Hirotatsu Murano

Dieldrin uptake and translocation in plants growing in hydroponic medium.

It has been known that the Cucurbitaceae family takes up a large amount of persistent organic pollutants from soils and that the translocation of those compounds in cucurbits is higher than those in non-cucurbits. To understand the persistent organic pollutant uptake mechanisms of plant species, we compared the dieldrin absorption and transportation potentials of several plants in hydroponic medium. Sorghum (Sorghum vulgare Moench), sunflower (Helianthus annuus L.), soybean (Glycine max), komatsuna (Brassica rapa var. peruviridis), white-flowered gourd (Lagenaria siceraria var. hispida), cucumber (Cucumis sativus L.), and zucchini (Cucurbita pepo L.) were grown in a dieldrin-added hydroponic medium for 10 d, and then the amount of dieldrin in their shoots and roots was measured. All of the roots contained dieldrin, whereas only the cucurbits (white-flowered gourd, cucumber, and zucchini) contained considerable amounts of dieldrin in their shoots. The dieldrin uptake to the roots depended on the concentration of the n-hexane soluble components in the roots, regardless of whether the dieldrin in the roots was translocated to shoots or not. The dieldrin uptake from the solution to the roots was thought to be due to a passive response, such as adsorption on the roots. The translocation of dieldrin from the roots to the shoots was probably through the xylems. The amounts of dieldrin in the shoots per transpiration rates were higher for cucurbits than for non-cucurbits. It seems likely that cucurbits have uptake mechanisms for hydrophobic organic chemicals.

Dieldrin‐dissolving abilities of the xylem saps of several plant families, particularly Cucurbita pepo L.

The uptake ability of hydrophobic organic chemicals by plants and the nature of xylem sap of the plants were studied. The plants were grown in soil contaminated with dieldrin. High amounts of dieldrin were detected in the shoots of Cucurbita pepo and Cucumis sativus, but little was seen in the shoots of Brassica oleracea var. italica, Solanum lycopersicum, Glycine max, Zea mays, and Helianthus annuus. The xylem saps of C. pepo and C. sativus leached dieldrin adsorbed on C8 granules, but those of the other plants did not. The xylem saps of C. pepo and C. sativus eluted high amounts of dieldrin from the size-exclusion chromatography column near the fractions of RNase A (13.7 kDa) after Aprotinin (6.5 kDa), which has a larger molecular weight than dieldrin (381). The enhancement of dieldrin solubility by xylem sap was reduced by proteinase and heating. It was suspected that the protein-like materials in the xylem sap delivered dieldrin from the roots to the shoots.

Effects of the application of carbonaceous adsorbents on pumpkin (Cucurbita maxima) uptake of heptachlor epoxide in soil

Abstract The use of heptachlor, a cyclodiene-type insecticide, has been banned since the 1970s because of its carcinogenic potential. However, its metabolite, heptachlor exo-epoxide (HEPX), has still been detected in the fruit of cucurbits produced in some areas. It is important to reduce the daily intake of HEPX contained in food. To address this issue, the effects of carbonaceous adsorbents on the uptake of HEPX from the soil by Cucurbita maxima Dutch. (winter squash) were investigated. Amorphous organic carbons, such as peat moss and wood chips, did not affect the concentration of HEPX in the soil solution or the amount present in the shoots. In contrast, relatively condensed carbon, such as activated carbons, decreased the concentration of HEPX in the soil solution and in the shoots. The uptake amount in the shoot was closely correlated with the concentration of HEPX in the soil solution, which suggests that its uptake by C. maxima depends on its concentration in the soil solution. Activated carbons did not affect the growth of C. maxima. Therefore, the application of activated carbon to soil contaminated with HEPX appears to be an effective method of reducing the uptake of HEPX by C. maxima.

Suppressive effect of soil application of carbonaceous adsorbents on dieldrin uptake by cucumber fruits

The use of aldrin and dieldrin as pesticides was prohibited in 1975 in Japan. However, some of the soils still remain contaminated with dieldrin, because aldrin is easily oxidized to dieldrin and dieldrin is extremely stable in soil. In recent years, dieldrin at concentrations exceeding the limit set by the Food Sanitation Law of Japan (dieldrin < 0.02 mg kg–1 fresh weight) has been detected in cucumber fruits produced in some areas of Japan. We examined the effect of the soil application of selected adsorbents on reducing dieldrin concentrations in cucumber fruits in three steps of pot experiments. Among the three types of biochar made from wood chip, rice husk, and bamboo, wood chip charcoal was found to be the most effective (pot experiment 1). The effect of wood chip charcoal was enhanced by high-temperature burning and crushing (pot experiment 2). However, the effect of activated carbon was superior to that of optimized (high-temperature-treated and crushed) wood chip charcoal (pot experiment 3). Therefore, activated carbon was selected as the most effective adsorbent. The effect of activated carbon to reduce dieldrin concentrations in cucumber fruits was confirmed in a field experiment, and the effect continued to a certain extent for at least four years after the application. We calculated the cost of activated carbon necessary to maintain a sufficient suppressive effect in the field, and this cost would appear to be acceptable to cucumber farmers. Consequently, application of activated carbon to dieldrin-contaminated soils can be considered a promising practical technique for reducing dieldrin concentrations in cucumber fruits.

Relationship between Dieldrin Uptake in Cucumber and Solvent-Extractable Residue in Soil

To prevent the distribution of cucumbers with dieldrin contamination exceeding the limit set by the Japanese Food Sanitation Law, the extraction solvent for dieldrin-contaminated soil was selected prior to cultivation so that the dieldrin residue level in cucumber could be predicted. The exhaustive extraction from soil could not explain the dieldrin uptake by cucumber plants. However, significant correlation (R(2) = 0.966, P < 0.001) was observed between dieldrin concentrations in cucumber and dieldrin concentrations extracted with 50% (v/v) methanol-water solution from soils. This was a result of the phytoavailability of dieldrin to the cucumber plants. The extractability of soil dieldrin with the methanol-water solution decreased as the organic carbon content in the soils increased. This suggested that a 50% (v/v) methanol-water solution is the optimal solution for predicting dieldrin concentrations in cucumbers by soil analysis.

Effects of heavy metals in river waters in Japan on immobility and mortality of Daphnia magna and Oryzias latipes larvae

Samples of river waters containing high concentrations of zinc and other heavy metals but low concentrations of other anthropogenic contaminants were collected to investigate the relationship between toxicity of heavy metals and naturally present organic matters or hardness, as well as the effects of heavy metals on aquatic organisms. Acute toxicity tests were conducted for the water samples using Daphnia magna and medaka Oryzias latipes. Almost all the D. magna died in river waters containing high concentrations of zinc, but O. latipes in the same waters were hardly affected. Since the test organisms were not only exposed to zinc but also other heavy metals in the river waters, we examined the toxicity using toxic units composed of zinc, copper, lead, and cadmium. The results of a bioassay with the river waters showed that the mortality of D. magna did not depend solely on the total number of toxic units of heavy metals. The organic matters and the hardness of the river waters could decrease the acute toxicity of zinc and other heavy metals to D. magna.

Origin of the soil texture classification system used in Japan

Abstract The classification systems for soil particle size ranges and soil texture differ among countries and/or associations. Unique systems have also endured in Japan over the last six decades. However, the original reports explaining the rationale for these systems have gradually been lost, so there is no source written in either Japanese or English for authors to reference the origin of the Japanese soil classification systems. In this light, we reviewed the origin of the Japanese classification systems for soil particle size ranges and soil texture. The size range system was adopted from International Society of Soil Science (ISSS) standards. The soil texture classification system was introduced by Tommerup in his paper at the ISSS Commission I (Soil Physics) meeting in 1934. This soil texture classification system was modified by Yamanaka in 1955, and was henceforth adopted as the conventional soil texture classification system in Japan. This ISSS-defined soil texture classification system has been in use since that time.

Influence of humic substances and iron and aluminum ions on the sorption of acetamiprid to an arable soil

Humic substances (HS) in soil and sediments, and surface water influence the behavior of organic xenobiotics in the environment. However, our knowledge of the effects of specific HS fractions, i.e., humic acids (HAs), fulvic acids (FAs), and humin (HM), on the sorption of organic xenobiotics is limited. The neonicotinoid insecticide acetamiprid is thought to contribute to the collapse of honeybee colonies. To understand the role that soil organic matter plays in the fate of acetamiprid, interactions between acetamiprid and the above HS fractions were examined. Batch experiments were conducted using various combinations of a field soil sample and the above 3 HS fractions prepared from the same soil, and differences in isotherm values for acetamiprid sorption were investigated based on the structural differences among the HS fractions. The sorption of acetamiprid to soil minerals associated with HM (MHM) (Freundlich isotherm constant, Kf: 6.100) was reduced when HAs or FAs were added (Kf: 4.179 and 4.756, respectively). This can be attributed to hydrophobic interactions between HM and HAs or FAs in which their dissociated carboxyl and phenolic groups become oriented to face the soil solution. The amount of acetamiprid that was adsorbed to (MHM+HA) or (MHM+FA) increased when aluminum ions were added (Kf: 6.933 and 10.48, respectively), or iron ions were added (Kf: 7.303 and 11.29, respectively). Since acetamiprid has no affinity for inorganic components in soil, the formation of HS-metal complexes by cation bridging may have oriented the hydrophobic moieties in the HAs or FAs to face the soil solution and may also have resulted in the formation of dense structures, resulting in an increase in the amount of acetamiprid that becomes adsorbed to these structures. These results highlight the importance of interactions among soil components in the pedospheric diffusion of acetamiprid.

Adsorption of Herbicidally Active Degradate 2-(2,4-Dichloro-3-methylphenoxy)propanoic Acid on an Andosol

The adsorption of 2-(2,4-dichloro-3-methylphenoxy)propanoic acid (DMPA) on the surface horizon of a humus-rich Andosol was examined. To investigate the mechanisms of adsorption, chemically treated Andosols, such as organic matter removed Andosol, organic matter and active metals removed Andosol, and clay minerals of the Andosol, were prepared. Furthermore, humic acid was extracted from the Andosol. The mechanisms of the DMPA adsorption were identified by using those untreated and chemically treated Andosols and the humic acid. The amount of DMPA adsorbed increased with decreasing equilibrium pH value. Active surface hydroxyl groups were identified as the most important soil functional group in DMPA adsorption. The predominant mechanism of DMPA adsorption on the Andosol is a ligand-exchange reaction, in which an active surface hydroxyl on Al and/or Fe is replaced by a carboxylic group of DMPA. A comparative study revealed that the amount of DMPA adsorbed was slightly greater than that of (2,4-dichlorophenoxy)acetic acid (2,4-D), especially at equilibrium pH values below 5. This is because the octanol-water partition coefficient (log Kow) of DMPA in the equilibrium pH range is higher than that of 2,4-D, and SOM participates in the adsorption process through a hydrophobic interaction.

Novel 4-methyl-2-oxopentanoate reductase involved in synthesis of the Japanese sake flavor, ethyl leucate

Ethyl-2-hydroxy-4-methylpentanoate (ethyl leucate) contributes to a fruity flavor in Japanese sake. The mold Aspergillus oryzae synthesizes leucate from leucine and then the yeast Saccharomyces cerevisiae produces ethyl leucate from leucate during sake fermentation. Here, we investigated the enzyme involved in leucate synthesis by A. oryzae. The A. oryzae gene/cDNA encoding the enzyme involved in leucate synthesis was identified and expressed in E. coli and A. oryzae host cells. The purified recombinant enzyme belonged to a D-isomer-specific 2-hydroxyacid dehydrogenase family and it NADPH- or NADH-dependently reduced 4-methyl-2-oxopentanate (MOA), a possible intermediate in leucine synthesis, to D-leucate with a preference for NADPH. Thus, we designated this novel enzyme as MOA reductase A (MorA). Furthermore, an A. oryzae strain overexpressing morA produced 125-fold more leucate than the wild-type strain KBN8243. The strain overexpressing MorA produced 6.3-fold more ethyl leucate in the sake than the wild-type strain. These findings suggest that the strain overexpressing morA would help to ferment high-quality sake with an excellent flavor. This is the first study to identify the MOA reductase responsible for producing D-leucate in fungi.