Enantioselective effects of herbicide imazapyr on Arabidopsis thaliana.

The enantioselective toxicity of chiral herbicides in the environment is of increasing concern. To investigate the enantioselective effects of the chiral herbicide imazapyr on target organisms, we exposed Arabidopsis thaliana to imazapyr enantiomers and racemate. The results show that imazapyr was enantioselectively toxic to A. thaliana. The total chlorophyll content in A. thaliana was affected more by (+)-imazapyr than (±)-imazapyr and (-)-imazapyr. Concentrations of proline and malondialdehyde reflected a toxic effect in the order of (+)-imazapyr > (±)-imazapyr > (-)-imazapyr at every concentration. Acetolactate synthase (ALS) activity was inhibited more by (+)-imazapyr than (±)-imazapyr or (-)-imazapyr. At 100 mg L(-1) of imazapyr, ALS activity was 78%, 43%, and 19% with (-)-, (±)-, and (+)-imazapyr, respectively. The results suggest the significant enantioselective toxicity of imazapyr in A. thaliana for greater toxicity with (+)-imazapyr than (±)-imazapyr and (-)-imazapyr, which suggests that (+)-imazapyr has more herbicidal effect.

Formulas of components of citronella oil against mosquitoes (Aedes aegypti).

The mosquito Aedes aegypti is an epidemic vector of several diseases such as dengue fever and yellow fever. Several pesticides are used to control the mosquito population. Because of their frequent use, some mosquitoes have developed resistance. In this study, we used the Y-tube olfactometer to test essential oils of Cymbopogon species and screened specific formulas of components as repellents against Ae. aegypti. At 400 µL, the extracted oil of citronella grass (Cymbopogon nardus) and myrcene produced a low-active response by inhibiting mosquito host-seeking activity. Citronella grass, lemon grass (Cymbopogon citratus), citral and myrcene also produced a low-treatment response to repellents, for more potential to affect host-seeking behavior. Furthermore, the mixture of citral, myrcene, and citronellal oil (C:M:Ci = 6:4:1) greatly affected and inhibited host-seeking behavior (76% active response; 26% treatment response with 40 µL; 42.5%, 18% with 400 µL; and 19%, 23% with 1000 µL). As compared with the result for N,N-diethyl-3-methylbenzamide (DEET; 44%, 22% with 400 µL), adjusting the composition formulas of citronella oil had a synergistic effect, for more effective repellent against Ae. aegypti.

Phylogenetic changes in soil microbial and diazotrophic diversity with application of butachlor.

We investigated changes in population and taxonomic distribution of cultivable bacteria and diazotrophs with butachlor application in rice paddy soils. Population changes were measured by the traditional plate-count method, and taxonomic distribution was studied by 16S rDNA sequencing, then maximum parsimony phylogenic analysis with bootstrapping (1,000 replications). The bacterial population was higher after 39 than 7 days of rice cultivation, which indicated the augmentation of soil microbes by rice root exudates. The application of butachlor increased the diazotrophic population in both upper (0-3 cm) and lower (3-15 cm) layers of soils. Especially at day 39, the population of diazotrophs was 1.8 and 1.6 times that of the control in upper and lower layer soils, respectively. We found several bacterial strains only with butachlor application; examples are strains closest to Bacillus arsenicus, B. marisflavi, B. luciferensis, B. pumilus, and Pseudomonas alvei. Among diazotrophs, three strains closely related to Streptomyces sp. or Rhrizobium sp. were found only with butachlor application. The population of cultivable bacteria and the species composition were both changed with butachlor application, which explains in part the contribution of butachlor to augmenting soil nitrogen-fixing ability.

Effect of benzyl butyl phthalate on physiology and proteome characterization of water celery (Ipomoea aquatica Forsk.).

This study examined the effect of benzyl butyl phthalate (BBP), a phthalate ester (PAE) and an endocrine disruptor, on water celery, Ipomoea aquatica Forsk., one of the most popular leaf vegetables in Taiwan. After 28 days of cultivation, treatment with 100 mgL⁻¹ BBP retarded plant growth and decreased biomass and number of mature leaves and caused the accumulation of proline in leaves of water celery, but the concentrations of chlorophyll a and b in the leaves remained constant. 2-D gel electrophoresis and matrix-assisted laser desorption ionization time-of-flight mass spectrometry analysis of the proteome of leaf tissue revealed five protein spots with up- and down-regulated expression. The predicted protein XP_001417439 was down-regulated, which explained inhibition of plant growth, and the proteina XP_001417040, calreticulin, GAI-like protein 1, and (-)-linalool synthase were up-regulated, which indicates interference with the cell cycle and protein synthesis, as well as dwarfism of water celery. BBP is a stressor on the growth of water celery, and proteome analysis revealed the up- and down-regulation of genes involved in plant growth with BBP treatment.

Dissipation of herbicides chlorsulfuron and imazosulfuron in the soil and the effects on the soil bacterial community.

Dissipation of Sulfonylurea herbicides has rarely been studied due to their low application dosage. In this study, two herbicides, chlorsulfuron and imazosulfuron, were applied to both Podu (Pu) and Wolylin (Wl) soils at concentrations of 10 mg kg(-1) or 50 mg kg(-1) with soils at filled water holding capacity and incubation under 30 degrees C. Changes in the soil bacterial community were examined with denaturing gradient gel electrophoresis (DGGE), whereas the residue of the herbicides was measured by high performance liquid chromatography (HPLC). The dissipation mechanisms of the two herbicides were both chemical and biological. The half-life of chlorsulfuron is 6.8-28.4 days and that of imazosulfuron is 6.4-14.6 days. These both dissipate faster in a more acidic soil. A higher dosage inhibited 48 % of the dissipation of the chlorsulfuron in Wl soil. However, larger differences were not observed in other treatments. The half-lives of both herbicides for 10 mg kg(-1) or 50 mg kg(-1) concentrations were less than one month. The microbial community was changed after the chlorsulfuron and imazosulfuron were spiked. Two sulfonylurea herbicides changed the soil bacterial composition after they were amended, and the change was larger with imazosulfuron under 50 mg kg(-1) of concentration.

Biodegradation and microbial community changes upon shrimp shell wastes amended in mangrove river sediment.

Chitin, a homopolymer of N-acetyl-D-glucosamine (GlcNAc) residues linked by beta 1-4 bonds, is the most abundant renewable natural resource after cellulose. It is widely distributed in nature as the integuments of crustaceans and insects and as a component of fungi and algae. This study investigated the effects of a bifunctional chitinase/lysozyme-producing strain, Pseudomonas aeruginosa K-187, on degradation of shrimp shells and the survival conditions of bacterial strains in mangrove river sediment of Tamsui River. The structures of the whole bacterial community of the samples were measured by using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) technique. Results show that three bacterial strains (Acrobacter sp., Shewanella sp., and Marinobacterium sp.) which originated from the mangrove river sediment were found predominant in the 6 days-incubation sample of P. aeruginosa K-187 amended mangrove river sediment. Meanwhile, biomass, reducing sugar, and total sugar were found highest in the 6 weeks-incubation sample of shrimp shell powder and P. aeruginosa K-187-amended mangrove river sediment. According to the results, we assumed that the amendment of P. aeruginosa K-187 can enhance the biodegradation of shrimp shells in the seawater containing mangrove river sediment. We hope that these findings may provide some useful information for the reclamation of chitin-containing wastes in our environment.

Effect of carbendazim and pencycuron on soil bacterial community.

Soil bacterial composition is used as one of the important indicators of negative effects of the use of pesticides in agriculture. Very little is known on the effects of fungicides, particularly carbendazim and pencycuron on soil bacterial community. In this study, laboratory experiments were conducted to examine the effects of various concentrations of carbendazim and pencycuron on diversity of bacterial community in soils collected from strawberry field and incubated at different temperature conditions. The degradation rate of fungicides both in sterile and non-sterile soils were also investigated. Residues of fungicides were measured using high performance liquid chromatography (HPLC) and the change in bacterial community was examined by comparing the 16S rDNA bands on patterns by denaturing gradient gel electrophoresis (DGGE). The dissipation of carbendazim was affected by concentration applied, whereas that of pencycuron was affected by both concentration applied and incubation temperature. The microbial community could recover to its previous composition after 126 days of cultivation with the application of 10 mg/kg of carbendazim but not with the application of a high concentration, 100 mg/kg, of pencycuron. From cluster analysis, the bacterial community structure showed approximately 50% similarity throughout the experimental period, which indicated that the soil microbiota composition was not stable throughout the 120 cultivation days.

Molecular connectivity indices for predicting bioactivities of substituted nitrobenzene and aniline compounds.

Bioconcentration and toxicity of 22 substituted nitrobenzene and aniline compounds to aquatic organisms were assessed with quantitative structure-activity relationship (QSAR). Acute toxicities of aquatic organisms, including daphnia (Daphnia pulex) and carp (Cyprinus carpio), to 22 chemicals have been determined in our previous work. In this study, the bioconcentration factors (BCFs) for carp were further investigated. By the use of multiple-regression analyses, the molecular connectivity indices (MCIs) can describe both acute toxicity and bioconcentration for the test organisms. Applicable QSAR model (0.856

Effects of fungicides triadimefon and propiconazole on soil bacterial communities.

The impact of fungicides triadimefon and propiconazole on soil bacterial populations from a strawberry field was investigated. Two fungicides were applied to the soil at concentrations of 10 mg/kg or 100 mg/kg with soil water contents 20.2% (fresh soil water content) or 26.0% (field capacity). Changes in bacterial communities were assessed using DNA extraction, polymerase chain reaction (PCR) amplification of the 16S rDNA and denaturing gradient gel electrophoresis (DGGE). High performance liquid chromatography (HPLC) was utilized to detect the residue of fungicides in soils. The results showed that propiconazole was more persistent than triadimefon in soils, and the two soil water contents did not cause significant differences in dissipation rates between the two fungicides. A high concentration of propiconazole could inhibit the existence of soil microbes while one of triadimefon might induce the microbial population in the first stage. From unweighted pair-group method using arithmetic averages (UPGMA) dendrograms, the effect of triadimefon and propiconazole at the two applied concentrations on a soil bacterial community could be long term. After triadimefon was applied for 60 days and propiconazole for 75 days, the compositions of microbial communities were not recovered. From the viewpoint of environmental protection, it was of significant importance to pay more attention not only to the residues of pesticide but also to the change in soil microbial communities.

Multiresidue method for high-performance liquid chromatography determination of carbamate pesticides residues in tea samples.

A multiresidue method was developed to determine 19 carbamate pesticides in tea samples. Optimizations of different parameters, such as the type of extraction solvents, clean-up cartridges, and elution solvents were carried out. The developed method used acetonitrile as extraction solvent, amino cartridge for adsorbents and acetone-n-hexane as the eluting solution. Nineteen carbamate residues were then analyzed by high-pressure liquid chromatography (HPLC) with fluorescence detector. The present results showed good linearity by correlation coefficients of more than 0.9999 for all analyses. Limits of detection and quantification varied from 0.0005-0.023 mg L(- 1), 0.008-0.077 mg L(- 1), respectively. Recoveries of sixteen carbamate pesticides ranged from 65% to 135% at the spiked level of 0.5, 1.0 and 2.0 mg L(- 1). The relative standard deviations were lower than 20% and coefficient of variations were lower than 15%. The results indicate that the proposed method provides an effective multi and trace level screening determination of carbamate pesticides residues for tea samples.

Effects of herbicide butachlor on soil microorganisms and on nitrogen-fixing abilities in paddy soil.

The composition of culture-independent microbial communities and the change of nitrogenase activities under the application of butachlor in paddy soil were investigated. Nitrogen-fixation ability was expressed by the amount of acetylene reduction, and changes of microbial communities were studied by using denaturing gradient gel electrophoresis (DGGE) technique; afterward, minimum distance (MD, in brief) statistics was applied to determine the cluster numbers in UPGMA dendrograms. The results showed that the reduction of acetylene was suppressed shortly after butachlor application but was augmented after 37 days in both upper and lower layer soils. From UPGMA dendrograms, the diazotrophic divergences ranged from 33% to 64% throughout rice growth stages. For general bacterial communities, the diversities ranged from 28% to 52%. The divergences became higher with the cultivation period, and the application of butachlor imposed a significant variation on microbial community shift, which may be a reason for the boosting nitrogen-fixation ability in paddy soils.

Growth inhibition in Chinese cabbage (Brassica rapa var. chinensis) growth exposed to di-n-butyl phthalate.

The toxicity and effects of di-n-butyl phthalate (DBP), an endocrine disruptor, on the growth of Chinese cabbage (Brassica rapa var. chinensis) were studied. Etiolation occurred on leaves of Chinese cabbage plant treated with 50mg/L of DBP for 42 d. DBP even below 1mg/L had a significant effect on the concentration of chlorophyll in Chinese cabbage and the biomass showed a severe decrease under treatment with more than 30 mg/L of DBP. At a concentration below 1mg/L of DBP, no significant difference in accumulation was found, but treatments with concentration exceeding 10, 30, 50 and 100mg/L all resulted in significant accumulation of DBP. Six protein spots extracted from leaf tissue of DBP-treated Chinese cabbage displaying a differential expression are shown in 2-DE maps. According to proteome level studies, three protein spots were found to increase and were identified, respectively, as acyl-[acyl-carrier-protein] desaturase (acyl-ACP desaturase), root phototropism protein 3 (RPT3) and ferredoxin-nitrite reductase (Fd-NiR). The other three protein spots were found to decrease and were identified respectively as dihydroflavonol-4-reductase (DFR), aminoacyl-tRNA synthetase (aaRS) and ATP synthase subunit beta. The key finding is that the other closely related plant, Bok choy (Brassica rapa subsp. chinensis), the subspecies of Chinese cabbage, respond differently to the same chemicals.

Fate of anilide and aniline herbicides in plant-materials-amended soils.

The fate of herbicides trifluralin, pendimethalin, alachlor and metolachlor in paddy field soils amended with plant materials was investigated. The plant materials were purple sesbania, vegetable soybean and rice straw. The investigation was performed at two temperatures (25 and 40 degrees C) and two soil water moistures (60 and 90% water-holding capacity). The results showed linear and Freudlich equations described the adsorption of amide compound to soil. Adsorption coefficient (K(d)) fit to linear equation were in general greater in plant material-amended soils than in non-amended soil, especially in soil amending with rice straw. Increasing temperature and soil water moisture content shortened the half-lives of compounds in various treated soils. The movement of compounds in the soil columns showed the maximum distribution of aniline type compound, trifluralin and pendimethalin, appeared at the upper top of 0 to 5 and 0 to 10 cm of soil column, respectively, and of anilide type, alachlor and metolachlor, were distributed at 0 to 25 cm of the soil column. The mobility of chemicals in the different treated soils was simulated by the behavior assessment model (BAM). There was no significant difference among different plant material incubated soils on dissipation and mobility of compounds in soils.

Characterization of acetanilide herbicides degrading bacteria isolated from tea garden soil.

Three different green manures were added to the tea garden soils separately and incubated for 40 days. After, incubation, acetanilide herbicides alachlor and metolachlor were spiked into the soils, separately, followed by the isolation of bacteria in each soil at designed intervals. Several bacterial strains were isolated from the soils and identified as Bacillus silvestris, B. niacini, B. pseudomycoides, B. cereus, B. thuringiensis, B. simplex, B. megaterium, and two other Bacillus sp. (Met1 and Met2). Three unique strains with different morphologies were chosen for further investigation. They were B. megaterium, B. niacini, and B. silvestris. The isolated herbicide-degrading bacteria showed optimal performance among three incubation temperatures of 30 degrees C and the best activity in the 10 to 50 microg/ml concentration of the herbicide. Each bacterial strain was able to degrade more than one kind of test herbicides. After incubation for 119 days, B. cereus showed the highest activity to degrade alachlor and propachlor, and B. thuringiensis to degrade metolachlor.

Dissipation of carbofuran and carbaryl on Oolong tea during tea bushes, manufacturing and roasting processes.

Carbofuran (2,3-dihydro-2,2-dimethyl-7-benzofuranol-N-methylcarbamate) and carbaryl (1-naphthyl-N-methylcarbamate) are insecticides widely used in tea plantations. The objective of the present study was to evaluate the dissipation of carbofuran and carbaryl during the growth periods of Oolong tea, processing and roasting. Analysis of the residual insecticides was carried out using high-pressure liquid chromatography with a post-column fluorescence detector. Results showed that in the tea field carbofuran dissipated faster then carbaryl. Manufacturing processes of Oolong tea further reduced the carbofuran and carbaryl contents. The persistence of carbofuran and carbaryl was decreased with increasing roasting temperature. From the results, we conclude that the presence of carbofuran and carbaryl in tea can be reduced by proper field management, manufacturing and roasting processes.

Formulation factors that can reduce the formation of the phytotoxic impurity, N,N'-dibutylurea, from benomyl.

Fungicide benomyl is easily decomposed to carbendazim (MBC) and butyl isocyanate (BIC) in formulation, BIC is further hydrolyzed to butylamine. The BIC also reacts with butylamine to form N,N'-dibutylurea (DBU), a phytotoxic compound. The purpose of this study was to investigate the effects of selected additives and the manufacturing method of benomyl water dispersible granules (WG) on reducing DBU content in benomyl formulations. The manufacturing methods studied were granulation by extrusion, fluid bed spray, and spray dry. For the extrusion method, each benomyl powder formulation was homogenized by kneading with 20% v/w of 95% ethanol instead of water. After granulation, the percentages of the active ingredient benomyl and its degradation product carbendazim in each formulation were determined. For the fluid bed spray method, two formulations of wettable powders were formed. The first sample was granulated using 5% Na(2)SO(4) as the binder solution; the second sample used 2% urea. Changes in the active ingredient content after granulation were determined for each sample. For the spray dry method, four basic formulations of 70% benomyl, 5% sodium dodecyl sulfate (SDS) and 10% or 20% sodium sulfate were prepared, to study the effects of HMTA, urea and dispersant on reducing DBU formation in formulation. The DBU content of each formulation was measured for the fresh samples and after 1 year of storage. The results showed that urea had a stabilizing effect on benomyl, and reduced DBU formation. BIC increased benomyl yield during manufacturing, which reduced DBU content in fresh samples but allowed a greater potential for future DBU formation since it did not stabilize the extra benomyl. HMTA was found to reduce DBU in both aqueous BIC and prepared formulations. The study discusses how each of the selected constituents affected DBU formation and how commercial formulations can be improved to reduce DBU formation. From this study, it is clear that a safer benomyl formulation can be developed.

Correlations between experimental and predicted equilibrium distribution coefficient of chlorobenzene and chlorophenol compounds in soil-water systems using partial solubility parameters.

Many pesticides are degraded to become chlorinated aromatic compounds in soils. Equilibrium distribution of chlorobenzene and chlorophenol compounds in soil-water systems of Yangmingshan loam, Pingcheng silty clay loam and Annei silty loam was studied with the integral distribution equilibrium equation involving the partial solubility parameters of the chemicals. If the adsorption of chemicals on soils is partitioning in soil organic matter surrounding the soil mineral particles, the absorption constant (Kd) of a chemical in soil-water system could be stated as the distribution coefficient (or partition constant, Koc) of the chemical in the two adjunct immiscible phases--water and soil organic matter. The distribution coefficient (Koc) of chemicals calculated from the integral distribution equilibrium equation agrees well with the experimental adsorption coefficient (Kd, or experimental Koc) of chemicals determined in this study, for all the three different types of soils in water according to multiple-regression analysis. Reference data of Karger or Tijssen are employed to estimate the Koc for both polar and non-polar chemicals. The integral distribution equilibrium equation can exactly describe the distribution behavior of nonionic compound of chlorobenzenes and chlorophenols in soil-water systems.

Effects of endocrine disruptor di-n-butyl phthalate on the growth of Bok choy (Brassica rapa subsp. chinensis).

The effects of the endocrine disrupter, di-n-butyl phthalate (DBP), on the growth of leaf vegetable Bok choy (Brassica rapa subsp. chinensis, white stem Bok choy) were investigated. The results showed that leaves of Bok choy became white in color with the occurrence of chlorosis and necrosis upon treating with 30 mg l(-1) DBP for 42 days. Transmission electron microscopic images revealed that changes in the chloroplast structures accompanied the chlorosis. In addition, a decrease in biomass and chlorophyll, and accumulation of DBP, were found in DBP-treated Bok choy. The growth and morphology of Bok choy showed a significant dose-response relationship upon treatment with DBP in a hydroponic culture medium. The proteome of the leaf tissue was analyzed using two-dimensional gel electrophoresis (2-DE) and mass spectrometry (MS). Six protein spots were identified in 2-DE that showed reproducible differences in expression between the normal control and the DBP-treated sample. Based on proteome level studies two protein spots increased and were identified as superoxide dismutase (SOD) and peroxidase 21 precursor. These proteins are believed to increase in expression in response to free radical exposure as a detoxification mechanism. The other four protein spots that disappeared on treatment with DBP were identified as heat shock cognate protein 80, protein disulfide isomerase precursor, apocytochrome f precursor, and RNA polymerase beta subunit. The first two play an important role in polypeptide folding, the third is associated with electron transport, and the last has a critical function in DNA transcription. This study indicated that DBP affects the proteome formation as well as the physiology and the morphology of Bok choy during growth. The decrease in those four proteins might be related to the growth and development of a plant.

Reductive transformation of dieldrin under anaerobic sediment culture.

A pathway of dieldrin transformation to aldrin by epoxide reduction was found in this study. Investigation of dieldrin degradation under anaerobic conditions was performed with a mixed culture containing indigenous microorganisms obtained from sediment of the Er-Jen River in Taiwan. During the incubation, the transformation of dieldrin to aldrin was analyzed by GC-ECD and GC-MS. Effects of incubation factors including dieldrin concentrations, incubation temperatures and kinds of carbon sources on the degradation of dieldrin were also studied. Original concentrations (from 0.5 to 10 microg ml(-1)) of dieldrin affect the transformation rate of dieldrin, and lower concentrations indicated the higher degradation rates. But once the concentration higher than 100 microg ml(-1), almost no degradation occurred. The optimal temperature for degradation in mixed culture was found at 40 degrees C in this study. Dieldrin transformation rates varied with the type of major carbon sources in the mixed culture and were in order of yeast extract > sodium acetate > glucose. In addition, the denaturing gradient gel electrophoresis (DGGE) fingerprint revealed that four microbials evolved in dieldrin-amended cultures, but not in the dieldrin-free cultures. Partial sequence of 16S rDNA for these four organisms exhibited 94-99% similarity to those of genera Clostridium, Acidaminobacter and an uncultured bacterial group. These results suggest that the four microbials might promote the dieldrin transformation.