Geographical features of estuaries for neritid gastropods including Clithon retropictus to preserve thermostable direct hemolysin-producing Vibrio parahaemolyticus.

Thermostable direct hemolysin-producing strain of Vibrio parahaemolyticus was not detected from the alimentary tract of 7 neritid gastropods including Clithon retropictus at 9 estuaries of Southwest Islands in Japan in the present study. The strain has been detected from C. retropictus at 2 estuaries facing The Sea of Japan but not at 2 estuaries facing The Seto Inland Sea and The Pacific Ocean in Western Japan in our previous studies. In comparison with geographical features of the estuaries where the strain was detected and not, thick accumulation of muddy sediments at the riverbed and stagnation of brackish water at low tide seem to be essential for the strain to survive in neritid gastropods including C. retropictus.     

Studies on the change of respiratory system in roots in relation to the growth of plants

It has been observed that in nitrogen starved rice plants, the length of the root increased and became voluminous. The colour of the root appeared pale. Both the oxygen uptake and the oxidative power of the roots decreased during the vegetative stage of the plant (1, 2, 3). Under conditions of K deficiency, the length of the roots became shorter and the colour was light grayish black. These roots were very susceptible to damage (3). K deficient roots showed a low oxidative power (3, 4), while the uptake of oxygen was high during the vegetative stage of growth of the plant.     

Nitrogen assimilation in sunflower leaves and upward and downward transport of nitrogen

The assimilation of ammonium and nitrate nitrogen into amino acids of mature sunflower leaves and their transport to the other plant parts were investigated using nitrogen-15 as a tracer. In the leaf, to which ¹⁵N-labelled ammonium was vacuum-infiltrated, the ¹⁵N content of glutamine was always the highest of the amino acids tested and that of alanine was higher than that of glutamic acid and aspartic acid at 15 min after the infiltration. On the other hand in the leaf to which ¹⁵N-labelled nitrate was vacuum-infiltrated, the ¹⁵N content of glutamic acid and aspartic acid was superior to that of glutamine. The incorporation of ¹⁵N into serine was not active in the case of either ¹⁵N-labelled ammonium or nitrate. In the internodes above and below the treated leaf, through which photosynthates were transported into other parts, the ¹⁵N content of γ-aminobutyric acid and glutamine was markedly high when both nitrogen sources were supplied. There were no differences in the labelling patterns of amino acids between the upper and lower internodes. From these results it may be concluded that glutamine, glutamic acid, and aspartic acid play an important role in the assimilation of ammonium and nitrate nitrogen in leaves and that nitrogen is transported mainly in the forms of γ-aminobutyric acid and glutamine from the leaves to the other plant parts,     

Asparagine test in relation with the nitrogen nutritional status of crop plants: IV

In the preceding investigaions (1,2,3) some of the dynamic aspects of asparagine appearance in rice and barley were studied and it was well confirmed that asparagine appearance, in both the crops, has almost similar trends of appearance i.e. in continued darkness it can appear irrespective of the stage of the plant and the level of nitrogen supplied, its first appearance is parallel with the panicle formation, it can easily be detected in the youngest leaf, it shows concentrated appearance in the younger leaves before the maximum growth and after it in the older leaves, and the appearance of nitrate has no direct relation with its appearance at any stage of the plant. Furthermore, when ammonium sulphate was supplied basically to the rice, ammonium form among various forms of nitrogen topdressing was found to be the most favourable for the appearance of asparagine. However, since barley is solely an upland crop it seemed essential to study the latter aspects of asparagine appearance in the case of barley. A slight modification in the design of the experiment, as to know the effects of nitrate given basically, has been included.     

Studies on the effect of the paddy field soil kept under upland condition on the yield of rice

In Japan, the extent under paddy is approximately three million hectares and the average yield per hectare is about 3000 kg, though high yield gives as much as over 7000 kg per hectare. It is at present a serious problem as to what methods we can use to obtain a high yield of rice. Generally, in well-drained paddy fields where the system of double-cropping is practised, rice is cultivated under a flooded condition in summer, and upland crops such as barley or wheat is cultivated under upland condition in other seasons.     

pH and substrate regulation of nitrogen and carbon dynamics in forest soils in a karst region of the upper Yangtze River basin, China

Nitrogen (N) is the most limiting nutrient for forest development. In this study, using a natural pH gradient, N and carbon (C) mineralization was investigated and the effects of soil pH as well as the total C and N contents and the soil C/N ratio were evaluated in forest soils after mountain closure in a karst region. The N availability was poor based on the low N mineralization potential (N ₀) and the low active fraction of soil total N (N ₀/total N), while high microbial decomposition activity was indicated by a high mineralization rate constant (k _N). N ₀ was positively correlated with soil pH as well as the total C and N contents. Additionally, multiple regression analysis revealed that total CN (the product of the soil total C and total N contents) and the C/N ratio had more significant effects on N ₀ than soil pH. In contrast, the mineralization rate constants k _N and k _C were positively affected by soil pH. The results indicated that N availability was regulated by soil organic matter (SOM), while microbial activity was restricted by soil pH. Also, the lack of nitrification and the high C ₀/N ₀ ratio observed at soil pH <5.5 may be a strong indicator of alterations to the microbial composition prompted by severe soil acidification. Further research is required to determine the changes in soil microbial composition with the drop in soil pH and their effects on SOM decomposition and nutrient availabilities.     

Studies on the key aroma compounds in soy milk made from three different soybean cultivars

An investigation by aroma extract dilution analysis (AEDA) of the aroma concentrate of soy milk made from a major Japanese soybean cultivar, Fukuyutaka (FK), revealed 20 key aroma compounds having flavor dilution (FD) factors of not less than 64. Among them, 2-isopropyl-3-methoxypyrazine, cis-4,5-epoxy-(E)-2-decenal, trans-4,5-epoxy-(E)-2-decenal, 3-hydroxy-4,5-dimethyl-2(5H)-furanone, and 2'-aminoacetophenone were identified as the key aroma compounds in soy milk for the first time. (E,E)-2,4-Decadienal exhibiting a fatty note and trans-4,5-epoxy-(E)-2-decenal exhibiting a metallic/sweet note were detected as having the highest FD factors of 4096, followed by hexanal (green), (E)-2-nonenal (fatty), and (E,E)-2,4-nonadienal (fatty) having FD factors of 1024. Although all of these compounds might be generated from lipids, various aroma components, which were thought to be generated from amino acids, sugars, and ferulic acid, were detected having FD factors of 64-256. Investigation by comparative AEDA experiments of the soy milk aroma concentrates of two cultivars for soybean curd and soy milk, FK and Vinton81 (VT), and one cultivar for boiled beans, Miyagishirome (MY), revealed that most of the key aroma compounds were common to all of them, but 2-isopropyl-3-methoxypyrazine, exhibiting a pea-like/earthy note, was detected only in FK and VT. In addition, a sensory experiment revealed that the pea-like/earthy notes in FK and VT were significantly stronger than that in MY. These results demonstrated that a pea-like/earthy note contributed by 2-isopropyl-3-methoxypyrazine might be one of the essential characteristics to describe soy milk aromas.     

Numerical calculation of secondary discharge peak from a small watershed using a physically based watershed scale infiltration simulation

Numerical infiltration simulations were performed to reproduce secondary discharge peaks in a mountainous forest watershed (watershed area, 1.89 ha; average topsoil depth, 2.61 m; and bedrock geology, Mesozoic–Paleozoic) using a simplified physically based three-dimensional saturated and unsaturated water-flow model based on Richards’ equation. We were able to calculate the quick discharge during rain and a secondary discharge peak at the watershed simultaneously, using observed topographical information, the topsoil depth distribution, and soil hydraulic characteristics, and by dividing the watershed by 2.5 m horizontally and ten cells vertically. Although the calculated hydrograph did not agree entirely with the observed hydrograph, we conclude that the characteristics of the observed hydrograph were explained with better accuracy using the smaller soil porosity patterns than using the observed patterns. We verified that the simulation method based on Richards’ equation was effective to analyze the rainfall-runoff processes toward the intended watershed. Computational comparisons clarified that lower soil porosity quickens the timing of secondary discharge peaks and increases their volume. Additional examinations, such as the distribution of soil hydraulic characteristics and the actual condition of Hortonian overland flow, are necessary to simulate rainfall-runoff processes precisely at the intended watershed.     

Sustainable site productivity and nutrient management in a short rotation plantation of Gmelina arborea in East Kalimantan,Indonesia

New Forests - Sustainable Forest Management (SFM) requires information on plant growth and nutrient dynamics in forest ecosystems. To obtain fundamental information for SFM in short-rotation...