In a previous paper, no profitable combination was found for the improvement of quality of the fLax fibers, when the plants grown under natural photoperiod were transferred to various durations of short photoperiod, though some effects of photoperiod on the growth and formation of the fiberous tissue were recognized. In the present paper, the reverse combinations of those applied in the previous work were designed; i.e. the plants were transferred to natural long day (14hrs 20min to 14hrs 40min) after having received 2 (SC₁), 3 (SC₂) and 4weeks (SC₃) of the short day (8hrs). The short day (S) and natural long day (C) plots were provided as controls. The results obtained are summarized as follows: 1) When short day was followed by long day, the fLax plants grew rapidly and their stems elongated more than those of the C plot on the later growth stage. The, dicotyledonal axilla of the plants transferred from S to C in the earlier growth stage grew longer than those of the S plot. The longer period of the short day treatment, the longer branches were produced. These results may be attributable to the effects of short day. 2) The dry weight of the above-ground parts of the flax plant, when transferred from S to C, reduced in comparison with that of the C plot. This seems to ascribe to the effect of short day, because of the rapid elongation of the plants. 3) When the flax plants were transferred from S to C, the effect of short day was recognized in the date of anthesis. Date of anthesis in the SC₃ plot delayed only a little compared with that of the S Plot. 4) When Short day was followed by long day, the effects of short day were recognized in the contents of crude fibers of dried stems, the number of fiber-cells and the diameter of the fiber-cells, but they were smaller than those obtained in the C plot. Short day did not affect on the thickness of the cell-wall of the fiber-cells, this value was almost the same as that of the C plot. 5) The crude-cellulose contents decreased with increasing in the duration of the short day treatment, and the α-cellulose contents were not affected by short day. The lignin contents of the plants subjected to short day increased more than those of the C plot. And the effects of short day were remarkably rcognized

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The heading response of rice plants to daylength, temperature and nitrogen level was analysed under controlled environments in phytotron. 1. The heading response of rice plants (japonica) to temperature depended on daylength, and on the other hand, the response to daylength depended on temperature. The photo-sensitivity became duller under high temperature and more conspicuous under low temperature condition. These results indicated that the expression of thermo- and photo-sensitivity in heading response of a certain strain may vary with alternative conditions. 2. Nitrogen levels of culture medium did not influence on the growth duration from sowing to heading. No interaction was observed between nitrogen level and temperature or daylength in the heading response. 3. Under short day condition the sensitivity to temperature did not differ between early and late strains. But that of late strains was affected more strongly than early ones under long day condition. The heading of early strains was not affected by daylength under high temperature but affected slightly by daylength under low temperature. The heading of late strains was affected by daylength under high temperature, while it was more affected by daylength under low temperature than under high temperature. 4.These results may suggest that the rice plants in high latitudes have been lowered in the heading responsibility to daylength and growth temperature at several steps of the breeding Process

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It is important to make clear the differences of the photosythetic rate on each part of the leaf for analyzing the structure of canopy photosynthesis of crop plant population. The rate of photosynthesis of each part of the leaf was measured with a small chamber as shown in figure 1 for rice, corn and sorghum leaves. The plants were grown in pots. The rice plants were grown as a group of many potted plants, and the others in a thin density. 1) The photosynthetic rates of top-, middle- and base-part of leaf in the three crops were measured respectively with the small assimilation chamber (Fig.1). There are lage difference in maximum rate of photosynthesis among three parts of leaf, and also in light saturation point of that. It considered that the difference of the phosynthetic rate among the leaf parts due to nitrogen content per unit leaf area related to its chlorophyll content. 2) The maximum rate of net photosynthesis of the rice leaf in mg CO₂ absorbed per dm² per hour was 30 and that of corn and sorghum was 50-60 under the conditions of light saturations, 300 ppm CO₂ concentration and about 30°C temperature. The relationship between the light intensity (I) in K lux and the rate of gross photosynthesis (P) in each part of leaf can be expressed by the following equation: P=bI/I+aI, where a and b is constant. The rice leaves exisiting at a lower layer within the population and having a lower rate of photosynthesis were considered to be the shade leaves according to the values of constant in the above equation and the light saturating point decreased. 3) The rate of photosynthesis in each part of leaves of three crops had a high positive correlation to the nitrogen content and the respiratory rate of its part. Corn leaves, especially, had a negative correlation to specific leaf area (leaf area in cm² per gram dry leaf weight). There were large differences in the regression line between the rate of net photosynthesis and the nitrogen content in leaves, moreover, photosynthesis per unit of leaf nitrogen could be ranged in following order: sorghum, corn and rice

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[in Japanese]

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[in Japanese]

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[in Japanese]

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This experiment was carried out to see the influence of the specific gravity and weight of seed on seedling emergence of paddy rice sown under upland field condition. Variety used was Norin No.23 and seeds were covered with soil of 5cm in depth. Results obtained were as follows. 1. The weight and the uniformity of seeds increased with the increase in specific gravity 0f seed. 2. The ungerminated seeds were found considerably in the seeds with the smaller specific gravity (below 1.05), but not found in the larger ones (beyond 1.10). And the correlation co-efftcient between the specific gravity of seed and the time of seedling emergence was not significant. 3. At the 122nd hour after seeding, the length f coleoptile and primary leaf was longer in the seeds with the larger specific gravity (beyond 1.OO) than in the smaller ones (below 1.O0). But at the 208th hour after seeding, such a relationship was not observed. And the length of mesocotyl was longer in the seeds with the smaller specific gravity (below 1.05) than in the larger ones (beyond 1.10), when both results at the 122nd and 208th hour after seeding were combined. 4. The time of seedling emergence became earlier with increasing of seed weight. 5. At the 122nd hour after seeding, the length of coleoptile and the total length of mesocotyl and coleoptile and the diameter of coleoptile was correlated positively with seed weight. At the 208th hour after seeding, the length of coleoptile, primary leaf, leaf sheath of first leaf and second internode was correlated positively with seed weight. And the length of mesocotyl was correlated negatively with seed weight, when both results at the 122nd and 208th hour after seeding were combined

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In order to clarify the difference of increasing capability of tillers and branchings between the hills of orchardgrass and Ladino clover, we attempted to make the comparative tests of the aspects of increasing of tillers (blanchings) and the develipment form of tillers (branchings) among orchardgrass, Ladino clover, tall fescue and Kentuky bluegrass grown under the isolated culture system. The test results are summarized as follows...... 1) The hills of four species spreaded, respectivery, to the horizontal direction in proportion to the increase in the number of tiller or branching, but the extent of increases in the number of tiller per hill was lowest in orchardgrass than that in the other species. In case of orchardgrass, the tiller number showed a rapid increase when tiller number was still less, but after the tiller number increased, they had come to equilibrium. On the other hand, in case of Kentucky bluegrass and Ladino clover, tiller and branching number continued to increase, and the hills spreaded endlessly. In case of tall fescue, the tiller number increased slowly during the season from late Spring to early Autumn, but from late Autumn to next Spring the tiller number increased strikingly and the hill spreaded. 2) In case of orchardgrass, the tillers had come into contact with each other, and the increase of tiller led to the spreading of hill, but when tiller numer increased and tillers crowded strikingly, the birth of new tillers had come to cease. But in case of tall fescue and Kentucky bluegrass, in former, almost all the young tillers formed the mesocotyls during April and May, and in latter, some of the tillers formed the rizomes in any seasons, the distribution of tillers over a wide range at first had acceralated the birth of new tillers in later days. In case of Ladino clover, branching number observed an increase keeping pace with the elongation of the mother branching endlessly. It was seen that the elongation of branching was vigorous in bare area, and bare area had a tendency to be covered by stolons rapidly. 3) From the above stated test results, it can be concluded that the increasing capability of tiller in the hill of orchardgrass was strikingly lower than that in the hill of Ladino clover, and the difference may be caused by the difference in the development form of the tillers and branchings between the two species

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The experiment was carried out to observe the development of proliferated spikelets (propagules) in rice cultivated in flooded soil and attempts were made to discuss the significance of the development of propagules in the propagation of rice. The propagules used in the experiment were obtained from ears of two mutant strains (P₀), one induced by ethylene imine on the cultivar of Akibare (strain II) and the other induced by X-ray irradiation on the cultivar Reimei (strain II). It was observed that three propagules, two from strain I and one from strain II, could produce roots and ears (P₁) when transplanted in flooded soil. And each of them produced spikelets with same kind of abnormalities as those in P₀ plants. Abnormalities observed in case of strain I were as follws; 1) Successive initiation of leaf-like glumes forming a leafy shoot from the base of the spikelet, 2) Initiation of adventitious roots at the basal portion of spikelets, 3) Remarkable elongation of empty glumes having more veins than the normal ones, and 4) Initiation of rachilla-like protuberance in the stems. In case of strain II abnormalities were, 1) Remarkable elongation of the lemma having more veins than the normal ones, 2) Aditional initiation of glumes at the inner portion of lemma and palea, and 3) Production of more number of pistils and lower numbr of stamens than the normal ones. Fertility of spikelets in P₁ were very poor in case of both strains, specialy in case of strain II the spikelets were almost sterile. P₁ S₁ plants developed from the seeds of P₁ plants in strain I had also the same morphological abnormalities in their spikelets as those of P₀ and P₁. Therefore, it was considered that the mutant characteristics in the spikelets of P₀ were genetically fixed. In respect of propagation of rice by propagules initiated on the ears, a very interesting point needs mentioning that the plants produced from the propagules encircled their life cycles by the diplont nuclear phase only omitting its sexual phase which is related to the formation of pollens and egg cells and their fertilization. Considering the general tendency of the plant kingdom as a whole, the more the plant evoluted the longer becomes the diplont nuclear phase in the life cycle shortening the haplont ones, the propagules seemed to be one of the progressive type of propagations in seed plant. It will also not be overemphasized to mention that the vegetative propagation of rice by propagules would obviously compensate the sterility of the spikelets

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In order to confirm the process of dry matter accumulation into the Kernel, 20 panicles heading the even date were collected every day from 5 days after heading till maturity, and the spike-lets on the panicles were assorted according to the location on panicle into E, M, M' and L groups as in fig.4. The dry weight of each group collected every day was measured. The rsults obtained are summerized as follows: (1) In Tyukyo-Asahi, E. M, M' and L took 28, 30, 33 and 40 days to gain maximum dry-weight respectively, whereas 19, 20, 23 and 25 days were taken in Bluebonnet, as shown in fig.4. Indica varieties attained faster to mature stage and the disparity in days required to gain maximum dry-weight between E andL was less in comparison with japonica varieties. (table 1) Therefor, the divergence in moisture content among the kernels harvested in a field may be less in indicas and this character of indicas is considered to be more suitable for use of the combined-harvester and rapid drying of paddy. On the other hand, the competition for dry matter absorption among the kernels in a panicle will be harder in indicas for reason of short duration of dry matter absorption and large number of kernels per panicle. (2) In general, dry matter accumulation in rice kernels begins to concentrate 7-9 days after flowering at the central part of kernel and gradually spreads to the outer regions, and translucency follows the dry matter accumulation in the same order. (fig.1) At the time of the central part of kernel being translucent, indicas gained 33-35 per cent dry weight as compared to 25-28 per cent in japonicas. (fig.4, table 1) During translucency progressed from central part till 1/3 of lateral diameter on the transverse section of fully ripened kernel, indicas gathered 24-26 per cent weight, whereas japonicas gathered l5-19 per cent weight. During translucency spread from 1/3 of lateral diameter till 2/3 of lateral diameter, indicas got 21-24 per cent and japonicas got 25-29 per cent. After 2/3 stage, 20 per cent and 30 per cent was gained by indicas and japonicas respectively till fully ripened stage. The difference between indicas and japonicas in the process of dry matter accumulation is considered to be correlated with the difference of hardness (density of dry matter) distribution in the transverse section of kernel. (fig.7)

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The initial cells of crown root primordia have been shown by the authors to have been found in the upper and lower parts of the shoot unit of rice plants¹²⁾, but the developmental process from initiation to emergence of the crown root primordia have not been investigated. In the present study this process was found to be divided into the following 12 stages. At first, in the initial cells, the radial elongation of the cells and the enlargement of the nuclei and the nucleoli were observed, and the protoplasmic density of these cells became gradually higher (Stage 1). Subsequently, the initial cells began anticlinal and periclinal divisions. The outer cells adjacent to the crown root primordia showed the same cytological features as the initial cells did in the stage 1, and these outer cells constituted a Part of the primordia (Stage 2, Fig. 3). In the next stage the "epidermal-endodermal initials" were formed by only anticlinal divisions of the cells in the outermost layer of the divided cells in the stage 2. The cells which had been added to the primordia at the stage 2 began to mainly make anti-clinal divisions and formed the "root cap initials" (Stage 3, Fig. 4). After the stage 3, the epidermis and the endodermis of the primordia were differentiated by a periclinal division of all but two or three centrally located cells of the "epidermal-endodermal initials" (Stage 4, Fig. 5). Subsequently, these endodermal cells began to form the cortical cells of the primordia (Stage 5, Fig. 7). The cells of the "root cap initials" began at the 6th stage to form columella by periclinal divisions, and the stelar cells of the primordia continued to divide anticlinally and priclinally to form "dome shape". In this stage the essential pattern of apical organization of the primordia was accomplished as observed in the apices of the ordinary elongated crown roots. And the procambia of the " connecting phloem strands" which were linked with the transversely oriented procambia in the periphery of the stem were differentiated by periclinal and radial divisions of basal-peripheral cells of the stele (Stage 6, Fig. 8). In the central part of the stele, the meristematic strands of the "larger late meta-xylem vessel initials" were observed. These showed active transversal divisions and transversal elongation of cells (Stage 7, Fig. 10). After the stage 7, the meristermatic strands of the "primordial phloem initials" were observed in the peripheral part of the stele, which extended from the procambia of the "connecting phloem strands". These cells showed high protoplasmic density. The basal cells of the primordial endodermis continued to divide tangentially and formed the transversely oriented cortical cell files (Stage 8, Fig. 11). Subsequently, between these meristematic strands of the "primordial phloem initials" (observed in the transversal sections of the primordia), the strands of the "early meta-xylem vessel initials" were differentiated. The cells of the "primordial phloem initials" began to divide tangentially and radially at this stage (Stage 9, Figs. 12 and 13). After the 9th stage, several series of sieve elements were observed to differentiate acropetally in the "connecting phloem strands". The cells in the basal part of the cortex divided transversally and formed the longitudinally oriented cell files (Stage 10, Figs. 14 and 17). At the stage 11, the "connecting vessels" were differentiated between the "connecting phloem strands" as observed in the transversal sections of the primopdia. These vessels were differentiated from series of the basal stelar cells extended from a vessel element of the transversely oriented vascular bundles in the periphery of the stem to the base of the meristematic strands of the "early meta-xylem vessel initials". [the rest omitted]

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Under various conditions such as culture in gravel, framed soil and paddy field, rice plants (var. Manryo) were grown at the different levels in the nitrogen amount of basic dressing and top-dressing at young panicle formation stage for 8 years from 1964 to 1971. The dry weight and the nitrogen content of rice plants from 252 treatments in all were determined at the stages of 70 and 90 in leaf number index. After the measurement of the length of upper three leaves, culm and lower three internodes, the degree of lodging and the yield components at the maturity, the author tried to clear the effect of the amount of nitrogen absorbed by rice plants on the above mentioned characteristics. Results obtained were summarized as follows: 1. Both the amount of nitrogen absorbed up to the stage of LNI 70 (N₁) and of nitrogen absorbed during the period of LNI 70-90 (ΔN=N₂-N₁) facilitated the elongation of upper three leaves and lower three internodes, and increased the degree of lodging. In this instance these effects of N₁ were larger than those of ΔN, while in the case where N₁ was divided into the dry weight (W₁) and the nitrogen content (n₁), these effects of W₁ were also larger than those of n₁. 2. To maintain the degree of lodging less than about 3.0 in the case of about 500 in the number of panicles per square meter, it was required that the length of upper three leaves, culm and lower three internodes was less than about 130, 80 and 15 cm, respectively. 3. For the purpose of restricting the characteristics within limits mentioned above, it seemed that following conditions were necessary; a) N₁ was less than 7g/m², b) W₁ less than 200g/m² and c) ΔN less than 4-6g/m². Consequently, it was supposed that the upper limit of the amount of nitrogen absorbed up to the stage of LNI 90 (N₂) was about 11g/m² under the conditions of this experiment. 4. The schematic diagram of the mutual relation among above mentioned factors was proposed and the relative effect of these factors on those which were located in the direction indicated by the arrow was estimated

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[in Japanese]

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1. On mechanical transplanting using Mat-type seedling at the 4th leaf stage, it was observed that 11.0∼42.3% of the transplanted seedling sustained different types of injury by machines. The two common types of the injury were scratches on basal leaf sheaths and buckling of upper leaf blades: both of less significance to the yield. Less than 10% of transplanted seedlings suffered buckling and cutting at the basal part of seedlings, which has important effects on the plant growth after transplanting. 2. Close relations were observed between the injury (scratch, buckling and cutting) to the basal part of seedlings and the physical characters (buckling stress, modulus of elasticity, angle of buckling, plant height, buckling index and natural deflection ratio). This means that the injury is hard to occur to the short seedlings with hard and elastic leef sheaths and with erect, short leaf blades. 3. Three main characters, plant height, buckling index and natural deflection ratio, were selected as practical criterions of seedlings suited for mechanical transplanting. It is recommended for mechanical transplanting to prepare seedling shorter than 20∼22cm in plant height, less than 0.35∼0.40 in buckling index and less than O.15∼0.20 in natural deflection ratio

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