Nitrogen flux patterns through Oxisols and Ultisols in tropical forests of Cameroon,Central Africa     

Makoto Shibata  Soh Sugihara  Antoine David Mvondo-Ze  Shigeru Araki  Shinya Funakawa 《Soil Science and Plant Nutrition》2013,59(3):306-317

We lack an understanding of nitrogen (N) cycles in tropical forests of Africa, although the environmental conditions in this region, such as soil type, vegetation, and climate, are distinct when compared with other tropical forests. Herein, we simultaneously quantified N fluxes through precipitation, throughfall, and 0-, 15-, and 30-cm soil solutions, as well as litterfall, in two forests with different soil acidity (Ultisols at the MV village (exchangeable Al³⁺ in 0–30 cm, 126 kmol_c ha^–1) and Oxisols at the AD village (exchangeable Al³⁺ in 0–30 cm, 59.8 kmol_c ha^–1)) over 2 years in Cameroon. The N fluxes to the O horizon via litterfall plus throughfall were similar for both sites (MV and AD, 243 and 273 kg N ha^–1 yr^–1, respectively). Those values were remarkably large relative to other tropical forests, reflecting the dominance of legumes in this region. The total dissolved N flux from the O horizon at the MV was 28 kg N ha^–1 yr^–1, while it was 127 kg N ha^–1 yr^–1 mainly as NO₃^–-N (~80%) at the AD. The distinctly different pattern of N cycles could be caused by stronger soil acidity at the MV, which was considered to promote a superficial root mat formation in the O horizon despite the marked dry season (fine root biomass in the O horizon and its proportion to the 1-m-soil profile: 1.5 Mg ha^–1 and 31% at the MV; 0.3 Mg ha^–1 and 9% at the AD). Combined with the published data for N fluxes in tropical forests, we have shown that Oxisols, in combination with N-fixing species, have large N fluxes from the O horizon; meanwhile, Ultisols do not have large fluxes because of plant uptake through the root mat in the O horizon. Consequently, our results suggest that soil type can be a major factor influencing the pattern of N fluxes from the O horizon via the effects of soil acidity, thereby determining the contrasting plant–soil N cycles in the tropical forests of Africa.  相似文献   

Solubility and application effects of African low-grade phosphate rock calcinated with potassium carbonate     

Satoshi Nakamura  Takashi Kanda  Toshio Imai  Jacques Sawadogo  Fujio Nagumo 《Soil Science and Plant Nutrition》2013,59(3):267-273

This article indicates solubility improvement of African low-grade phosphate rock (PR) through calcination with potassium carbonate. We showed calcination with potassium carbonate made its citric acid solubility up to 100%, and reinforcement of its application effect. In sub-Saharan Africa, although many phosphate deposits have been found, farmers are facing high prices of P fertilizers because of the low solubility of the African PRs. We previously reported PR calcination with Na carbonate improves the solubility, but their application produced limited crop growth, especially in upland conditions. It was speculated soil Na accumulation caused plant growth inhibition. Therefore, we tried to elucidate the effect of calcination with potassium carbonate on PR solubility and its application effects for lowland rice and maize through pot experiments. We used Kodjari PR produced in Burkina Faso for the calcination. Powdered PRs were mixed with K₂CO₃ in five doses to achieve the target K₂O compositions of 200, 250, 300, 350, and 400 g kg^-1. The pelletized PR-K₂CO₃ mixtures were calcined at 900, 1000, 1050, and 1100 °C for 10 min. The pot experiments were conducted for 56 days, monitoring the growth of rice and maize under several application rates. Calcination with K carbonate generated K-rhenanite (KCaPO₄) and kaliophilite (KAlSiO₄), and the solubility reached about 100% in 20 g L^-1 citric acid and about 40% in water. This shows that K carbonates behave like Na carbonate in the solubilization of Kodjari PRs. Although the calcinated Burkina PR (CB) application significantly reduced plant growth when it was applied at an excessive rate, reduced application rates yielded comparable plant growth to that of triple super phosphate (TSP). K carbonate calcination deterred Na accumulation in the soil, and it was effective for plant growth. However, CB easily causes plant damage in excessive application, and it may contain phytotoxicant substances.  相似文献   

Characteristics of brown forest soils developed on the paleozoic shale in northern Kyoto with special reference to their pedogenetic process     

Hideaki Hirai  Shigeru Araki  Kazutake Kyuma 《Soil Science and Plant Nutrition》2013,59(2):157-170

Abstract

Morphological and chemical properties of brown forest soils and podzolic soils developed on paleozoic shale under beech and/or cryptomeria have been studied with special reference to the eluviation-illuviation characteristics of Fe and Al.

Mobilization of Al was observed even in brown forest soils and its pattern was similar to that in podzolic soils. Its intensity was higher in the brown forest soils developed on the ridge under cryptomeria than in those on the slope under beech. Hence, podzolization is considered to be one of the genetic processes involved in the brown forest soils in question.

Furthermore, the value of (Fep+Alp)/clay that is employed to define a podzolic B or spodic horizon indicated the presence of a podzolic B horizon even in the brown forest soils studied, while no spodic horizon was found even in the podzolic soils with a clearly recognizable albic horizon. Moreover, the examination of the degree of podzolization showed that the brown forest soils almost corresponded to Ochreous brown earths.  相似文献   

Development of a Novel Staining Procedure for Visualizing the Gluten–Starch Matrix in Bread Dough and Cereal Products     

Tatsuro Maeda  Mito Kokawa  Makoto Miura  Tetsuya Araki  Masaharu Yamada  K ji Takeya  Yasuyuki Sagara 《Cereal Chemistry》2013,90(3):175-180

A novel staining procedure has been developed to visualize the gluten– starch matrix in wheat flour dough. Dough samples mixed to the final stage were stained with 26 fluorescent reagents, and each stained sample was observed with three sets of fluorescence filters (blue, green, and red). Of all the combinations of reagents and filters, the combination of acid magenta and the blue fluorescent filter set was the most effective in distinguishing starch granules from gluten network structure. Its effectiveness was further demonstrated with gluten and starch granule samples, in which the contrast was clearer when observed with the blue fluorescent filter set than without any fluorescent filter. Visualizing the gluten–starch matrix in dough samples at four mixing stages with the same procedure resulted in clear identification of the changes in gluten network structure because of the differences in mixing stages. The same procedure also enabled us to distinguish starch from gluten in white salted noodles, baked cookies, and flour particles. The proposed procedure is quicker, simpler, and has a lower risk of altering the sample than other conventional ones, and it is expected to become a useful tool in cereal studies.  相似文献   

Design and synthesis of peptide-cellulose conjugate molecules —Aspects from energy/steric profiles—     

Kousaku Ohkawa  Masakazu Hachisu  Kesavan Devarayan  Jun Araki 《Fibers and Polymers》2013,14(12):1970-1974

A multipurpose chemical modification of cellulose to yield soluble cellulose derivatives was investigated on the basis of (i) O-acylation of the parent cellulose using N-Boc-protected Gly, αAla, and βAla, and subsequent Boc-removal, (ii) N-acylation of amino acid-modified cellulose in homogenous solution reaction system using Boc-oligopeptides with multiple types of the side-chain functionalities, and (iii) N-acylation of βAla-Cellulose using 10 kinds of simple Boc-oligopeptides. As for the (i), Thermochemical computation to estimate ΔG transition was well coincided with the observed yields in Oacylations. In the case of (ii), beside the similar ΔG-schemes, a strain energy profile, which is coupled with the preferred conformer transition of the amino acid-modified cellulose, was involved to rule out the N-acylation. The symmetric anhydrate in the N-acylating agents in the (iii) are tend to be in torsions due to the β-strand-like steric stabilizations in the peptides, resulting in the highest N-acylation yields as much as 98 %.  相似文献   

Comet 81P/Wild 2 under a microscope     

Brownlee D  Tsou P  Aléon J  Alexander CM  Araki T  Bajt S  Baratta GA  Bastien R  Bland P  Bleuet P  Borg J  Bradley JP  Brearley A  Brenker F  Brennan S  Bridges JC  Browning ND  Brucato JR  Bullock E  Burchell MJ  Busemann H  Butterworth A  Chaussidon M  Cheuvront A  Chi M  Cintala MJ  Clark BC  Clemett SJ  Cody G  Colangeli L  Cooper G  Cordier P  Daghlian C  Dai Z  D'Hendecourt L  Djouadi Z  Dominguez G  Duxbury T  Dworkin JP  Ebel DS  Economou TE  Fakra S  Fairey SA  Fallon S  Ferrini G  Ferroir T  Fleckenstein H  Floss C  Flynn G 《Science (New York, N.Y.)》2006,314(5806):1711-1716

The Stardust spacecraft collected thousands of particles from comet 81P/Wild 2 and returned them to Earth for laboratory study. The preliminary examination of these samples shows that the nonvolatile portion of the comet is an unequilibrated assortment of materials that have both presolar and solar system origin. The comet contains an abundance of silicate grains that are much larger than predictions of interstellar grain models, and many of these are high-temperature minerals that appear to have formed in the inner regions of the solar nebula. Their presence in a comet proves that the formation of the solar system included mixing on the grandest scales.  相似文献   

Keratoconus in a cynomolgus monkey     

Kodama R  Yang X  Araki T  Sato M  Iwashige S  Tanigawa Y  Uchimura M  Ishimaru K  Sasaki Y  Kamimura Y  Maeda H 《Journal of toxicologic pathology》2010,23(1):53-58

In a seven-year-old male cynomolgus monkey, erythema of the upper eyelid and forehead and corneal opacity, edema and conical protrusion in the eye were observed. At necropsy, ophthalmological and serological examinations revealed binocular corneal opacity and conical protrusion and a high IgE level, respectively. Thinning of the epithelium and stroma of the cornea were noted histopathologically. At the center of the corneal epithelium, the number of epithelial cells was reduced, their cytoplasm was poorer and the basal cells were flatter than at the periphery. Bowman's membrane was folded with partial loss or breakage. Collagen fibers were compacted or disarranged, and the keratocytes were increased in the stroma, with focal pyknosis or loss of the endothelium and folding of Descemet's membrane. Electron microscopical examination revealed atrophy of the corneal epithelial basal cells. This is the first report of a case of keratoconus in a cynomolgus monkey.  相似文献   

Protective effects of Chinese propolis and its component, chrysin, against neuronal cell death via inhibition of mitochondrial apoptosis pathway in SH-SY5Y cells     

Izuta H  Shimazawa M  Tazawa S  Araki Y  Mishima S  Hara H 《Journal of agricultural and food chemistry》2008,56(19):8944-8953

Endoplasmic reticulum (ER) stress has been implicated in the pathogenesis of neurodegenerative and ischemic disorders. The purpose of this study was to evaluate the effects of Chinese propolis and its constituents [chrysin, galangin, pinocembrin, caffeic acid, and caffeic acid phenethyl ester (CAPE)] against tunicamycin-induced neuronal cell death in SH-SY5Y cells. Both Chinese propolis and chrysin concentration-dependently inhibited such cell death, the tunicamycin-induced activation of caspase-3, and the effects of tunicamycin on mitochondria [release of cytochrome c into the cytosol and disruption of the mitochondrial membrane potential (DeltaPsim)]. Furthermore, Chinese propolis and chrysin each inhibited staurosporine-induced cell death. These findings indicate that the inhibitory effects of Chinese propolis against neuronal cell death induced by ER stress or staurosporine may be exerted primarily by chrysin. Moreover, the mechanism underlying the protective effects may, at least partly, involve inhibitions of caspase-3 activity and the mitochondrial apoptotic pathway.  相似文献   

Half a century of genetic interaction between farmed and wild Atlantic salmon: Status of knowledge and unanswered questions          下载免费PDF全文

Kevin A Glover  Monica F Solberg  Phil McGinnity  Kjetil Hindar  Eric Verspoor  Mark W Coulson  Michael M Hansen  Hitoshi Araki  Øystein Skaala  Terje Svåsand 《Fish and Fisheries》2017,18(5):890-927

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Comparison of soil moisture effects on surface conductance between late dry and rainy seasons in an evergreen forest of central Cambodia     

Koji Tamai  Akira Shimizu  Tatsuhiko Nobuhiro  Naoki Kabeya  Makoto Araki 《Paddy and Water Environment》2008,6(1):47-53

Some forests in the Asian monsoon region are reported to transpire actively, even in the late dry season. The evergreen forest in central Cambodia is included in them. The surface conductance was estimated for an evergreen forest in central Cambodia in the late dry (May) and rainy (August) seasons, and the effects of environmental conditions on surface conductance were compared between seasons. The effects of soil moisture did not differ between seasons, indicating that soil water drought in the late dry season does not limit transpiration from the entire forest community. Evergreen forests in central Cambodia are thought to transpire actively in the late dry season.  相似文献