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PubMed2000

Effects of 2,4-D, glyphosate and paraquat on growth, photosynthesis and chlorophyll-a synthesis of Scenedesmus quadricauda Berb 614.

The effects of 2,4-D, glyphosate and paraquat on growth, photosynthesis and chlorophyll-a synthesis by a freshwater green alga, Scenedesmus quadricauda Berb 614, were determined. These herbicides are the most often used in Hong Kong. Within the concentration range 0.02-200 mg/l, paraquat was more toxic than glyphosate and 2,4-D to the growth, photosynthesis and chlorophyll-a synthesis. The presence of 0.02, 0.2 or 2 mg/l of 2,4-D was not toxic to the alga. Algal growth, photosynthesis and chlorophyll-a synthesis were stimulated by the presence of low concentrations (0.02 or 0.2 and 0.02 mg/l, respectively) of 2,4-D and glyphosate. The presence of 0.02 or 0.2 mg/l of paraquat, 2 mg/l of glyphosate or 20 mg/l of 2,4-D was significantly inhibitory to the three test parameters, whereas the presence of 2 or more mg/l of paraquat, 20 or more mg/l of glyphosate or 200 mg/l of 2,4-D completely inhibited algal growth, photosynthesis and chlorophyll-a synthesis. The use of the alga as a bio-indicator of herbicide contamination in freshwater environment was discussed.

2,4-Dichlorophenoxyacetic Acid↗

PubMed2003

The teratogenic potential of the herbicide glyphosate-Roundup in Wistar rats.

The aim of this study was to assess the teratogenicity of the herbicide glyphosate-Roundup (as commercialized in Brazil) to Wistar rats. Dams were treated orally with water or 500, 750 or 1000 mg/kg glyphosate from day 6 to 15 of pregnancy. Cesarean sections were performed on day 21 of pregnancy, and number of corpora lutea, implantation sites, living and dead fetuses, and resorptions were recorded. Weight and gender of the fetuses were determined, and fetuses were examined for external malformations and skeletal alterations. The organs of the dams were removed and weighed. Results showed a 50%, mortality rate for dams treated with 1000 mg/kg glyphosate. Skeletal alterations were observed in 15.4, 33.1, 42.0 and 57.3% of fetuses from the control, 500, 750 and 1000 mg/kg glyphosate groups, respectively. We may conclude that glyphosate-Roundup is toxic to the dams and induces developmental retardation of the fetal skeleton.

Abnormalities, Drug-Induced↗

PubMed1993

Solid-state NMR determination of intra- and intermolecular 31P-13C distances for shikimate 3-phosphate and [1-13C]glyphosate bound to enolpyruvylshikimate-3-phosphate synthase.

Rotational-echo, double-resonance (REDOR) 31P NMR was used to obtain internuclear distances for shikimate 3-phosphate (S3P) and N-(phosphonomethyl)-[1-13C]glycine (glyphosate) bound to 5-enolpyruvylshikimate-3-phosphate (EPSP) synthase, a 46-kDa enzyme essential for the synthesis of aromatic amino acids in plants and microorganisms. An intermolecular 31P-13C distance of 7.2 A was measured between the phosphate of S3P and the labeled carbon of glyphosate. This means that S3P and glyphosate are in proximity in the binding site of the enzyme. An intramolecular 31P-13C distance of 5.6 A was measured between the phosphonate 31P and the labeled carbon of glyphosate. This distance can be achieved only if glyphosate is completely extended when bound to EPSP synthase.

3-Phosphoshikimate 1-Carboxyvinyltransferase↗

PubMed2003

Glyphosate applied preharvest induces shikimic acid accumulation in hard red spring wheat (Triticum aestivum).

Glyphosate is a nonselective herbicide used as a harvest aid in a variety of crops. Glyphosate is absorbed into the foliage and translocated to metabolically active regions in the plant where it interferes with the shikimic acid pathway. Experiments were conducted to determine the accumulation and distribution of shikimic acid in wheat treated with glyphosate at soft and hard dough stages of kernel development and to determine the fate of shikimic acid during milling and bread making. Elevated levels of shikimic acid were detected throughout the wheat plant. Shikimic acid concentrations peaked 3-7 days after treatment and then declined until harvest. Shikimic acid content was 3-fold greater in flour and 2-fold greater in the bread derived from treated wheat than nontreated wheat. Similarly, elevated levels of shikimic acid were found in the crumbs and crust of bread made with flour from glyphosate treated wheat. Glyphosate applied preharvest resulted in shikimic acid accumulation in hard red spring wheat and subsequent end-use products.

Glycine↗

PubMed2005

Effects of incorporated corn residues on glyphosate mineralization and sorption in soil.

In modern agricultural systems employing conservation tillage practices, glyphosate is widely used as a preplant burndown herbicide in a wide range of crops. Conservation tillage systems are characterized by a significant presence of crop residues at the soil surface so that glyphosate is applied to a soil matrix rich in poorly decomposed crop residues. Incorporation of corn residues in the range from 0.5 to 4% caused different effects on mineralization and sorption of [14C]glyphosate in sandy and sandy loam soils. More specifically, low levels of incorporated corn residues did not affect or slightly stimulated herbicide mineralization in the sandy and sandy loam soils, respectively. In the sandy soil, incorporation of the highest level of corn residues (4%) caused a decrease in [14C]glyphosate mineralization. [14C]Glyphosate sorption on both soil types was reduced in samples receiving high amounts of incorporated corn residues.

Adsorption↗

PubMed2006

Influence of Cry1Ac toxin on mineralization and bioavailability of glyphosate in soil.

The impact of transgenic plants containing Bacillus thuringiensis (Bt) toxin on soil processes has received recent attention. In these studies, we examined the influence of the lepidopterean Bt Cry1Ac toxin on mineralization and bioavailability of the herbicide glyphosate in two different soils. The addition of 0.25-1.0 microg g(-1) soil of purified Cry1Ac toxin did not significantly affect glyphosate mineralization and sorption in either a sandy loam or a sandy soil. In contrast, extractable glyphosate decreased over the 28 day incubation period in both soils. Our findings suggest that the reduction in the bioavailability of glyphosate was not influenced by the presence of Cry1Ac toxin but rather the results of aging or sorption processes. Results from this investigation suggest that the presence of moderate concentrations of Bt-derived Cry1Ac toxin would have no appreciable impact on processes controlling the fate of glyphosate in soils.

Adsorption↗

PubMed1999

Glyphosate effects on phenolic metabolism of nodulated soybean (Glycine max L. merr.).

Glyphosate is a herbicide that blocks the shikimic acid pathway. Three Bradyrhizobium japonicum strains with different sensitivities to glyphosate were used to test the effect of this herbicide on the phenolic metabolism of nodulated soybeans and on the bacteroid nitrogenase activity. Glyphosate caused an inhibition in the bacteroid nitrogenase activity that was related with the sensitivity of the nodule-forming strains. Both leaves and nodules accumulated huge amounts of shikimate and phenolic acids (mainly protocatechuic acid), indicating that the herbicide was translocated to the nodule and disturbed phenolic metabolism. However, this accumulation was not clearly related to the sensitivity of the different strains. Bacteroids from control plants were incubated with the same concentration of shikimate, and phenolic acid accumulated in glyphosate-treated plants. Despite the high levels found in nodules, they were not responsible for the decrease of the nitrogenase activity. Glyphosate by itself caused a small inhibition of the bacteroid nitrogenase activity.

Bradyrhizobium↗

PubMed1999

Uptake of the herbicidal glyphosate by Escherichia coli K-12.

The uptake of the aminoacid biosynthesis inhibitor, used as the broad-spectrum herbicide ingredient, glyphosate (N-[phosphonomethyl]-glycine) was investigated in E. coli as a model to study mechanisms of cell resistance to antimetabolites as drugs and pesticides. Unlike the glyphosate-degrading Arthrobacter sp. strain for which the first successful measurement of glyphosate uptake and its inhibition by orthophosphate was reported, E. coli K-12 cannot take up this inhibitor either in the presence of orthophosphate, or after a prolonged starvation for it. However, cells made "competent" after an overnight cold CaCl2 exposure followed by dimethyl sulfoxide (DMSO) treatment could take up this compound (Km for glyphosate uptake, 274 microM). Neither amino acids, belonging to a single transport system, nor orthophosphate gave essential inhibition of glyphosate uptake by these cells.

Escherichia coli↗

PubMedDate not supplied

Subtle effects of herbicide use in the context of genetically modified crops: a case study with glyphosate (Roundup).

Research on the effects of glyphosate and seed germination spans 30 years. Despite several studies reporting detrimental effects of the herbicide on seedling germination and growth, glyphosate is still being registered for use as a weed killer and preharvest desiccant. Its nonselective nature and low chance of species developing resistance has lead to the development of genetically modified crops tolerant to the herbicide which also raises concerns about increased reliance on herbicide use, and subtle ecological impact. This paper presents the result of a literature review on past studies mostly, on crop species, and the results of a new experiment performed with emphasis on noncrop species. The new experimental part attempted to determine whether glyphosate (Roundup) would have an effect on the germination and growth of the F1 generation of seeds produced by plants sprayed with the herbicide. It was designed to mirror spray drift which might affect noncrop plants in nontarget drift zones. Of the 11 species tested using treatments of 0% (control), 1%, 10% or 100% of a 890 g a.i./ha label rate solution sprayed near seed maturity, seven showed a significant effect of the glyphosate treatment on germination and/or growth characteristics. Results of this experiment together with several previous studies reviewed in this paper suggest that there are significant effects to keep in mind when using herbicides such as glyphosate as severe ecological changes could occur.

Germination↗

PubMed1993

Photo-oxidation of 5-enolpyruvoylshikimate-3-phosphate synthase from Escherichia coli: evidence for a reactive imidazole group (His385) at the herbicide glyphosate-binding site.

Photo-oxidation of Escherichia coli 5-enolpyruvoylshikimate-3-phosphate synthase, a target for the non-selective herbicide glyphosate (N-phosphonomethylglycine), in the presence of pyridoxal 5'-phosphate resulted in irreversible inactivation of the enzyme. The inactivation followed pseudo-first-order and saturation kinetics with a Kinact. of 50 microM. The inactivation is specifically prevented by preincubation of the enzyme with the combination of shikimate 3-phosphate and glyphosate. Increasing glyphosate concentration during preincubation resulted in a decreasing rate of inactivation. On 95% inactivation, approximately one histidine per molecule of enzyme was oxidized. Tryptic mapping of the enzyme modified in the absence and presence of shikimate 3-phosphate and glyphosate as well as analyses of the histidine content in the isolated peptides indicated that His385, in the peptide Asn383-Asp-His-Arg386, was the site of oxidation. These results suggest that His385 is the most accessible reactive imidazole group under these conditions and is located close to the glyphosate-binding site.

3-Phosphoshikimate 1-Carboxyvinyltransferase↗

PubMed2001

Investigation of the herbicide glyphosate and the plant growth regulators chlormequat and mepiquat in cereals produced in Denmark.

An LC-MS/MS method for analysing glyphosate and aminomethylphosphonic acid (AMPA) in cereals was developed. The method is based on extraction with water and detection of the ions from the fragmentation m/z 170-->88 (glyphosate) and m/z 112-->30 (AMPA), using electrospray interface in the positive mode. Investigation from the harvests of 1998 and 1999 showed residues of glyphosate and/or its degradation product AMPA in more than half of the cereal samples produced in Denmark. The average concentration of glyphosate in 46 samples from the 1999 harvest was 0.11 mg/kg compared with 0.08 mg/kg for the 1998 harvest (n = 49). Thus, the figures were well below the maximum residue limit (MRL) and no violations were observed. The plant growth regulators chlormequat and/or mepiquat were investigated in cereals from the Danish harvest of 1999 where 83% of the samples contained chlormequat (n = 46) compared with 87% of the samples from the 1997 harvest (n = 52). The average concentration of chlormequat in 1999 was 0.32 mg/kg compared with 0.23 mg/kg in 1997. At 2.9 mg/kg, one sample of wheat bran was exceeding the MRL of 2 mg/kg for wheat. The intakes of the pesticides through the diet of cereals were estimated to comprise 0.04% of the acceptable daily intake (ADI) for glyphosate and 1% of the ADI for chlormequat for an adult Dane.

Chlormequat↗

PubMed2003

Analysis of glyphosate residues in cereals using liquid chromatography-mass spectrometry (LC-MS/MS).

A fast and specific method for the determination of glyphosate in cereals is described. The method is based on extraction with water by ultrasonication. The samples are cleaned up and separated by high-performance liquid chromatography on a polystyrene-based reverse-phase column (clean-up) in series with an ion chromatography column (separation) using NaHCO(3) as eluent. A micro-membrane suppressor was inserted after the separator column to remove the Na(+) ions before detection by electrospray ionization mass spectrometry in the negative-ion mode. In MS/MS, mode the following transitions were monitored m/z 168--> 150 (glyphosate) and 170-->152 (internal standard 2-(13)C(15)N-glyphosate) for quantification. The mean recovery was 85% (n=32) at spiking levels from 0.03 to 0.33 mg kg(-1). From 1998 to 2001, from the analysis of about 50 samples per annum, a reduction in the glyphosate residues was observed owing to a Danish trade decision not to use grain with glyphosate residues for milling or bread production.

Chromatography, High Pressure Liquid↗

PubMed1991

Occupational exposure of forest workers to glyphosate during brush saw spraying work.

The purpose of this study was to measure forest workers' exposure to the herbicide glyphosate during silvicultural clearing work done with brush saws equipped with pressurized herbicide sprayers. Both the exposed (study) group and the nonexposed (control) group contained five persons who were medically examined before and after their 1-week working period (including laboratory tests) for possible health effects. In addition, exposure to glyphosate was measured in the study group from samples taken from the workers' breathing zone and from urine samples collected during the afternoons of the workweek. The laboratory tests and urinary glyphosate analyses were repeated for the exposed group 3 weeks later, when the men had entirely stopped their work with the herbicide. Exposure to glyphosate through the workers' breathing zone was low. The highest value found was 15.7 micrograms/m3. In this study, a biological monitoring method was also developed to monitor the workers' exposure to glyphosate. Urine concentrations were under the gas chromatographic detection level of less than 0.1 ng/microL (less than 1.0 mumol/L). No major differences were noted, either in medical examinations or in the laboratory tests performed, between the exposed and control groups before and after the work period.

Adult↗

PubMed2005

Effect of manure on glyphosate and trifluralin mineralization in soil.

Manure additions to soil may alter soil chemical, physical, and biological characteristics, and thereby change pesticide fate processes in soil. This is the first study to examine the impact of liquid hog manure amendments on glyphosate and trifluralin mineralization in soil. Experiments were conducted in soil microcosms in the laboratory for a total of 332 (glyphosate) and 430 (trifluralin) days. The rate and amount of mineralization of both glyphosate and trifluralin were significantly influenced by the additions of fresh manure to soil in the laboratory and by the history of manure applications in the field. However, the maximum difference in herbicide mineralization between soils that were free of manure application and those amended with manure in the field or in the laboratory was only 6.1% and 7.3% of that initially applied, for trifluralin and glyphosate, respectively. Therefore, we conclude that liquid hog manure application to soil will have no significant effect on the mineralization of glyphosate and trifluralin under field conditions.

Animals↗

PubMed1992

Glyphosate degradation by immobilized bacteria: field studies with industrial wastewater effluent.

Immobilized bacteria have been shown in the laboratory to effectively remove glyphosate from wastewater effluent discharged from an activated sludge treatment system. Bacterial consortia in lab columns maintained a 99% glyphosate-degrading activity (GDA) at a hydraulic residence time of less than 20 min. In this study, a pilot plant (capacity, 45 liters/min) was used for a field demonstration. Initially, activated sludge was enriched for microbes with GDA during a 3-week biocarrier activation period. Wastewater effluent was then spiked with glyphosate and NH4Cl and recycled through the pilot plant column during start-up. Microbes with GDA were enhanced by maintaining the pH at less than 8 and adding yeast extract (less than 10 mg/liter). Once the consortia were stabilized, the column capacity for glyphosate removal was determined in a 60-day continuous-flow study. Waste containing 50 mg of glyphosate per liter was pumped at increasing flow rates until a steady state was reached. A microbial GDA of greater than 90% was achieved at a 10-min hydraulic residence time (144 hydraulic turnovers per day). Additional studies showed that microbes with GDA were recoverable within (i) 5 days of an acid shock and (ii) 3 days after a 21-day dormancy (low-flow, low-maintenance) mode. These results suggest that full-scale use of immobilized bacteria can be a cost-effective and dependable technique for the biotreatment of industrial wastewater.

Biodegradation, Environmental↗

PubMed1999

Clinical impact of upper gastrointestinal tract injuries in glyphosate-surfactant oral intoxication.

Fifty patients with glyphosate-surfactant oral ingestion were studied with upper gastrointestinal (UGI) endoscopic grading using Zargar's modified grading system for mucosal corrosive injury. Esophageal injury was seen in 68% of the patients, gastric injury in 72%, and duodenal injury in 16%. There were no grade 3 injuries. The upper gastrointestinal tract injuries caused by glyphosate-surfactant were minor in comparison with those by other strong acids. The WBC count, amount of glyphosate-surfactant ingested, length of hospital stay and the occurrence of serious complications increased markedly in the group which had grade 2 esophageal injuries. Thus, the severity of the esophageal injuries may be a prognostic factor for the patient with glyphosate-surfactant ingestion. The UGI endoscopy may be indicated for grading esophageal injury in patients who have ingested glyphosate-surfactant in amounts greater than 100 ml. Physicians should pay more attention to the patients with grade 2 or 3 esophageal injuries to prevent serious complications and to provide aggressive supportive care.

Administration, Oral↗

PubMed2006

Toxicity of glyphosate as Glypro and LI700 to red-eared slider (trachemys scripta elegans) embryos and early hatchlings.

More than 8.2 billion ha of cropland, gardens, and forests are treated with the herbicide glyphosate each year. Whereas the toxicity of glyphosate and associated adjuvants has been measured in other vertebrates, few, if any, studies have looked at their effects in reptiles. In some instances, management of turtle habitat requires control of successional stages through application of herbicides. Adults and juvenile turtles may be exposed directly, whereas embryos may contact the chemicals through the soil. In the present study, we exposed eggs of red-eared sliders (Trachemys scripta elegans) to single applications of herbicide ranging from 0 to 11,206 ppm wet weight of glyphosate in Glypro and 0 to 678 ppm of the surfactant, LI700. Hatching success at the highest concentration was significantly lower (73%) than in other treatments (80-100%). At hatch, turtles at the highest concentration weighed less than those at other concentrations. During a 14-d holding period, we observed dose-response relationships in the ability of hatchlings to right themselves when turned on their backs. At the end of the holding period, hatchlings at the highest dose level were still lighter, and somatic indices were lower, than those in other treatments. Genetic damage, as measured by flow cytometry, increased with treatment concentration except for the highest dose. We conclude that because of the high concentrations needed to produce effects and the protection offered by several centimeters of soil or sediment, glyphosate with LI700 poses low levels of risk to red-eared slider embryos under normal field operations with regards to the endpoints measured in the present study. Carelessness in handling glyphosate or failure to follow label directions may produce adverse effects. There also is a risk that the health of turtle embryos may be affected in ways not measured in the present study.

Animals↗

PubMedDate not supplied

Determination of glyphosate residues in plants by precolumn derivatization and coupled-column liquid chromatography with fluorescence detection.

A rapid method was developed for the trace-level determination of glyphosate in olives. After extraction of the glyphosate with water-dichloromethane and simultaneous removal of the olive oil, an aliquot of the aqueous extract is derivatized with 9-fluoroenylmethyl chloroformate (9-fluorenylmethoxycarbonyl chloride; FMOC-CI) to produce a highly fluorescent derivative. A 2 mL aliquot of this extract is injected directly into a coupled-column liquid chromatography system with fluorimetric detection (LC/LC-FD). The procedure was validated by recovery experiments at 3 spiking levels; recoveries ranged from 80 to 97% with relative standard deviations of 3-6%. The limits of detection and quantitation were estimated to be 0.01 and 0.05 mg/kg, respectively. The method was also applied to other plant materials, i.e., tomato plants, strawberry plants, and pear trees (branches, leaves, and fruits) suspected to be contaminated by glyphosate. In all these cases, the extraction was performed in aqueous media. The derivatization reaction was modified by increasing the FMOC-CI concentration, to ensure a quantitative reaction between analyte and reagent in the presence of high levels of coextractives, which also react with FMOC-CI. The final determination was by LC/LC-FD, yielding a rapid, selective, and sensitive method for the determination of glyphosate residues in these samples. The method was tested with real-world samples after application of glyphosate to the surrounding area of crops.

Chromatography, Liquid↗