Kinetics of glyphosate and aminomethylphosphonic acid sorption onto montmorillonite clays in soil and their translocation to genetically modified corn.

The co-occurrence of glyphosate (GLP) and aminomethylphosphonic acid (AMPA) in contaminated water, soil, sediment and plants is a cause for concern due to potential threats to the ecosystem and human health. A major route of exposure is through contact with contaminated soil and consumption of crops containing GLP and AMPA residues. However, clay-based sorption strategies for mixtures of GLP and AMPA in soil, plants and garden produce have been very limited. In this study, in vitro soil and in vivo genetically modified corn models were used to establish the proof of concept that the inclusion of clay sorbents in contaminated soils will reduce the bioavailability of GLP and AMPA in soils and their adverse effects on plant growth. Effects of chemical concentration (1-10 mg/kg), sorbent dose (0.5%-3% in soil and 0.5%-1% in plants) and duration (up to 28 days) on sorption kinetics were studied. The time course results showed a continuous GLP degradation to AMPA. The inclusion of calcium montmorillonite (CM) and acid processed montmorillonite (APM) clays at all doses significantly and consistently reduced the bioavailability of both chemicals from soils to plant roots and leaves in a dose- and time-dependent manner without detectable dissociation. Plants treated with 0.5% and 1% APM inclusion showed the highest growth rate (p ≤ 0.05) and lowest chemical bioavailability with up to 76% reduction in roots and 57% reduction in leaves. Results indicated that montmorillonite clays could be added as soil supplements to reduce hazardous mixtures of GLP and AMPA in soils and plants.

Impact of phosphate on glyphosate uptake and toxicity in willow.

Phosphate (PO4(3-)) has been shown to increase glyphosate uptake by willow, a plant species known for its phytoremediation potential. However, it remains unclear if this stimulation of glyphosate uptake can result in an elevated glyphosate toxicity to plants (which could prevent the use of willows in glyphosate-remediation programs). Consequently, we studied the effects of PO4(3-) on glyphosate uptake and toxicity in a fast growing willow cultivar (Salix miyabeana SX64). Plants were grown in hydroponic solution with a combination of glyphosate (0, 0.001, 0.065 and 1 mg l(-1)) and PO4(3-) (0, 200 and 400 mg l(-1)). We demonstrated that PO4(3-) fertilization greatly increased glyphosate uptake by roots and its translocation to leaves, which resulted in increased shikimate concentration in leaves. In addition to its deleterious effects in photosynthesis, glyphosate induced oxidative stress through hydrogen peroxide accumulation. Although it has increased glyphosate accumulation, PO4(3-) fertilization attenuated the herbicide's deleterious effects by increasing the activity of antioxidant systems and alleviating glyphosate-induced oxidative stress. Our results indicate that in addition to the glyphosate uptake, PO4(3-) is involved in glyphosate toxicity in willow by preventing glyphosate induced oxidative stress.

The arbuscular mycorrhizal fungus Glomus mosseae can enhance arsenic tolerance in Medicago truncatula by increasing plant phosphorus status and restricting arsenate uptake.

A pot experiment examined the biomass and As uptake of Medicago truncatula colonized by the arbuscular mycorrhizal (AM) fungus Glomus mosseae in low-P soil experimentally contaminated with different levels of arsenate. The biomass of G. mosseae external mycelium was unaffected by the highest addition level of As studied (200 mg kg(-1)) but shoot and root biomass declined in both mycorrhizal and non-mycorrhizal plants, indicating that the AM fungus was more tolerant than M. truncatula to arsenate. Mycorrhizal inoculation increased shoot and root dry weights by enhancing host plant P nutrition and lowering shoot and root As concentrations compared with uninoculated plants. The AM fungus may have been highly tolerant to As and conferred enhanced tolerance to arsenate on the host plant by enhancing P nutrition and restricting root As uptake.

Actividades citotóxicas y antibacterianas de las raíces de Capparis zeylanica Linn / Antibacterial and Cytotoxic Activities of Capparis zeylanica Linn Roots

Se analizaron extractos crudos y un ácido graso, ácido octadec-7-en-5-ynoic (1), de la corteza de la raíz de Cappariszeylanica Linn. (familia de las Capparidaceae) para observar sus actividades antibacterianas frente a la bacteria Gram positiva y Gram negativa. Entre los extractos crudos, el extracto de cloroformo mostró una buena actividad frente a todos los organismos de prueba. El ácido graso (1) aislado del extracto de cloroformo mostró actividades antibacterianas frente a todos los organismos de prueba, a excepción de E. coli. Las actividades se compararon con un antibiótico estándar: la kanamicina. Las concentraciones inhibitorias mínimas (CIH) de 1, determinadas mediante la técnica de dilución en serie, fueron 64 mg/ml frente a Bacillus subtilis y Shigella dysenteriae. Las actividades citotóxicas del extracto crudo y del ácido graso (1) se observaron mediante el bioensayo de gambas en salmuera yel valor de LC50 del compuesto fue 6,27 mg/ml (AU)

Crude extracts and a fatty acid, octadec-7-en-5-ynoic acid (1), from the root bark of Capparis zeylanica Linn. (Fam. Capparidaceae) were screened for their antibacterial activities against Gram positive and Gram negative bacteria. Among the crude extracts, chloroform extract showed good activity against all test organisms. The fatty acid (1) isolated from chloroform extract exhibited antibacterial activities against test organisms except E. coli. The activities were compared to a standard antibiotic- kanamycin. The minimum inhibitory concentrations (MICs) of 1, determined byserial dilution technique, were found to be 64 mg/ml against Bacillus subtilis and Shigella dysenteriae. The cytotoxic activities of crude extract and fatty acid (1) were observed by brine shrimp biassay and LC50 value of the compound was found to be 6.27 mg/ml (AU)

Ethoxylated rapeseed oil derivatives as non-ionic adjuvants for glyphosate.

In a study aimed at finding environmentally benign adjuvants for glyphosate, ethoxylates of rapeseed oil and of methylated rapeseed oil were synthesized, with ethylene oxide (EO) content up to 40 and 8 respectively. They had less influence on spray retention by barley shoots than ethoxylated (15 EO) tallow amine (ETA). At 10 g L(-1), ethoxylated rapeseed oil with 30 or 40 EO and ethoxylated methylated rapeseed oil with 6 or 8 EO promoted glyphosate uptake by barley leaves to a greater extent than ETA at the same concentration. However, uptake rates were similar when the concentration was lowered to 2.8 and 3.1 g L(-1) for rapeseed oil derivatives and ETA respectively. In the case of ethoxylated methylated rapeseed oil with 8 EO (MeOil-8), glyphosate uptake increased when MeOil-8 concentration was raised from 5 to 10 g L(-1). In bioassays under controlled conditions, ethoxylated rapeseed oil with 40 EO (Oil-40) and MeOil-8 were slightly less effective than ETA in favouring the efficacy of glyphosate on barley. The same was found on ryegrass. However, both rapeseed oil derivatives compared well with glyphosate formulants such as ethoxylated diethylamine and alkyl ethoxy phosphate. In one field experiment, the efficacy of glyphosate in the presence of Oil-40, MeOil-8 or ETA was comparable with that of a commercial formulation. In another trial, MeOil-8 was as effective as ETA, but Oil-40 performed less well. It is concluded that ethoxylates of rapeseed oil and of methylated rapeseed oil are a promising chemistry for glyphosate adjuvants, provided that their ethylene oxide content is high.

Sequestration of a fluorinated analog of 2,4-dichlorophenol and metabolic products by L. minor as evidenced by 19F NMR.

Fate of halogenated phenols in plants was investigated using nuclear magnetic resonance (NMR) to identify and quantify contaminants and their metabolites. Metabolites of 4-chloro-2-fluorophenol (4-Cl-2-FP), as well as the parent compound, were detected in acetonitrile extracts using 19F NMR after various exposure periods. Several fluorinated metabolites with chemical shifts approximately 3.5 ppm from the parent compound were present in plant extracts. Metabolites isolated in extracts were tentatively identified as fluorinated-chlorophenol conjugates through examination of signal-splitting patterns and relative chemical shifts. Signal intensity was used to quantify contaminant and metabolite accumulation within plant tissues. The quantity of 4-Cl-2-F metabolites increased with time and mass balance closures of 90-110% were achieved. In addition, solid phase 19F NMR was used to identify 4-Cl-2-FP which was chemically bound to plant material. This work used 19F NMR for developing a time series description of contaminant accumulation and transformation in aquatic plant systems.

Chemical control of ambrosia Artemisiifolia on non-crop areas: are there alternatives to glyphosate?

We compared glyphosate, glufosinate and metsulfuron-methyl to control Ambrosia artemisiifolia under non-crop conditions. A laboratory study showed that A. artemisiifolia is an easy-to-wet species and that glufosinate and glyphosate are quickly absorbed by its leaves (nearly 100% in 24 h). Metsulfuron-methyl absorption was slower (about 50% in 24 h) but was strongly promoted by terpenic alcohol and esterified rapeseed oil. In the greenhouse, all three herbicides were efficacious against A. artemisiifolia, with ED50s of <23, 23 and 0.8 g ha(-1) for glufosinate, glyphosate and metsulfuron-methyl, respectively. These results were confirmed on a non-crop area for glufosinate and glyphosate, which at half the registered dose reached high efficacies at both the 4 to 6-node and flowering stages of A. artemisiifolia. By contrast, metsulfuron-methyl showed no efficacy. However, after treatment at the 4- to 6-node stage, new emergence of A. artemisiifolia led to the presence of vigorous plants that bore numerous flowers and produced high levels of pollen. After treatment at the flowering stage, flower production by A. artemisiifolia was not significantly affected, but achene weight was decreased by 60 to 70% and seed viability was only 8 to 13% for the treated plants, as compared to 85% for the control. No significant difference was observed between the two herbicides and between the doses. It is concluded that glufosinate can be an alternative to glyphosate for the chemical control of A. artemisiifolia on non-crop areas. However, with both herbicides, it is difficult to attain the two objectives of reducing seed production and pollen production by means of only one treatment.

Microsomal detoxification enzymes in yam bean [Pachyrhizus erosus (L.) urban].

Cytochrome P450s and glutathione-S-transferases (GSTs) constitute two of the largest groups of enzyme families that are responsible for detoxification of exogenous molecules in plants. Their activities differ from plant to plant with respect to metabolism and substrate specificity which is one of the reasons for herbicide selectivity. In the tuber forming yam bean, the legume Pachyrhizus erosus, their activities at the microsomal level were investigated to determine the detoxification status of the plant. The breakdown of the herbicide isoproturon (IPU) to two distinct metabolites, 1-OH-IPU and monodesmethyl-IPU, was demonstrated. GST activity was determined with model substrates, but also by the catalysed formation of the fluorescent glutathione bimane conjugate. This study demonstrates for the first time microsomal detoxification activity in Pachyrhizus and the fluorescence image description of microsomal GST catalysed reaction in a legume.

Comparative metabolism of 2,4-dichlorophenoxyacetic acid (2,4-D) in rat and dog.

1. There is a significant species difference in the toxicity of 2,4-dichlorophenoxyacetic acid (2,4-D). The oral no overall adverse effect level (NOAEL) for chronic toxicity of 2,4-D in rat is 5 mg kg(-1) day(-1) and in dog is 1 mg kg(-1) day(-1). The maximum tolerated dose (MTD) in rat is 150 and 75 kg(-1) day(-1) for male and females, respectively. The MTD in dog is 7.5 mg kg(-1) day(-1) for males and females. 2. In an attempt to explain the increased sensitivity to 2,4-D in dog, male and female rats and dogs were orally dosed with either 5 or 50 mg kg(-1) 14C-2,4-D. The rates and routes of excretion were investigated along with plasma toxicokinetics and biotransformation of the compound. 3. Elimination of the radioactive dose of 2,4-D from rat plasma was significantly faster than in dog. The approximate t(1/2) were 1.3-3.4 h for rat and 99-134 h for dog following a 5 or 50 mg kg(-1) dose, respectively. This led to large differences in the calculated AUC(0-infinity) 21-57 microg eq. h g(-1) for rat and 4889-5298 microg eq. h g(-1) for dog at 5 mg kg(-1), and 122-2358 microg eq. h g(-1) for rat and 34,110-44,296 microg eq. h g(-1) for dog at 50 mg kg(-1)). 4. In rat, the major route of excretion was in the urine. Excretion was essentially complete after 24 h for the low dose and after 48 h for the high dose. For dog, elimination was incomplete over the sampling period with only about 50% of the dose recovered. Urine was the principal route of excretion at the low dose, but about equal amounts were excreted in urine and faeces at the high dose over 120 h. 5. In rat, 2,4-D was unmetabolized and excreted in urine as the parent compound. In dog, the dose was excreted mainly following metabolism. 2,4-D in dog was conjugated forming the taurine, serine, glycine, glutamic acid, cysteine, sulphate and glucuronide conjugates, plus an unidentified metabolite, which were excreted in urine. Plasma, however, only contained unmetabolized 2,4-D. 6. The results show that the body burden of 2,4-D in dog is significantly higher than in rat for an equivalent dose, which is consistent with the increased sensitivity of dog to 2,4-D toxicity.

Long-term fate of the herbicide cinosulfuron in lysimeters planted with rice over four consecutive years.

In order to elucidate the long-term fate of the sulfonylurea herbicide cinosulfuron, the 14C-labelled chemical was applied to a clay loam soil, encased in two lysimeters, 22 days after rice (Oryza sativa L.) transplanting, and rice plants were grown for four consecutive years. Throughout the experimental period, leaching through soil profiles, absorption and translocation by rice plants, and distribution of 14C by downward movement in the soil layers were clarified. The total volume of leachates collected through the lysimeter soil over the four years amounted to 168 and 146 L in lysimeters I and II, respectively. The leachates contained 2.43% and 2.99% of the originally applied 14C-radioactivity, corresponding to an average concentration of 0.29 and 0.41 microg/L as the cinosulfuron equivalent in lysimeters I and II, respectively. The total 14C-radioactivity translocated to rice plants in the third and fourth year was 0.69% and 0.60% (lysimeter I), and 1.02% and 0.84% (lysimeter II) of the 14C applied, respectively. Larger amounts of cinosulfuron equivalents (0.54-0.75%) remained in the straw in the fourth year than in any other parts. The 14C-radioactivities distributed down to a depth of 70 cm after four years were 56.71-57.52% of the 14C applied, indicating the continuous downward movement and degradation of cinosulfuron in soil. The non-extractable residues were more than 88% of the soil radioactivity and some 45-48% of them was incorporated into the humin fraction. The 14C-radioactivity partitioned into the aqueous phase was nearly 30% of the extractable 14C, suggesting strongly that cinosulfuron was degraded into some polar products during the experimental period. It was found out in a supplemental investigation that flooding and constant higher temperature enhanced mineralization of [14C]cinosulfuron to 14CO2 in soil, indicating the possibility of chemical hydrolysis and microbial degradation of the compound in the flooded lysimeter soil.

A study of the potential for a herbicide formulation containing 2,4-d and picloram to cause male-mediated developmental toxicity in rats.

Male Vietnam veterans have repeatedly expressed concern that exposure to herbicides in Vietnam may have caused birth defects in their offspring. The second most used herbicide was a mixture of 2,4-D and picloram called Agent White. This study is an investigation into the possible male-mediated reproductive toxicology of this herbicide. Male rats were gavaged for 5 days per week for 9 weeks with a mixture of 2,4-D and picloram called Tordon 75D(R) (the Australian derivative of Agent White). Three doses were tested; the high dose was considered the maximum tolerated dose. Each male was mated with two untreated females during weeks 2 and 3, 4 and 5, and 8 and 9 of treatment, and with four untreated females after an 11-week recovery period. Negative controls were males dosed with distilled water, and positive controls were males dosed with cyclophosphamide at 5.1 mg/kg/day. All mated females were killed on day 20 of gestation, and the fetuses were weighed and examined for either structural malformations or skeletal development. Litter size, fetal weight, and malformation rate were all unaffected by treatment. The cyclophosphamide positive controls showed the expected large increase in postimplantation loss. In general, within the limitations of the power of the study, the results did not show any evidence that exposure to a herbicide formulation containing 2,4-D and picloram is likely to cause male-mediated birth defects or other adverse reproductive outcomes.

Plant and soil enantioselective biodegradation of racemic phenoxyalkanoic herbicides.

The biodegradation of the chiral phenoxyalkanoic herbicides 2-(2,4-dichlorophenoxy)propionic aid (2,4-DP) and 2-(4-chloro-2-methylphenoxy)propionic acid (MCPP) was investigated using enantioselective HPLC and chiroptical detection. Racemic mixtures of 2,4-DP and MCPP were applied to three species of turf grass, four species of broadleaf weeds, and soil. Preferential degradation of the S-(-) enantiomer of each herbicide was observed in most species of broadleaf weeds and soil, while the degradation in all species of grass occurred without enantioselectivity. The biodegradation in all systems appeared to follow pseudo first-order kinetics with the fastest degradation occurring in broadleaf weeds, followed by the grasses. The slowest degradation was observed in soil. The results of this work illustrate the need to characterize both enantiomers of chiral agrochemicals in order to have an accurate understanding of their distribution and fate in the environment.

Sex-dependent differences in the disposition of 2,4-dichlorophenoxyacetic acid in Sprague-Dawley rats, B6C3F1 mice, and Syrian hamsters.

2,4-Dichlorophenoxyacetic acid (2,4-D), a widely used broadleaf herbicide, is under investigation in a study of peroxisome proliferators. To supplement that study, male and female rats, mice, and hamsters were dosed with 14C-2,4-D orally at 5 and 200 mg/kg and tissue distributions were determined. Blood, liver, kidney, muscle, skin, fat, brain, testes, and ovaries were examined. At early time points tissues from female rats consistently contained higher amounts of radioactivity than did corresponding tissues from males (up to 9 times). By 72 hr, tissue levels were equivalent and males and females had excreted equal amounts of radioactivity. This sex difference was absent in mice. In hamsters, males had higher tissue levels than females. Taurine, glycine, and glucuronide conjugates of 2,4-D were excreted along with parent. Metabolite profiles differed between species qualitatively and quantitatively; however, differences between sexes were minimal. Plasma elimination curves were generated in male and female rats after iv and oral administration. Kinetic analysis revealed significant differences in elimination and exposure parameters consistent with a greater ability to clear 2,4-D by male rats relative to females. This suggests that at equivalent doses, female rats are exposed to higher concentrations of 2,4-D for a longer time than males and may be more susceptible to 2,4-D-induced toxicity. These sex-dependent variations in the clearance of 2,4-D in rats and hamsters may indicate a need for sex-specific models to accurately assess human health risks.

Inhibition of intracellular Ca2+ signalling, cytotoxicity and antitumor activity of the herbicide oryzalin and its analogues.

PURPOSE: Studies were conducted on oryzalin (3,5-dinitro-N,N-di(n-propyl)sulfanilamide), a widely used dinitroaniline sulfonamide herbicide, which was identified from plant extracts as an inhibitor of mitogen- and growth factor-mediated intracellular free Ca2+ ([Ca2+]i) signalling in mammalian cells. METHODS AND RESULTS: Oryzalin inhibited vasopressin, bradykinin and platelet-derived growth factor [Ca2+]i signalling in Swiss 3T3 fibroblasts with IC50 values of 14, 16 and 18 microM, respectively. 45Ca2+ uptake into nonmitochondrial stores of saponin-permeabilized Swiss 3T3 cells was inhibited by oryzalin with an IC50 of 34 microM. Oryzalin inhibited colony formation of HT-29 colon carcinoma cells with an IC50 of 8 microM and inhibited the growth of a number of other cancer cell lines and primary human tumors in vitro with IC50 values in the range 3 to 22 microM. A number of oryzalin analogues were studied and an association was found between the ability to inhibit [Ca2+]i signalling and inhibition of the growth of HT-29 human colon cancer cells (P = 0.001) and of CCRF-CEM human leukemia cells (P = 0.016). Oryzalin at doses up to 600 mg/kg administered orally or subcutaneously daily to mice for 3 to 10 days beginning a day after tumor inoculation inhibited the growth of murine B16 melanoma by 63% but showed no appreciable activity when administered subcutaneously or intraperitoneally to mice beginning a number of days after tumor inoculation against a variety of human tumor xenografts. The peak plasma concentration of oryzalin following repeated subcutaneous administration of oryzalin at 600 mg/kg per day to mice was 37 microM and of its major metabolite N-depropyl oryzalin was 53 microM. CONCLUSION: It is unlikely that the absence of significant antitumor activity of oryzalin is a result of the inability to achieve adequate plasma concentrations.

Thermospray liquid chromatographic-mass spectrometric method for the analysis of metribuzin and its metabolites.

A thermospray liquid chromatographic-mass spectrometric (TSP LC-MS) method has been developed for the analysis of the herbicide metribuzin and its three major metabolites in plant tissue. Metribuzin and its metabolites exhibited widely varying sensitivities in positive-ion TSP, with metribuzin being the most sensitive and deaminated diketo metribuzin being the least sensitive. All four compounds of interest were detected in an extract of a soybean plant which had been treated with metribuzin.