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ABSTRACTA hydrolyzable tannin, oenothein B, has recently been identified as a novel type of Al-binding and detoxifying ligand in a highly aluminum (Al)-resistant tree, Eucalyptus camaldulensis. Oenothein B is mainly localized in the root symplast, where the known ligands, citrate and oxalate, are also present. In this study, to investigate whether oenothein B can form complexes with Al in the presence of citrate and oxalate, we analyzed the chemical form of Al in multiple - ligand mixtures containing Al, oenothein B, citrate, and oxalate in vitroat concentrations mimicking those in the symplast of E. camaldulensisroots. In the mixture, 27% of total Al was detected in the insoluble fraction, and 28% in the high-molecular mass (> 10 kDa) soluble fraction. This means that more than half of Al in the mixture interacts with oenothein B, because among the three ligands only oenothein B can predominantly form insoluble or high molecular mass soluble complexes with Al. The 27Al-nuclear magnetic resonance analyses of the mixture showed that low-molecular mass soluble Al was not mainly composed of simple Al–citrate or Al–oxalate complexes. These results support our hypothesis that oenothein B contributes to internal detoxification of Al in the symplast of E. camaldulensisroots.

Tricholoma matsutake, a basidiomycete, forms ectomycorrhizas with Pinus densifloraas the host tree. Its fruiting body, “matsutake” in Japanese, is an edible and highly prized mushroom, and it grows in a circle called a fairy ring. Beneath the fairy ring of T. matsutake, a whitish mycelium-soil aggregated zone, called “shiro” in Japanese, develops. The front of the shiro, an active mycorrhizal zone, functions to gather nutrients from the soil and roots to nourish the fairy ring. Bacteria and sporulating fungi decrease from the shiro front, whereas they increase inside and outside the shiro front. Ohara demonstrated that the shiro front exhibited antimicrobial activity, but the antimicrobial substance has remained unidentified for 50 years. We have identified the antimicrobial substance as the (oxalato)aluminate complex, known as a reaction product of oxalic acid and aluminum phosphate to release soluble phosphorus. The complex protects the shiro from micro-organisms, and contributes to its development.

Environmental contextRice is a major human dietary source of arsenic. We identified a novel organoarsenic species, arsinothricin, produced by a bacterium in the rice rhizosphere. This result suggests diverse biochemical dynamics and microbial biodiversity of arsenic metabolism in the rice rhizosphere. AbstractMethylated arsenic compounds in rice grains originate from the action of soil bacteria in the rice rhizosphere. Here, we investigated the chemical structures of arsenic compounds produced by a bacterium, Burkholderia gladioli strain GSRB05, in the rice rhizosphere. When cultured in liquid R2A medium containing arsenite (AsIII), strain GSRB05 produced two unknown novel arsenic compounds that were later identified as arsinothricin (AST, 2-amino-4-(hydroxymethylarsinoyl)butanoic acid), an arsenic mimetic of the herbicide phosphinothricin, and a probable hydroxyl precursor of AST, termed AST-OH (2-amino-4-(dihydroxyarsonoyl)butanoic acid). The chemical structure of AST was determined by means of liquid chromatography–high-resolution tandem mass spectrometry and NMR analyses, whereas that of AST-OH was estimated by means of ultra-high-performance liquid chromatography–tandem mass spectrometry. Time-dependent AsIII transformation by strain GSRB05 showed that AST was produced after AST-OH. Compared with AsIII, AST showed higher absorption by, and was more toxic to, Escherichia coli DH5α cells in M9 minimal medium, which lacks amino acids. These findings have implications for the environmental transfer of arsenic, and human health consequences in terms of our dietary burden of arsenic.

We tested whether vegetation recovery on an oceanic island after the eradication of feral goats is related to disturbances by goats and recovery of seabird nesting in an island. To test, we investigated relationships among the aboveground biomass of herbaceous vegetation, nutrient concentrations in the soil after goat eradication, and vegetation degradation before goat eradication and seabird nesting after the eradication. The investigation was conducted on the island of Nakoudojima, a subtropical island situated in the northwestern Pacific Ocean with consideration of fine-scale variation of topography and structure of current vegetation. The aboveground biomass of herbaceous vegetation was correlated with the presence of vegetation degradation before goat eradication but not with seabird nesting after eradication. Concentrations of carbon and nitrogen in the soil were correlated with both the presence of vegetation degradation and seabird nesting. The concentration of available phosphorus in the soil was correlated with nesting seabirds but not with vegetation degradation. The presence of nesting seabirds was correlated with differences in dominant species in the vegetation after goat eradication and with topography. Our results suggested that fine-scale heterogeneities of the aboveground biomass of herbaceous vegetation and the concentrations of nutrients in the soil after goat eradication in an island could be related to vegetation degradation and subsequent erosion of surface soil caused by goats and seabird nesting after the goat eradication.

We analyzed the physicochemical and spectroscopic properties of three charred plant fragments (CPF) that were isolated from three volcanic ash soils in Japan. Values of 13C showed that the CPF originated from C3and C4plants. The contribution ratio of C4plants to the CPF was much higher in Soils 1 and 3 than in Soil 2. Values of 15N of the CPF were higher in Soil 3 isolated from the deeper soil horizons. Light reflectance values suggested that part of the CPF experienced combustion temperatures higher than 400°C in Soil 2 and less than 400°C in the other soils, respectively. Atomic HC and OC ratios suggested that the CPF were subjected to weathering (oxidative degradation and hydrolysis) in soil for a long period after burning. The degree of weathering was considered to be larger in Soils 1 and 3. Spectra of 13C-NMR of the CPF, except the area of alkyl-C, were similar. Infrared (IR) spectra of three CPF, except aliphatic C-H stretching, were also similar to each other. The X-ray diffraction patterns of the CPF in Soil 2 clearly revealed the presence of graphite-like structure. From these findings, it was assumed that the physicochemical and spectroscopic characteristics of the CPF were strongly influenced by the type of burnt vegetation.

Abstract: Mealybugs, which include several agricultural pests, are small sap feeders covered with a powdery wax. They exhibit clear sexual dimorphism; males are winged but fragile and short lived, whereas females are windless and less mobile. Thus, sex pheromones emitted by females facilitate copulation and reproduction by serving as a key navigation tool for males. Although the structures of the hitherto known mealybug pheromones vary among species, they have a common structural motif; they are carboxylic esters of monoterpene alcohols with irregular non-head-to-tail linkages. However, in the present study, we isolated from the Matsumoto mealybug, Crisicoccus matsumotoi (Siraiwa), a pheromone with a completely different structure. Using gas chromatography–mass spectrometry and nuclear magnetic resonance spectroscopy, we identified the pheromone as 3-methyl-3-butenyl 5-methylhexanoate. Its attractiveness to males was confirmed in a series of field trapping experiments involving comparison between the isolated natural product and a synthetic sample. This is the first report of a hemiterpene mealybug pheromone. In addition, the acid moiety (5-methylhexanoate) appears to be rare in insect pheromones.

Batch adsorption and consecutive desorption experiments were performed under different pH conditions to assess the pH dependency of 2,4-dichlorophenoxyacetic acid (2,4-D) adsorption and desorption in Andosol (having pH-dependent surface charge characteristics) and kaolinite. The adsorption-desorption isotherms for both Andosol and kaolinite were well fitted by the Freundlich isotherm model. Adsorption of 2,4-D onto Andosol increased markedly with decreasing pH and was higher than for kaolinite under the same pH condition. Hysteresis, expressing the nonsingularity of the desorption compared with the adsorption isotherm, was found at all concentrations and each pH for both Andosol and kaolinite. For Andosol, the fitted Freundlich parameters for desorption, Kf,dand nd, showed a negative, linear and a positive, exponential relationship, respectively, with pH. Higher hysteresis index (), expressing the degree of partial irreversibility of 2,4-D adsorption, was obtained under lower pH, indicating that less adsorbed 2,4-D was released back from the Andosol under acidic condition. The effect of pH on 2,4-D desorption from kaolinite was less pronounced as compared with Andosol. Combining the measured data in this study with previously reported data on 2,4-D adsorption-desorption in several types of soil including Andosols, the possible mobility of adsorbed 2,4-D in soil was evaluated. Results show that adsorbed 2,4-D in soils exhibiting a total adsorption percentage of less than 55 of the applied pesticide typically exhibited a greater potential to be mobile in the soil-water system. Opposite, a total adsorption percentage greater than 55 implied higher residual adsorption and a prolonged existence of adsorbed 2,4-D in the soils.

We investigated 10 soils from six states in the United States to determine the relationship between potentiometric titration derived soil surface charge and the concentration of water‐extractable P (WEP). Phosphorus‐31 nuclear magnetic resonance (NMR) spectroscopy was used to determine the chemical speciation of soil P. The surface charge value at the native soil pH was correlated to the WEP concentration, indicating that electrostatic interactions are involved in determining soil phosphate solubility. The titration curves were fit to a two‐site Langmuir model and analysis showed that the native pH surface charge was accounted for by the low pH Type 1 (S‐OH2+) site, attributed to positively charged metal (oxy)hydroxides. The 31P NMR data indicated that 98% of the inorganic form of P was composed of orthophosphate species and 95% of the organic P was composed of the P monoester class compounds. The inorganic orthophosphate form of P was directly related to the total soil P content, suggesting that external fertilizer inputs control the level of this form of soil P. In contrast, P monoester class compound content was not related to total soil P content, suggesting that organic soil P is controlled by P cycling independent of external P inputs. The 31P NMR speciation data indicated that the inorganic orthophosphate, pyrophosphate, and DNA P concentrations in the soils were significantly associated with oxalate‐extractable Al and Fe concentrations, which further demonstrates that metal (oxy)hydroxides are important surfaces where P species are interacting with soils.

Abstract: In this study, we discovered and isolated an attractant for a mealybug-parasitic wasp Anagyrus sawadai from an esterification product prepared with commercialized lavandulol (2-isopropenyl-5-methyl-4-hexen-1-ol) and butyryl chloride. Using gas chromatography-mass spectrometry (GC-MS) and nuclear magnetic resonance spectroscopy, we determined the structure of the compound to be (2,4,4-trimethyl-2-cyclohexenyl)methyl butyrate (cyclolavandulyl butyrate). This is a novel compound as far as we know, although the alcohol moiety has been known as a cyclization product from lavandulol. Cyclolavandulyl butyrate has two enantiomers, and the (−)-isomer, which is suggested to have S configuration, showed higher attractiveness. A potential use for the A. sawadai attractant for mealybug management in agricultural fields is discussed.

To identify the important soil components involved in 2,4‐dichlorophenoxyacetic acid (2,4‐D) adsorption on Andosols, 2,4‐D adsorption on a surface horizon of an Andosol was compared with that on hydrogen peroxide (H2O2)‐treated (soil organic matter [SOM] was removed), acid‐oxalate (OX)‐treated (active metal hydroxides and SOM were removed), and dithionite‐citrate‐bicarbonate (DCB)‐treated (free and active metal [hydr]oxides and SOM were removed) soil samples at equilibrium pHs ranging from 4 to 8. Although the untreated soil contained a large amount of organic C (71.9 g kg−1), removal of SOM had little effect on 2,4‐D adsorption. Active surface hydroxyls, which were attached to the active and free metal (hydr)oxides and metal SOM complexes, were identified as the most important soil functional group for 2,4‐D adsorption. The dominant mechanism of the 2,4‐D adsorption was a ligand exchange reaction in which the carboxylic group of 2,4‐D displaced the active surface hydroxyl associated with metals and formed a strong coordination bond between the 2,4‐D molecule and soil solid phase. The ligand exchange reaction reasonably accounted for the selective adsorption of 2,4‐D over Cl−, competitive adsorption of phosphate over 2,4‐D, reduction in plant‐growth‐inhibitory activity of soil‐adsorbed 2,4‐D, and the high 2,4‐D adsorption ability of Andosols. Although a humic acid purified from the soil did not adsorb 2,4‐D, the presence of the humic acid increased 2,4‐D adsorption on Al and Fe, probably by inhibiting the hydrolysis and polymerization of Al and Fe resulting in the preservation of available adsorption sites on these metals. The adsorption behavior of 2,4‐D on soils could be a good index for predicting the adsorption behavior of other organic acids in soils.

Allophanes are poorly crystalline and quasi-stable aluminosilicate minerals, the structures of which are sensitive to chemical treatment. In the present study, solid-state 27Al and 29Si nuclear magnetic resonance (NMR) spectra of allophane samples were monitored as they went through several purification procedures. It was confirmed that no significant structural changes were caused by boiling with 6% H2O2to remove organic matter, by size fractionation (sonification), by sedimentation, by precipitation at pH 4.0, or by dithionite-citrate-bicarbonate treatment for the removal of Fe (hydr)oxides. Hot 5% Na2CO3treatment for the removal of reactive silica-alumina gels and adsorbed citrate from allophane samples, however, decreased signal intensity corresponding to imogolite-like Si (Q33VIAl, −78 ppm in 29Si NMR) and increased signal intensities corresponding to IVAl (55 ppm in 27Al NMR) and possibly X-ray amorphous aluminosilicates (centered at −85 ppm in 29Si NMR). Cold (room temperature) 5% Na2CO3treatment for 16 h proved to be effective in avoiding these structural changes.

3-(3',4'-Dihydroxyphenyl)-L-alanine (L-DOPA), which is a component of velvetbean (Mucuna pruriens), displays a high inhibitory activity to plant growth. The inhibitory activity is influenced by the presence of soils, because L-DOPA is eliminated in soils. In the present study, the effect of several soil types (volcanic ash, calcareous, and alluvial soils) on the L-DOPA disappearance was investigated at constant equilibrium pH values. In the presence of soils, L-DOPA disappeared with the reaction time, and the disappearance was associated with three reactions: adsorption reaction (characterized by fast and sudden disappearance of L-DOPA within the initial 8 h period), catalytic transformation reaction (constant L-DOPA disappearance throughout the reaction period), and biotransformation caused by microbial activity (accelerated L-DOPA disappearance observed after 72 h of reaction time). The adsorption and transformation reactions consisted of physicochemical reactions mediated by the presence of soils. The amount of L-DOPA adsorbed was largest in the presence of volcanic ash soil among the three soil types. It is likely that the mechanism of L-DOPA adsorption includes a ligand exchange reaction. In the presence of soils, L-DOPA transformation was observed at equilibrium pH values higher than 4 and it increased with increasing equilibrium pH values. In the absence of soil, however, L-DOPA transformation did not occur at an equilibrium pH value lower than 6.0, indicating that L-DOPA transformation was accelerated by the presence of soil. The rate of L-DOPA transformation mediated by soils at constant equilibrium pH value was in the following order: alluvial soil > calcareous soil > volcanic ash soil. The plant-growth-inhibitory activity of L-DOPA was also reduced by the presence of soils, and the reduction in the case of L-DOPA was more obvious than in the case of 2,4-dichlorophenoxyacetic acid (2,4-D). Based on the reduction effect of soils on the plant-growth-inhibitory activity of L-DOPA (without pH-adjustment), calcareous soil ranked first, followed by volcanic ash soil, then alluvial soil. This was because the calcareous soil showed the highest soil pH value (7.8), and thereby the L-DOPA transformation reaction was accelerated. In soils with high pH values, the plant-growth-inhibitory activity of L-DOPA could therefore not be detected.

Abstract Robinia pseudo-acacia L. (black locust) is a nonindigenous species currently invading the central part of Japanese grasslands. Several allelochemicals were identified and characterized from the leaf tissue. The growth of both radicle and hypocotyl in the tested species (barnyard grass, white clover, lettuce, and Chinese cabbage) was reduced when grown in soil mixed with the leaves of R. pseudo-acacia at various concentrations. Aqueous leaf extracts, when bioassayed, exhibited a significant suppression of radicle growth. Chromatographic separation of an ethanolic extract of R. pseudo-acacia leaves resulted in isolation of three compounds, identified as robinetin (1), myricetin (2), and quercetin (3) by nuclear magnetic resonance and mass spectroscopy. All inhibited root and shoot growth of lettuce. Robinetin, found in a large amount, caused 50% suppression of the root and shoot growth of lettuce at 100 ppm. The presence of these bioactive substances in leaf tissue suggests a potential role for flavonoids in R. pseudo-acacia invasion in introduced habitats.

To clarify the weathering process of volcanic glass to allophane, solid-state 29Si and 27Al magic angle spinning (MAS) nuclear magnetic resonance (NMR) signals of four Japanese volcanic glasses and two (Al- and Si-rich) allophanes were assigned. The volcanic glasses showed a broad 29Si NMR signal between −80 and −120 ppm with the peak centered at ~ −104 ppm, indicating that they were rich in Si-O-Si bridging structure (silica gel-like polymer Si). Aluminum was present in tetrahedral form in the four volcanic glass samples. In both Al- and Si-rich allophanes, octahedral Al (3 ppm by 27Al NMR) and imogolite-like Si (Q33VIAl, −78 ppm by 29Si NMR) were the major components. In a Si-rich allophane, NMR signals centered at around −85 ppm for 29Si and 55 ppm for 27Al were also observed, although it is possible that those signals were derived from impurities. Impurities could have originated from the soils and/or been unexpectedly synthesized during the purification procedures, e.g.during hot 2% Na2CO3treatments. Based on the NMR spectra of size-fractionated soil samples, the weathering process of volcanic glass to allophane was proposed as follows: (1) dissolution of Al from volcanic glass accompanied by the transformation of IVAl to VIAl; (2) formation of a gibbsite-like sheet resulting from the hydrolysis of the dissolved Al; (3) dissolution of silica gel-like polymer Si in volcanic glass resulting in the formation of monosilicic acid; and (4) formation of Si(OH)(OVI,Al)3structure (Q33VIAl) as a result of the reaction between the gibbsite-like sheet and the monosilicic acid. These formation reactions of allophane could occur in solution as well as on the surface of volcanic glass.

Velvetbean (Mucuna pruriens) has been reported to release 3-(3',4'-dihydroxyphenyl)-L-alanine (L-DOPA) as an allelochemical that inhibits the growth of other plants, although the inhibitory activity depends on the soil type and it is extremely reduced in Andosols. To clarify the effects of Andosols and their components on the chemical structure and plant-growth-inhibitory activity of L-DOPA, an L-DOPA solution was reacted with an Andosol and its components (weathered pumice and purified allophane), and the resultant solution was subjected to 1H nuclear magnetic resonance and ultraviolet-visible spectral analyses, and plant-growth-inhibitory activity tests. When the L-DOPA solution was added to the soil components, the concentration of L-DOPA in the solution decreased by adsorption and transformation (polymerization) reactions. The adsorption mechanism included a ligand exchange reaction. The rate of L-DOPA transformation was faster at higher pH values. The soil components displayed a catalytic activity and accelerated the transformation of L-DOPA. Similar transformation occurred when light was irradiated. At pH values higher than 4.0, the transformed products from L-DOPA consisted of humic substances-like heterogeneous components, whereas specific components with low molecular weight were included when L-DOPA was transformed at a pH value of 9.7 or higher. The plant-growth-inhibitory activity of L-DOPA was extremely weakened when L-DOPA was adsorbed on or transformed (polymerized) by soil components. Therefore, in soils with high abilities of adsorption and transformation of L-DOPA such as in Andosols, it was likely that the L-DOPA concentration in the soil solution decreased quickly by adsorption and transformation reactions and the allelopathic activity of L-DOPA was lost.

Abstract Crude extracts of the leaves of Spiraea prunifolia Sieb. showed high plant-growth-inhibiting activity comparable to that of S. thunbergii extracts. To isolate the causal compound in S. prunifolia, we performed bioassay-directed purification by monitoring the biological activity per unit weight of the organism containing the bioactive compound (total activity). We isolated 1-O-cis-cinnamoyl-β-D-glucopyranose (cis-CG) and identified it as the most important growth-inhibiting constituent in the crude extracts. We did not detect 6-O-(4′-hydroxy-2′-methylenebutyroyl)-1-O-cis-cinnamoyl-β-D-glucopyranose (cis-BCG) in S. prunifolia, though it is a major plant growth inhibitor in S. thunbergii together with cis-CG. We estimated the cis-CG content in S. prunifolia to be 3.84 mmol  kg−1 F.W. This amount is comparable to the cis-CG plus cis-BCG content in S. thunbergii (3.59 mmol  kg−1 F.W.). This indicates that S. prunifolia and S. thunbergii have equally high potential to inhibit plant growth, and cis-CG acts as the most important plant-growth inhibitor in S. prunifolia extracts.

To gain a better understanding about the δ13C values of organic constituents and possible source of humic substances in Japanese volcanic ash soils, we determined the δ13C values of charred plant fragments, humic and fulvic acids, and whole soils, using 10 volcanic ash soil samples. Furthermore, the characteristics of the humic acid obtained from the dil. H2O2-treated residues of charred plant materials, which were produced during the burning of a grassland, were compared with those of black (type A) humic acids in volcanic ash soils. The δ13C values of the charred plant fragments, humic and fulvic acids, and whole soils studied ranged from −25 to −17‰, −25 to −17‰, −23 to −15‰, and −24 to −17‰, respectively. The δ13C values of the whole soils were highly correlated with those of the charred plant fragments (r= 0.968, significant at 0.1% level), humic acids (r= 0.947, significant at 0.1% level) or fulvic acids (r= 0.900, significant at 0.1% level), suggesting that in Japanese volcanic ash soils, the δ13C data of whole soils are valuable for discussing and estimating the origin of carbon of charred plant fragments as well as humic and fulvic acids. The δ13C values of the charred plant fragments were highly correlated with those of the fulvic acids (r= 0.792, significant at 1% level) and especially humic acids (r= 0.951, significant at 0.1% level). The contribution ratios of C4-plant-derived carbon on the carbon in the charred plant fragments, humic and fulvic acids, and whole soils ranged from 15 to 69%, 16 to 65%, 29 to 86%, and 24 to 66%, respectively. The 13C-NMR spectrum and X-ray diffraction pattern of the humic acid obtained from the oxidative degradation products of the charred plant materials were similar to those of type A humic acids reported previously. Based on these findings, it was assumed that both charred C3- and C4-plant materials merit close attention as an important source of humic substances in Japanese volcanic ash soils.

Abstract Spiraea thunbergii Sieb. contains 1-O-cis-cinnamoyl-ß-d-glucopyranose (CG) and 6-O-(4'-hydroxy-2'-methylene-butyroyl)-1-O-cis-cinnamoyl-ß-d-glucopyranose (BCG) as major plant growth inhibiting constituents. In the present study, we determined the inhibitory activity of CG and BCG on root elongation of germinated seedlings of lettuce (Lactuca sativa), pigweed (Amaranthus retroflexus), red clover (Trifolium pratense), timothy (Phleum pratense), and bok choy (Brassica rapa var chinensis) in comparison with that of two well-known growth inhibitors, 2,4-dichlorophenoxyacetic acid (2,4-D) and (+)-2-cis-4-trans-abscisic acid (cis-ABA), as well as two related chemicals of CG and BCG, cis-cinnamic acid (cis-CA) and trans-cinnamic acid (trans-CA). The EC50 values for CG and BCG on lettuce were roughly one-half to one-quarter of the value for cis-ABA. cis-Cinnamic acid, which is a component of CG and BCG, possessed almost the same inhibitory activity of CG and BCG, suggesting that the essential chemical structure responsible for the inhibitory activity of CG and BCG is cis-CA. The cis-stereochemistry of the methylene moiety is apparently needed for high inhibitory activity, as trans-CA had an EC50 value roughly 100 times that of CG, BCG, and cis-CA. Growth inhibition by CG, BCG, and cis-CA was influenced by the nature of the soil in the growing medium: alluvial soil preserved the bioactivity, whereas volcanic ash and calcareous soils inhibited bioactivity. These findings indicate a potential role of cis-CA and its glucosides as allelochemicals for use as plant growth regulators in agricultural fields.

Two distinct electroantennographycally active (EAG-active) components, A and B, and a weakly active component C were found in a solvent extract from virgin females of the Ishigaki strain of the tussock moth, Orgyia postica(Walker). Components A, B, and C were found in the extract of the females at 4.0, 0.5, and 4.0 ng/female respectively. Components A, B, and C were identified as (6Z,9Z,11S,12S)-11,12-epoxyhenicosa-6,9-diene [(11S,12S)-1: posticlure], (6Z)-henicos-6-en-11-one (2), and (6Z,9Z)-henicosa-6,9-diene (3), respectively. Component B was absent in the extract from the Okinawa strain, in which components A and C were present at 2.0 and 1.5 ng/female respectively. (11S,12S)-1and the racemic mixture showed attractiveness for both the Okinawa and Ishigaki strains, whereas (11R,12R)-1did not. The addition of 2significantly reduced the trap catches with (11S,12S)-1on the Okinawa strain which lacked 2, while there was no significant inhibitory effect on the Ishigaki strain. The addition of 3to (11S,12S)-1did not significantly affect trap catches at Ishigaki or Okinawa. This confirmed that the attractant pheromone of O. posticaof the Ishigaki strain is also (11S,12S)-1.

The PCS (commercial products by Field Science Co, Japan, used for air fresheners) was analyzed for the presence of bioactive constituents and their role as root growth promoters. Chromatographic separation of the methanolic solution of PCS resulted in the isolation of an promoting active substance, which was identified using GC-mass spectrometry and NMR spectroscopy as 1,2-propanediol (CH3CH(OH)CH2OH). Lettuce seedling growth bioassay as test plant revealed that 1,2-propanediol can act as potent root growth promoter; enhancing the growth of lettuce seedling radicle at a concentration 0.01 ppm. The concentration of 1,2-propanediol in PCS mixture was estimated as 4 g/l. These studies suggest that 1,2-propanediol might play an important role in the plant growth promoting activity of PCS.

We investigated the influences of humic acid on the removal of Al tridecamer (Al13) from a hydroxyaluminum (HyA) solution at various humic acid/Al ratios. The Al species contained in the solution were analyzed by using a liquid‐state 27Al‐NMR and an atomic absorption spectrometer and fractionated into three Al species: (i) Al13, (ii) Al monomer and dimer (AlSYM), and (iii) other undefined species including aggregated/precipitated Al (AlNON). By the addition of humic acid to the HyA solution, the concentration of Al13was rapidly decreased within 0.007 d (10 min). The decrease in Al13and the increase in AlNONwere more pronounced at a higher humic acid/Al ratio. When the molar ratio of humic acid carboxylic groups to Al exceeded 0.8, Al13was undetected from solution within 0.007 d. The formation of Al13–humic acid complexes and the aggregation/precipitation of those complexes were a predominant mechanism in removing aqueous Al13at the early stage of the reaction. Approximately 10 mol of carboxylic groups in humic acid were required to remove 1 mol of Al13from the HyA solution. Aqueous Al13had greater preference in precipitating with humic acid than AlSYMAfter 5 to 570 d of aging, the concentration of Al13and AlNONalso decreased and increased, respectively, both in the presence and absence of humic acid. In conclusion, aqueous Al13would not exist in soil solution under a high humic acid condition.

Allelopathic potential of Ophiopogon japonicuswas investigated. The methanolic extract of O. japonicusroots strongly inhibited root and hypocotyls growth of lettuce. Sequential partitioning of the methanol extract with organic solvents showed that the diethyl ether and n-butanol extract possess strong plant growth inhibitory activities. The allelopathic constituents of the diethyl ether extract were isolated and identified as salicylic acid and p-hydroxybenzoic acid by NMR spectroscopy. Both of these phenolic acids were found in the aqueous extracts of leaves as well. The concentration of salicylic acid in roots and leaves were estimated as 0.011 and 0.02%, respectively, and it inhibited the root and shoot of tested plants by 50% even at less than 3 ppm. The p-hydroxybenzoic acid on the other hand was in less abundance (0.005%) and inhibited the plant growth to a lesser extent. The biological activity of commercially available O-methyl derivatives of these phenolic acids was also determined to establish structure–activity relationship. Among these, salicylic acid was found to be the most active one. These results suggest that Ophiopogon japonicusproduces plant growth inhibitors, which are responsible for its potential allelopathic activity.

AbstractEffects of soil organic matter (80M) on P sorption of soils still remain to be clarified because contradictory results have been reported in the literature. In the present study, pH-dependent P sorption on an allophanic Andisol and an alluvial soil was compared with that on hydrogen peroxide (H202)-treated, acid-oxalate (OX)-treated, and dithionite-citrate- bicarbonate (DCB)-treated soils. Removal of 80M increased or decreased P sorption depending on the equilibrium pH values and soil types. In the H2O2OX-, and DCB-treated soils, P sorption was pH-dependent, but this trend was not conspicuous in the untreated soils. It is likely that 80M affects P sorption of soils through three factors, competitive sorption, inhibition of polymerization and crystallization of metals such as AI and Fe, and flexible structure of metal-80M complexes. As a result, the number of available sites for P sorption would remain relatively constant in the wide range of equilibrium pH values in the presence of 80M. The P sorption characteristics were analyzed at constant equilibrium pH values (4.0 to 7.0) using the Langmuir equation as a local isotherm. The maximum number of available sites for P sorption (Qmax) was pH-dependent in the H202-, OX-, and DCBtreated soils, while this trend was not conspicuous in the untreated soils. Affinity constants related to binding strength (K) were less affected by the equilibrium pH values, soil types, and soil treatments, and were almost constant (log K≈ 4.5). These findings support the hypothesis that 80M plays a role in keeping the number of available sites for P sorption relatively constant but does not affect the P sorption affinity. By estimating the Qmaxand Kvalues as a function of equilibrium pH values, pH-dependent P sorption was well simulated with four or two adjustable parameters. This empirical model could be useful and convenient for a rough estimation of the pH-dependent P sorption of soils.

AbstractAlthough aluminum (Al) is abundant in soil environments, it is not an essential element and it is toxic to most organisms. Since the toxicity of Al depends on their chemical forms, the importance of Al speciation has been recognized worldwide. Difficulties in Al speciation are caused by the complex coordination chemistry of Al for the hydrolysis and formation of polynuclear species with a variable degree of solubility in aqueous solution. Nondestructive analyses, such as nuclear magnetic resonance (NMR) spectroscopy, could supply primarily im-portant information on the chemical forms of Al and may enable to evaluate the results ob-tained by other methodologies. In the present report, NMR spectral characteristics of environmentally important Al-containing components, such as hydoxyaluminum ions, Alinorganic complexes, Al-organic complexes, and primary and secondary minerals, are summarized for the nuclei of 27Al and 29Si determined by solution NMR and solid-state magic angle spinning (MAS) NMR. Applications of NMR techniques to soil science, including speciation of phytotoxic Al in soil environments and whole soil NMR studies, are described.

A sex pheromone component of Pseudococcus cryptushas been isolated and identified. The crude pheromone extract obtained by airborne collection was fractionated by liquid chromatography (LC) on Florisil, and further purified by high performance liquid chromatography and preparative Gas Chromatography (GC). The pheromone component was shown to be an ester, the alcohol part of which was identical to the known alcohol moiety of the pheromone of Planococcus citri. The chemical structure was determined to be 3-isopropenyl-2,2-dimethylcyclobutylmethyl 3-methyl-3-butenoate by MS and 1H NMR analyses. The absolute configuration of the pheromone was assigned as (1R,3R) by comparison of the retention time of the alcohol derived from the P. cryptuspheromone with those of the alcohol derived from P. citripheromone, and a synthetic sample of alcohol enriched in the (1R,3R)-enantiomer, using a chiral GC stationary phase. The structure of the pheromone was confirmed by synthesis, and by bioassays in a glasshouse.

Cyanamide was isolated from the leaves and stems of hairy vetch (Vicia villosa), guided by plant growth inhibitory activity against lettuce (Lectuca sativa) seedlings. A large proportion of the inhibitory activity in the crude extract was explained by the presence of cyanamide, suggesting it to be a possible allelochemical in this species. The amount in a 9-day-old seedling, which had been grown without nutrients, reached approx. 40 times that of a nongerminated seed, demonstrating cyanamide biosynthesis in the seedlings. This is the first report on the isolation of a possible allelochemical from hairy vetch and also of the finding of cyanamide as a natural product.

The allelopathic potential of buckwheat (Fagopyrum esculentum) was investigated. Field study showed that living buckwheat reduced weed biomass compared with plots without buckwheat. Laboratory study revealed that root exudates suppressed root and shoot growth of weeds and reduced weed dry weight. Sequential partitioning of the aqueous ethanolic extract of the aerial parts of buckwheat showed that the chloroform extract caused an 80% reduction in radicle elongation of lettuce seedlings at a concentration of less than 100 p.p.m. Fagomine, 4‐piperidone and 2‐piperidinemethanol were isolated and identified by 1H and 13C nuclear magnetic resonance from the chloroform extract. These compounds caused a 50% inhibition of radicle elongation in lettuce seedlings at concentrations of less than 100 p.p.m. These results suggest that compounds 1, 2, and 3 might act as allelochemicals and affect the growth or germination of different plant species.

L-Canavanine is a nonprotein amino acid contained in jack bean [Canavalia ensiformis (L.) DC] and shows a plant inhibitory effect. The inhibitory effect was determined by an immersion test and a microdrop test that employed rice seedlings. L-Canavanine inhibited elongation of the second leaf sheath of rice seedlings more than other natural bioactive substances, such as salicylic acid and cinnamic acid. The modified microdrop test revealed that the mode of action of L-canavanine had no relation to gibberellin synthesis. In the microdrop test, the inhibitory effect of L-canavanine was decreased by simultaneous addition of L-arginine, an analog of L-canavanine. Free amino acid analysis of rice shoots clearly showed that L-canavanine induced an unusual accumulation of L-arginine. However, accumulation of L-arginine did not cause the inhibitory effect on plant growth. These results suggest that the mechanism of inhibition of L-canavanine is closely related to the inhibition of arginine metabolism.

AbstractMugineic acid (MA), which is a multidentate phytosiderophore, is exuded to the rhizosphere by the roots of graminaceous plants (e.g. barley) growing under Fe-deficient conditions, resulting in the dissolution of Fe as a form of MA-Fe111complex (MAFe). To clarify the effects of soil chemical properties on the amount of Fe dissolved by MA, an experiment to study the reaction of MA using 38 soil samples was conducted, and the concentrations of free MA (uncomplexed and non-adsorbed MA) and MAFe in solution and the amounts of MA adsorbed on the soils were determined after the reaction. Soil pH value was a good indicator to predict the behavior of MA in soils. A large proportion of added MA was adsorbed on soils or formed MAFe in solution in acidic soils, whereas it did not react with soils and occurred as free MA in alkaline soils. These features were in good agreement with the interaction of MA with Fe (hydr)oxides, as reported in previous papers. Other soil chemical properties, such as soil organic carbon (SOC) content and the amount of amorphous (hydr)oxide components, also affected the behavior of MA in the soils. The Fe dissolution ability of MA was compared with that of diethylenetriaminepentaacetic acid (DTPA) soil test. Although the amounts of extractable Fe were similar between the MA extraction and DTPA soil test, factors influencing the amount of Fe dissolved (formation constant with Fe111, reaction pH, rate constant, etc.) were different between both chelating compounds.

2-Methoxy-2-(2-naphthyl)propionic acid 1and 2-hydroxy-2-(2-naphthyl)propionic acid 2were prepared by the Grignard reaction of 2-naphthylmagnesium bromide with (1R,2S,5R)-(−)-menthyl pyruvate. The absolute configurations of (+)-1and (+)-2were determined to be Sby the 1H NMR anisotropy method.

AbstractMugineic acid (MA; (2S, 2′S, 3′S, 3″S)-N-[3-carboxy-3-(3-carboxy-3-hydroxypropylamino)-2-hydroxypropyl]-azetidine-2-carboxylic acid), a multidentate complexing agent, is exuded by the roots of graminaceous plants (e.g. barley) growing under Fe-deficient conditions. The nature of the interactions of MA with Fe (hydr)oxide minerals in soils is thus of considerable practical importance. To examine the availability of MA in dissolving Fe (hydr) oxides, we investigated the amounts of Fe dissolved from 24 samples of Fe (hydr)oxides by 100 μM MA (FeMA) and 200 mM NH4-oxalate (Feo).The Feovalues were much larger than the FeMAones, though the crystallinity of the Fe (hydr)oxides was a significant factor. For Fe (hydr)oxides consisting of goethite, hematite, ferrihydrite, and their mixture, FeMAincreased with the increase of Feo, indicating that FeMA would be correlated with FeD, that is the amount of short-range ordered Fe minerals including ferrihydrite. For goethite, hematite, magnetite, maghemite, and lepidocrocite with a high crystallinity, MA was relatively ineffective in dissolving Fe, although a part of crystalline magnetite, maghemite, and lepidocrocite could be dissolved by NH4-oxalate. For soils containing significant amounts of magnetite, maghemite, lepidocrocite, it is unlikely therefore that Feowould be a useful indicator of plant-available Fe.

To differentiate chemical species of Al in soil solutions, a method using nuclear magnetic resonance (NMR) was applied to laboratory preparations of hydroxyaluminum (HyA) and hydroxyaluminosilicate (HAS) ions ([OH]/[Al] = 2.0), and 1 MKCl extracts from acidic soils. The Al in a Al‐OH‐Si(OH)4mixture was separated into three fractions: Al13([AlO4Al12(OH)24(H2O)12]7+), AlSYM, and AlNON. The Al13and AlSYMwere quantitatively determined by 27Al‐NMR at 63 and 0 ppm, respectively. The AlNONwas defined as the Al that cannot be determined by 27Al‐NMR. The AlSYMwas attributed to electrically symmetric octahedral Al including monomer (and dimer) HyA ions, and the AlNONwas attributed to electrically asymmetric Al including HAS and polymer HyA ions. The concentrations of Al13decreased with increasing Si/Al molar ratio of the mixed solutions, and Al13was not detected at Si/Al ≥ 0.28. With increasing Si/Al molar ratio, the concentration of AlSYMincreased slightly, while AlNONincreased significantly. In the KCl extracts from soils, the Al13was not detected at all. This result suggests that Al13is not formed in these soils, or that the persistence of Al13in the soil solution is strongly inhibited by adsorption or precipitation reactions. The presence of organically complexed Al (AlORG) was also directly detected in KCl extracts from upper horizons by 27Al‐NMR spectra. The chemical shift of resonance peak of AlORGwas close to that of the 1:1 complex of Al oxalate. On average, 92 and 96% of the KCl‐exchangeable Al existed as AlSYMand AlSYMplus AlORG, respectively.

AbstractExtractUnder iron (Fe)-deficient conditions like in calcareous and/or high pH soils, mugineic acid family phytosiderophores (MAs: mugineic acid (MA), 2′-deoxymugineic acid (DMA), 3-hydroxymugineic acid (HMA) etc.) are secreted from graminaceous plants and solubilize the slightly soluble Fe in soil as MAs-Fe complexes (Takagi 1976, 1993). Due to their high availability to higher plants (Roemheld and Marschner 1986), the behavior of MAs and their Fe complexes in the soil environment is of interest in connection with the iron nutrition of these plants.

We quantified the cyanamide content of young leaves of nine Viciaspecies, Lens culinaris, and Robinia pseudo-acaciausing a modified analytical procedure that made it possible to measure the cyanamide content of a single leaf. Recent molecular phylogenetic analysis suggests that cyanamide is present in V. benghalensis, which is placed in a monophyletic group with cyanamide-biosynthesizing plants, V. villosaand V. cracca; this suggestion was verified.

Root mucilage is gelatinous polysaccharide-containing material exuded from the outer layers of the root cap. Although mucilage has been suggested to play several roles in plant growth, its role in mineral uptake has not been well understood. Melastoma malabathricumL. is an aluminum (Al) accumulator growing in tropical acid soils. This species accumulates more than 10 mg Al g-1 DW in leaves and roots. Root mucilage is generally known to immobilize metal cations such as Al in the rhizosphere. However, we found that roots of M. malabathricumexuded large amounts of mucilage. Using the Zea maysL. mucilage as a control, we have recently shown that mucilage of M. malabathricum has unique physical and chemical characteristics, and facilitates Al uptake in this species. Since M. malabathricumcannot grow well in Al-deficient soil (nonacid soils), this species might have developed a mechanism for Al acquisition. We have also discussed the reason for this species' requirement of Al, a nonessential element.Addendum to: Watanabe T, Misawa S, Hiradate S, Osaki M. Characterization of root mucilage from Melastoma malabathricum, with emphasis on its roles in aluminum accumulation. New Phytol 2008;178:581-9.

Cyanamide (NH2CN) is found in nature, although it has long been recognized as an industrial product. Distribution of cyanamide in the plant kingdom was investigated using a direct quantitative determination method to detect and measure cyanamide by stable isotope dilution gas chromatography–mass spectrometry (the SID–GC–MS method). The SID–GC–MS method proved to be a robust way to quantify cyanamide contents in the extracts of 101 species of herbaceous plants. The average recovery of cyanamide from all plants tested was 55.6±20.3%. Vicia villosaand V. craccacontained cyanamide at 369–498 μg/gFW and 3,460–3,579 μg/gFW respectively, while the other 99 species contained no detectable cyanamide (<1 μg/gFW). This result suggests that distribution of cyanamide in the plant kingdom is limited and uneven.

To survive in harsh environments, phyllosphere microorganisms have developed numerous adaptive strategies against stressors. One such strategy is the synthesis of compounds that absorb ultraviolet A radiation (UVA). The chemical structure of a UVA-absorbing compound from Methylobacteriumsp. strain W-213 was elucidated by spectroscopic analyses. 1H, 13C, and two-dimensional nuclear magnetic resonance spectra indicated the presence of N-methyl-α-galactosamine. The entire structure was revealed by interpretation of INADEQUATE and high-resolution liquid chromatography/electrospray ionization mass spectra. The absolute configuration was established by X-ray analysis and the compound was identified as 2-{(4aR, 6R, 7R, 8R, 8aR)-7,8-dihydroxy-6-hydroxymethyl-1,2-dimethyl-4aH, 6H, 7H, 8H, 8aH-pyrano[2,3-b][1,4]oxazin-3-yl}-2-iminoacetic acid and named ‘methylobamine'. Methylobamine shows promise for pharmaceutical and cosmetic applications due to its high polarity, UVA absorption properties, and stability under UVA exposure.

It had been suggested that cyanidin 3-O-(6″-O-monomalonyl-β-glucopyranoside) and another unknown compound occur as major pigments in the purplish-red flower of chrysanthemum (Dendranthema grandiflorum). We determined the structure of the unknown compound as cyanidin 3-O-(3″,6″-O-dimalonyl-β-glucopyranoside) by FAB-MS and 1H-NMR. This is the first report of the identification of the cyanidin 3-dimalonyl glucoside as a flower pigment.

A crude methanol extract of Goniothalamus andersoniiJ. Sinclair strongly inhibited elongation of lettuce (Lactuca sativaL.) radicles. We conducted bioassay-guided purification of G. andersoniibark extract and obtained goniothalamin as the major bioactive compound. Its EC50values against elongation of lettuce radicles and hypocotyls were 50 and 125 μmol L−1, respectively. Among the six species tested, timothy was the most sensitive to goniothalamin. Quantification of this compound in other Goniothalamusspecies suggested that the plant inhibitory activity of this genus is explainable by goniothalamin, with G. calcareusas an exception.

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