Grain size is one of the important yield components and it has influences on grain yield as well as grain quality. However, it has not been well understood how grain size is determined. Certainly, glume size is one of the important factors affecting grain size. We analyzed in detail the growth of glume (floral glume) of several rice varieties differing in sizes of their glumes. 1. The growth of glume in both length (lemma length) and width (floret width) were well fitted to a logistic curve (Fig. 1). This indicates that the growth pattern of glume can be characterized by parameters estimated from the logistic curve. In every variety, the growth of the glume in length ceased earlier than that in width (Figs. 2 and 3). Thus, the growth of glume in length did not synchronize with that in width. The intervarietal differences of growth period did not correspond with those of the glume length. However, the maximum growth rate of glume in length correlated highly with the final glume length, indicating that the differences in the final glume length was due to the differences in the maximum growth rate of glume length among the variesies (Table 1, Fig. 2). on the other hand, in the glume width, we could not detect any distinct intervarietal differences in growth period or maximum growth rate (Table 2, Fig. 3). It must be noticed that the relatively wide glume of "Arborio" was caused by the prolonged growth but not by the high growth rate (Table 2). 2. The growth patterns of glume in length and in width are different and the length and width of glume may be controlled by different regulatory systems. In this point, we need to analyze the growth pattern of glume and the mechanism of determination of its size in more detail. 3. Intersecting lines comprising three straight lines could be fitted to the allometric growth between the glume length and width (Fig. 4). In every variety, the coefficient of allometry was minimum in the second section and maximum in the last (Table 3). Intervarietal differences were detected in the coefficients of allometry and the positions of intersecting points. It is clarified that the shape of glume is affected by both the ratio of growth rate in length and to that in width of glume and the time lag of the growth period in the width relative to that in the length. 4. The present results show that the size and shape of rice glume are controlled by various parameters and we cannot assign any single factor determining the size or shape of glume during its growing process.

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The purpose of the present investigation was to get the informations on breeding for high protein rice variety. Parents used were a high protein cv. Brimful (Scented rice from Nepal) and a Japanese ordinary rice cv. Koshihikari. A crossing was carried out in 1977. F₆ and F₇ generations derived from the hybrid were grown in paddy field in 1983 and 1984. Protein and amino acid contents in grains and some agronomic characters were determined. The results summarized as follows : 1. Mean value of protein content in F₆ and F₇ plants was varied from 10.1% to 12.5% and nearly equal to that in F₄ and F₅ plants. By examining variance of protein content from F₆ and F₇ populations, it was shown that they decreased gradually since F₆ generation (Tables 1 and 4). The variance was nearly equal to that of cv. Koshihikari. The results showed the tendency of being bred actually connected with high protein content in F₇ generation. 2. In F₆ generation, although there was a significant negative correlation between protein and ear length, no significant correlation was observed between protein and other agronomic characters (Tbale 2). There was no significant correlation between high protein property and grain yield in F₇ plants (Fig.2). 3. In F₆ generation, significant differences were observed among plants in lysine and threonine contents per dry weight, and those two amino acids in F₆ and F₇ generations were much higher than those in cv. Koshihikari (Tables 3 and 5). 4. Significant correlations were observed among protein content and lysine per dry weight in F₆ generation (Fig. 1). But, significant correlation was not observed between protein content and lysine content per protein. 5. From the results, it was suggested that high protein content in rice grain could be increased by breeding without decreasing grain yield.

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In our previous studies on diurnal courses of photosynthesis, transpiration and diffusive conductance of the leaf in the rice plants grown in the paddy field, it was recoginized that the photosynthetic rate decreased with the decreasse of diffusive conductance due to high vapor pressure deficit under sufficient light intensity in the fine midday. It has been pointed out that water stress affects photosynthetic rate through the decrease of both CO₂ supply to mesophyll through stomata and photosynthetic activity in mesophyll. This study was conducted to examine whether high vapor pressure deficit reduced photosynthetic activity by measuring light and CO₂ utilization efficiencies at low quantum flux density and CO₂ concentration under different vapor pressure deficit, respectively. The results were as follows : 1) Transpiration rate increased rapidly, and photosynthetic rate, diffusive conductance and intercellular CO₂ concentration (Ci) decreased gradually with changing vapor pressure deficit from low to high (Figs. 1 and 2). 2) Light utilization efficiency, which was shown by the degree of inclination of light dependent straight line of photosynthesis under low quantum flux density, decreased under high vapor pressure deficit (Figs. 3 and 4). And also CO₂ utilization efficiency, shown by the degree of inclination of the straight line expressing the relation between photosynthetic rate and low intercellular CO₂ concentration, decreased under high vapor pressure deficit (Figs. 5, 6 and 7). As light and CO₂ utilization efficiencies were thought to indicate photochemical and carboxylation activity of photosynthesis, respectively, it was suggested that not only diffusive conductance but also photosynthetic activity related to photochemical and carboxylation activities were affected by high vapor pressure deficit. 3) Intercellular CO₂ concentration decreased with the decrease of photosynthetic rate and diffusive conductance under high vapor pressure deficit (Fig. 1). Furthermore, it was found that the degree of inclination of the straight line, expressing the relation between ambient CO₂ and intercellular CO₂ concentrations, was smaller under high vapor pressure deficit than that under low vapor pressure deficit (Fig. 9). These facts indicated that the decreasing of diffusive conductance was more effective on the decrease of photosynthesis under high vapor pressure deficit than the decreasing of photosynthetic activity. 4) The three following equations were obtained on the basis of the relation between intercellular CO₂ concentration and photosynthetic rate (Fig. 6) and on the fact that transpiration rate was proportional to diffusive conductance under constant vapor pressure deficit. In this case, GAASTRA's concept was also considered. P=(44.99×C)/(C+0.377) Ci=(350×C+18.86)/(C+0.377) T=3.43×C The figure (Fig.8) drawn by using these equations showed that the relations between diffusive conductance (C) and photosynthetic rate (P) and between diffusive conductance and intercellular CO₂ concentration (Ci) were hyperbollic, while the relation between diffusive conductance and transpiration rate (T) was linear. Thus, if diffusive conductance were decreased without decreasing the photosynthetic activity in mesophyll, water use efficiency (photosynthetic rate to transpiration rate ratio) could be increased.

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In order to study the difference in the growth of excised seminal roots (root-tips) in vitro culture between Japonica and Japonica-Indica hybrid rices, different concentrations of sucrose, casamino acids (casein acid hydrolysate) or vitamins (thiamin, pyridoxin and nicotinic acid) in the culture medium were investigated. Effect of cultural temperature and degree of pH value of the medium on the excised seminal root growth were also tested. Unless otherwise mentioned, a Japonica rice cultivar (Nipponbare) and a Japonica-Indica hybrid rice cultivar (Milyang 30) were used as materials. All the experimental procedures were same with those described in the previous paper⁵⁾. 1. Under the temperatures of 19° to 34°C, the excised seminal root growth of the Japonica-Indica hybrid rice was better than that of the Japonica rice (Fig. 1). 2. The optimum pH value of culture medium for the excised seminal root growth were 4.0 to 4.5 in the Japonica rice and 4.5 to 5.5 in the Japonica-Indica hybrid rice (Fig. 2). The optimum concentrations of sucrose for the root growth were 6 to 8% in the former and 4 to 6% in the latter (Table 1). On the other hand, effect of concentrations of vitamins on the root growth remained unclear in the both type of rices (Table 4). In all the culture media, however, the excised seminal root growth were better in the Japonica-Indica hybrid rice than in the Japonica rice. 3. In the Japonica rice, the excised seminal root grew well with increasing of concentration of casamino acids in the culture medium. On the other hand, in the Japonica-Indica hybrid rice, the dry root weight increased with increasing the concentration of casamino acids in the medium, while the main root length decreased with the casamino acids concentration (Table 2). When the excised seminal roots of each 20 cultivars of Japonica and Japonica-Indica hybrid rices were cultured in the medium containing 0% and 0.2% casamino acids, the root growth of all the Japonica rice cultivars and that of about one-third of Japonica-Indica hybrid rices were better in the 0.2% casamino acids medium than in 0% casamino acids. In the two-thirds of Japonica-Indica hybrid rices, however, the main root length was longer in the 0% casamino acids than in the 0.2% casamino acids, but the dry root weight was larger in the latter than in the former (Table 3). Thus, the effect of casamino acids on the excised seminal root growth clearly differed between the Japonica rice cultivars and the majority of the Japonica-Indica hybrid rices.

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This investigation has been carried out to group soybean varieties into several types by yield components and to characteraize these types as to plant type and growth habit. Out of one hundred three varieties, collected from western part of Japan and examined, data of 84 varieties which yielding more than 200g/m² were analyzed. And the following informations were obtained. 1) Soybean varieties were grouped into five types (Grain-Number type, Semi Grain-Number type, Medium type, Semi Grain-Size type, Grain-Size type) on the basis of Seed Number·100-Seed Weight ratio. Grain-Number (GN) type has the largest Seed Number·100-Seed Weight ratio and Grain-Size (GS) type has the smallest one. 2) GN type included more blanched type and blanch-spreaded type, based on the plant type classification suggested by WATANABE et al.¹⁴⁾ in 1975. 3) GN type had longer vegetative period, whereas GS type had longer reproductive period. 4) On growth habits, GN type had more vigorous both vegetative and reproductive growth than GS type, and GN type had more vigourous growth of branches. 5) GN type was supposed to be advantageous under favourable conditions and GS type vice versa. 6) Recent soybean breeding in Japan seems to give too much weight to seed size. It might be necessary to consider balance of seed number and seed size.

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Patterns of starch accumulation and ethylene evolution during the course of regrowth in different types of alfalfa, cultivars from tropical and temperate areas, were examined. Results were discussed in relation to the differences between cultivars and seasonal changes. 1. No changes were detected in plant hight in varieties of extremely non-hardy, non-hardy and intermediate type, however in the extremely hardy type, the plant height was less than the others (Fig. 2). 2. Stem number of the tropical and the extremely hardy types were larger than those of the others, and the former showed rapid increase but the latter did not (Fig. 3). 3. After cutting, regrowth in the top took precedence to that in the root, and when there were not enough assimilation products, starch was retranslocated from the root to the top. So starch accumulation in the root arose from surplus assimilation products ln the top. The differences in starch accumulation in the root might be brought about by differences in the top (Figs. 4, 6). 4. The decrease in starch accumulation in the root was brought about mainly by growth in the top ; when growth in the top was high in activity, the changes in starch accumulation were less (Figs. 5, 7). 5. The cause of the differences in ethylene evolution was thought to arise from differences in growth activity. These differences may be mainly caused by aging of plants at the beginning of the flowering stage. Ethylene evolution rates changed at each growth stage. After flowering, ethylene evolution was decreased (Figs. 8, 9). 6. Starch accumulation and ethylene evolution during the regrowth period accompanied with each other ; therefore, ethylene may promote the increase and decrease of starch accumulation. So, in the future, it is necessary to clarify the relationship between starch accumulation and ethylene evolution.

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In the present paper the factors associated with the cracking of tuberous roots of sweet potatoes (Ipomoea batatas Lam.) were analyzed. Emphasis was placed on the observation of cracking under low temperature and dry conditions during the early stage of tuber formation, using rooted leaf pot culture. The development of cracking in the field was also studied. The results obtained are summarized as follows : 1. Three typical symptoms consisting of white-cracking (Fig. 2A), white-flatness (Fig. 2B) and red-flatness (Fig. 2C) were observed in the tuberous roots of the cv. Beniazuma that were exposed to low temperature and/or dryness for 5 days at 20 and 25 days after transplanting. Low temperature treatments (16/12°C, 12/12h) during periods ranging from 20-25 days and 25-30 days after transplanting increased the incidence of white-cracking (Fig. 3). The dry treatments associated with moisture percentages of the vermiculite medium below 120% on a dry weight basis (Fig. 1) during a period ranging from 20-25 days after transplanting also promoted white-cracking (Fig. 3). An increase in the incidence of cracking was observed when the normal tuberous roots developed under the low temperature and dry treatments were put in water, and especially those subjected to dryness during a period from 20-25 days exhibited considerable cracking 24 hours after being placed into water (Fig. 3). Those tuberous roots subjedted for 5 days to the low temperature and/or dry conditions described above showed thin cortices (Table 1). 2. White-cracking, which is considered to be a symptom occurring immediately after cracking, was observed on the 20th day after transplanting, and white-flatness, which is considered to be an early healing symptom, was observed on the 25th day in plants not subjected to the low temperature and dry treatments. Furthermore, on the 30th day some of the white-flatness symptoms on the tuberous roots are considered to be changed to red-flatness symptoms (Fig. 4). Based on these findings it is considered that the cracking of the tuberous roots of sweet potatoes which occurs easily even without exposure of the plants to low temperature and/or dry conditions, may heal through the occurrence of flatness symptoms under favorable conditions. 3. The white-cracking symptoms on the 25th day after transplanting remained until the 35th day under the low temperature treatment and/or dryness induced by 10% solution of polyethylene glycol (PEG 6, 000) treatments (Fig. 5). This result suggests that low temperature and dry conditions delay the healing of cracking. 4. It was also found that cracking occurred and healed at the early stages of tuber formation in the cvs. Beniaka, Kokei No.14 and Beniazuma in the field. The white-cracking symptoms observed in the 5th week after transplanting was considered to be changed to red-cracking and red-flatness symptoms in the 10th week. The red-cracking symptoms, which correspond to cracking at harvesting time, may represent an incomplete healing symptom of cracking. Red-cracking of the tuberous roots grown under the polyethylene-mulch treatment in the 10th week was more frequently observed than in the nontreated materials (Fig. 6). It is considered that the healing can not take place easily due to the rapid swelling of tuberous roots and the cracking symptoms persisted under the polyethylene-mulch treatment. From these results, it is suggested that cracking is induced when tuberous roots grow fast in the early stages of tuber formation, and heals readily under favorable conditions. Thus low temperature and dry conditions may prevent healing, and consequently increase the incidence of cracking.

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イネの一代雑種が収量で顕著なヘテロシスを示すことはすでに明らかにされているが, 作物の物質生産の立場からヘテロシスについて研究した例は少ない. 本研究では, 物質生産要素におけるヘテロシスについて検討するために, 個葉の光合成速度, 窒素含量, 比葉面積(SLA), 株当り葉面積および1株穂重の測定を実施した. 結果は次の通りである. 1. 個葉の光合成速度において顕著なヘテロシスを示す組合せがみられ, 最も優れたF₁は中間親, 高い方の親をそれぞれ57%, 51%も凌駕し, いずれも統計的に有意であった(第1表, 第2表). 2. 光合成速度におけるヘテロシスは弱光域よりも強光域において高かった(第1図). 3. 葉身の窒素含量でもかなりのヘテロシスがみられた(第1表). 4. 光合成速度と窒素含量の間には正の相関がみられ, 親品種では有意であった(第2図). 5. 光合成速度とSLAの間では一代雑種, 親品種とも負の有意な相関を示した(第2図). 6. 窒素含量とSLAの間でも親品種では負の有意な相関を示した(第2図).

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タイ国東北地域の3-6試験地において, 3年間にわたりロゼル-ラッカセイの間作試験を実施した. ロゼルのラッカセイに対する遮光の影響を緩和する意図で, 複条(paired row)法を導入して個体密度一定の下にロゼルの複条距離をかえ, 窒素(N)条件を組合わせて収量の反応を比較し, 次の結果を得た. 1) 間作ロゼルの乾燥繊維収量は全区3年間の平均で, 単作の場合より僅かしか(4-18%)低下しなかったが, ラッカセイの莢実収量は大巾な(67-85%)低下を示した. 2) ラッカセイ/ロゼルの収量比は条間距離のみならず, 年次, N供給量によっても大巾に変動した. 3) 複条区と単条区を通じて, 合計収量は条間距離が増大するほど, すなわち全体としての条間距離が均一化するほど, 増大する傾向を示し, 50cm単条区で最高で, ロゼルの収量も同じ傾向を示した. しかし-N条件下ではこのような傾向は消失した. 4) Land equivalent ratio (LER)も上と同じ傾向を示し, 50cm単条区で最高となった. 以上のことから, ロゼル-ラッカセイ間作体系への複条法の導入は単条法に比べて特別な利点を持たないことがわかった.

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タイ国東北地域の2-5試験地圃場において, 3年間にわたりロゼル-リョクトウ間作試験を実施した. ロゼルのリョクトウに対する遮光の悪影響を緩和する意図で, 複条法(paired row technique)を導入して, 固体密度一定, 窒素(N)供給2段階の条件下に, 条間距離を変えて2作物を栽培し, 収量の反応をいろいろな面から比較した. 得られた主な結果は次のとおりである. 1) 単作に比べて間作ロゼルの乾燥繊維収集は各種条間3年間平均で, 僅かしか低下しなかったが, リョクトウの種子収集は単作の42-65%に低下した. 2) ロゼルに対するリョクトウの収集比は, 条間距離のみならず, 年次, N条件によっても変動した. 3) 合計収量の反応には2つの傾向がみられた. 1つは複条と単条とにかかわらず, 条間距離の増大に伴って増大する傾向であり, 他の1つは10-15cmという狭い複条々間距離に収量の第2の山が現われる傾向である. ロゼル収量も同様な反応を示したが, リョクトウ収量は異なる反応を示した. N無施肥に対する反応にはロゼルとリョクトウ間に差は認められなかった.

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タイ国東北地域の4-5試験地圃場を用い, 2年間にわたって実施したロゼル-ラッカセイ間作試験において, ロゼルのラッカセイに対する遮光の悪影響を緩和して増収をはかる意図をもって, ロゼルの播種をラッカセイよリ1-3週間遅らせる方法を試みた. 得られたおもな結果は次のとおりである. 1. ロゼルの播種が遅れるほどその繊維収量は低下し, ラッカセイの莢実収量は増大した. 両者の関係は一般に場所別に一つの双曲線に当てはまることがわかった. 2. ロゼルとラッカセイの合計収量はロゼルの播種が遅れるほど低下した. 3. Land equivalent ratio (LER)はロゼルの遅延播種によっては改善されなかった.

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本報告は, 1985年7月11日から1986年1月11日まで, 日本学術振興会とインド科学アカデミーの特定国派遣研究者事業の一環として行われた調査, 研究の一部である. 本調査はインド・デカン高原(海抜550m)における水稲栽培の実態を調査し, 問題点を明らかにしようとしたものである. デカン高原における水稲栽培は, Kharif (rainy season) と Rabi (dry season)に大別されるが, 本調査はKharifについて行われた. 苗床への播種は5月下旬～6月中旬に行われ, 本田移植は6月下旬～7月中旬であった. 調査に用いた栽培品種は, 改良品種として Vijayamahsuri, Sonamahsuri, 在来品種として, 香り米のBasmatiとHR59 (Kakirekkalu)であった. 耕起, 代かきは牛耕で, また田植えは手植えで行われるが, かなり不均一であった. 作土は20.4～34.7 cmと深く, 一株当りの植付け苗数は4.3～5.5本であった. 深植えが依然として行われ, Vijayamahsuriの5.8cm以外は8cm以上であった. 深植えに伴なう二段根や三段根の発生, 初期生育の遅れおよび分げつの抑制が見られた. 植え付け密度は品種によって著しく異なり, Basmatiは330個体/m²であった. 苗の各葉位の葉緑素含量にも著しい差異が認められた. 従って, 健苗育成や肥培および水管理の重要性が指摘された.

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本報は, 1935年7月11日から1986年1月11日まで, 日本学術振興会とインド科学アカデミーの特定国派遣研究者事業の一環として行われた調査・研究の一部である. インド・デカン高原のハイデラバードの農業研究所附属農場で慣行法で栽培されていた水稲について, 石原の改良浸潤法によって気孔開度を測定した. 改良品種としてVijayamahsuri, Sonamahsuri, 在来品種として香り米のBasmatiとHR 59を用いた. また, 国立稲作総合研究所の実験圃場に品種保存用に栽培されていた36品種について気孔開度の品種間差異について登熟期に測定を行った. 1985年のKharifは異常気象で, ほとんど降雨がなく, 登熟期に濯慨用の水が不足し, 水稲は水不足の状態にあったので, 水ストレスに対する気孔開度反応について調査した. 気孔開度は, いずれも展開上位4葉の合計値で表わした. 分げつ最盛期のVijayamahsuriの気孔開度は著しく大で, 終日大きい値を維持した. BasmatiとHR 59はVijayamahsuriよりは小さく, また日変化を示した. 改良品種のSonamahsuriもVijayamahsuri と同程度の大きい開度を示した. Vijayamahsuri, Basmati, HR 59の気孔開度と富士葉色板による葉色との間に高い正の相関関係が認められた. また, 36品種の気孔開度と葉色との間にも高い正の相関関係が見られた. 改良品種のVijayamahruriとSonamahsuriは日没後および日の出前においても気孔が開いていた. 旱ばつによる登熟期の水不足の状態において, わずかの濯水によって気孔は開いた.

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水田における有機物分解量の推定は, 土壌有機物の動態を明らかにし, 地力の維持機構を解明するうえで, 重要である. 本報告は湛水期間中の水田において, 田面水と土壌表層の酸化層を含む系における有機物分解量を調べ, あわせてその変動の要因について検討を行なったもので, 得られた結果は次のとおりである. なお有機物分解量は, 田面水中の酸素消費速度の測定により求めた. 1. 有機物分解速度は, 測定開始(6月29日, 移植後約1月)以降季節の進みにともない下降した(第1図). 2. 有機物分解速度の Q₁₀ は平均2.6で高温により顕著に促進された(第1表). 季節の進みにともなう有機物分解速度の低下と, 水温の低下の間には相関関係がみられた(第2図)が, この関係から求めた Q₁₀ は4.8と高く, 水温以外の要因も分解速度の低下に関与していると考えられた. 3. 同一水田内でも場所によって有機物分解速度に差異があった. この差異は, そこに生育するソウ類の有機物生産量と関連している場合が多く, 有機物生産量の多い場所で, 有機物分解量も多いという傾向があった(第3図). 季節の進みにともなう有機物分解速度の低下と, ソウ類の総生産速度の低下の間には相関関係がみられた(第4図). 4. ソウ類の現存量の指標としてのクロロフィルaと, 消費者によるソウ類の摂取量の指標としてのフェオフィチンaについて, 土壌中の水平・垂直分布をみると, 両者の分布は密接な並行関係がみられた(第5図). このことから, ソウ類の有機物生産が多い場所で, 有機物分解の活発なことには, 消費者の摂食が活発であることが関与していると考えられた. 5. 以上より, 田面水・土壌表層における有機物分解速度は, 少なくとも, 水温とソウ類による有機物生産量の2つの要因によって, 影響を受けていると考えられた.

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サツマイモ苗の取り置きが苗の発根に及ぼす影響をコガネセンガンと高系14号について2年間調査した. 苗の取り置きは1983年は18℃, 90%RH, 1985年は14.5℃, 95%RH, それぞれ弱光下で, 0, 5, 10, 15日間行った. 発根実験は, 土耕により, 28/20℃の制御環境下で行った. 得られた結果は次のとおりである. 1. 取り置き期間が延びるにしたがい苗の生重は減少し, 苗の乾物率は増加した. 苗の下位葉は10日目から枯死し始め, 15日目にはその2～3葉が枯死した. 取り置き中に苗の発根が見られ, 1983年は10日目, 1985年は15日目に最大に達した(第1図). 2. 取り置き処理により挿苗1週間後の苗当たり根数は減少した. 逆に根の伸長は取り置き処理により促進され, 平均根長が増加した. このため総根長も取り置き処理により増加した. 根の乾物重も取り置き処理で増加したが, 15日取り置くと減少する傾向が認められた. 挿苗1週間後の展開葉数は15日取り置き区で最も少なかった(第2図). 3. 各区の最大根15本の組織学的観察によると, 根の発育ステージは取り置きしたものの方が進んでいた(第3図). また, 1次形成層の活性も取り置き区で高かった. 中心柱の木化は15日取り置き区で進んでいた(第1表). 以上の結果から, サツマイモ苗の5-10日間取り置きは, 苗の活着及び塊根分化を促進することが示唆された.

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?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ??, ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ??, ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? IAA, ABA ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? . ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? . 1. ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ??, ?? ?? ?? ?? ?? ?? ?? ?? ?? 15 ??, ?? ?? 14 ?? ?? ?? 10 ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ( ?? 2 ?? ). 2. ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? 15 ?? ?? ?? ?? ?? ?? ?? ?? ?? ??, ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ( ?? 3 ?? ). ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? . ?? ?? ?? ?? 5-10 ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? . ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ??, ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ??, ?? ?? 14 ?? ?? ?? 5-10 ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ( ?? 4 ?? ). 3. ?? ?? ?? ?? ?? IAA ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? . ?? ?? ?? ?? ?? ABA ?? ?? ?? 5-10 ?? ?? ?? ?? ?? ?? ?? ?? ?? ??, 15 ?? ?? ?? ?? ABA ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ( ?? 1 ?? ). 4. ?? ?? ?? ?? ?? ?? ??, 5-10 ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ??, ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ??, ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? . ?? ??, ?? ?? IAA ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? .

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?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ??, ?? ?? ?? ??, ?? ?? ?? ?? ?? ??, ?? ?? ?? ?? ??, ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ??, ?? ?? ?? ?? ??, ?? ?? ?? ?? ??, ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ( ?? 1 ?? ). ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? 3 ?? ??, ?? ?? ?? ?? ?? ?? ?? ( ?? 1 ?? ), ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? . ?? ??, ?? ?? ?? 4 ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ??, ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ??, ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? . ?? ?? (28.4kg/10a) ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ( ?? 2 ?? ), ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? 115∼125% ?? ?? ?? ?? ?? ??, ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? . ?? ??, ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ( ?? 3 ?? ), ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ??, ?? ?? ?? ?? ?? ?? ?? ??, ?? ?? ?? ?? ?? ?? -1 ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? 110∼120% ?? ?? ?? ?? ?? . ?? ??, ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? 5∼18% ?? ?? ?? ?? ??, ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? -1 ?? ?? ?? ?? ?? ?? 6∼8% ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? . ?? ?? ?? ?? ?? ?? ??, ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ??, ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? .

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岐阜県海津郡の木曾, 長良, 揖斐の三河川に囲まれた地方は, 海抜60cm位の低地で, 治水の十分に行われない明治末期までの150年間に堤防の決壊は44回にもおよび, 水害のため稲は3年に1度しか収穫できなかったといわれる. そのため農民は鋭意, 水害に強い稲品種を選択してきたといわれ, 清水太八(1912)^*は水害に強い品種として11品種をあげている. そのうち5品種(目黒, 強力, 七福神, 青鬼, 竹成)が農水省農業生物資源研究所に保存されているのを見出したので, その深水下での節間伸長性をしらべた. これらの在来品種は, 連続照明下で栽培させた場合は多少の程度の差はあるがいずれも, 花芽分化なしに深水下で節間伸長性を示すことを認めた. また, 深水中で伸長した節間の節よりは, 不定根の発生がみられた. しかし, 熱帯アジアの浮稲品種と比較すれば, 節間伸長性も, 高節位よりの発根性も, その程度ははるかに及ばない. GA₃は外から与えると, 水に浸漬後の節間伸長を促進し, また浸漬前にGA生合成阻害剤で処理すると, 深水伸長性は全くみられなかった. これらの日本在来稲品種の深水下の節間伸長においても, 内生GAが重要な役割を演じているものと推定された. 従来, 日本稲においては花芽分化なしの節間伸長は, 高濃度のGA₃で処理した時などの外には, 知られていないので, この在来品種における深水下での節間伸長性の存在は, 育種材料としても興味あるものと考えられる. (^*清水太八, 1912, 水に強き稲の種類, 大日本農会報第367号:64-66).

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