Soybean is dependent upon N fixed by nodule bacteria (Rhizobium japonicum) as well as combined N from soil and fertilizer in order to produce seeds. P and K applications promote the nodulation or the nodule activity of soybean. Our study was conducted to determine the responses of seed yield and nodulation in wild and cultivated soybeans (Glycine soja Sieb. et Zucc. and G. max (L.) Merrill) to P and K application. The plastic pots which contain 4.0 kg paddy field soils on dry basis were fertilized by three levels of P and K before planting (Table 2). Ten early cultivated varieties were planted on 13 May in 1980 and 1981, and ten late cultivated ones and a wild line on 27 July in 1980 and 9 July in 1981. (Tables 1 and 4). The following results were obtained. 1. Norin No. 2, Orihime and Lincoln in early varieties, Akiyoshi, Oshokuakidaizu and Akisengoku in late ones responded better in seed yield to P and K application than the other ones for two years. K-01 line (a wild line) responded a little in 1980 and didn't in 1981 (Table 5). 2. Most early and late varieties responded the better in a year when the seed yield level was the lower (Table 5). 3. Leaf and nodule dry weights per plant increased in response to P and K application in cultivated varieties. But K-01 line showed a small increase in these characters in 1980 and no increase in 1981 (Table 6). 4. There were varietal difference in the increased rate of nodule dry weight by P and K application in cultivated soybean. The more the varieties increased their nodule dry weight, the better they tended to respond to P and K application (Tables 5 and 7). 5. Nodule dry weight per plant was significantly correlated with the amount of accumulated N per plant at early pod filling stage in early and late varieties in 1980 and 1981 (Fig. 1).

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A new technique was explored for classifying roots according to their ages, and it was applied for the analysis of root system development of the 1-to 7-year-old clonal tea plants (Camellia sinensis (L.) O. Kuntze cv. Yabukita) grown under field conditions. In the technique, the root ages were expressed progressively as Age I, Age II etc., by the number of annual rings, which were easily detected by staining cross sections of the roots with phloroglucinol-alcohol solution. Total root weight increased almost linearly with plant age. Annual increase of root dry weight amounted to about 110g per plant from the third to the seventh year after planting. The quantitative ratio of white roots, which are superior in nutrient absorption and biosynthesis of amino acids, maintained the highest ratio throughout every plant age examined. This suggests importance of white roots to plant growth and green tea quality. In contrast, Age III and IV roots occupied the smallest percentage among total roots. Roots that were formed within 3 years after planting continued to grow in the successive years. Most of those that were formed later in 4 or 5 years after, however, failed to grow in the successive years. Consequently, it is considered that growth of roots which were formed during the younger plant ages is of great importance for the formation of tea root system.

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Growth retardation and wilting of corn seedlings frequently occur in spring in Hokkaido, the northernmost island in Japan. In order to elucidate the process of the growth retardation and wilting, the effect of aboveground and underground environmental factors on the balance between transpiration from leaves and water babsorption by roots and the photosynthetic rate were examined by model experiments. The transpiration rate of corn seedlings increased with increase in light intensity and saturation deficit in the air (Fig. 1 and 2). The evaporation rate from a filter paper atmometer increased steeply with increase in wind velocity, though it was less influential on the transpiration rate (Table 1). The water absorption rate and photosynthetic rate of corn seedlings were strongly affected by the water potential of culture solution (Fig. 4 and 5). The photosynthetic rate decreased rapidly to less than 60 % in about 40 minutes after the water potential in the culture soultion was reduced from 0 to -0.6 bar by ammonium sulfate (Fig. 5). The environmental condition at the seedling stage of corn in the main corn area of Hokkaido is characterized by high solar radiation, strong wind, low precipitation (Table 2) and heavy application of fertilizer (about 10 kg/10 a of N). High transpiration rate under high solar radiation may reduce the water content in corn seedlings. The water uptake by roots may be restricted by the soil water deficiency resulting from both low precipitation and high evaporation due to strong winds. In addition, this may be accentuated by the reduction in soil water potential caused by heavy fertilizer application. The transpiration-water absorption imbalance produced by these environmental conditions is regarded as a main cause of the growth retardation and wilting of corn seedlings. The outline of the growth retardation and wilting process is schematically represented in Fig. 6.

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Histological changes in the developing rice endoperm and nucellus were observed with attention to the translocation pathway of reserve substances. Results were discussed by comparison with those of two-rowed barley which reported in the previous papers. 1. On the young endosperm (9-10 days after anthesis), some irregular shaped cells were found in the midway area between peripheral and center of the lateral portions. However, they were remarkably less in number than those of two-rowed barley (Fig. 1). 2. In the aleurone and subaleurone cells of lateral and ventral portions, zigzag modification of the wall as found in barley was could not observed throughout the developing stage. 3. Anticlinal cell walls of nucellar epidermis increased in area about several tens times by expanding of the cell as the endosperm grew fat, and they increased more by folding. A large number of plasmodesmata were formed in the anticlinal cell walls. This may be a proof that the nucellar epidermis developed as the conductive tissue from dorsal vascular bundle to the ventral side (Figs. 2∼10). 4. Wall-ingrowth structure that symbolizes the figure of transfer cell was found in some young dorsal aleurone cells (Fig. 12). However, the transfer cells were small in number in rice, and this differed from two-rowed barley in which many transfer cells were formed in the dorsal portion as reported previously. 5. Dorsal aleurone tissue was composed of 6-8 cell-layers in rice. On the 9-10th day after anthesis, some "unusual cells" were observed sporadically in the young dorsal aleurone tissue. They were stained with toluidine blue darker than ordinary aleurone cells, and were mutually connected with their characteristic uneven cell walls to form a channel across the aleurone tissue (Figs. 13, 14). They degenerated and were depressed gradually in contrast with the normal aleurone cells developed (Figs. 15-17), and that they were found as rather thick traces even in mature aleurone tissue (Fig. 18). The "unusual cells" might be cause of the irregular arrangement of the dorsal aleurone cells. The channels made of connection of the "unusual cells" may play an important role as the translocation pathways through thick aleurone layers which cells were fully packed with aleurone grains etc.

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TAKAHASHI, HAYASHI and MORIYA (1975) have demonstrated in their studies with a large number of V-v isogenic line pairs that the two-rowed strains were about two percent higher in general in crude protein content of the grain than the corresponding six-rowed strains. This study was planned to approach the underlying cause of the difference in crude protein content (%) between two types of isolines. In the first experiment change of crude protein content with the progress of the kernel growth was investigated using a six-rowed late cultivar (Kikai Hadaka) and a two-rowed early cultivar (Seijo 17). Seed samples were taken from 17 days after anthesis to maturity at 6-day intervals. The result indicated that percentage of crude protein accumulated in the kernels was not so much different between varieties at any stage of kernel growth (Fig. 1). Next, crude protein content of the central and lateral kernels was compared in the second experiment with three six-rowed varieties, which showed no appriciable difference existing between central and lateral kernels (Table 2). Finally, effects of removing lateral kernels of six-rowed strain at different times of kernel growth on final protein content of central kernel was studied in the third experiment. Three pairs of V-v isogenic paired lines (KA-26, KT-16 and GT-17) which had been produced by TAKAHASHI et al. were used. The removal of lateral kernels was made firstly on one or two days before anthesis, and repeated five times at 5-day intervals after anthesis (from 5th to 25th days). In KA-26 and KT-16, one-half of the spikes within plant was used for treatment and remaining half for untreated control. In GT-17, treatment was made within population regardless of the plant. The removal of lateral kernels resulted generally in an increase in crude protein content of remaining central kernels, and the increasing effect of the removal was most evident when the treatment was made before anthesis (Figs. 2 and 3). However, the increase of crude protein content became smaller and smaller with the later date of the treatment, and the treated spikes reached the same crude protein percent as the intact plot on 25th day after anthesis. Removal of laterals affected a little on 1000 kernel weight. From this study, the cause of difference of protein content between two-rowed and six-rowed isolines may be explained as follows : Protein is mainly synthesized in leaves from nitrogen absorbed from the roots, and is distributed almost uniformely to central and lateral kernels in intact six-rowed spike. But when lateral kernels have been removed from the spike, the protein which ought to be allotted to the lateral kernels will be distributed to and accumulated excessively in the central kernels. Consequently, if so-called source size is not different between two-rowed and six-rowed types, crude protein percent of the kernels will be higher in two-rowed type with small size of so-called sink than those of six-rowed ones.

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By means of the "leaf-cutting" method, the development of lateral root primordia of rice plants was investigated in relation to the diameter as well as the growth rate of crown roots on which they were formed. 1. The distance from the crown root tip to the youngest lateral root was variable among the crown roots examined. That is, the tip-to-lateral distance was greater in the thick and rapidly growing crown root than in the thin and slowly growing one. However, the time required for the development of each lateral root primordium was almost constant, irrespective of the diameter or the growth rate of its parent crown root (Figs. 4 and 5). 2. The lateral roots of rice plants have generally been divided into thick and thin group. The difference of their thickness was found to occur at a developmental stage, when each primordium reached 60-70 μm in length (Figs. 6 and 7). The stage coincided with the time when the primordium established its own organization with distinctive epidermis, cortex, stele and root cap (Fig. 8). Later, the thickness of each primordium increased and reached the maximum just before its emergence from the epidermis of the crown root (Fig. 7). 3. When the crown roots were decapitated, abundant thick laterals were formed in the remaining proximal portions. However, the primordia already aquiring their own organization mentioned above were not affected by the manipulation (Fig. 11). This suggests that a certain factor may determine the thickness of lateral roots during their early primordial stages.

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[in Japanese]

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[in Japanese]

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[in Japanese]

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The present work was undertaken to investigate the effect of nitrogen top-dressed at the different growth stages in rice plants on its leaf area growth and on the nitrogen levels in the individual leaf blades, and furthermore to establish nitrogen translocation and distribution into the various plant parts. For these purposes, ¹⁵N-labelled ammonium sulfate was used as a tracer in order to measure absorption of nitrogen fertilizer, and to follow the translocation of absorbed ¹⁵N-labelled nitrogen into grains from the other plant parts. The results obtained are as follows. 1. A marked increase was found in leaf area growth of the rice plant by top-dressing of nitrogen during the growth stages of tillering to branch differentiation, but it was not found to occur after the boot stage. During the ripening period a decrease of the leaf area growth was significantly suppressed by top-dressing. The contents of total nitrogen, soluble and Fraction-1 proteins in the leaf blades greatly increased by top-dressing after the boot stage and these values were much higher than the corresponding values at the tillering and branch differentiation stages. 2. The leaf area growth of individual leaf blades was effectively promoted when nitrogen was top-dressed sometime before the emergence of the leaf in question. For example, the growth of 12th and 13th leaf area was more accelerated by top-dressing at the 11th leaf elongating stage and the growth of 13th and 14th leaf area by top-dressing at the 12th leaf elongating stage. However, after the boot stage nitrogen fertilization was ineffective on the leaf area growth. 3. Of the two rice varieties used, Kamenoo showed a relatively higher growth of leaf area as compared with Hatsukaori. By top-dressing of nitrogen, the increased leaf area growth was more obvious in the former variety than in the latter one. The extent of leaf area growth was marked when nitrogen fertilizer was top-dressed at the tillering or branch differentiation stages. On the contrary, Hatsukaori showed higher levels of total nitrogen, and soluble and Fraction-1 proteins in the leaf blades rather than increasing the leaf area growth by top-dressing of nitrogen. 4. The translocation of top-dressed nitrogen into individual leaf blades differed considerably with the growth stages at which labelled nitrogen was supplied. ¹⁵N-labelled nitrogen supplied at the tillering stage (11th leaf stage) tended to accumulate into the just elongating 12th leaf blades whereas ¹⁵N supplied at the stage of branch differentiation stage (12th leaf stage) was predominatingly translocated and deposited in the upper 13th and 14th leaf blades. However, after the boot stage little or no difference was found in distribution of ¹⁵N-labelled nitrogen among the individual leaf blades, and ¹⁵N-labelled nitrogen tended to accumulate mainly into the developing ears rather than the other plant parts (leaf blades and leaf sheath+culms). 5. The percentages of ¹⁵N distributed to sink were 52, 58, 70 and 72 for nitrogen top-dressed at the tillering, branch differentiation, boot and heading stages, respectively. These data agreed with the results that the grain-N content together with glutelin (one of the reserve proteins) increased markedly by top-dressing of nitrogen at the boot and heading stages.

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Three temperate grasses : orchardgrass (Dactylis glomerata L.), Italian ryegrass (Lolium multiflorum LAM.) and tall fescue (Festuca arundinacea SCHREB.), were grown singly or in mixture with red clover (Trifolium pratense L.) in 1/5000 a pots. The results are summarized as follows. 1. Red clover significantly accelerated the growth of companion temperate grasses in terms of dry weight and nitrogen content 22 days after mixed cropping in poor nitrogen soil (Figs. 1 and 2). This acceleration was also obtained 10 days after mixed cropping in solution culture containing no nitrogen fertilizer (Fig. 9). 2. This acceleration effect varies with grass species. In orchardgrass and Italian ryegrass, the effect was marked, whereas it was not marked in tall fescue (Figs. 1 and 2). 3. In case of no nitrogen fertilizer, the dry weight and nitrogen content per plant of orchardgrass were larger in mixed cropping with red clover than in single cropping 20 days after planting. With nitrogen 1 kg and 5 kg/10a, however, the orchardgrass dry weight was less in mixture than in single cropping. Nitrogen content of orchardgrass with nitrogen application was larger in mixture than in single cropping 90 days after planting (Figs. 5 and 6). 4. Culture solution of the single cropping of red clover and of the mixed cropping had a greater amount of organic nitrogen than the single cropping of orchardgrass 15 days after planting (Table 2.) 5. Dry weight and nitrogen content per plant of succeeding millet and wheat increased in cases where preceding cropping was single cropping of red clover and mixture. This acceleration effect varied with the species of three grasses in preceding cropping (Figs. 3 and 4). It is found from these results that growth of three temperate grasses are accelerated by mixed cropping with red clover soon after the beginning of cultivation in cases where the soil contains little nitrogen and also that the acceleration effect varies with the species of temperate grasses. It is suggested that growth acceleration of grasses raised with red clover in early stage of cultivation is probably due to absorbing nitrogen excreted directly from root system of red clover.

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