[in Japanese]

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Soils with different degrees of acidity were prepared by adding varying amounts of lime to "Kuroboku" (volcanic ash soil rich in humus). The effects of different kinds of fertilizers on the growth of Italian ryegrass and milk vetch on these acidic soils were compared. Test plots established for this experiment were: standard, calcium cyanamide, phosphate deficient, potassium deficient and magnesium deficient ones. The test results are summarized as follows: (1) As the rate of germination of milk vetch showed a close correlation with the early-or late-start in germination of seeds and the plant growth in the early stage, such factors as soil acidity and kinds of fertilizers which have bearings on the plant growth are thought to have acted from the start in germination of seeds. However, th toxic effect of calcium cyanamide on milk vetch was greater in times of germination of seeds than in the early plant growth stage. In cace of Italian ryegrass, it showed little correlation between the rate of germination of seeds and the plant growth in the early stage. (2) In both cases of milk vetch and Italian ryegrass, the plant growth in the early stage showed a high correlation with the yields, but it showed poorer plant growth in the later stage of milk vetch in the cases of strongly and weakly acidic plots. (3) Marked decreases in Y₁ and activated aluminum were caused by the changes in soil pH. Namely, within the range of the pH (KCl) from 4.2 to 4.5, it showed great increases in the crop yields by the additional application of lime. Within the range of pH from 4.5 to 6.5, however, the yields of Italian ryegrass showed increases little by little by the liming, while the yield of milk vetch resulted is decreases. (4) Within the range of soil pH hi gher than 4.5, in the case of Italian ryegrass, the fertilizer effects of applications of phosphate, potassium and magnesium were greater than the raise in soil pH, and the applications of these fertilizers of optimum concentration gave particularly marked effects on the yield of milk vetch. (5) When calcium superphosphate was applied according to the conventional method to the layer at 5 cm under soil surface of strongly acidic soil (calcium- and phosphate- deficient soil), it showed greater effect by the deficiency in calcium than in phosphate.

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The treatment of seeds with four kinds of carbohydrase, four kinds of acid and its corresponding ammonium salt, ethyl ether and chloroform was carried out in order to clarify the cause of the impermeability, especially the substance concerned in it. The results obtained are as follows. 1) When yet the swelled seeds which were nearly ripe, were pretreated by soaking in a 1 per cent pectinase solution for 2 hours, the hard seed content decreased from 64.8 per cent to 8.3 per cent; and in the same pretreatment for 4 hours, the content decreased to 4.3 per cent; and in the same pretreatment for more than 8 hours, the hard seed content was not found at all. This fact indicates that pectinase prevents the hardening of seeds. However, this preventive effect was not found in cellulase, α-and β-amylase using the same pretreatment. 2) A remarkable preventive effect was found in the presoaking treatment, using the same seeds in 0.5 per cent oxalic acid and 0.5 per cent ammonium oxalate solution for 1 hour respectively: the hard seed content was decreased from 56.8 per cent to 0.8 per cent. When the same pretreatment was continued for 2 hours, the content was decreased to 0.5 per cent; and in the same pretreatment for more than 4 hours, the hard seed content was not found at all. If the treatment was prolonged, some decrease of hard seed content was also fouud in the presoaking treatment using the following combinations: 0.5 per cent citric acid and ammonium citrate; acetic acid and ammonium acetate; and hydrochloric acid and ammonium chloride. 3) The effectiveness in breaking hard-coatedness of a 1 per cent pectinase solution, and of a 0.5 per cent oxalic acid and ammonium oxalate, was not found in the case of strong hard seeds which remain hard for 51 days and 100 days respectively after placing on the seed-bed. 4) The soaking treatment with ethyl ether and chloroform gave no indications of being effective in the breaking of hard-coatedness, although it did show signs of effectiveness in the promotion of softening of seeds and germination. 5) From the results obtained, it was concluded that the pectic substances, presumably in the form of pectates, in the strophiole and palisade layers were involved in causing the impermeability of seeds, and that the impermeability was not caused by cuticula, though the cuticula controlled the velocity of seed-swelling and germination.

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In order to find out factors in "Kuroboku" of acidic soil injurious to the growth of Italian ryegrass and milk vetch, water cultivation was carried out. The results are as follows: (1) Hydrogen ion concentration: Even Italian ryegrass, which is moderately tolerant to the acidity of soil, the yield showed decrease, when the pH in the culture solution was lowered to 4.3. At pH 4.3, the percent content of calcium and phosphorus on dry weight basis was suppressed. In the culture solution at pH 4.3 the growth of milk vetch markedly decreased and the percent content of calcium and potassium was suppressed. On the other hand, the yield of milk vetch also decreased, when pH value was raised from 5.3 to 6.3. The percent content of inorganic matter was decreased, similarly to the phenomenon observed at pH 4.3. This might be one of the cause for the low yield of milk vetch on slightly acidic soil. (2) Aluminum: Aluminum at the concentration of as low as 0.5 ppm inhibited the growth of milk vetch. However the same concentration of aluminum promoted the plant growth of Italian ryegrass. For both of the forage crops, the dry weight percentage of phosphorus was severely suppressed and their growth was strongly reduced by the aluminum concentraction of 5 ppm. For milk vetch, the suppression of the dry weight percentage of calcium, potassium and magnesium was also observed. In this experiment, the decrease of phosphorus uptake was probably largely due to the precipitation of calcium phosphate in the culture solution. (3) Lime: The low concentration of both lime and magnesium was highly injurious to the growth of plant. The optimum concentration of calcium in the culture solution of milk vetch was higher than that of Italian ryegrass. According as the concentration of lime in the nutrient solution has increased, calcium percentage in the top also increased, Magnesium content in both plants dereased under this condition. However, suppression of phosphorus percentage was observed only in the case of milk vetch. Potassium percentage has increased when the concentration of lime in the nutrient solution was raised from low level to standard level. However potassium percentage in Italian ryegrass greatly has increased when the concentration of both lime and magnesium in the nutrient solution was lowered. (4) Magnesium: The optimum concentration of magnesium in the culture solution for milk vetch was lower than that for Italian ryegrass. When concentration of magnesium in the culture solution was low, lime, phosphorus and patassium percentage in the dry matter of Italian ryegrass were also low, but calcium percentage of milk vetch was increased. On the other hand, when magnesium concentration showed increase from standard level to high level, calcium percentage decreased to a level of lime defficient value and phosphorus and potassium percentage also decreased at the same time. (5) Nitrate: The optimum concentration of nitrate nitrogen in culture solution was low for milk vetch, and the yield decreased markedly according to the heightened concentration of nitrate nitrogen. This fact is thought to be the cause for the crop decrease in the case of weakly or slightly acidic soil. The increasing supply of nitrate reduced the growth severely, accompanied by the decrease in the starch content in leaf blades. Thc optimum concentration of nitrate nitrogen in the culture solution for Italyan ryegrass was higher and so much difference was not found in the starch content in leaf blades, when the concentration of nitrate was varied. (6) Nitrite: Nitrite nitrogen in culture solution was injurious to the growth of milk vetch at the low concentration of 2 ppm. However the growth of Italyan ryegrass was promoted at the same concentration, suggesting the high tolerance of this plant to the nitrite nitrogen.

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Histological aspects of growing callus tissue derived from rice embryo have been reported in this paper. Studies with callus tissue were performed with three varieties differing appearence of callus, Cody showing loosely friable callus, Kinmaze showing compact callus, and Te-Tep showing the most compact and huge tissue mass. The growth of rice callus is accompanied by division of layers or groups of meristematic cells in surface region. The callus tissue derived from the surface meristem forms newly friable callus apart from the nurse callus tissue. In the tissue mass showing compact callus, the growth is preceded by activity of both surface and inner meristem accompanied with differentiation and breaking in parenchymatous cells, such as formation of meristematic nodules, tracheid-like cells and lacuna. When grown in a medium containing 10 μM of 2, 4-D any root growth was not observed morphologically but root tip was observed in the inner callus microscopically (fig. 11, 12, 24 and 32). According to these results some discussions were dealt with on histological aspects.

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This experiment was conducted for investigation of the varietal difference of the physiological activity of the root and its relation to the growth of rice plant between a Japanese variety Norin No. 29 and a Korean variety Nongkwang. These rice plants were cultured in the normal soil (Konosu soil), humus-rich soil (Matsuo soil) and poor sandy soil (Oami soil). From the experimental result, the following varietal differences were found under the reduced humus-rich soil condition. 1. At tillering stage, the physiological root activity of Japanese variety Norin No. 29 tended to be higher than that of Korean variety Nongkwang. But at ear-formation stage, Nongkwang showed much higher root activity than Norin No. 29 under reduced condition. 2. The formation of silicicated epidermal cell of top leaf blade tended to be more influenced by reduction of soil than by the content of available silica of soils. The above cells were found to be more in top leaf blade of Nongkwang than in Norin No. 29. 3. The degeneration of spikelets was assumed to be caused by reduced condition in humus-rich soil. In this soil, the decrease in the number of spikelets of Norin No. 29 tended to be higher than that of Nongkwang.

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Studies were conducted to investigate the varietal difference of nutrient absorption between a Japanese variety Norin No. 29 and a Korean variety Nongkwang. The rice plants were cultured in the normal soil (Konosusoil), humus-rich soil (Matsuo soil), and poor sandy soil (Oami soil). From the experiment, the following differences were found. 1. No difference was observed in the nitrogen and phosphorus absorption. 2. There was a difference in nutrient absorption between the two varieties when planted in the humus-rich soil under reduced condition. Potassium and silica contents in Nongkwang were higher than those in Norin No 29.

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In case of early-season cultivation, the ripening period was moved up to warmer season by about 30 days earlier than in the case of ordinary-season culture, and the daily mean temperature at the ripening stage in the early cultural season was by 2°C higher than that of the ordinary cultural season. The experimental results obtained from the test for 4 Japonica varieties are summarized as follows: Length of the longitudinal diameter of endosperm obtained from early-season cultivation was slightly shorter than that of endosperm under the ordinary-season cultivation. While, it showed no difference in the number of cell layers of endosperm grown under the two cultural conditions. As to the dorsal radius of endosperm, the size and number of cell layers of endosperm grown in early-season were almost similar to those of endosperm grown in the ordinary-season. However, the number of starch cell layers showed somewhat decrease e in case of early-season cultivation from that in case of the ordinary-season culture owing to the increase of aleuron cell layers. The most remarkable differences were observed on the ventral radius. Comparing with the ordinary-season cultivation, early-season cultivation showed 6.0 to 22.5% decrease in length and a 8.7% decrease on an average in the number of cell layers, respectively. No significant differences were found in the lateral radius of endosperm according to the different cultural seasons. It seemed that the number of cell layers might be more invariable than the length, in other words, the cell division is less affected adversely by the enviromental conditions in the ripening stage than the elongation of the cells. The ratio of dorsal radius to ventral radius of endosperm grown in the early-season was larger than that of endosperm grown in ordinary-season. The ratio of breadth (sum of the dorsal radius and ventral radius) to thickness (twofold of the lateral radius) of endosperm gorwn in early season was less than that of endosperm grown in the ordinary-season. Namely, the shape of endosperm developed under the early-season cultural condition showed shorter and more roundish than that developed under the ordinary-season cultural condition.

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Size of endosperm and number of cell layers of endosperm were measured for 32 common paddy rice sample varieties (including 4 glutinous and 28 non-glutinous varieties), 4 varieties of large-grain strain and 4 varieties of small-grain strain. On the longitudinal diameter, some varietal differences were observed both in the length and the number of cell layers. However, in the longitudinal length of the individual cells, no varietal difference was found. Accordingly, it can be said that the length of the longitudinal diameter and number of cell layers were in proportion, and the relationship was expressed by formula: Y=28.2X+3.8, where, Y is number of cell layers and X is length in mm of the longitudinal diameter. Although varietal difference in the longitudinal diameter was generally small in case of common varieties, but, in details, a slight tendency was found in that the varieties cultivated in southern districts of Japan were longer than those prevailing in northern districts. In the dorsal, ventral and lateral radii, varietal difference was scarecely found. The dorsal radius was longer than that of the ventral one in all varieties, and that the former was superior to the latter in the number of cell layers. The dorsal radius had a relationship with the breadth (sum of the dorsal and ventral radii) of endosperm both in the length and number of cell layers. There was a tendency that varieties cultivated in northern districts of Japan were superior to those cultivated in south Japan both in the breadth and thickness (twofold of the lateral radius). No difference was found in the cellular structure between glutinous and non-glutinous varieties. There is a very fair possibility that the size of endosperm (elongation and enlargement of cells) was affected by the different cultural conditions, especially by temperature in the early ripening period. On the other hand, the number of cell layers (cell division) was fairly invariable, and the characteristics of a variety might remain unchanged even under the condition under which the size of endosperm might changed. Based upon the results of these observations, it was confirmed that the developmental process of endosperm tissue described in the Reports 1, 2 and 3 of this series using a sample variety "Yoneshiro" might safely be regarded as common with all Japanese paddy rice varieties.

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In this report, the test for Japanese upland rice varieties was dealt with, and then the size of endosperm and number of cell layers in the whole Japanese rice varieties were discussed, comparing with the paddy rice varieties reported previously. In case of the longitudinal diameter of the endosperm, upland varieties were longer by 7 % on an average than paddy ones, and the number of cell layers was also 10% over the paddy varieties. There was a positive correlation between the length and number of cell layers. This relationship was very similar to that found in the paddy varieties. As to the dorsal radius, upland varieties were almost similar to paddy ones both in the length and number of cell layers. However, number of starch cell layers in case of upland varieties was slightly less than that in the case of paddy varieties in view of the difference in the number of aleuron cell layers. As to the ventral radius, upland varieties were longer by 10 % than paddy ones, but there was no difference in the number of cell layers between upland and paddy varieties. The ratio of dorsal to ventral radius of upland varieties ranged from 0.9 to 1.6 against to 1.1 to 1.9 in case of paddy varieties. In case of a few varieties of upland rice, the ventral radius was longer than the dorsal radius. Since such case has never been found in the case of paddy rice, it was regarded as one of the characteristics of upland rice. As to the lateral radius, upland varieties were slightly superior to the paddy ones both in the length and number of cell layers. Both long and short grain varieties did not show any peculiarity ad to the dorsal, ventral and lateral radii compared with common (middle-size grain) varieties. There was no difference in the morphological characteristics between glutinous and non-glutinous varieties of upland rice. On the whole of Japanese rice varieties, varietal differences in the cellular structure of endosperm existed in the longitudinal diameter, but little or no difference in the cross section. Therefore, volume of the endosperm and whole number of the endosperm cells has a close correlation with the length (or number of cell layers) of the longitudinal diameter.

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The present experiment, with the same purpose as the 8th report, was undertaken to make clear the effects of potassium deficiency at the early growth stage on the development of tillering buds in rice seedlings by a water culture method. The results obtained are as follows; 1. Even if the potassium deficiency at the early growth stage extended for quite a long period, the 2nd tillering bud grew well and tillered. Also among the 1st tillering buds, some tillers developed. However, as the period of potassium deficiency at the early growth stage became longer, the development of the 3rd tillering buds and subsequent tillering buds was remakably in hibited. 2. After having been shifted from potassium deficient level to the standard level, the 3rd tillering buds and the subsequent tillering buds in the treated plots were superior to the standard plot in their develoment, and they developed so well as the period of potassium deficiency became longer.

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[in Japanese]

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[in Japanese]

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Flax plants (var. Saginaw No. 1) were grown in pots under different light intensities as follows: 100% (control), 43% (shaded I) and 17% (shaded II) of the solar radiation. The stem length of the plants grown in the shaded conditions became larger according to the larger elongation of internode of the stem. Dry weight of above-ground parts and bolls of the plant became smaller as the light intensity decreased. Number, diameter and cell membrane thickness of fiber-cells found in the cross section of the stem became smaller as the light intensity decreased. Particularly, the development of thickness of the cell membrane was greatly decreased by the lower light intensity. Thus, the fiber yield per plant and the fiber percentage in the dry weight of the stem became poorer as the light intensity decreased. The contents of α-cellulose in the crude cellulose were decreased by the shade treatment. On the contrary, the contents of (β+γ)-cellulose and lignin became higher by the same treatment. As the results, the shaded conditions not only reduce the fiber yield in the flax plant but also induce the reduction of the quality of the fiber.

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With a view to clarifying the yield-determining process of rice and to improving the rice cultivation as well as its growth diagnosis, the authors examined the responses of rice plants grown under different types of weather conditions to different fertilizing methods. Dividing the whole growth period of rice plants into three periods, i. e. the first, second and third, and giving a favourable weather condition (non-shading treatment) or an unfavourable weather condition (shading treatment) to each period, thus creating 8 different types of weather conditions (See Table 1) through a whole growth period, and then applying 8 different fertilizing methods (See Table 1) to 8 different rice plants which were growing under 8 different types of weather conditions, the authors carried out the experiment in a paddy field in Konosu in 3 randomized replicates during 3 seasons (1959∼1961). As a result, in every fertilizing method 8 different types of weather conditions had come to be classified into 2 types, one is an increasing yield type and the other is a decreasing one, from the response of grain yield of rice plants to weather condition in the third period (ripening period), in other words, the weather condition in the third period (ripening period) was found to have the largest influence on yield, i. e. however long the period of an unfavourable weather condition might last before heading, if it was fine in the third period, almost no detrimental effect was found on the yield of rice, while however long the period of a favourable weather condition might last before heading, if it was unfavourable in weather condition in the third period, the yield of rice was markedly reduced. Furthermore, the worst or best fertilizing method was not found through all the types of weather conditions. Two fertilizing methods, however, i.e. all the amount of fertilizer applied basically (f₁) and half applied basically and a half applied at full heading time (f₆), are quite effective in increasing yield in most types of weather conditions, and these two fertilizing methods are both characterized by increasing the percentage of ripened grains. On the contrary, a fertilizing method, a half applied basically and half applied at the neck-node differentiation stage (f₃), showed the lowest or near lowest yield in most types of weather conditions, and the fertilizing method was characterized by increasing the number of spikelets per unit area and by decreasing the percentage of ripened grains. These results can be considered to be ascribed to the fact that in the experimental field in Konosu the grain yield of rice is mostly influenced by the percentage of ripened grains and consequently the fertilizing methods which increase the percentage of ripened grains are usually much better in increasing yield than the fertilizing methods which increase the number of spikelets per unit area.

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In a previous paper, it was reported that the yield of rice of various districts in Japan was influenced by the weather conditions, particularly by the temperature and the amount of solar radiation in the ripening period. A high correlation was found between the yield and the amount of solar radiation. As to the effect of temperature, however, it was, shown that there exists a certain optimum temperature. The present experiment was carried out to apply this theory to a practical phase and to avoid the ill-effect of high soil-temperature and at the same time to increase the utilization of radiation energy of rice population by increasing reflection at the soil surface. The surface of paddy field was covered with white, foamed styrol board from the panicle-formation-period to harvest. The effect of such treatment on the soil-temperature, reflection of radiation, dry matter production and yield was investigated. A medium-term variety, Norin 29, was used. Three different seasans of cultivation were adopted. The period of mulching treatment was two, a long term one (from 40 days before heading to harvest) and a short term one (from 25 days before heading to harvest). 1. In treated plots, grain yield was increased about 10-15% compared with the non-treated plots in the standard and late cultivations but no increase in early cultivation. 2. In treated plots, daily maximum soil temperature was lowered and the reflection of radiation at soil (mulch) surface was increased. 3. In treated plots, the respiratory activity of root at later growth stages was maintained higher than non-treated plots. 4. Any enhancement of the photosynthetic activity of leaves was not brought about by the treatment. It was supposed that the favorable effects of higher activities of roots were masked by the decrease in nitrogen content in leaves as a result of the retarded decomposition of organic nitrogen in the soil due to lower soil temperature. 5. In spite of this, in treated plots the quantity of assimilated products which were assimilated after heading stage was more than that in non-treated plots. It was considered that this phenomenon was due to the increased reflection of radiation from the soil surface. 6. This treatment was effective only when it was applied at comparatively late growing stage. Before panicle formation period, it was found to be unfavorable for the growth as well as for the grain yield.

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Using a glutinous, an indica and several non-glutinous varieties on rice plants, the histochemical investigation was carried out on the localization and properties of polysaccharides, except for cellulose, hemicellulose, mucilages and gums, at various stages of seed development until 7 days after flowering. Within 3 days after flowering non-starch polysaccharides localized markedly in the epidermis of nucellus, inner integument and funicles, and they have had amylose-like properties, which were indicated by α-and β-amylase treatment, PAS and I₂ reactions. Three days after flowering, a large amount of polysacharides was found in the endosperm tissues evenly, in which three or four cell layers had been formed already. Their properties were just similar to the marginal tissues mentioned above. On the 4th day the embryo sac was almost filled with the endosperm cells. On and after the 4th, the polysaccharides as yet, were found distributed in the inner integument and funicles but did not be found in the epidermis of nucellus. Coincidently the wall between epidermis of nucellus and inner integument being thickened and the radial cell wall of the epidermis of nucellus being indistinct in cross sections the structure of the epidermis of nucellus developed as a pipe sourrounding the endosperm tissues. On the 5th day after flowering, the aleuron layers were differentiated from the endosperm tissues. Amylose-like, non-starch polysaccharides were strikingly detectable in this aleuron layers adjacent to the epidermis of nucellus. At that stage the starch in the pericarp began to decrease. From these results, it is assumed that the sugars necessary for starch synthesis in the endosperm are mainly translocated (1) from dorsal vascular bundles via funicles, (2) from marginal tissues centripetally, and (3) from dorsal vascular bundles via epidermis of nucellus and aleuron layers. It seems to locate through the pathways of (1) and (2) within 3 days after flowering but (1) and (3) after 4 days. With jodocium response, the starch in endosperm cells was shown liquid and pink in japonica varieties while granular and light-brown in CENTURY PATNA, (an indica variety) on the 4th day. The results on the amylase treatments and the jodocium reaction seems to indicate that the starch is amylose-like, consisted of short chains α-D glucopyranose units, and low molecular compound having of a glycogen-like structure in japonica and CENTURY PATNA varieties respectively. These starches increased number of branches and developed chains as the seed matured. The polymerization pattern of japonica varieties is illustrated in figs. 35 to 41. However such pattern can not be observed in CENTURY PATNA. It can be concluded that the distribution of phosphorous body in the endosperm tissue, which is considered to be related to starch synthesis, corresponds with starch polymerization in japoica varieties but not in CENTURY PATNA.

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[in Japanese]

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Transpiration of sugar beet plant was measured as a loss in weight of detached leaf blade. A leaf blade (100-300 cm²) randomly sampled from the field plant was weighed by a top pan balance immediately after sampling. After direct exposure horizontally to the sun on the balance for five minutes, the leaf blade was weighed again. In preliminary experiments, it was ascertained that behavior of stomata and temparature of detached leaf were scarcely changed for about 20 minutes after detaching. The difference between the first and the second weight may be regarded as a loss mainly due to transpiration. Among several evironmental factors, the horizontal solar radiation seemed to have a predominant influence on transpiration. When thn loss in weight was plotted against the horizontal solar radiation, a linear relation was observed and the points were fitted by a regression line. The relation of transpiration to the horizontal solar radiation was by the following equation. t/dm-2. 5 minutes=(0.35x+0.02 where t=quantity of transpiration x=mean horizontal solar radiation (cal) for five minutes This equation was applied to estimate transpiration of a whole plant and of plants in unit field area. t/plant. 5 minutes=(0.35·x·R+0.02) L/plant t/unit field area·5 minutes=(0.35·x·R+0.02) L/unit field area where L=leaf area exposed to light R=mean solar radiation in all leaves exposed to light/horizontal solar radiation

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Ultra-thin sections of root nodule of Glycine max infected with Rhizobium Japonicum were investigated by means of an electron microscope. Materials were fixed in buffered glutaraldehyde and post fixation was done by osmium tetroxide. In the initial phase of infection, bacteria were embedded in low dense material and were surrounded with plant cell wall. Cellulose layers infected by bacteria were thicker than the original plant cell wall, and the cellulose layer became gradually thin toward the tip of the infection thread. Bacteria after released from infection thread were surrounded by the membrane which might be derived from the host cell membrane, and this enclosing membrane remaind around the bacterial bodies after the host cytoplasm was broken down. Compact cytoplasm, nuclei, Golgi bodies and mitochondria were found in young nodule cells, and peripheral tissues in nodule contained many amyloplasts. Needle-like structures were obseved in vacuole of nodule cells, although their charactors were not yet clearly understood. Bacteria in nodule cell were rod-shaped, and had nuclear region with microfibrils. Electron-dense bodies were observed in nuclear region. In both ends of nodule bacteria, electron translucent parts were recognized.

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The present study was carried out to obtain some information about the effects of topping on the growth, the translocation and accumulation of carbohydrates in corn plants, using the variety "Shiratamamochi" as material. The effects of topping treatments by removing six leaves at each of the three stages, silking (T₁), early-maturing (T₂) and mid-maturing (T₃), were investigated by comparing with non-topped controls. The results obtained may be summarized as follows: 1. Toppings at any of the three stages resulted in the reduction of not only the grain yield but also the dry weights of various aphotosynthetic organs, especially of stalks, and the reductions were greater in earlier treatments. 2. In the treated plots, the chlorophyll content in leaf-blades was reduced after the treatment, but the senescence of lower leaves, which received comparatively sufficient light, was slightly delayed. 3. In the control plots, the Brix readings in stalks increased until the mid-maturing stage, while in the treated plots, these decreased immediately after the treatment. 4. As regards the variations of carbohydrate contents in various organs of the treated plots, the contents of reducing, non-reducing sugars and starch proceeded generally lower than those in the control plots, except for the temporary increase of reducing sugar content in the plots treated at silking stage. 5. Judging from the results obtained, it is evident that the reduction of grain yield by topping is due to the reduction of photosynthates which are primarily due to the loss of upper leaves, and that the greatest effect of the treatment takes place during the stages from silking over to early-maturing.

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Cyto-histological observations were carried out on the morphogenetically abnormal rice spikelets caused by a low temperature, 14∼18°C. Several cyto-histological abnormalities were found on the stamens, such as, unusually swelled anthers with stigmatic pieces, loculi with tapetal hypertrophy, plasmodium-like matters and abortive pollens etc., as seen in figs. 1∼3. The complex types of various kinds of abnormalities as seen in figs. 2, 3 and 6 were found frequently, suggesting that these abnormalities not were independent each other, but were caused fundamentally by a common physiological background of feminization. On the female organ, various grades of additional ovary formation from carpel-like structures to ovaries as seen in figs. 16∼25, were observed and a good many of the varied multi-pistils and the pistils with multi-ovaries were found in the spikelets consequently. In general, these tendencies of feminization has been said to be brought about by the level-up of the endogenous auxin content. From the fact that the morphological and cyto-histological abnormalities due to the low temperature are quite similar to those induced by the application of gibberellin, it is considered that the gibberellin-like substances may have some strong connection with the spikelet morphogenesis under the low temperature and may act to promote the feminization effects of auxin at the later stage of spikelet formation. About the outgrowth phenomena of the unknown tissues from the ovaries, they were clarified to be resulted from the followings, these were, the unusual development of integuments-particularly the outer one as shown in figs. 8∼11, the disclosure of ovule itself as shown in figs. 12 and 13, and the continuous growth of a part of the fasciated portion of two ovaries as shown in figs. 14 and 15 etc., seemingly due to the so-called "flower vegetativation". Occasionally, the vessel-like cells with partially thickened cell wall as seen in fig. 26 were found at the undeveloped embryo sac mother cell or tetrads and some their neighboring cells. Not only the irregular arrangement of egg cell, synergids, antipodes and polar nuclei in the embryo sac but also abnormal enlargement or degeneration of them, as seen in figs. 27 and 28, were also observed frequently. It was indicated that the sexually intermediate structures changed from stamens appeared most repeatedly on the stamens initiated at the palea side, above all on the right or left one which has developed at the most proximity of the female organ.

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Several methods for the quantitative extraction and estimation of nucleic acids were applied to the crop plants. The results obtained may be summarized as follows; 1. It is impossible to estimate RNA quantitatively with the Schmidt-Thannhauser procedure, because proteins are released into the RNA fraction during alkali digestion in spite of reducing the time of hydrolysis in 0.5 N KOH at 37°to 1 hour. For the estimation of RNA with the Schmidt-Thannhauser procedure, such impurities may be surmounted by the use of an ion-exchange chromatography. 2. A modification of the Ogur-Rosen procedure was proved to be satisfactory for the extraction and estimation of nucleic acids in the crop tissues, which was shown in Fig. 5. 3. The effect of temperature on the extraction of DNA from crop tissues with 0.5 N HClO₄ was tested. Three 15 min extractions at 90°were found to give maximum yields, and estimates of DNA checked with values obtained by the modified diphenylamine procedure (by Burton), because u. v. spectra of the DNA extracts were not pure,

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The results obtained may be summarized as follows; 1. A rapid decline in levels of protein and RNA in detached rice leaves was highly suppressed by kinetin of 2-20ppm, and these concentrations of kinetin (1-50ppm) inhibited the rooting largely. On the other hand, lower concentrations of kinetin (0.01-0.1ppm) promoted the rooting of such plants in spite of no effectiveness to the protein level of detached leaves. 2. As regard to the relation of the nitrogen compounds between blade and sheath in the detached italian ryegrass leaves, it was showed that protein and RNA breakdown occurred in leaf blade, and concomitantly, increased soluble-N translocated and accumulated in leaf sheath. However, in kinetin treated leaves, it was showed that levels of protein and RNA were highly maintained in leaf blade, and accordingly, content of soluble-N was very lower in both organs of leaf blade and sheath. 3. Especially, high ratio of RNA to DNA was maintained in kinetin treated leaves. and these results were close agreed with the data given by Osborne. It is suggested that kinetin, by maintaining RNA level, thus maintains protein synthesis which is essential for the survival of the the detached leaves.

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The cover-culture of tobacco is now spread all over the districts of Japan to get enough quantity of yield and the better qualities of leaves, but occasionally there happens in the cultivation the case in which the tobacco plant produces too many leaves over the moderate level. Consequently it delays maturity of leaves and adversely affects quality of leaves harvested. For removing these defects, it is essential to establish the theory for the technique to regulate number of leaves. Number of leaves of tobacco depends upon the rate of leaf initiation and days for flower-bud initiation affected by temperature and daylength. About environmental factors for the rate of leaf initiation, many investigations suggested temperature was one of the factors, but the reports dealt with tobacco plants in this subject were not found. From these reasons mentiond above, we studied on the relationship between temperature and the rate of initiation of tobacco under the cover-culture in the field. The following results were obtained. (1) The rate of leaf initiation of tobacco is dependent on temperature affected with the coverings. This effects of temperature has two steps; when the temperature rose from low level, leaves were produced faster than would be expected from the prevailing temperature, however when temperature furthermore varied upwards, it decreased the rate of leaf initiation. (2) The border of these contrasting effects is estimated at about 34°C. (3) It is moreover found that when the temperature varied, the rate of leaf initiation was immediately influenced. This fact suggests that the after-effect of temperature scarcely exists for the rate of leaf initiation.

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