate heading date in paddy of young seedling transplanting cultivation in cool region.

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Using an unbonded strain gauge transducer (1 kg) and an automatic balancing null recorder, the vertical elongation force (Ef) exerted by a seedling was measured at 24-26°C in darkness. The materials were thirty-four soybean cultivars (Glycine max (L.) Merr.) and six cultivars of six leguminous species including kidney bean (Phaseolus vulgaris L.), green gram (P. radiatus L. var. typicus Prain), lupin (Lupinus spp.), hyacinth bean (Dolichos lablab L.), asparagus bean (Vigna sequipedalis Wigth) and peanut (Arachis hypogaea L.). One seed was sown in a plastic pot 5 cm in diameter and 10 or 12 cm in depth. The seedbed was made from sandy loam soil which had been sieved through a 2.38-mm screen and which had about 13% moisture by volume. The soil was compacted to about 0.1 kg/cm³. The seeds were covered with 3 to 7 cm of loose, uncompacted soil. The seedlings were then grown in a dark chamber at 24-26°C. When the seedling had grown to 3, 5 or 7 cm in height, just emerging from the soil, the cotyledones of seedlings were attached to the force receptor of the transducer which was adjusted to 0 vertical force. Light effects on seedling growth were minimized byT handling them quickly under dim green light. Hypocotyl diameter was measured for calculation of stem area on seedlings which were grown under the same conditions as those used for the Ef tests. When the seedling had grown to 3 cm in height and was beginning to emerge, the loose surface soil was removed. The diameter at the center portion of the seedling, 1.5 cm above the stemroot junction, was measured to 0.1 mm using a caliper. Five to 16 seedlings of each entry were used for the Ef test, and three seedlings were used in the measurement of the diameter of hypocotyl. The results obtained were as follows. 1. The maximum Ef of 3 cm tall seedling in soybean varied according to seed mass of the same variety. In each material, the maximum Ef increased about 40g in small seed lot and about 10g in large seed lot with increasing 50mg of a seed weight. 2. In 3cm tall soybean seedlings, the mean value for the maximum Ef of a variety was positively correlated with seed mass (h=0.949). The maximum Ef per unit mass of seed was smaller in large-seeded soybean compared to small-seeded soybean. Furthermore, highly positive correlations were found between seed mass and strm area (r=0.952), and stem area and maximum Ef (r=0.934). The results indicate tha the large-seeded soybean produce large stems and therefore a large Ef. 3. In each of 3, 5 and 7cm tall seedlings, when seed mass is the same among soybean variety and another leguminous species which produed a hypocotyl, the mean value for the maximum Ef of a species was almost the same between soybean and green gram or lupin. However, the Ef was less in soybean than in kidney bean, hyacinth bean, asparagus bean and peanut.

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In the first experiment, ultrastructure of the chloroplasts was observed by an electron microscope from rice seedlings grown in controlled nursery environments under combinations of seeding density and temperature. Large amounts of starch grains were accumulated in chloroplasts of the uppermost fully expanded leaves grown under the combination of lower seeding density (9 cm²/seed) and lower temperature (25.1°C day max./11.3°C night min.), while the chloroplasts from the combination of higher seeding density (2 cm²/seed) and higher temperature (29.5°C day max./11.3°C night min.) had smaller starch grains. Chloroplasts from leaves grown under the lower seeding density and lower temperature had well-formed grana consisting of more number of overlapping thylakoids than those from the higher seeding density and higher temperature. In the second experiment, the effects of temperature and light intensity were studied on accumulation of starch grains and on formation of grana in chloroplasts of the uppermost fully expanded leaves. At the lower temperature (21.7°C day max./11.5°C night min.), increased amounts of starch grains were accumulated in the chloroplasts, but the grana were little affected by the lower temperature. Chloroplasts from leaves grown under the lower light intensity (60% shade in glasshouse) had many rudimentary grana consisting of 2-4 overlapping thylakoids. Consequently, the total number of grana thylakoids per chloroplast section was markedly reduced at the lower light intensity.

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The effects of mixed planting on lodging and yield were examined at different nitrogen levels with direct sowing on well drained paddy field and with transplanting. Two cultivars 'Koshihikari', good tasting but tall and lodging-susceptible, and 'Kanto 100', short-startured and lodging-resistant, were used. Both of them are of the same maturity. Koshihikari and Kanto 100 were planted alternately to four rows and two rows, or two and two, or one and one, respectively. Results of the experiment can be summarized as follows: 1. The lodging of Koshihikari was clearly reduced by mixed planting. About 60% of the reduction was contributed by the propping effect of Kanto 100, and about 40% by the increase in lodging resistance of Koshihikari due to mixed planting. The number of photosynthetic leaves and leaf-sheaths, the stem diameter and the breaking strength of lower internode of Koshihikari in the mixed stand were increased than those in the pure stand. 2. Mixed planting increased the yield. The yield of Koshihikari obviously increased in mixtures and that of Kanto 100 tended to decrease. However, the yield increase in Koshihikari could abundantly compensate for the yield decrease in Kanto 100. On an average, the yield of the mixed stand increased by 6.7% more than the mean yield of the pure stands of the two cultivars. 3. The competition effects of varietal mixtures on the yield were analysed by setting up the artificial condition of no lodging through stretching a net for prevention of lodging. The yield increase in Koshihikari was nearly equal to the yield reduction in Kanto 100, therefore, the yield in the whole conlmunity did not increase. These results demonstrate that the yield increase by mixed planting without a net resulted mainly from prevention of lodging of Koshihikari, and this corresponded to about 60% of the yield increase in Koshihikari grown in the mixed stand, and that the remainder, about 40% of the yield increase in Koshihikari, was due to the competition compensating for the yield reduction in Kanto 100.

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根系に関する交配親の特性と交配分離集団の特性との関係を明らかにするため,早生の男爵薯とトヨシロを母本,熟性の異なる3系統を花粉親とする交配より分離した6集団を供試し,地上部最大期(7月下旬)の根,葉および塊茎乾物重ならびに収穫期の塊茎乾物収量を調査した. 1. 根乾物重(根重)の大きな晩生系統を花粉親とする交配分離集団(CM集団)では早生系統を花粉親とする分離集団(AM集団およびBM集団)に比べ,根乾物重の集団内変異が大きく,また集団平均値が大であった. さらに,生育日数ならびに塊茎収量も大きかった. しかし,葉重には集団間に有意な差異が認められず,また地上部最大期の塊茎重は逆にCM集団で小さな値を示した. 2. 根重および葉重の大きな男爵薯を母本とする交配分離集団(DF集団)はトヨシロを母体とする分離集団(TF集団)に比べ,根重および葉重が大きかった. しかし,生育日数および塊茎収量には集団間に有意な差異が認められず,根重および葉重に対する塊茎収量の割合はTF集団の方がDF集団に比べ有意に高い値を示した. 3. 各々の集団内で,根重は葉重,生育日数および塊茎収量と有意な正の相関関係を示した. 以上の結果より,根重の大きさは熟性に関係する遺伝子の多面発現による影響を受けるものと推察された. 塊茎収量は生育日数と密接に関係しており,晩生系統を交配親に用いた分離集団では,根重が大きく晩性で高収の系統の頻度が高まるといえる. また,同一熟性の交配親間に認められる根重の差異も分離集団に遺伝することが明らかとなり,トヨシロのように野生種に由来する系統を交配親とする分離集団では,根重に対する塊茎収量の割合が高まることが示唆された.

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Physiological damage showing rapid yellowing was widely observed on the fully expanded upper leaves of flue-cured tobacco, cv. MC, in Kanto provinces, in July, 1979 and 1980, just after the continuous course of unusually low temperature and little sunshine. The ultrastructure of damaged leaf tissues was examined by electron microscope. The ultrastructures of naturally senescent leaf tissues and of rapidly yellowing ones by foliar spraying of two chemicals (2-chloroethyl phosphonic acid and maleic hydrazide) and infection with bacterial wilt, were also examined by comparison. In the mesophyll cells of reddish-yellow spots on the damaged leaves, the choroplasts showed some singular ultrastructural changes, such as the presence of electron-dense membrane-bound bodies, striped or latticed unidentified bodies with complex structure, and pseudocrystalline bodies. Many unidentified protuberances were also observed on the cell walls adjoining to intercellular space, whose inner structure was filled with electron-dense and small granular materials. In the mesophyll cells of naturally senescent leaves and of rapidly yellowing ones by other causes, the chloroplasts showed same well-known and usual degenerative changes, such as destruction of lameller system, increase in plastoglobules and so on. Ultrastructural differences mentioned above suggest that some metabolic abnormality might have occurred in the rapidly yellowing leaves with the progress of this damage.

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モミラクトンAとBは,稲種子のモミに含まれる生長抑制物質であり,種子の休眠機構の一つの原因になっていることが指摘されている. 最近これらのモミラクトンは,ファイ卜アレキシン様物質である可能性が示唆された. 本報は稲のイモチ病抵抗性とモミラクトンAとBの関係を明らかにする意図の下に,まずモミラクトンAとBの迅速分離法の確立を日的として検討したものである. モミラクトンの分離は,ガスクロマトグラフ法では本物質が分解されるため適当でない. しかしTLC法とFID法の原理を具備したIatron法が最も適当である. その特徴は物質の単離が迅速に行えるばかりでなく,試料の損失が少なく,かつ特定の呈色試薬を用いることなく行いうる利点がある. 本法を用い検討した結果,イモチ病抵抗性をもたぬササニシキは,モミラクトンAとBはいずれも欠除していた.

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Two azuki bean cultivars, Takarashozu (medium) and Akatsukidainagon (late), were grown in the equidistant square pattern at five population densities, and dry matter accumulation in the plant communities were analyzed. The main results obtained were summarized as follows: 1. The maximum dry matter production was not differed in densities over 16 pls./m², irrespectively of variety, and was about 620 g/m². 2. With increase in population density, dry weight of branches decreased remarkably and disappeared at the highest density. 3. CGR and LAI during growing season shifted higher with higher densities for Takarashozu, but were relatively constant for density for Akatsukidainagon. NAR dropped temporarily at the late July in the higher densities for Akatsukidainagon. 4. Relative light intensity at the bottom of the canopy was associated with LAI. The regression value (Ks) differed between varieties, and the LAI required for 95% light interception was 5.0 and 3.3 for Takarashozu and Akatsukidainagon, respectively. 5. The decrease in NAR with the increase of LAI initiated from LAI about 0.3. 6. The estimated values of LAIopt. and CGRmax. varied with varieties and stages. The maximum values of LAIopt. and CGRmax. were 4.1 and 14.7 g/m²/day, and 3.7 and 16.7 g/m²/day for Takarashozu and Akatsukidainagon, respectively. 7. The efficiency of dry matter accumulation per unit photosynthetically-active radiation (PAR) intercepted (EPAR, dry weight mg/kcal.) attained to the maximum near the maximum leaf area stage, then decreased. 8. Significant simple correlation coefficients were recognized between LAIopt., CGRmax. and EPAR (mean value of each stage), suggesting that the variations in LAIopt. and CGRmax. were partially due to photosynthetic activity changing with growth.

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The diurnal variation in ethylene evolution in leaf and panicle was investigated. The results are as follows: 1. The pattern of ethylene evolution differed between leaf and panicle. The peak of ethylene evolution was observed in the day time in the panicle and at night in the leaf. 2. Illumination treatment of leaf at night had an inhibitory effect on the phenomenon previously observed and the peak ethylene evolution at night was no longer observed. On the other hand the amount of ethylene evoluted in leaf decreased following shading treatment in the day time, while the pattern of diurnal variation was not differed from that in the control plot. From these results, it was assumed that the peak of ethylene evolution at night in leaf was due to the lack of light.

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This study was done in phytotoron under natural light to clarify the processes of discoloration of rice leaves under low tenperature (17°/12°C), and their restoration to green under normal temperature (25°/20°C) switched from low temperature pretreatment, with respect to chlorophyll content and pigment compositions. Results obtained are summarized as follows: 1. The yellowing degree of leaf blades by low temperature coincided with the detree of decrease in chlorophyll content, being highest in IR 24 and lowest in Sasanishiki. The chlorophyll content of leaf blades at the 7th day under normal tenperature after low temperature pretreatment for a week increased more than that grown for 2 weeks under normal tempreature. The degree of increase was Sasanishiki > Milyang No. 23 > IR 24 in order. 2. The heights of absorption peaks of ethyl estracts of yellowing leaf blades under low temperature decreased compared with those of green leaves under normal temperature. The degree of decrease was IR 24 > MIlyang No. 23 > Sasanishiki in order. The maximal absorbance at the red (657 nm) and blue (432, 451 nm) bands under low temperature decreased compared with those under normal temperature, and that at the red band decreased more than at the blue band. 3. The heights of absorption peaks of ethyl ether extracts of greening leaf blades at the 7th day under normal temperature after a week of low temperature pretreatment increased than those under normal temperature for 2 weeks. The degree of increase was Sasanishiki > Milyang No. 23 > IR 24 in order. The rate of increase at the red band was greater than that at the blue band. 4. By low temperature treatment, the relative amount of the yellowish pigments increased more than that of the greenish pigments, and the rate of increase of the former pigments was IR 24 > Milyang No. 23 > Sasanishiki in order. The acetone-and water-soluble pigments (anthocyanin) increased under Iow temperature treatment and the degree of increase was IR 24 > Milyang No. 23 > Sasanishiki in order. 5. It was suggested that the yellowing of rice leaves by low temperature was caused by a decrease of chlorophyll content and by an increase in the ratio of yellowish/greenish pigments in amount, although the contents of both pigments decreased by low temperature. The order of yellowing of leaf color under low temperature was coincided with the order of decrease in chlorophyll content and increase in yellowish/greenish Pigments.

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