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Two Gram-stain-negative, terminal endospore-forming, rod-shaped and aerotolerant bacterial strains designated D1-1T and B3 were isolated from soil samples of an organic paddy in Japan. Strain D1-1T grew at 15–37 °C, pH 5.0–7.3, and with up to 0.5 % (w/v) NaCl. Phylogenetic analysis of the 16S rRNA gene revealed that strain D1-1T belonged to the genus Clostridium and was closely related to Clostridium zeae CSC2T (99.7 % sequence similarity), Clostridium fungisolvens TW1T (99.7 %) and Clostridium manihotivorum CT4T (99.3 %). Strains D1-1T and B3 were whole-genome sequenced and indistinguishable, with an average nucleotide identity value of 99.7 %. The average nucleotide identity (below 91.1 %) and digital DNA–DNA hybridization (below 43.6 %) values between the two novel isolates and their corresponding relatives showed that strains D1-1T and B3 could be readily distinguished from their closely related species. A novel Clostridium species, Clostridium folliculivorans sp. nov., with type strain D1-1T (=MAFF 212477T=DSM 113523T), is proposed based on genotypic and phenotypic data.

Awamori is a traditional distilled alcohol beverage unique to Okinawa, Japan. This study evaluated the potential of ultraviolet–visible (UV–VIS) spectroscopy in the assessment and differentiation of different Awamori samples. Thirty-one Awamori samples that could be classified differently based on attributes such as their distillation methods (atmospheric distillation and vacuum distillation), aging periods (0–18 years), batches (years 2017 and 2014), and distilleries of origin were investigated by UV–VIS spectroscopy and chromatographic analysis. Principal component analysis (PCA) of UV–VIS spectra showed that Awamori of atmospheric distillation and vacuum distillation could be clearly distinguished based on low and high PC1 scores, respectively; both young Awamori (aged less than 3 years) and Awamori from the 2017 batch exhibited low PC1 scores and high PC2 scores. Wavelength ranges with high loading values that correspond to the volatile compounds which have high correlations with PC scores, such as furfural, phenethyl alcohol, vanillin, and benzaldehyde, were observed in the UV–VIS spectral profiles. These volatile compounds with unique aroma characteristics can characterize Awamori attributes. Therefore, UV–VIS spectroscopy with the aid of chemometric analysis was demonstrated as a high potential technique for the rapid and low-cost evaluation and characterization of Awamori samples.

‘Fuji’ apples stored under depressed ethylene by 1-MCP treatment (1-MCP) or in CA storages with 1.5% or 5.0% CO2 (CAL or CAH) were profiled for volatile production related to flesh browning severity after 4, 6 and 8 months of storage. Among the volatiles observed, methyl esters correlated with browning area at the developing stage. This relationship was further demonstrated using apples harvested the following year. Expression levels of genes related to senescence and alcohol synthesis were compared and expression of MdPME2 tended to be higher in injured apples. However, methyl esters increased with MdPME2 levels only in healthy individuals, suggesting that pectin methyl esterase (PME) may regulate methanol liberation from pectin well before visible browning development. Thus, methyl ester generation reflected flesh browning of ‘Fuji’ apples, which may be associated with PME activation that induces methanol liberation and oxidative stress after long storage.

Watercore is a physiological disorder in apple (Malus × domesticaBorkh.) fruits that appears as water-soaked tissues adjacent to the vascular core, although there is little information on what exactly occurs at cell level in the watercored apples, particularly from the viewpoint of cell water relations. By combining picolitre pressure-probe electrospray-ionization mass spectrometry (picoPPESI-MS) with freezing point osmometry and vapor pressure osmometry, changes in cell water status and metabolisms were spatially assayed in the same fruit. In the watercored fruit, total soluble solid was lower in the watercore region than the normal outer parenchyma region, but there was no spatial difference in the osmotic potentials determined with freezing point osmometry. Importantly, a disagreement between the osmotic potentials determined with two methods has been observed in the watercore region, indicating the presence of significant volatile compounds in the cellular fluids collected. In the watercored fruit, cell turgor varied across flesh, and a steeper water potential gradient has been established from the normal outer parenchyma region to the watercore region, retaining the potential to transport water to the watercore region. Site-specific analysis using picoPPESI-MS revealed that together with a reduction in turgor, remarkable metabolic modifications through fermentation have occurred at the border, inducing greater production of watercore-related volatile compounds, such as alcohols and esters, compared with other regions. Because alcohols including ethanol have low reflection coefficients, it is very likely that these molecules would have rapidly penetrated membranes to accumulate in apoplast to fill. In addition to the water potential gradient detected here, this would physically contribute to the appearance with high tissue transparency and changes in colour differences. Therefore, it is concluded that these spatial changes in cell water relations are closely associated with watercore symptoms as well as with metabolic alterations.

To clarify the physiological factors associated with the development of tomato leaf marginal necrosis associated with potassium deficiency, tomato leaf blades prior to development of the symptoms were collected, and profiles of water-soluble metabolites were analyzed using gas chromatography–mass spectrometry. Multivariate analysis was conducted to screen for a component that was related to potassium deficiency-induced leaf necrosis among the 60 metabolites detected in tomato leaves. Polyamines, sugars, and branched amino acids were ranked highly. Putrescine was most strongly and negatively correlated with potassium concentration and exhibited an exponential response, regardless of the site or plant body. In addition to putrescine, glucose, xylose and l -isoleucine are known to play important roles in stress response and ion balance control, and it is thought that changes in metabolite profiles are linked to tomato leaf marginal necrosis associated with a decrease in endogenous potassium concentration. These findings will be useful for cultivation management to mitigate this physiological disorder of tomato.

For quick, noninvasive, and high-sensitivity surface analysis of foods and agricultural products, a touch sensor was developed and applied to sheath-flow probe electrospray ionization/mass spectrometry (sfPESI/MS). Upon making contact with the sample, the probe stopped by detecting the current flowing through the circuit and analytes on the sample surface were extracted in the solvent preloaded in the plastic capillary. By lifting up the probe to the default position, an electrospray ionization mass spectrum of the sample was obtained. By scanning the sample stage using a programming tool, a point analysis of targeted positions of biological samples with a spot diameter of ≤0.3 mm was achieved. It took less than 10 s for one sample spot. This method was applied to various plants and animal tissues.

In previous work, probe electrospray ionization/mass spectrometry (PESI/MS) and sheath-flow probe electrospray ionization/mass spectrometry (sfPESI/MS) were reported for the rapid and minimally invasive analysis of food. In this work, a modified version of sfPESI will be reported. The sample surface was pricked with an acupuncture needle inserted in the sfPESI probe that protruded from the terminus of the tip by 5 mm. The invasion depth of the needle into the sample was ∼1 mm. After sampling, the needle was retracted into the solvent-preloaded capillary with a protrusion length of 0.1–0.2 mm from the tip. A mass spectrum of the sample captured on the needle was obtained by applying a high voltage to the needle. This method could be applicable to profiling analyses of plants with the epicuticular wax covering on the surfaces that are difficult to analyze by sf-PESI. The on-site mass spectrometric analysis for a growing apricot in the field was performed to monitor the developing stage of the fruit.

To reduce food loss from stored products by insect attack, monitoring and early detection of insects are essential. Presently, monitoring with pheromone traps is the primary method for detection; however, traps are effective only after the insects propagate. Detection and identification of the early volatile biomarkers arising from insect-infested brown rice was performed in this study to develop an alternative detection strategy. Brown rice was infested with eggs of seven insect species, including Sitophilus zeamais and Plodia interpunctella. Infested rice emitted at least one of the volatile compounds prenol, isoprenol, dimethyl disulfide, and dimethyl trisulfide (DMTS). In particular, isopentenols were generated by moths within one week of infestation, whereas they were not released from non-infested rice. DMTS was detected from all insect-infested brown rice, especially S. zeamais and P. interpunctella. These volatiles are potential early biomarkers for the presence of insects in brown rice.

Mechanisms underlying the effects of organic amendments on the metabolites in vegetable crop plants remain unclear for the most part. Organic fertilizers are believed to help produce “high quality” vegetables; however, the relationships between organic amendment and vegetable quality are not understood. We took a metabolite profiling approach that comprehensively analyzed both the major and minor constituents of plants. Manure amendments consistently affected the metabolite composition of various vegetable organs in field experiments. Moreover, it was shown that both manure and organic fertilizer amendment caused clear metabolic changes in pot experiments using mizuna (Brassica rapa L. var. Nipponsinica). It is suggested that the amendment of organic matter does indeed influence metabolite composition in vegetables. Further research is needed on the mechanisms responsible for changes in metabolites and on the factors affecting the quality characteristics of foods.

Bacterial ACC deaminase is one of the key tools to ameliorate plant stress by lowering ethylene level in plants. The effects of ACC deaminase-producing bacteria on the volatile profiles in plants have not been examined to date. To address this, we performed metabolic profiling of volatiles in carrots following inoculation of the bacteria producing ACC deaminase. We isolated ACC deaminase-producing bacteria from the inner part of the fruits and vegetables grown on organic farms by culturing on ACC-containing media, and screened them with PCR for the acdS gene, mungbean growth assay, and in vitro ACC deaminase activity. The isolated endophytes were evaluated for their ability to alter volatile profiles in carrots. Eleven bacterial strains possessing the activity to cleave ACC were selected among the 60 isolates grown on the medium containing ACC as a sole N source. Three of them that belonged to Pseudomonas could reduce the levels of (E)-2-hexenal and the other green leaf volatiles (GLVs) and terpenoids in the carrot leaves following inoculation of the seeds. The isolated endophytes with ACC deaminase activity could alter the composition of volatiles in plants, probably through lowering ethylene level in the plant.

Watercore is a so-called physiological disorder of apple (Malus domestica L.) that commonly occurs in several well-known cultivars. It is associated with a rapid softening of the flesh that causes a marked changed in flavor and texture. In Asia, apples with watercore are preferred and considered a delicacy because of their enhanced sweet flavor. The ‘Fuji’ cultivar, the first cultivar with rich watercore that is free from texture deterioration, has played a key role in the development of the market for desirable watercored apples. This review aimed to summarize and highlight recent studies related to the physiology of watercore in apples with special focus on ‘Fuji’ and related cultivars.

This study revealed the cellular dynamics for heat-induced chalky formation and nitrogen-enhanced heat adaptive mechanism by conducting a newly developed on-site cell-specific analysis coupled with time-course analysis via microscopy., Heat-induced chalkiness of rice grains is a major concern for rice production, particularly with respect to climate change. Although the formation of chalkiness in the endosperm is suppressed by nitrogen, little is known about the cell-specific dynamics of this process. Here, using picolitre pressure-probe electrospray-ionization mass spectrometry together with transmission electron microscopy and turgor measurements, we examine heat-induced chalkiness in single endosperm cells of intact rice seeds produced under controlled environmental conditions. Exposure to heat stress decreased turgor pressure and increased the cytosolic accumulation of sugars, glutathione, and amino acids, particularly cysteine. Heat stress also led to a significant enlargement of the protein storage vacuoles but with little accumulation of storage proteins. Crucially, this heat-induced partial arrest of amyloplast development led to formation of chalkiness. Whilst increased nitrogen availability also resulted in increased accumulation of amino acids, there was no decrease in turgor pressure. The heat-induced accumulation of cysteine and glutathione was much less marked in the presence of nitrogen, and storage proteins were produced without chalkiness. These data provide important information on the cell dynamics of heat acclimation that underpin the formation of chalkiness in the rice endosperm. We conclude that rice seeds employ multiple strategies to mitigate the adverse effects of heat stress in a manner that is dependent on nitrogen availability, and that the regulation of protein synthesis may play a crucial role in optimizing organelle compartmentation during heat adaption.

Plant growth promoting bacteria (PGPB) endophytes that express 1-aminocyclopropane-1-carboxylate (ACC) deaminase reportedly confer plant tolerance to abiotic stresses such as salinity by lowering stress-related ethylene levels. Two preselected ACC deaminase expressing endophytic Pseudomonas spp. strains, OFT2 and OFT5, were compared in terms of their potential to promote plant growth, leaf water contents, photosynthetic performance, and ionic balance of tomato plants under conditions of moderate NaCl stress (75 mM). Salinity stress strongly affected growth, leaf water contents, and photosynthetic performance of tomato seedlings, and inoculation with either OFT2 or OFT5 ameliorated these adverse effects. Decreases in plant biomass due to salinity stress were significant in both uninoculated control plants and in plants inoculated with OFT2 compared with plants without NaCl stress. However, no reductions in total biomass were observed in plants that were inoculated with the OFT5 strain. Strain OFT5 influenced growth, physiological status, and ionic balance of tomato plants more efficiently than strain OFT2 under NaCl stress. In particular, inoculated OFT5 reduced salt-induced ethylene production by tomato seedlings, and although it did not reduce shoot uptake of Na, it promoted shoot uptake of other macronutrients (P, K, and Mg) and micronutrients (Mn, Fe, Cu, and Zn). These nutrients may activate processes that alleviate the effects of salt, suggesting that OFT5 can be used to improve nutrient uptake and plant growth under moderate salt-affected conditions by reducing stress-related ethylene levels.

Plant cells have multiple strategies to adapt to environmental stresses. Rice endosperms form chalkiness in a part of the tissue under heat conditions during the grain-filling stage, although nitrogen supply reduces chalky rice. Air spaces formed in the cells cause an irregular light reflection and create chalkiness, yet what exactly occurs remains unclear at cell level. Through on-site cell-specific analysis, we show that heat-treated cells adjust osmotically and retard protein synthesis to preserve protein storage vacuoles in the cytosol, resulting in air space formation. Application of nitrogen enhances heat tolerance to sustain protein body and amyloplast development during strong osmotic adjustment, which diminishes air spaces to avoid chalkiness. Hence, we conclude that rice endosperm cells could alter organelle compartments spatially during the heat adaptation, depending on the available nitrogen level. Our findings provide new insight into the cellular mechanism of rice chalky formation as a strategy for heat acclimation.

This study utilises (1)H NMR-based metabolic profiling to characterise apples of five cultivars grown either in Japan (Fuji, Orin, and Jonagold) or New Zealand (Fuji, Jazz, and Envy). Principal component analysis (PCA) showed a clear separation between the Fuji-Orin-Jonagold class and the Jazz-Envy class, primarily corresponding to the differences in sugar signals, such as sucrose, glucose, and fructose. Multistep PCA removed the influence of dominant sugars and highlighted minor metabolites such as aspartic acid, 2-methylmalate, and an unidentified compound. These minor metabolites separated the apples into two classes according to different geographical areas. Subsequent partial least squares discriminant analysis (PLS-DA) indicated the importance of the unidentified metabolite. This metabolite was isolated using charcoal chromatography, and was identified as L-rhamnitol by 2D NMR and LC/MS analyses. The remarkable contribution of L-rhamnitol to geographic discrimination suggests that apples may be characterised according to various factors, including storage duration, cultivation method, and climate.

We analyzed a metagenome of the bacterial community associated with the taproot of sugar beet (Beta vulgaris L.) in order to investigate the genes involved in plant growth-promoting traits (PGPTs), namely 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase, indole acetic acid (IAA), N2 fixation, phosphate solubilization, pyrroloquinoline quinone, siderophores, and plant disease suppression as well as methanol, sucrose, and betaine utilization. The most frequently detected gene among the PGPT categories encoded β-1,3-glucanase (18 per 10(5) reads), which plays a role in the suppression of plant diseases. Genes involved in phosphate solubilization (e.g., for quinoprotein glucose dehydrogenase), methanol utilization (e.g., for methanol dehydrogenase), siderophore production (e.g. isochorismate pyruvate lyase), and ACC deaminase were also abundant. These results suggested that such PGPTs are crucially involved in supporting the growth of sugar beet. In contrast, genes for IAA production (iaaM and ipdC) were less abundant (~1 per 10(5) reads). N2 fixation genes (nifHDK) were not detected; bacterial N2 -fixing activity was not observed in the (15)N2 -feeding experiment. An analysis of nitrogen metabolism suggested that the sugar beet microbiome mainly utilized ammonium and nitroalkane as nitrogen sources. Thus, N2 fixation and IAA production did not appear to contribute to sugar beet growth. Taxonomic assignment of this metagenome revealed the high abundance of Mesorhizobium, Bradyrhizobium, and Streptomyces, suggesting that these genera have ecologically important roles in the taproot of sugar beet. Bradyrhizobium-assigned reads in particular were found in almost all categories of dominant PGPTs with high abundance. The present study revealed the characteristic functional genes in the taproot-associated microbiome of sugar beet, and suggest the opportunity to select sugar beet growth-promoting bacteria.

Grain filling ability is mainly affected by the translocation of carbohydrates generated from temporarily stored stem starch in most field crops including rice (Oryza sativa L.). The partitioning of non-structural stem carbohydrates has been recognized as an important trait for raising the yield ceiling, yet we still do not fully understand how carbohydrate partitioning occurs in the stems. In this study, two rice subspecies that exhibit different patterns of nonstructural stem carbohydrates partitioning, a japonica-dominant cultivar, Momiroman, and an indica-dominant cultivar, Hokuriku 193, were used as the model system to study the relationship between turgor pressure and metabolic regulation of non-structural stem carbohydrates, by combining the water status measurement with gene expression analysis and a dynamic prefixed 13C tracer analysis using a mass spectrometer. Here, we report a clear varietal difference in turgor-associated starch phosphorylation occurred at the initiation of non-structural carbohydrate partitioning. The data indicated that starch degradation in Hokuriku 193 stems occurred at full-heading, 5 days earlier than in Momiroman, contributing to greater sink filling. Gene expression analysis revealed that expression pattern of the gene encoding α-glucan, water dikinase (GWD1) was similar between two varieties, and the maximum expression level in Hokuriku 193, reached at full heading (4 DAH), was greater than in Momiroman, leading to an earlier increase in a series of amylase-related gene expression in Hokuriku 193. In both varieties, peaks in turgor pressure preceded the increases in GWD1 expression, and changes in GWD1 expression was correlated with turgor pressure. Additionally, a threshold is likely to exist for GWD1 expression to facilitate starch degradation. Taken together, these results raise the possibility that turgor-associated starch phosphorylation in cells is responsible for the metabolism that leads to starch degradation. Because the two cultivars exhibited remarkable varietal differences in the pattern of non-structural carbohydrate partitioning, our findings propose that the observed difference in grain-filling ability originated from turgor-associated regulation of starch phosphorylation in stem parenchyma cells. Further understanding of the molecular mechanism of turgor-regulation may provide a new selection criterion for breaking the yield barriers in crop production. Fil: Wada, Hiroshi. National Agriculture and Food Research Organization; Japón Fil: Masumoto Kubo, Chisato. National Agriculture and Food Research Organization; Japón Fil: Tsutsumi, Koichi. National Agriculture and Food Research Organization; Japón Fil: Nonami, Hiroshi. National Agriculture and Food Research Organization; Japón Fil: Tanaka, Fukuyo. National Agriculture and Food Research Organization; Japón Fil: Okada, Haruka. National Agriculture and Food Research Organization; Japón Fil: Erra Balsells, Rosa. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones en Hidratos de Carbono. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones en Hidratos de Carbono; Argentina Fil: Hiraoka, Kenzo. The University of Yamanashi; Japón Fil: Nakashima, Taiken. National Agriculture and Food Research Organization; Japón Fil: Hakata, Makoto. National Agriculture and Food Research Organization; Japón Fil: Morita, Satoshi. National Agriculture and Food Research Organization; Japón

1-Deoxynojirimycin (DNJ) is a potent α-glucosidase inhibitor and thus beneficial for prevention of diabetes. While we have succeeded in obtaining the culture supernatant extract (CSE) rich in DNJ from microorganism source, information regarding its anti-hyperglycemic effect and safety were still limited. Therefore, this study was aimed to evaluate the anti-hyperglycemic effect and safety of microorganism DNJ. Oral sucrose tolerance test was performed, and the result showed that CSE was able to significantly suppress the blood glucose elevation and suggested DNJ as the main active compound. To determine its safety, the absorption and excretion of microorganism DNJ were evaluated using 15N labeling method. Our findings investigated the recovery rate of 15N from DNJ reached 80% up to 48 hours after oral administration, suggesting its rapid excretion, suggesting the safety of DNJ. This study verified the functional properties and safety of DNJ from microorganisms, suggesting its potential use for functional purpose.

Flavors of “Fuji” apple cultivated with or without synthetic agrochemicals were compared using quantitative descriptive analyses (QDA) and metabolite profiling for 3 seasons. Experimental plots included conventional crops (with agrochemicals) and organic crops (without agrochemicals) at our institute and organic and conventional farms. Additionally, mass market samples were analyzed. Organic apples were weak in sweetness and floral characteristics and had enhanced green and sour flavors. Most esters and sugars were present in lower concentrations in organic than in conventional apples. Close relation of principal component 1 of QDA and metabolite profiles, to ethylene production suggested that ethylene is considerably involved in flavor synthesis. Reduced ethylene associated with immaturity accounted for insufficient flavor synthesis and weak aroma and flavor attributes of organic apples. Furthermore, organic apples from the farm were more flavorsome than those from the institute in 2012, suggesting possible recovery of ethylene production after a long organic cultivation period.

(1) ホウレンソウより抽出した遊離Aspと遊離GluのGC/C/IRMSによるδ15N測定値は,土中の有機成分の影響を受けない水耕栽培が最も小さく,窒素施肥量が同じ条件では化学肥料のみ施用,化学肥料と有機肥料半分ずつ(慣行),有機肥料のみの順にプラス側に大きくなった.さらに有機肥料のみ三倍施用した場合はより大きくなり,他の測定値との間に統計的に有意な差が見られた.これらのδ15N測定値と有機肥料施肥量との間には,遊離GluでR2=0.9336,遊離AspではR2=0.8788の高い相関があった.また,IRMSによる全植物体のδ15N測定値と有機肥料施用量との関係は,GC/C/IRMSでの結果より相関は低いが,同様の結果であった.これらの結果から,δ15N測定値は有機肥料の施肥量が多くなるに従い大きくなり,ホウレンソウの栽培条件,有機肥料を与えたか否かを推定できた.(2) ホウレンソウ全植物体中のδ15Nが有機肥料の施肥量に従って大きくなるのは,遊離やタンパク質を構成するアミノ酸類,特にGluおよびAspに重窒素が蓄積されることを反映したものであった.

The natural 15N abundances (δ15N values) were measured for nitrate and free and bound amino acids from the leaves of field-grown spinach (Spinacia oleracea L.) and komatsuna (Brassica campestris L.), as well as ureides and free and bound amino acids in the leaves and roots of hydroponically grown soybean (Glycine max L.) totally depending on dinitrogen. Nitrate from the spinach and komatsuna leaves and ureides from leaves and roots of soybean showed higher δ15N values than the total tissue N and N in free or bound amino acid fractions. The δ15N values of individual free and bound amino acids, determined by GC/C/MS using their acetylpropyl derivatives, were similar in leaf tissues except for proline but varied in soybean root tissues. The order of 15N enrichment was similar in the four samples: aspartic acid > glutamic acid > threonine, proline, valine > glycine + alanine +serine, γ-amino butyric acid, and phenylalanine.

Absrtact The application of fresh wheat or barley straw often inhibits the growth and N uptake of paddy rice plants in the establishment phase. This inhibition is mainly attributed to the deficiency of available N in soil, resulting from a large N assimilation by soil microbes in soils supplied with straw (Rao and Mikkelsen 1976). In a previous report (Tanaka and Nishida 1996), we showed that the activity of 15N uptake from 15NH4 + introduced into the soil decreased by straw application. We found the accumulation of some aromatic acids in soils to levels inhibitory to root elongation when fresh wheat straw was applied (Tanaka 1990; Tanaka et al. 1990). No attempt were made to investigate the effects of aromatic acids on N uptake by rice seedlings. Here we report on examination on whether aromatic acids such as 2-phenylpropanoic acid (2P), 3-phenylpropanoic acid (3P), and benzoic acid (BA), found in paddy soils, may inhibit N uptake and transport in rice plants.

This experiment was carried out to determine whether the delay in rice growth associated with wheat straw application, especially at the early stage, was due to the acceleration of N assimilation or N uptake inhibition. Tracer 15N was used for rice plants cultivated in pots. After 24 h of tracer application the plants and soils were sampled for analysis. Seventeen days after transplanting, N uptake of rice decreased and the amount of unavailable tracer remaining in soil increased by wheat straw application. At the booting stage, 6 d before heading, N uptake was larger and the amount of remaining tracer was lower in the plots in which wheat straw was applied than in the control. It was obvious that the decrease of N uptake by wheat straw application was caused by N uptake inhibition and not by N starvation for a period of time at the early stage. The inhibition was removed at the booting stage.

An analytical method to measure 13C abundance in 13C enriched oxalate using gas chromatograph/combustion/isotope ratio mass spectormeter (GC/C/IRMS) was established. The 13C atom% values of oxalate measured by GC/C/IRMS were nearly equal to those measured by automated nitrogen and carbon analyzer-mass spectrometer (ANCA-MS) giving a high degree of correlation (r2=0.9999) and good reproducibility (CV=0.224%). This method will be applicable in the study of oxalate metabolism in spinach.

A simplified method for the determination of benzoic 2-phenylpropionic, 3-phenylpropionic, and 4-phenylbutyric acids in paddy field soils using a gas chromatograph-mass spectrometer equipped with a capillary column is described. The entire procedure of this method involves the collection of the soil solution, extraction with chloroform, methylation of the acids with diazo- methane and analysis by gas chromatography-mass spectrometry. In this method, extracts were prepared by shaking the soil solution with chloroform at room temperature for 60 min. The use of a chloroform extractant instead of ether enabled to omit the procedure for the removal of water after the extraction process. This method showed a high sensitivity and high selectivity in the analysis of the aromatic acids dissolved in the soil solution. The sample of soil solution collected through a porous cup was concentrated on a hot plate and extracted with chloroform after acidification. Aromatic acids in a dilute solution whose concent...

Rice root elongation was markedly inhibited by the solution extracted from flooded soil incubated with wheat straw. The toxicity was mainly due to the ether extractable fractions under acidic conditions. The following organic acids were detected in the ether extract of the soil solution: aliphatic acids; formic, acetic, propionic, butylic, and iso-valeric acids; aromatic acids; benzoic, 2-phenylpropionic, and 3-phenylpropionic acids. In another experiment, the soil solution from the field amended with wheat straw contained 2-hydroxybenzoic acid and the aromatic acids described above. The results of a bioassay with aromatic acids for rice seedlings showed that 2-phenylpropionic and 3-phenylpropionic acids exerted a severe inhibitory effect, which reduced rice root elongation by 73.3 and 30.7%, respectively at 4×10−5M.