In the previous article, it was suggested that oxygen consumption by seed coats was associated with a mechanism of dormancy in Bupleurum falcatum seeds, and that the seed coats contained germination inhibitors. In these experiments, the germination inhibitors which were related to the oxygen absorption, were isolated from the seed coats of Bupleurum falcatum seeds, and then, the physiological properties of germination inhibitors had been investigated. The results obtained are as follows: 1. The germination inhibitors were extracted with methyl alcohol from such experimental materials as intact seeds, stripped seeds and seed coats. The inhibition by the extract of the seed coats showed higher activity than other two materials. 2. The ethyl ether fraction obtained from seed coats clearly inhibited the germination in lettuce seeds, and the rate of oxygen absorption in water by the ethyl ether fraction was also higher than the other two fractions. 3. Ethyl ether fraction was divided into three parts: precipitate, sodium hydro-gencarbonate fraction, and sodium carbonate fraction. Significant inhibition of germination in lettuce seeds was recognized in the two fractions of precipitate and sodium hydro-gencarbonate. These substances were denoted as inhibitors A and B, respectively. 4. Inhibitors A and B showed the inhibition of germination in lettuce seeds and increased oxygen absorption in dormant Bupleurum falcatum seeds. The physiological activities of inhibitor B were higher than those of inhibitor A, even though the growth inhibition in lettuce seeds were only observed by inhibitor A. 5. On the paper chromatograms using the solvent of ammonia saturated n-butyl alcohol, five spots were found from inhibitor A, while six spots were from inhibitor B. But the inhibition of germination in lettuce seeds was observed only in one spot of inhibitor B which showed the typical color reaction with the phenol reagents.

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2穂型トウモロコシの生理・生態学的特性をさらに明かにするため, 着生雌穂数について異なる北交22号(2穂型系統)と北交18号(1穂型系統)の乾物生産特性を十分な土壌水分条件下の疎植区(2,560 個体/10a)と密植区(10,078 個体/10a)において, 比較・検討した。1. 8月8日(絹糸抽出期)において, 異なる数の雌穂をもった個体の分布に疎植区の両系統間で大きな差異は認められなかったが, 北交22号の2段目雌穂乾物重は, 北交18号に較べ著しく大きかった。密植区では, 北交18号の無雌穂個体の割合が, 北交22号の2倍以上認められた。2. 8月8日を中心とした前期で, 両系統の個体当葉面積に大きな差異はなかったが, 北交22号の純同化率(NAR)および個体当乾物増加速度(CGR)は北交18号より高い値を示した。3. 後期における北交22号の雌穂に対する分配率は, 北交18号に較べて高く, 稈と葉鞘に対しては著しく低いことが認められた。以上の結果から, 2穂型系統は, 高い純同化率により絹糸抽出期までの2段目雌穂の発達を促進し, さらにそのSink sizeの増大によって同化産物の効率的蓄積を行うものと推察された。

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多穂型トウモロコシにおける2段目雌穂の発現と生理・生態的諸特性との関係を明らかにするため, 多穂型一代雑種4系統およびホクユウを供試し, 2段階の密度条件(疎植-2,560個体/10a, 密植-5,050 個体/10a, 1973年度)ならびに慣行栽植条件(4,444 個体/10a, 1974年度)下に栽培し, 絹糸抽出期における諸特性と収量構成要素との関係について検討し, 次のような結果を得た。1. 単位面積当の子実収量は, 密植条件下では2段目雌穂の着生頻度と, 慣行栽植条件下では2段目雌穂の平均子実重と強い正の相関を示した(第1図)。2. 栽植密度の増加に伴う各器官の乾物重, 葉面積および収量構成要素(いずれも個体当)の減少率についてみると, 絹糸抽出期においては2段目雌穂乾物重, 収穫期においては2段目雌穂の着生頻度における減少程度が最も大きかった(第2図)。3. ホクユウを除く4系統の間では, 密植および慣行栽植条件下で最も多収を示した系統は, 絹糸抽出期における着雌穂数, 2段目雌穂乾物重およびR/L比(葉面積に対する根の乾物重の比)が最も高く, 葉身乾物重および葉面積は最も小さかった。また, 最も低収であった系統はこれと全く逆の特性を示した(第1, 2, 3, 5表)。4. 個体当子実収量は, 疎植条件下では絹糸抽出期における各器官の乾物重, 葉面積, R/L比のいずれとも有意な相関を示さなかったが, 密植条件下では, 着雌穂数, 2段目雌穂乾物重およびR/L比との間に5%で有意な正の相関が認められた。2段目雌穂の平均子実重は葉身乾物重および葉面積と強い負の相関を示し, 着生頻度は密植条件下で葉身乾物重および葉面積を除く各要素と正の相関を示した。また, 密植条件下で得られた関係は, 慣行栽植条件下でもほぼ同様に認められた(第3図, 第6表)。5. 収量構成要素と葉面積およびR/L比との関係を各密度条件を込みにして検討してみると, 各収量構成要素は葉面積指数と負, 2段目雌穂の平均子実重および着生頻度はR/L比と正の有意な相関を示した(第7表)。以上の結果から, 2段目雌穂の発現は, 相互遮蔽(ヘイ)による群落内部の光条件の悪化や密度の増加に伴う水分競合の影響を最も強く受けるものと考えられた。従って, 多穂型トウモロコシにおいては, 葉が直立で比較的小さく, 高いR/L比を持つ系統が密植条件下において多収を示すものと判断された。

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生長解析法は, 作物の生長を光合成組織としての葉面積を基盤として, 定量化するところから始った。しかるに, 個体の生育量は, 地上部生育と地下部生育との和として示され, かつ, 生長の源となる養・水分が, 根の生理活性や, 地上部-地下部の相互関連性を, 媒介として吸収され,地上部へと移動することを考慮した場合, 地上部-地下部の相互関連性と, 地下部の生理活性を定量化した上で, 個体の生育を論じる必要性が生じてくる。そこで, 筆者らは, 上記の考え方に基づいて, 個体の相対生長率(RPGR)を, 根の生理活性の程度(URA)と, 乾物の分配率(RWR), それに, 根の生理活性の強さに対する個体の生長率の程度(RAR)という, 3つの要素の積として表示する可能性を示唆した。結果の概要は以下の通りである。1. 地下部の生理活性(根のα-ナフチルアミン酸化力)や地上部一地下部の相互連関性を定量化した形での個体の生長解析法を検討すると, 以下の関係式が成立する。[numerical formula] (RPGR)=(URA)×(RWR)×(RAR) (ここで, Pwは個体乾重, Rwは地下部乾重, Root Activityは単位時間当のα-NA酸化量を示す。)従って, 個体の相対生長率は, 上記の3つの要素の積として示され, 作物群内での個体の生長を, 地下部の生理活性と, 地上部-地下部の相互関係から検討できることが示された。2. (個体の全α-NA酸化量/hr)/(根乾重)を, Unit Root Activity (URAと略記)と呼ぶ。URAの培地養分レベル間での差異はほとんど認められなかったが, 栽植密度間での差異は顕著であった。3. 個体全乾重に対する地下部乾重の割合を, Root Weight Ratioといい, RWRで表示すると, これは生産された乾物の分配率を示すことになる。RWRの栽植密度間差異は, 高NO₃-N培地(50 ppm)では, 認められなかったが, 低NO₃-N培地(10 ppm)では, 認められ, 培地養分濃度が低下すると, いずれの栽植密度においても, RWRは増加を示した。4. 根の生理活性の強さ(α-NA酸化量の程度)に対する, 個体の乾物増加率の比を, Root Assimilation Rate (RAR)と呼ぶ。RARは, 栽植密度が小さいほど大となる傾向を示し, 生育が進むにつれ, 栽植密度間で, RAR値は, 大きくなる傾向を示した。5. 個体の乾物増加率は,(1/(Pw))・(d (Pw)/dt)で示され, RPGRは生育が進むにつれ, 減少する傾向が認められた。RPGRは, 栽植密度が小さいほど大となる傾向を示し, また, 養分濃度(培地NO₃-Nレベル)を低下させると, RPGRの値も減少する傾向を示した。6. 草型の違いによる, 競合機構の違いを, Root Growth Analysisの方法で検討してみると, 低濃度培地で, A sp. (Weeping type)のRWRが, B sp. (Erect type)より大きい傾向が認められたが, 他の要素に関しては, 草型による顕著な差は, 認められなかった。

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1. Relation between the self-heat production and the deterioration in stored paddy. When the rough rice of six grades of moisture, from 17% to 22%, was stored in insulated wooden boxes of 43 l capacity, the paddy of above 19% did heat produce. The paddy which self-heated 3°C higher than the normal condition began to deteriorate (Figs. 1, 4). When the high and low moisture content rough rice were stored in either mixed or stacked conditions in a box, they heated to higher temperatures and showed more deterioration than the paddy of homogeneous moisture which was equal to the mean moisture of the mixed or the stacked paddies (Figs. 2, 4). The seal-stored paddy was lower in temperature and the density of gas (light-reflect) was higher than that in the open box. The spotted grains were fewer in the sealed box than in the open one (Figs. 3, 4). But the cooked rice was smelled. 2. Effect of controlled temperature in self-heating paddy. The newly threshed rough rice of 28% moisture was stored in wire mesh tanks (5701). The paddy that was self-heated to 40°C and that kept at 18-24°C by periodically forcing air began to deteriorate to spot grains the next days, and deteriorated 40-60% of the grains after 5 days; the latter had somewhat fewer deteriorated grains than the former. The paddy which was constantly forced by room air was dried to 17% within 6 days, and it was not deteriorated (Figs. 5, 6). 3. Effect of storage temperature on the deterioration of stored paddy. When the high moisture rough rich which was controlled at several grades of moisture content from 18% to 25% was stored at 32°C, room temperature, and then at 8°C, the high moisture rough rice deteriorated earlier and grater at 32°C; while in the temperature, deterioration was later and less. The relation between the moisture content of paddies (X) and the storable terms (Y) are shown in the following formulas, (1) log Y=4.47-0.17X in the high temperature. (2) log Y=5.01-0.18X in the room temperature (10-30°C). (3) log Y=5.31-0.18X in the low temperature. When a significant difference was recognized between (1) and (2) or (2) and (3) at these storable terms in equal moisture rough rice; the difference of storage temperature was above 10°C (Table 2). From above facts, the storage of rough rice which was higher than 19% and partial deflection of moisture was danger. If the self-heated rice was cooled there are no effect for control of deterioration.

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Statistical methods to summarize the trend of ripening process were discussed, and the varietal and the cultural differences were compared in view of the quality in rice grains. As the better methods, it was proposed to fit the regression model of intersecting straight line with a plateau to the relationship of the percentage of ripened grains on the accumulated temperature after heading. Applying this method, trends of ripening process were characterized in a few parameters, the increasing rate of percentage of ripened grains just after heading (b), the accumulated temperature attaining to plateau of percentage of ripened grains (X) and the value of plateau of percentage of ripened grains (Y). Comparing those characteristics between varieties and between methods of fertilizer application by means of analysis of variance, (b) and (X) were significant in differences between methods of fertilizer application, while (Y) showed higher variation between varieties rather than between methods of fertilizer application. Analyzing the aspects about ripening process of whole grains into the primary rachis grains and the secondary rachis grains, it was clear that both (b) and (Y) showed significant differences between methods of fertilizer application only in the secondary rachis grains. From those results, it was emphasized that the control of maturation of the secondary rachis grains through the way of cultivation should be important in view of the better quality in rice grains.

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Experiments were carried out on the new method for tracing of internode length in wheat. Measurements were made on the process of the elongation in leaf sheath, spike and internode, and the process of the height in lamina joint and spike tip. Leaf sheaths, spike and internodes were beyond the sweep of the eye, since these organs were covered by the alien organs. Soft X-rays, therefore, were applied to tracing the lenght of these organs. The heights from the ground surfacc to lamina joint and spike were traced, after these organs had come into sight from the lower lamina joints. These measurements were carried out for the main stem of the single plant. S₁:S₂:..., I₁:I₂:... indicated the order of leaf sheaths and internodes from the uppermost to the lower ones, the spike being indicated as S₀ (Fig. 1), respectively. 1. The elongation process of respective organs showed the S-shaped curves (Fig. 2). The main elongating periods differed with organs and node order. The dates of the highest activity of the elongation were repeated regularly from the lower to the upper. The dates occured at intervals of a week as a general rule, however, the dates of I₀ and I₁ were nearly the same (Table 1). 2. Immediately after the end of the main elongating period of leaf sheaths, the beginning of the main elongating period of internodes started in the same order. The date of emergence of lamina joints was synchronously observed with the end of the main elongating period of leaf sheaths in the same order (Table 2). These facts showed that the growth of the lamina joint height was due to the elongation of the internodes in the same order. The interdode length, therefore, is related to the leaf sheath or the spike lenght and the lamina joint or the spike tip height as follows: I_{n, t}= (L_{n, t}-S_n)-(L_{n+1, t}-S_n+1) [1] where, I_{n, t} is the n-th internode length at the time t; L_{n, t} is the n-th lamina joint height or the spike tip at the time t; S_n is the final length of the n-th leaf sheath or the spike. 3. The estimates of the internode length applied to the formula [1] agreed well with the measurements by using X-rays, exclusive of the starting phase in elongation. Supposing we applied the formula [1], we would be able to perform for tracing of the elongation of internode (Table 3). Judging from previous studies of rice, it should be possible to apply this formula derived from wheat to the investigation of internode length of rice.

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前報に引き続き短日処理程度の出穂まで日数におよぼす影響について, 種間と種内変異を調査する目的で, 種々の緯度に分布する稲属5種20系統を用いて実験を行った。自然日長区および短日処理20区を設け, 80日令と85日令に達した時, 12時間30分明期の短日処理を行った。そのさい, 短日処理期間中に種々の程度に自然日長条件を挿入し短日条件の累積効果を調査した。累積効果の内容によって全系統は11群に分類された。一般に栽培種は野生種に比較して, また高緯度地方に分布している系統は低緯度地方に分布している系統に比較して, いずれも短日条件の効果は累積し易い事, および短日条件中の長日条件が短かい程, また短日前処理が長ければ長い程, いずれも累積効果が大きい事, などの傾向が認められた。前報の結果と合わせ考えると, このような分析方法で示される短日処理の累積効果は, 感光性を表示する場合の一つの指標として有効であると言える。

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旱ばつがグレインソルガムの水分ポテンシャル, 拡散抵抗ならびに収量におよぼす影響を明らかにするため, 非抵抗性, 抵抗性の2品種を供試し, その品種間差異について検討した。旱ばつ時の水分ポテンシャル, 拡散抵抗には品種間差異が認められ, 耐旱性品種のC 42yは, E59にくらべ水分ポテンシャル, 拡散抵抗ともに高かった。水分ポテンシャルの日変化は適湿条件下, 旱ばつ条件下ともほぼ同様な変化を示したが, 旱ばつ条件下の水分ポテンシャルは適湿条件下よりかなり低く, また夜間の回復もきわめて緩慢と思われた。拡散抵抗は適湿条件下でも早朝, 夕方は気孔が閉じているため高いが, 日中は低かった。しかし旱ばつ条件下では, 日中の拡散抵抗は著しく高かった。水分ポテンシャルと拡散抵抗との関係は, スレショールド型を示し, -19 barより低下すると拡散抵抗が著しく高まった。品種間に差がみられ-19 bar以下ではC 42yがE 59より拡散抵抗が高く, これがC 42yの水分損失を防ぎ高い水分ポテンシャルを維持した要因の一つと考えられた。旱ばつが穀実収量におよぼす影響は穂旱期で最も大きく, ついで乳熟期, 栄養生長期であった。品種間では, C 42yがいずれの生育時期に旱ばつをうけてもE59より減収率が低く, かつ収量も多く耐旱性品種として有望と思われた。

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The starch grains were localized in the lamina joint of the second etiolated leaves of rice plants, and an inversive and horizontal displacement of the leaves caused a sedimentation of the starch grains across the cell. Therefore, it is probable that the starch grains behave as statolith in the gravity perception mechanism of geonastic growth movement of the lamina joint. However, the sedimentation time less than about 2 hours in this experiment was much shorter than 6 to 17 hours, the presentation time reported in Maeda's previous paper. It is important to study why the latter is so long. An electron microscopical study showed the presence of etioplasts in lamina cells, amyloplasts in lamina joint cells and etioplasts containing starch grains in leaf sheath cells. The observation also implies the necessity for an attention to small size organella, e.g. mitochondria etc., for an analysis of the discrepancy between the sedimentation time and the presentation time.

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The growth of tobacco in Miyako Is., the representative district of tobacco leaves-production area in Okinawa, was researched, as compared with that of tobacco in Kagoshima, for the establishment of the best manners of tobacco culture. These results were obtained as follows; 1. The air temperature in Miyako Is. was higher than that in Kagoshima at the early growth stage of tobacco, but in that duration, the daylength in this island was comparatively shorter than that in Kagoshima (Fig. 1, 3). Those environmental conditions made little difference between the total leaves of tobacco in Miyako Is. and those in Kagoshima (Table 6). 2. Owing to the rather strong wind and comparatively small amount of the precipitation in Miyako Is., the soil was apt to be a little dry to tobacco. So, it grew more slowly than tobacco in Kagoshima at the early growth stage (Fig. 5, 7, 8). 3. But, the development of root of tobacco in Miyako Is. was relatively superior to the growth of the top, as compared with that in Kagoshima. It seemed that tobacco in Miyako Is. had adapted itself to the droughty and windy environment (Fig. 11). 4. After topping, tobacco in Miyako Is. grew more vigorously than that in Kagoshima, of which rate of dry matter production slowed down. On account of the vigorous growth at the late growth stage, the harvested leaves on the middle and upper stalk positions seemed to remain a little immature. So, the external qualities of the flue-cured leaves from tobacco in Miyako Is. was a little inferior to those in Kagoshima (Fig. 5, 6. Table 6). 5. Because of a small diurnal range of temperature in Miyako Is., the consumption of the substance by the respiration seemed to be comparatively greater at night than that of tobacco in Kagoshima. So, the dry matter weight of tobacco in Miyako Is. per unit leaf area was smaller than that in Kagoshima. It indicates that tobacco in Miyako Is. was inferior to that in Kagoshima on the efficiency in the accumulation of dry matter produced in unit leaf area (Fig. 2, Table 5). 6. When tobacco was planed on the ridge mulched with polyethylenc film which had been pitched after rain in Miyako Is., it grew more vigorously than tobacco on the non-covered ridge (conventional culture in Miyako Is.) at the early growth stage (Fig. 5, 6). As the film over the ridge interfered the supply of the moisture from precipitation into the ridge, the growth of tobacco was a little depressed just after topping. (Fig. 5, 8) But, tobacco on the mulched ridge got vigorously again after the more expansion of root system at the late growth stage, and this contributed to much yield, spoiling the external qualities of the flue-cured leaves in comparison with those on the conventional culture (Table 6).

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In order to determine the best planting time for tobacco culture in the district of Okinawa, tobacco (flue-cured tobacco variety, SC72) was planted at three different days (on January 10, 30 and February 20), and investigated about number of total leaves, growth process, yield and price per kg of the flue-cured caves, etc. in Miyako Is., the representative district of tobacco leaves-production area in Okinawa in 1976. The results were obtained as follows; 1. There was a tendency for number of total leaves to decrease as the planting time was advanced; 27.6, 30.8 and 33.0 leaves on tobacco planted on January 10, 30 and February 20, respectively (Table 1). 2. The growth of tobacco planted on January 10 was depressed on account of slightly low temperature and small amount of precipitation in the early stage. In the later stage, this tobacco showed vigorous growth and its prosperous growth was prolonged to the harvesting time. Tobacco planted on February 20 grew vigorously in the early stage, and its rate of dry matter production increased again owing to much amount of precipitation in the harvesting time. The growth process of tobacco planted on January 30 was comparatively moderate (Fig. 3, 4 and Table 3). 3. Width/length ratio of the harvested leaves on lower stalk position decreased as the planting time was advanced (Fig. 7). 4. The area of the harvested leaves was greater on each stalk position of tobacco planted on February 20 than that on the comparable stalk position of tobacco planted on January 10 or January 30, though there was not such a difference between tobacco planted on January 10 and that planted on January 30 (Fig. 7). 5. But, in dry leaf weight per unit leaf area of harvested leaves, tobacco planted on February 20 was not superior to tobacco planted on other day. On the contrary, the upper leaves of this tobacco were apparently inferior to those of tobacco planted on January 30 in dry leaf weight per unit leaf area. There was similar difference at the upper leaves between tobacco planted on January 10 and that planted on January 30. These results may indicate that the upper leaves harvested from tobacco planted on January 10 or February 20 seemed to be a little immature, in comparison with those harvested from tobacco planted on January 30 (Fig. 8). 6. Yield of the flue-cured leaves per 10a increased as the planting time was retarded, i.e., 269.0 kg, 282.8 kg and 363.3 kg in the plots planted on January 10, 30 and February 20, respectively. However, in the price per kg of cured leaves, the plot planted on Fcbruary 20 was inferior to other plots. The highest price per kg of cured leaves was gained in the plot planted on January 30 (Table 4). Judging from the results mentioned above, it is concluded that the last 10 day-period of January seems to be the best planting time for tobacco culture in Miyako Is. and the district near this island.

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"Stunted" roots of rice plants (roots less than 5 cm in full length) were investigated morphologically and anatomically, with materials taken from an actual paddy field. "Stunted" roots were identified as crown roots which stop growing soon after their emergence from the stems. According to their tip structures, "stunted" roots were classified into the following types : (1) tapering type; (2) cessation type; (3) deterioration type; (4) swelling type; and (5) other teratological types, respectively. Each type includes roots of various branching habits and also of different lengths. Anatomical investigations of "stunted" roots revealed the following anomalous behavior, as compared with the normally elongated ones : (1) a decrease in the number of cortical cell layers and also in the diameter of the stele (tapering type); (2) eccentricity of the stele in cross-sections and excessive development of the hypodermal sclerenchyma (cessation type); (3) necrotic symptoms in the cortex (deterioration type); (4) hypertrophy of the cortical cells (swelling type); and so on. Some possible relationships between the "stunted" root formation and the physical or physiological condition of the plants were discussed. Further, agricultural practices, such as nitrogen top-dressing and herbicide application, were suggested to be closely related to the formation of some types of "stunted" roots.

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The authors attempted to estimate the amount of depression in apparent photo-synthesis due to some different factors under field conditions. Here, we deal with three kinds of depression; the one due to a direct effect of current low temperature in the daytime, the one due to an after-effect of low temperature at the preceding night, and the one occurring in the afternoon on fine days in spring. 1. In winter air temperature in the field was lower than optimum for photosynthesis throughout the daytime. Therefore, it was considered that in winter photo-synthetic depression by current low temperature in the daytime always occurred throughout the daytime. This depression was larger in the morning than in the afternoon. 2. In order to confirm the existence of photosynthetic depression due to an after-effect of low temperature at the preceding night, we devised to separate the depression due to current low temperature in the daytime from the total depression. As a result, it was confirmed that on fine days subsequent to a cool night in winter, photosynthetic value in the morning was smaller than in the afternoon due to an after-effect of low temperature at the preceding night. 3. On fine days in winter slight photosynthetic depression occurred in the afternoon. This was in nature the same as the one observed on fine days in spring. 4. The photosynthetic depression due to current low temperature occurred throughout the daytime until the beginning of May. 5. On fine days in spring great photosynthetic depression due to unknown cause occurred in the afternoon. When the depression due to a direct effect of current low temperature was eliminated by calculation, this depression became greater. 6. We tried to estimate above-mentioned two kinds of photosynthetic depression on three fine days in winter. Correcting apparent photosynthesis data for the two kinds of photosynthetic depression, we calculated total amount of apparent photosynthesis during daytime. As compared with the total amount of apparent photosynthesis, the photosynthetic depression due to a direct effect of current low temperature in the daytime was 5∼20% and that due to an after-effect of low temperature at the preceding night was about 10%. 7. On fine days in spring, it was inferred that the depression due to a direct effect of low temperature decreased gradually with the progress of season, and that the depression in the afternoon was about 10%.

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Rice plants, cultivar "Mubo- Aikoku", were grown in Wagner pots under conditions of 50 per cent shade, removing about half of each panicle, foliar spraying with 5 per cent glucose or 1 per cent urea solution four times and control. Treatments were carried out during the period between young panicle formation stage and full ripe stage, at which the formation of superficial roots could be observed. Regarding shade grown plants, the length of both primary roots and secondary lateral roots as well as the density of both secondary and tertiary lateral roots were lower than those of control. Concerning panicles removing and foliage spraying grown plants, the opposite trend was true as compared with shade treatment, i.e., the investigated features of superficial roots formation were several times higher than those of control. With respect to the formation of lateral roots, visual observation showed that spraying grown plants branched up to forth or fifth order, while those of shade treatment branched only up to tertiary. The formation rate of "lion-tail-like root", was greatly different among the treatments, i.e., this rate was higher for shade plants than control, and the opposite was true with panicles removing grown plants. According to the conjecture that both panicles removing and foliar application of nutrients are favourable for the nutrio-physiological conditions of tested plants, while shade is hazard; from the above results, it can be concluded that the formation of superficial roots as well as "lion-tail-like roots" was closely connected with nutrio-physiological conditions.

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The effects of defoliation, shading, and foliar application of sugar on root hair formation and growth in crown roots has not yet been determined. The present investigation was carried out to study the morphogenetical effects of carbohydrates on the development of root hairs in crown roots. The following results were obtained. Roots of plants cultured in the control plot bore root hairs longer and more dense than those in the defoliated and shaded plots (Table 3 and 4). The foliar application of sugar accelerated the formation and growth of root hairs (Table 5). It was also found that glucose (10%) is somewhat superior to, or as effective as, sucrose and fructose in aiding root hair formation and growth in rice seminal roots cultured by "bi-media culture". It is evident that a prima facie connection exists between root hair formation and carbohydrates supplied from the top.

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イネの減数分裂期に冷温処理をおこない, 葯の発育にともなう窒素, 燐酸化合物および炭水化物含量の変化をしらべた。処理葯のたんぱく態-N, 酸可溶性-N, リピッド-P, RNA-P, DNA-P, 還元糖およびでんぷん含量は, 処理後3～4日ころまでは正常葯とほぼ同様に増加したが, その後の増加は抑制された。これらの成分の増加抑制は, 冷温処理により小胞子中期ころから始まる花粉充実不良を反映するものである。一方, 冷温処理終了時に, 正常葯含量より無機-Pおよび酸可溶性有機-Pは低下し, 非還元糖は増加していた。これらの成分の低下あるいは増加は, 冷温処理期間中に誘起されたものと考えられる。

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小胞初期に1～4日の冷温処理をしたイネの葯を, 頴花長により厳密に花粉の発育時期を揃え, 処理中の窒素・燐酸化合物および炭水化物含量の変化をしらべた。処理葯のたんぱく-N, 酸可溶性-N, リピッドP, RNA-P, DNA-Pおよび還元糖は, 正常葯含量とほとんど差はみられなかった。一方, わずか1～2日の冷温処理により無機-P含量は減少し, 非還元糖含量は増加していた。これらの変化は冷温処理により誘起された初期異常と考え, 冷温より不受精に至るまでの生理的過程について考察した。

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Two kinds of experiments were carried out to confirm after-effects of CO₂-treatments on the apparent photosynthesis, dark respiration and dry matter production of crop plants kept under normal CO₂ concentration. The following results were obtained: 1. Five crop species possessing C₈- and C₄-photosynthesis characteristics were cultured in plastic growth chambers placed outdoors for 7 to 15 days under 4 different CO₂ concentrations (160 to 3200 ppm), natural light and temperature in optimal growth seasons for each species. Apparent photosynthesis and respiratory activities of these plants were determined in the same ambient air (ca. 350 ppm). In 6-rowed barley, rice and soybean (C₃-species), the after-effects of CO₂-treatments were observed to exist. Low CO₂ (160 ppm)-treated plants exhibited higher photosynthetic activity, and high CO₂ ( 1000, 3200 ppm)-treated plants exhibited lower photosynthetic activity than those kept under normal CO₂ (350 ppm). Dark respiration was somewhat enhanced by high CO₂-treatments, but the degree was too small to cause the reduction in the apparent photosynthetic rate. In Japanese millet and maize (C₄-species), the after-effects of CO₂-treatments were scarcely observed to exist (Table 1, Fig. 2). 2. A 9 days' CO₂-treatment of rice and Japanese millet was conducted in the same way as described above. At the end of treatment, plants were transferred to a glasshouse and their subsequent growth was analyzed by use of the growth analysis method (Fig. 1). In rice, after-effects of high CO₂-treatments were clearly revealed out in RGR and NAR just after the termination of treatments, disappearing in subsequent period. RLGR was not affected so much. In Japanese millet, a C₄ species, these after-effects were comparatively small. Low CO₂-treatment somewhat promoted RGR just after the termination of treatment (Table 2, Fig. 3). 3. From these observations, it was concluded that CO₂ concentration in the atmosphere gives after-effects on photosynthetic activity of plants, with high CO₂ concentration (above 1000 ppm) decreasing the potential of photosynthesis by some factors (for example, increase in stomatal or mesophyll resistance, etc.) other than dark respiration.

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In the previous paper, the conversion efficiencies (Eφeff) of photosynthetically active radiation (PhAR) in net photosynthesis of rice and soybean plant population were reported. In the present paper, with an object to estimate the conversion efficiency (Eφeff(g)) of PhAR in gross photosynthesis of crop stands, attempts were made to detail the expression of respiration. For this purpose, in accordance with McCree's formula, respiration rate was divided into following two components, i.e. the maintenance and consutrctive respiration. The results obtained were as follows; 1. Dark respiration rates (maintenance and constructive respiration) per unit dry weight of soybean were higher than rice plant, especially in leaf and fruit (ears or pods) (fig. 1). 2. Dark respiration rates of rice plant population (per unit ground area) were higher than soybean population, in spite of lower respiration rate per unit dry weight in rice. That was caused by the fact that the dry weight per ground area of rice plant population were higher than soybean (table 2). 3. As both of the conversion efficiency (Eφeff) in net photosynthesis and dark respiration rate R of rice plant population were higher than soybean population, the conversion efficiency (Eφeff(g)) in gross photosynthesis of rice were higher than soybean. Eφeff(g) were 5.35-12.74% and 4.18-9.14% for rice and soybean plant, respectively (table 3). 4. Maintenance coefficients m were found almost same in both plants but the maintenance respiration rate Rm of rice were always higher than soybean (table 5). The maintenance respiration rate Rm of crop population increased with accumulation of dry matter, and it exceeded more than a half of dark respiration rate (table 5). Therefore, it would be desirable for the crop to have lower maintenance coefficient for saving loss of dry matter in maintenance respiration. 5. Despite very little difference in dry matter production efficiency Yg and maintenance coefficient m between rice and soybean plant population, there was a clear difference in Eφeff(g) in gross photosynthesis. Those must be caused by the fact that the absorbed energy needed for unit gross photosynthetic production was different in both crop stands (table 5).

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In this study, three experiments were conducted to clarify the effect of subambient oxygen concentration during light or darkness on the growth, especially the leaf expansion of rice plant (Oryza sativa L. cv. Norin No. 18) in C₃-plant and barnyard millet (Echinochloa crus-galli Beauv. var kasaharae Ohwi) in C₄-plant. Exp. I. Seedlings of rice plant and barnyard millet were grown for 7 days under four experimental conditions, that is, 21% O₂ during both light and darkness, 21% O₂ during light and 2.5% O₂ during darkness, 2.5% O₂ during light and 21% O₂ during darkness, and 2.5% O₂ during both light and darkness. The growth parameters of both plants were investigated at the start and the end of each experiment. Exp. II. The leaf elongation rate during light or darkness of both plants was measured in the phytotron (constantly 20, 25 and 30°C) and outdoors under normal air condition. Exp. III. Seedlings of rice plant were grown for 7 days under two experimental conditions, that is, 21% O₂ during both light and darkness, and 2.5% O₂ during light and 21% O₂ during darkness. The leaf elongation rate during light or darkness was measured. The results obtained are summarized as follows: 1. The dry matter production (ΔW) and relative growth rate (RGR) of rice plant were enhanced with 2.5% O₂ during light, but not during darkness. Those of barnyard millet were little affected by 2.5% O₂ during both light and darkness. This increased growth occuring only in light is related to a reduction in photorespiration. 2. The partitioning of assimilates in both plants was controlled by 2.5% O₂ during light, but not during darkness, that is, unloading of assimilates to the leaf blades decreased and that to the roots increased. 3. Increase of leaf area, and relative growth rate of leaf area (RLGR) of both plants were unaffected by 2.5% O₂ during both light and darkness. However, plant height, and the area of the leaf blade which emerged and fully expanded in both plants during experimental period decreased by 2.5% O₂ during light similar to that previously observed for continuous exposure, but were unaffected during darkness. The number of tillers in both plants increased by 2.5% O₂ during light, but not during darkness. 4. The leaf expansion of rice plant during both light and darkness was suppressed by 2.5% O₂ during light. These results suggest that this O₂ process which controls the leaf expansion and the partitioning of assimilates is directly or indirectly related to a light reaction.

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