1. Concerning the growth of womr crop plants in their own community, 【○!a】relation between the magnitude of whole plant in terms of dry weight per unit area or average hill (W) and that of parts -leaf blabe (F) and the rest (C), or root (R) and top (T)- or leaf area (f) were inquired, and 【○!b】some aspects deduced from these relations were discussed in conection with dry matter production and its distribution to parts in crop plants concerned. 2. Data used for the purpose were collected from the results of field experiments organized by Professor Togari in response to JIBP/PP and granted by the Ministry of Education, carried at seven locations for rice, five location for soybean, and each three locations for corn and sugar beet, in 1966-68. The author was one of the member incharge of rice plant at Konosu. At each place, one or two varieties adapted to each locality were cultivated under such condition as to get maximal dry matter production with reasonable economic yield. Total and partial dry weight or leaf area was measured four to six times with almost three weeks interval. 3. Throughout the growth of crop plants concerned in their own community, relations berween the magntiude of W and that of F, C, R, T, or f can be represented by formulae as follows (figs. 1, 3, 5) [table] Relations in this table seem somewhat different at early stage of growth, when the ratio of F/W in likely to stand constant. That is to say, the terms higher than the second order are negligibe in F-W equations (Fig. 2). 4. In cases of rice and soybean, the meximum of F or f appears at the time when W takes a value of μ/2ν or ε/2ζ, showing the value of μ²/4ν or ε²/4ζ, respectively. The time of appearance of F(max) is generally preceded by that of f(max). In a normal growth pattern of corn and sugar beet, F-W curves show maximum or minimum point before or behind the point of inflexion (namely, 3μλ<ν²), but, in case of sugar beet grown in warmer region, the sitllation is different (Fig. 3). Excepting the latter case, a positive linear regression is seen between values of ν/3λ and μ/ν within the extent of 3μλ<ν²<4μλ, and between values of μ nad ν (Fig. 4). 5. Relations between dry weight of parts, C/F, R/T, or their reciprocals can be expressed as functions of W, and, in the actual growth of a certain plant, those are indices of the magnitude of W (Fig. 7). 6. Differential forms such as dF/dW, dC/dW, dR/dW, dT/dW should represent the distribution ratio of dry matter increment to each part. As it is obvious that dF+dC = dR+dT = dW, dF/dC, dR/dT or their reciprocals are also dry matter distribution ratios between F-C and R-T, respectively. And those are coefticients therein, such as μ, ν, λ, in F-C or ρ, σ, τ in R-T. In respeet of dry matter reproduction, dF/dW or dF/dC should be of importance. All these distribution ratios are also expressed as functions of W. 7. If the formula of dry matter inerement by Monsi, ΔW=(p-r)F-r'·C where, p:rate of photosynthesis r and r':rate of respiration in F and C in which F and C are eliminated by substituting F-W and C-W equations, is integrated with respect to time (t), handling provisionally the rates of photosynthesis or respiration as constant, W-t equations can be obtained, representing a bfsic relation between growth and assimilation, dissimilation or dry matter distribution. These W-t equations are interpreted graphically as logistic (sigmoid) curve in cases of rice or soybean, and as W_shaped curve in cases of corn or sugar beet (if F/W ratio is constant at early stage of these crop plants, W-t relation is exponeptial). These curves may not fit to actual growth curves as they are, because of changes in rate of the physiological functions. [the rest omitted]

View full abstract

Intact or excised tobacco root tips and tobacco anthers were incubated in various gas conditions, in order to determine the effect of exygen concentration upon the mitosis of root apex. The results obtained were as follows: 1. The mitotic index of root apex cells showed that the rate of cell division was highest at the position of the differentiation of sieve tube cells in transverse sections. 2. The optimum concentration of O₂ for the cell division in root apex of the intact seedlings was around 7ppm, but in the media of 24 ppm and 1 ppm the mitosis was arrested. Furthermore, some differences in the diurnal variation of cell division was found among the concentration of O₂. 3. In the air or in the gas containing l00% oxygen, the mitotic ratio of excised root tip rapidly decreased in 4 hours after the treatment, but in the atmosphere of industrial nitrogen the decrease of mitotic index was obviously retarded. Exchange of nitrogen to air accelerated cell division, and in consequence, decreased mitotic index rapidly. 4. Meiosis was quickly accomplished in oxygen, whereas in nitrogen it proceeded slowly.The auther concluded from the experiment descrived above that the exposure to oxygenlack or surplus, all have the effect of preventing cells from entering mitosis, i.e. passing from interphase into prophase, and that the former represent an arrest of the proceeding of nuclear division phase.

View full abstract

Flax plants (var. Saginow No. 1) were grown in pots under different day length (8. 12, 14.and 16 hours). The length of the plants became longer in long days, and the flowering was promoted by the long days. However, in the short day the growth of the plant was restrained and the flowering was delayed. The number and growth of the basal branch sprouted from dicotyledonal axile increased in the short day. The long day condition increased the yield of the fibers and enlarged the diameter of the fiber cells, but the cell wall thickness of the fiber cells became larger in the plants cultivated in short day such as 8 hours. The fibers of better quality were obtained in the short day, for their fibers contained larger quantity of α-cellulose than those in the long days such as 12, 14, or 16 hours. However, in the short day such as 8 hours the lignin contents became larger than those in the longer day length plots.

View full abstract

[in Japanese]

View full abstract

In the previous work, a survey of acid soluble nucleotides in whole rice plants was carried out at their different growth-stages, and only adenosine nucleotides were found to show the remarkable change at the ripening stage. The present study was done to make clear which part of the rice plant is attributable to these changes. Rice plants were harvested at one month after heading and divided into grains and leaved including culms. Nucleotides were extracted from each sample and fractionated. Furthermore, nuclectides were surveyed on the plant whose ears were cut off at the flowering stage, and the pattern of nucleotides was compared to that of the non-treated plant. Seventy-two grams of each plant part were homogenized with 0.6 N cold perchloric acid in a cold room. The extract was concentrated in vacuo and fractionated with Dowex-1 anion exchange column chromatography. Stepwise elution of "HC1-NaC1" system was carried out. Outline of the method was illustrated in fig.1. The ion exchange chromatograms of the extracts from rice plants were shown in fig. 2. In this figure, the following materials were used :(a); grains, (b); leaves and culms, and (c) ;leaves and culms of the plant whose ears were cut off at the early flowering stage. The nucleotides in each peak were identified by the following measurements; the position of the peaks on the ion exchange chromatogram, absorption spectra (210-310mμ), absorbance ratios (250mμ/260 mμ, 280 mμ/260 mμ, and 290 mμ/26Q mμ) and paper chromatography. As shown in fig. 4, each peak-VI from the samples (a) and (c) contains ADP-glucose (adenosine diphosphate glucose). As shown in fig. 2, grains contained ADP-glucose (peak-VI) but leaves and culms little. By the cutting off of the ear, ADP-glucose was accumulated in the leaves and culms. The appearance of peak-VIII, which contains ATP (adenosine triphosphate), was also similar to that of ADP-glucose. But, the accumulation of ATP by the cutting off of the ear was not clear as compared to ADP-glucose. Peak- VII, which contailns UDP-glucose (uridine diphosphate glucose), appeared in all samples. Peak-V appeared typically in leaves and culms, but the substance responsible for this peak may not be the nucleotide. Localization of these nuclectides between each sample was summarized in table 3. As shown in this table, UDP-glucose and UTP (uridine triphosphate) uniformly existed in every part. Adenosine nucleotides such as AMP (adenosine monophosphdte), ADP-glucose and ATP, and uridine nucleotides such as UMP (uridine monophosphate) and UDP (uridine diphosphate) existed a small amount in the part of leaves and culms, but there were large amounts of these nucleotides in the part of grains. By the removal of the ear, AMP, ADP-glucose, ATP and UMP accumulated in the part of leaves and culms. From the results of the present experiments, adenosine and uridine derivatives were found to be rich in the ripening rice plant. But other nucleotides such as cytidine mono-, di-, and tri-phosphate were little. These results were also observed by Asada and Kasai. They reported that the rather high content of uridine derivatives in the ripening ricd grains is of interest for their special role in the metabolism of sugars. But the present auther wants to point out that ADP-glucose may take a role in the biosynthesis of starch in the ripening rice plant as indicated by Murata et al. Because ADP-glucose was present only in grains but UDP-glucose was uniformly present in the ripening rice plant.

View full abstract

Morphology and development of proteoplast or protein-forming plastid in rice endosperm tissue were studied electron microscopically. Proteoplast deposition commences at the 6 th or 7 th day from anthesis. The proteoplasts were found to be abundunt in the peripheral part of the endosperm, and their number decreased with decreasing distance from the center. Proteoplast has an outer membrane which is composed of two or three, or partially more layer of thin lamella, and it encloses a protein body of almost round shape. Protein bodies in the young stage of development are almost l-1.5 μ in diameter, and those in the mature cell are of 3- 4 μ. A few electron-denes areas are present in the periphery of the protein body. The internal structure of protein body in the young stage (less than 1 μ in diameter) is uniform in electron density. However, protein bodies in the middle stage (1-2μ in diameter) and in the mature (2-3μ) have two or more concentric zonal structure which consists of electron-dense and -thin zones arrayed alternatively. The respective zones have a width of almost 0.3 μ or more. The greater magnification of the protein body usually appears to have a number of minute granules. They show exceedingly high electron density, and are of diameter approximately 200Å. They are superior in number in the electron-dense zone than in the electron-thin zone. In some proteoplasts, an additional protein body is formed within the enclosure of outer membrane by the tinle when it enters the middle stage. Many of these proteoplastst talce on an amoeba-like form and some of them show the constricted forms. These findings may suggest that the proteoplast has, to some extent, the self-propagation nature.

View full abstract

[in Japanese]

View full abstract

The authors found out from the results of previous experiments that some morphologicali changes of corn plants by the wilting treatments were due to the raising of auxin level in the neighbouring of nodes, but it has been unknown what is a main cause in its process, namely, whether the raising of tryptophan (TTP) as the precursor of IAA produced of common proteins by hydrolysis or the conversion of bound auxin to free auxin. In order to discuss these problems, the spray treatments on corn plants with tryptophan (TTP) and naphthalene acetic acid (NAA) solutions were tried. 1. Both NAA-spray treatment and TTP-spray treatment on corn plants accelerated the internodal elongation, and the differential influences have beep observed remarkably in the case of the former treatment in comparison with the latter. The former made the interrnodal elongation accelerate considerably on each internode which had finished their elongation or was elongating vigorously. On the internodes which were going to elongate, the latter made those elongation accelerate, but the former made them reduce even with lO ppm solution. 2. The slack influence appeared on the elongation of leafblades under TTP-spray treatment, because each of leaves appeared after the treatment was made to increase in length. NAA-spray treatment have influence on the elongation of all leafblades which were elongating and it accelerated those elongation directly with lOppm solution, but reduced with lOppm solution. 3. The influence of TTP-spray treatment on the growth of born plants was confirnled repeatedly and the results were like the wilting treatment that brought on the increace of the length of internodes and leafblades. 4. It seems that the increase of auxin content in the neighbouring of nodes under the wilting condition is due to the raising of TTP produced of common proteins by hydrolysis.

View full abstract

Noticing the fact that even under natural light of equal horizontal intensity, the rate of carbon assimilation of a rice plant population was not always equal. The authours examined the relation between the percentage of the amount of diffused light to the total amount of sunlight and the light curve of carbon assimilation under natural conditions. 1) When the light-curves of carbon assimilation on various days differing in the percentage of the amount of diffused light to the total amount of sunlight (hereinafter written as %-D.L.) were compared with one another, there were clear differences amnog the curves. 2) Even if a rice plant population has received the light of the same intensity on horizontal surface, the rate of carbon assimilation in the population was increased as %- D.L. was increased. In general, the light-curve of carbon assimilation in high %-D.L. was always drawn higher than that in low %-D, L, 3) As a result of the investigation reported in this paper, the authors round that the variation in light-reveiving degree of individual leaf in a rice plant population was much larger under the condition of low %-D.L. than that under the condition of high %-D.L. the change in the rate of carbon assimilation caused by the change in %-D.L. might be ascribed to the range of variation in light-receiving degree of each leaf-in the plant population. 4) The effect of diffused light on the rate of carbon assimilation differed with the plant type : the effect was much larger in the plant population with straight and errect leaves than in that with curved and drooped leaves. The light-curve of crabon assimilation of a plant population seemed to be changed with light conditions, particularly the %-D.L., and plant types.

View full abstract

In the field conditions the leaf-blades of rice plants receives sunlight on its abaxial side as well as on its adaxial side. Therefore, the authors studied the relation between the light intensity and the amount of CO₂ absorption on the abaxial side as well as the adaxial side of a sigle leaf to clarify the amount of carbon assimilation in each side respectively, using the attached flag-leaves of Norin No.25 and Kinmaze. 1) The amount of CO₂ absorption on both sides of a leaf were increased respectively, increasing the light intensity (artificial incandescent light) on the abaxial side and giving no light on the adaxial side. The amount of CO₂ absorption on the abaxial side attaind a maximum level at the light intensity of 0.6 cal/cm²/min., while that of adaxial side was still increasing. These facts mean that the abaxial side is already saturated but the adaxial side in not saturated with light. The abaxial side in always much larger than the adaxial side as far as the amount of CO₂ absorption is concerned, and vice versa. 2) The amount of CO₂ absorption on both sides are always equal when both adaxial and abaxial side are illuminated at the same light intensity. 3) If the total light intensity on both sides were equel, total amount of CO₂ absorption on a single leaf might be the largest when the light was differently projected, and might be always the smallest when the light was projected only from one side.

View full abstract

Growing rice plants in solution culture under community conditions and stopping nitrogen supply for 21 days at intervals of l0 days at successive growth stages, the authors studied the effects of nitrogen deficiency at different growth stages on the growth, grain yield, plant type and lodging resistance. The results obtained can be summarized as follows: 1. A maximum grain yield (6.84 tons per ha.) was obtained in treatment No.3 which was subjected to nitrogen deficiency for 21 days from 72 to 87 in the leaf-number index (50∼29 days before heading), and the yield was characterized by the highest percentage of ripened grains among the treatments. 2. As the treatment time delayed, the number of panicles per unit area increased, while the number of spikelets per panicle decreased in treatments after the stage of neck-node differentiation. The number of spikelets per unit area ran parallel to the number of panicles per unit area in all the treatments. 3. Since the effectiveness of the nitrogen depletion treatment on the plant growth such as the increase in number of tillers and in dry weight decreased progressively with the delay of treatment time, the treatment at relatively early stages was considered desirable for controlling the plant type in case of an enough number of tillers having been obtained. 4. The most suitable time of nitlogen depletion treatment for improving the plant type as well as increasing the percentage of ripened grains appeared to be the time of Treatment No.3 (72∼87 in the leaf-number index) and No.4 (77∼89 in the leaf-number index) from the viewpoint of the shortening in the length of upper 3 leaves and the controlling of the leaf-area in plants, while it was considered to be the time of Treatment No.2 (61∼78 in the leaf-number index) and No.3 from the view-point of the lodging resistance (which is closely related with the height of plant, the length of lower internodes and the number of culms with 6-th elongated internodes). 5. The high resistance for lodging in Treatment No.2 and No.3 could be characterized by the strong breaking strength at the base part (15 cm from below) of culms in the period of 20-30 days after heading and also by the big bending stress of culms at maturity. 6. On the basis of the facts above mentioned the most reasonable time for improving the plant type and increasing lodging resistance and consequently increasing the percentage of ripened grains as well as yield by means of nitrogen depletion for 21 days was considered to be the period centering around the time of Treatment No.3 (72∼87 in the leaf-number index).

View full abstract

The authors examined the effects of nitrogen deficiency in the middle growth period (69∼92in leaf-number index, 43∼20 days before heading) on the physiological activity of roots of rice plants grown under water cultures as well as soil cultures. The results obtained can be summarized as follows. 1. In water cultures the physiological activity of roots increases with an increasing amount of aerated air and a decreasing amount of S0₄ in the medium. 2. In case of the nitrogen supply being completely interrupted in water cultures, the physiological activity of roots considelably goes down on account of the medium being changed for the worse. However, in case of the nitrogen supply being reduced to one fifth or on tenth of an ordinary level, the physiological activity of roots scarcely goes down. 3. In soil cultures (under field conditions) nitrogen supplply have also been controlled by using nitrate nitrogen and by drying up soil, but the depression of physiological root activity can hardly be recognized. The root activity seems to be influenced by the kinds of soil, facility of drainage and methods of watering. 4. Accordingly, the depression of physiological root-activity by nitrogen deficiency in the middle growth period can hardy be recognized under actual field conditions, because the nitrogen supply is completely interrupted only in very few cases and furthermore the soil in paddy field is commonly aerated by the practise of drying up soil in the middle growth period. 5. Sometimes it can clearly be recognized the phosphats and potash, not to speak of nitrogen, are absorbed the more by the plants in the period after the nitrogen supply is temporarily interrupted, as reported by the other authors.

View full abstract

The seasonal changes in irrigation requirement were measured 1967 to 1969 in the Northwest coast of West Malaysia using three varieties, Ria (IR-8), Bahagia (sister line of IR-5) and Radin Ebos 33 (local long term variety) under flooded field condition. The evaporation ratio (E/Em, E: evaporation from water surface in paddy field, Em: pan evaporation in meteorological observation field), transpiration ratio (T/Em, T: transpiration from plant surface) and evapo-transpiration ratio (ET/Em) were mainly used for discussion in order to eliminate the weather effects. The results obtained are summarized as follows: 1. The E/Em gradually decreased due to the mutual shading of paddy plants according to the increase of leaf area index (LAI) and dry matter of plants (table 1, fig.1-3). On the contrary against for the above the T/Em and ET/Em were smaller during the early stage of growth and later on increased gradually. Two peaks were noticed the maximum tillering stage as a rule which fell roughly on 45 days after transplanting and heading stage (fig.1-2). The fornler peak was lower than the later, followed by a depression between two peaks. 2. The changes in the T/Em were largely due to the size of growth particularly LAI. However this was not always parallel with LAI and the exponential function was obtained between the T/Em per unit leaf area and LAI (fig.3). As such the T/Em per unit leaf area was constant and scarcely affected by growth when LAI became larger than 3.5. The fact and a depression of transpiration mentioned above might be largely due to the mutual shading of paddy plants. 3. The mean value of T/Em was about 0.6 and was almost equal to that of E/Em (table 1). The ET/Em showed the mean value of l.2 though it varied 1.0-1.2 during the early stage, 1.2∼1.3 during the maximum tillering stage and 1.4 during heading stage (fig.1∼2). Daily mean value of ET were 6.4 mm in the Off season (dry period) and 5.9 mm in the Main esason (wet period). It was also found that the longer in growing period, the greater in total ET. 4. The seasonal changes of ET was the dominant factor which caused the changes in irrigation requirement. Under the continuous flooded condition, the irrigation requirement including rainfall for Bahagia 130-140 days variety, was estimated approximately to be l, 340 mm (9.5 mm/day) during the 0ff season and 980 mm (7.4 mm/day) during the Main season (table 2). The 38% difference in the irrigation requirement could be attributed to the greater Em and lO days increase of growing period of the former.

View full abstract

The experiment was carried out by pot using five leading varieties for three seasons at Telok Chengai Padi Experiment Station of West Malaysia. Five varieties tested were classified into two, that is three short term varieties for double cropping and two local long term varieties. The results obtained are summarized as follows : 1. The maximum value for transpiration per day was obtained around the heading stage and lesser values were obtained during the early and later stage of growth in general (fig.1). The changes in the increase of dry matter per day was similar tendency to that of transpiration. Both the transpiration and increase of dry metter per day in the Off season (dry period) were greater as compared with those of Main season (wet period). A distinct correlation between the above two itemes was observed particularly in the short term varieties (fig.2). 2. The higher value for water requirement (water required to produce 1 gram of dry matter) was obtained during the early stage and the least in the mid-growth stage and highest were obtained during the ripening stage in general (fig.1). It was noted that the paddy plant utilized the water most efficiently when demand for water was greater (fig.2). This was particularly evident in the short term varieties. 3. The water requirement (y) and dry matter production were directly proportional to the number of days (x) from transplanting to harvest. The linear equations were shown in fig.3. From these equations, water requirement was calculated in the Main season to be as 250∼320 for the short term varieties and 430∼530 for the long term varieties. In the Bahagia (short term variety), the water requirement in the Off season was comparatively higher as compared with that of Main season. The figures in the short term varieties of Main season were not much different to that of Japan. 4. The longest term variety needed twice as much water as the shortest term variety. The grain yield was normally poorer in the long term varieties as compared with that of the short term varieties (fig.4). It can thus be concluded that the use of longer growing period variety is inadvisable as the grain yield does not commensurate with the water consumed. The findings mentioned above are rether similar to the results obtained by Mr. T. Murakami in Ceylon but partly inconsistent with the results obtained by Dr. S. Matsushima in Malaysia.

View full abstract

The results obtained in the present study were summarized as follows. 1) The amount of nitrogen in the bleeding sap of the rice plant increased toward the early spikelet intiation stage and after that decreased rapidly to the boot stage. The relative composition of amino acids in the bleeding sap chiefly consisted of asparagine, alanine and glutamine, whereas aspartic acids, glutamic acid, valine, leucine and γ-aminobutyric acid were also found to occur in small amounts. Among these amino acids, especially asparagine and alanine disappeared sensitively reflecting the the nitrogen level in the rhizosphere ranging from the early spikelet intiation stage to the boot stage, and these amino acids increased considerably in the plant when nitrogenous fertilizer was supplied at the early spikelet initiation stage. However, a preponderance of alanine was recorded with additional nitrogen supply at the full heading stage, whereas asparagine and glutamine were absent after this stage. 2) A remarkable increase in response to the higher level of nitrogen supply was observed to occur in the main constituents of the soluble nitrogen, such as asparagine, alanine and glutamine (notably increase of asparagine and alanine being greater than that of glutamine) in leaf sheath plus culms of the rice plant, whereas not so much changes as described above were noted in those of the soluble nitrogen in the leaf blade, the relative amounts of aspartic acid, glutamic acid, alanine and γ-aminobutyric acid being constant. 3) The soluble nitrogenous compounds were also investigated in the bleeding sap and various organs of the hybrid sorghum with increasing levels of fertilizer nitrogen. The constituents of the soluble nitrogen in the bleeding sap such as asparagine showed a considerable increase in response to the increasing level of nitrogen, (particularly that of asparagine being greater than glutamine), and the same tendency was observed to exist in leaf sheath plus culms. On the other hand, in the leaf blade, the response to the nitrogen level was somewhat less conspicuous as compared with that of the bleeding sap and leaf sheath plus culms. From these facts, it was suggested that the diagnosis of nitrogenous nutrition in the crop plants might be made possible by detecting the amounts of amino acids particularly in the bleeding sap.

View full abstract

[in Japanese]

View full abstract

Photosynthesis of the top leaves of rice plant (var. Norin-17) pretreated with temperature, light intensity and air-humidity of long and short duration was estimated under a definite standard condition (temperature; 28-30°C, light intensity; 7000 f.c.). Shading with 70% light reduction of long duration decreased the dry weight and nitrogen content per leaf area, and depressed the photosynthesis rate probably through changes in structure and cell numbers of the leaf. The effect of short term shading was not clear. Temperature treatments of both long and short period also affected the photosynthesis. In general, the higher temperatures increased the rate although dry weight and nitrogen content per leaf area decreased. 35/30°C seemed to be a little too high for the optimum photosynthesis, with less nitrogell concentration. Under higher temperatures the higher relative humidity of air deprssed the more the photosynthesis with the decrease in dry weight and nitrogen content per leaf area.

View full abstract

The first experiment was carried out to make clear the effect of Ethrel and ethylene on the growth and development in rice plant at various growth stages. In the next one evolution of ethylene from rice plant was measured. The results obtained were as follows: 1. Elongation of the second leaf-sheath was accelerated with 50 to 10O ppm of Ethrel, while plant height after transplanting stage was retarded. 2. The plant age was slightly promoted by the application of Ethrel at young seedling stage. 3. An abnormal elongation of internode was caused by the application of Ethrel at young seedling stage. The same tendency was found at the internode elongation stage. 4. Promotion of tillering by the application of Ethrel was clearly see. For instance in Ethrel-applied seedlints tillers emerged from coleoptile and the first leaf nodes, the axillary buds of which usually remain dormant. 5. Panicle weight was decreased by the application of either Ethrel or ethylene dueing mainly to degeneration of rachis branches and spikeles. 6. Young seedlings were damaged by a high concentration of Ethrel. The degree of damage was varied among the varieties. Generally speaking, indica varieties were more susceptible than japonica ones. The same tendency was seen by ethylene treatment. 7. Ethrel as well as ethylene caused an epinastic response in rice plants. 8. Chlorophyll destruction which is related to leaf senesence was accelerated by the application of either Ethrel or ethylene. 9. It was confirmed that ethylene is evolved from rice seedlings.

View full abstract

Having an intension to develop a rice transplanter in the back ground, this experiment was carried out to examine the influence of the paper-pot transplanting of rice on its growth and yield. This practice is familiar with the transplantation of sugar beet. Another purpose of this experiment was to establish a cultivation method of rice by using a paper-pot. The experiment was carried out in the paddy field of Atsugi farm during a period of 1966 to 1967. As a result, the following findings have been obtained : I) A paper-pot accelerated the growth of rice seedlings in a nursery bed, and the growth of rice in the initial period in the paddy field became vigorous. II) The direction of root development was regulated by the paper-pot, and the distribution area of roots tended to concentrate near the surface of ground. III) The growth was depressed after about the terminal period of the vegetative growth, thus resulting in the decline of the total dry matter weight and of ripening and the grain yield, but any significant difference was not observed. For futher development of the paper-pot cultivation of rice, such important problems as appropriate handling of water, suitable period of earthing-up, method of top-dressing and so on must be solved.

View full abstract

As a result of examining the influence of the depth of transplanting and earthing up by the difference of the seedling age on the growth and yeild of rice plant with the paper-pot, the following findings have been obtained as a tendency of an entire growth. Regarding the influence of the different time of transplanting, the growth became vary vigorous in the transplanting of twenty-day-old seedlings, especially the number of tillers became large, and the growth were slightly retarded in the transplanting of thirty-day and fourty-day-old seeldings. Further, regarding the influence of the depth of transplanting and erthing up, in comparison with the vary vigorous in shallow transplanting, it was worse in the deep transplanting. It was also observed that the vigorous growth was retarded by the practice of earthing up. As to the influence on yield, the difference due to the different time of transplanting was apparent, that is, the number of non-bearing tillers was large in the transplanting of twenty-day-old seedling in the decline of yield, and on the other hand, it became clear that the transplanting of fourty-dayold seedling as well as the practice of earthing up rose the percentage of bearing tillers and also increased the panicle weight and the number of spikelets resulting in the increase of yield. Seeing from these findings, in the practice of growing seelding by paper-pot, fourty-days-old seedlings in a rice nurcery seem to be pertinent when the fertilizing conditiones are same. It became also clear that shallow transplanting assumed an aspect of direct sowing rice and decrased ultirnately the percentage of bearing tillers and the number of spikelets per panicle, showing a declining tendency of yield. On the other hand, deep transplanting assumed an aspect of upright stading type irrespective of the difference in the seedling age, and kept down the number of non-bearing tillers resultling in the increase of yield by maintaining to a certain extent the numbers of bearing tillers. Pratice of earthing up tn shallow transplanting controls the increase of the number of non-bearing tillers and enhances ripening, and it is effective to prevent the lodging of rice plant as in the practice of deep transplanting. This trend is larger in the transplanting of fourty-day-old seedlings resulting in the increase of yield, but further research seems to be necessary as to the time of earthing up and the degree of deep transplanting.

View full abstract