Experiments were conducted to make clear the differences of floral induction in rice plants as affected by air temperature during short day treatment, using a daylength-sensitive variety "Zuiho". The plants of 12∼14 leaf stages were subjected to 10-hour photoperiod under various air temperatures in growth cabinets with natural light. The results obtained are summarized as follows. 1. The plants were subjected to 10-hour photoperiod under various constant temperatures; 12°, 16°, 20°, 25°, 30°, 35° and 40°C. The short day effect was largest at 30°C, and decreased with rising or falling of temperature from the optimum, 30°C(Fig. 1). Short day treatments gave no effect at 12°C or 40°C. The optimum temperature for the short day induction was somewhat lower than that for leaf emergence (Fig. 2). 2. The plants were subjected to 10-hour photoperiod under lightperiod temperature from 16°C to 40°C and darkperiod temperature from 12°C to 35°C (Table 1). Both the optimum temperature for lighperiod and darkperiod were 30°C although 25°C during the darkperiod gave the same effect as 30°C (Table 1, Table 2, Fig. 3). Short day effect decreased when the temperature was lower or higher than the optimum one. Differences in short day effect due to lightperiod temperatures were almost the same as those due to darkperiod temperatures with the exception of temperatures higher than 30°C (Table 3). When the range of temperature between the light- and darkperiod was 5°C, the effect of short day was almost the same as that under constant temperature throughout the both periods (Fig. 4). A smaller effect was obtained when the range was larger than 10°C.

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There is a contradictory point of view against Matsushima's diagnoses concerning the rice plant of which first bract was modified to the flag leaf. Therefore, the characteristics of the rice plant with the modified flag leaf were investigated. Three types were observed in the morphology of the neck node. The first type developed one or no primary rachis-branch and formed complete annular protuberance around the whole circumference of the neck node. This type is usually seen and is considered as a normal one. The second type had incomplete annular protuberance around the neck node and contained two subtypes. One resembled the normal type but a part of the circumference of the neck node was lacking in protuberance (Fig.1, A). The other had two or three primary rachis-branches on the neck node and a part of its circumference was lacking in protuberance (Fig. 1, B). The third type had twin or triplet whorled primary rachis-branches and had complete annular protuberance around the neck node (Fig. 1, G and D). The rice plant having a normal neck node did not possess a car or a bud in the axil of the flag leaf except for one which had a bud (Table 1). And the bud was true one of a tiller. Many plants with the other two types of neck nodes carried the axillary car or bud at the flag leaf (Tables 1, 2 and Fig. 2, A, B and C), though there were also a lot of plants having none (Tables 1 and 2). The morphology of the ear was as follows. A prophyll was absent (Fig. 3, A). Earlets were formed alternately on the two linear planes of the axis of the ear (Fig. 3, E). 0ne or two basal earlets had a bract-like structure, some of which were developed well (Fig. 3, E). One or two basal earlets had a bract-like structure, some of which were developed well (Fig. 2, B and Fig. 3, B). But it was bladeless (Fig. 3, B) and did not encircle the axis of the ear (Fig. 3, C and D). The axis of the ear was not hollow and showed a typical feature of an atactostele in the transverse section (Fig. 4, A). The number of large vascular bundles in the axis were two and almost one in the second internode and in the third one respectively, regardless of the number of diverged earlets (Table 3 and Fig. 4, A, B and C). The morphology of thirty-nine buds out of forty-three subtended by flag leaves of the rice plants with the second type or the third of the neck node was the undeveloped feature of the ear mentioned above. But about the remaining four, it was undistinguishable whether they were the buds of the ear or of a tiller, for they had only a leaf-primordium-like structure in which none was contained. The lowest elongated internode of the stem was longer or the number of elongated internodes was more by one in the rice plant of which neck node type was the second or the third, when compared with that of the first type (Table 4). From these results, it is considered that the ear in the axil of the flag leaf and the bud of which morphology was the undeveloped ear are not a tiller but a primary rachis-branch. Therefore, such the flag leaf as this is the one to which the first bract has been modified. And this results in the conclusion that the second type of the neck node morphology and the third one are the characteristic expression of the rice plant with the modified flog leaf from the first bract. Then, the problem still remains about rice plants which had undistinguishable buds or none in the axil of their flag leaves, although their neck node morphology was the second or the third type. But, as their feature of the stem internode elongation differed from the rice plant with he normal neck node and was the same as the one of which first bract had definitely been modified, those plants are also the rice plants of their first bract having been modified. [the rest omitted]

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Previously, the author clarified that in rice cultivars in Hokkaido and having ten to twelve or so leaves on the main stem, the number of shoot units without crown roots frequently happened to vary among the main stems which had the same number of leaves on them⁸⁾. So, the causal factor was investigated with reference to the modification of the first bract to the flag leaf, for it was made clear that the rice plant of which first bract had been modified to the flag leaf showed the characteristic feature of the internode elongation⁹⁾. The number of shoot units without crown roots was apt to be more in the rice plant of which first bract had been modified (Tables 1 and 4, where the number of shoot units without crown roots is expressed by the position of the top shoot unit with crown roots, for the shoot units upper than this is the ones without crown roots). This tendency was superior in the rice plant having twelve or thirteen leaves on the main stem than that with eleven leaves (Table 1). Increase in the number of shoot units without crown roots in the rice plant with the modified flag leaf was attributed to the change of the internode elongation, especially to the elongation of the fourth one (Fig. 1). The frequency of the modification of the first bract to the flag leaf was about sixty to seventy percent in these rice plants and it was markedly higher than in cultivars having more leaves (Tables 2, 3 and 5). Some discussions were made on why the modification of the first bract to the flag leaf happened so frequently in these rice plants.

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[in Japanese]

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In the paddy fields, plants in the outermost row next to the unplanted alley showed a general increase in yield and growth as compared with the center row. This penomenon has been referred to as 'border effect'. Main causes of border effect are considered to be advantageous environmental factors above the ground, such as higher solar energy, air circulation, etc. However, the magnitude of the border effects and the underground factors affecting the magnitude are not fully understood. This experiments addressed the above two questions. 'Sasanishiki', japonica type of rice, Oryza sativa L., was used as materials. The experiments were conducted at the Faculty experimental paddy field in the years 1979-1981. The plots included differences in levels of unplanted distances (0, 15, 30 and 47.5 cm), nitrogen fertilized (10 kg/10a) and unfertilized, and differences in levels of plant density (11.1, 22.2, 44.4, 88.9 and 177.8 hills per square meter). Results are summarized as follows: 1. The border plants in every treatment showed higher percentages of fertil tillers, shorter culms with the shortened internodes at lower positions, and greater rate of NAR, RGR and carbohydrate accumulation during early grain ripening stage. 2. The yield increase in plants in the outermost row was greater in plots with nitrogen supply in the alley and in plots with wider unplanted distances. The lowest yield response of border plants was observed in plots of narrow planting distances. This can be interpreted as due to availability of nitrogen from the space not occupied by other plants. 3. Among different densities of plant population, the magnitude of yield response in the border plants was the greatest in the highest density plots and least in the lowest density plots )249% and 45%, respectively, in the experiments of 1981). In conclusion, the underground conditions, particulary those affecting the nutritional supply have important contribution to the magnitude of yield increase in the outer-most plants. These underground factors must be taken into account along with aerial conditions in interpreting the phenomena of border effect.

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In sugar beet plants, Beta vulgaris var. saccharifera Alef. petioles serve not only as conductive tissues but also as intermediate storage pools^{6, 7, 8, 11, 13)}. Enzymatic conversion systems of sugar should be localized within the phloem and parenchyma cells of the petiole. In the previous paper⁵⁾, histochemical detection for the presence of UDPG-pyrophosphorylase in parenchyma cells was reported. The histochemical detection for thc presence of phosphoglucomutase in the petiol tissues is described here. A histochemical method described by YANO¹²⁾ for detecting the enzyme in cryostat sections of rabbit liver and muscle under light microscope was employed with slight modification in the present study. The composition of substrate mixture is shown in Table 1. Based on the principle, shown in Fig. 1., the activity of phosphoglucomutase was detected as the formation for diformazan which deposited in the cells in the form of dark blue granules. Procedure: Nonfixed hand-sections obtained from the raw-petiole of sugar beet cv. HKE-20 were used. After infiltration in distilled water, the sections were incubated in the test solution covered with toluene for 3 hours at room temperature (20°C). Prior to observation with a light microscope, the sections were mounted with glycerin after washing with distilled water. Histochemical observations: Dark blue granules which indicate the site of phosphoglucomutase activity were found to appear in cells of the sections that incubated in the test solution (Figs. 2-A∼E and 4-B). They were not found in the sections incubated in the substrate free mixture (Fig. 4-A). The reaction products were intensely detected in cytoplasms of guard cells (Fig. 2-B), phloems and bundle sheaths (Figs. 2-C and D). In parenchyma cells, the reaction products were moderately detected in cytoplasms, although intense reactions were detected around the nuclei. However, nuclei themselves were always negative (Figs. 2-A and E). The inhibitory effect of bellirium ion (BeSO₄·4H₂O), a specific inhibitor of the enzyme, was detected only in the concentration of 2 mM in the adult petiole, although this was found in the range from 4 to 5mM in the young petiole (Fig. 3). The presence of intense reaction of phosphoglucomutase in guard cells, phloems and bundle sheaths may indicate the occurrence of an active sugar metabolism in these tissue cells. In the parenchyma cells, the presence of intense reactions of the enzyme around the nuclei may suggest the interrelationship of the sugar metabolism occurred in nuclei and in cytoplasm.

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The effects of leaf disc size, extraction solvents and the time of heating and cooling on the ATP extraction from the green leaves as well as the optimal MgSO₄ concentration and pH on the luciferin-luciferase enzyme reaction system with ATP were investigated. Leaf discs were prepared by using the leaf disc-punch from the fully expanded top-leaf blade of rice (Oryza sativa L.) and soybean (Glycine max Merr, ) plants grown in the glass house or in the field in pot. These discs with buffer solution or distilled water (D.W.) were dipped in the boiling water for several minutes and then cooled for several hours with mild shaking under the cold condition (3°C) to extract ATP from leaves as a disc. ATP in the extract was determined from the luminescence intensity induced by the enzyme reaction between ATP in the extract and luciferin-luciferase in the FLE-50 (Sigma Chem. Co.). Luminescence intensity was measured by ATP photometer (Type 2000, SAI Tech. Co. USA). Following results were obtained: 1. In this experiment, 15 ml of 13.33 mM MgSO₄ were added to FLE-50, which contained 6.67 mM MgSO₄ as a kit, to give 20 mM MgSO₄ as a optimal concentration for enzyme reaction (Fig. 1). 2. Luciferin-luciferase reaction with ATP was inhibited by potassium-phosphate buffer and CaCl₂, but not by HEPES- and Tris-buffer and D. W. (Table 1). Then, 50 mM HEPES buffer (pH 7.2), which optimal pH of this enzyme reaction was 7.2-7.4 as same as explained in the FLE-50 kit, was used as the buffer of extraction and determination of ATP in the leaf discs. 3. The effective extraction of ATP from the discs by the boiling water extraction method was obtained by using the discs with 2.0-3.0mm diameter in size with HEPES buffer (pH 7.2, 5 pieces/2.5 ml), heating them for 0.5-1.0 min in the boiling water and subsequent cooling for about 5 hr at 3°C (Fig. 2 and Fig. 3). 4. The boiling water extraction method was compared with the cold perchlorate extraction. The data obtained by the boiling water method were consistently higher than by perchlorate extraction method (Table 3). 5. Each variety in rice and soybean plants has different ATP contents within the limits of experiment. The ranking of these varietal differences in each plant did not change between experiments except Shin No. 2, one of soybean variety (Table 4). 6. There were no clear correlationships between ATP and chlorophyll contents in each plant (Fig. 4). These results mentioned above were discussed with reference to the availability of the boiling water extraction method for ATP extraction from green leaves.

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The object of this report is to clarify the dry-matter accumulation habits and to investigate the effects of climatic factors on the dry-matter production and yield of maize for whole-plant silage in the north-marginal area in Japan. Experiments were repeated in the same method except variety and planting date over 6 years (1976∼'81). Heigen-wase (early hybrid) was used over a 3-year period (1976∼'78), and Wase-homare(early hybrid) was used over a 4-year period (1978∼'81). Both varieties were planted on 4 or 3 different dates from mid-May in each year. The dry-matter weight in each organ was measured at 3-week intervals, from 6 weeks before silking date, and dry-matter yields were measured at harvesting date. The results obtained were as follows: 1. The dry weight of leaf blade showed little variation during the ear-filling period. The dry weight of stem (culm+leaf sheath+tassel) increased slowly during the first half of the ear-filling period and then showed increase or decrease during the latter half of the ear-filling period. The dry weight of ear )kernel+cov+husk) increased linearly, and showed extremely large differences among years. The dry weight of top was affected remarkably by the weight of ear, which resulted in large differences among years in the dry weight of top (Fig. 2 and Fig. 3). 2. Top dry weight growth rate (CGR) changed like a shape of unimodal curve with a peak value occurring at about silking in each year, and showed a rapid decrease during the ear-filling period. Net assimilation rate(NAR) showed a tendency to have a maximum value during the period of 3 weeks before silking. Leaf area index (LAI) reached a maximum at silking or 3 weeks after silking and then decreased gradually (Fig. 4). 3. CGR in each growth period indicated highly positive correlation with different growth parameters: with LAI during the period of 6∼3 weeks before silking, with NAR during the period of 3 weeks before silking (period II) and the first half of the ear-filling period (period III), and with both of NAR and LAI during the latter half of the ear-filling period (period IV), respectively (Table 1). 4. CGR in the period II positively correlated with temperature of daily mean, maximum and minimum, and sunshine hours, but negatively correlated with rainfall. CGR in the period III and IV indicated highly positive correlation with the three temperature factors described above, sunshine hours and solar radiation, and indicated the highest positive correlation with daily maximum temperature. But CGR in the period IV indicated negative correlation with daily mean wind speed (Table 2). 5. Stover DM yield indicated positive correlation with CGR in the period II. Ear DM yield indicated highly positive correlation with CGR in the period III and IV. Although total DM yield was affected by the ear ratio, total DM yield indicated the highest positive correlation with CGR in the period III and IV. Both of percentages of dry-matter in ear and whole-plant, and ear/total ratio indicated highly positive correlation with CGR in later growth period. CGR during the latter half of the ear-filling period showed the greatest influence on yield and quality of maize for whole-plant silage (Table 4). 6. From above results, it was concluded that increase of CGR during the latter half of the ear-filling period was essential for stable and high yield and quality of maize for whole-plant silage under severe conditions in the north-marginal area.

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[in Japanese]

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[in Japanese]

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[in Japanese]

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The translocation of nitrogen and carbon from leaves to roots of the rice plant at vegetative stage was investigated using ¹⁵N and ¹³C as a tracer, emphasis being placed on the node position of the roots. The whole shoot of the plant at the stage of developing the 12th leaf (12L) and the 9th nodal roots (9nR) was fed with ¹³C-labeled CO₂ gas for 60 min after being sprayed with ¹⁵N-labeled urea solution, and the fate of ¹⁵N and ¹³C in the plant was followed over 12 days. A rapid transfer of ¹⁵N and ¹³C from the expanded leaves (3-11L) took place with-in 3 days and 1 day respectively, then a gradual transfer followed during the chase period. ¹⁵N and ¹³C were translocated to all parts of the plant, preferentially to the expanding leaf (12L) and the root system. Among the roots the upper roots (9nR) were the largest sink of ¹⁵N and ¹³C expected by the expanded laves. The lower roots (≤5nR, 6nR and 7nR) received substantial amount of ¹⁵N as well as ¹³C from the leaves, although they did not increase their N and C contents. Within 1 day when both translocated ¹⁵N and ¹³C in each nodal root increased, the ratio of ¹³C gain to ¹⁵N gain was the highest in the upper roots (9nR). The ratio decreased as the node position of the roots lowered. Whereas the ratio of ¹³C loss to ¹⁵N loss in the expanded leaves within 1 day was higher in the upper leaves (9-11L) than in the lower leaves (3-8L). The results indicate that not only the young upper roots but also the old lower roots are the sinks of the nitrogenous compounds translocated with the photosynthetic assimilates from the expanded leaves. The difference in the ¹³C/¹⁵N ratio among the nodal roots suggests that the C/N ratio of the foliar products imported by the roots varies with their node positions; lower roots receive the products containing more rich in N relative to C as compared with upper roots. Each leaf of different nodes seems to play a specific role to supply the root system with the products of varietical C/N ratio; upper leaves supply the products of higher C/N ratio mainly to upper roots, while lower leaves feed the products of lower C/N ratio to lower roots.

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