Doses Of Glyphosate Research Articles

Impact of Glyphosate herbicide on blood parameters and selected tissues organs of rabbits (oryctolagus cuniculus)

Numerous studies have demonstrated that pesticides are toxic and harmful to human, animal, and environmental health. Glyphosate is the most widely used herbicide globally. This research aimed to assess the impacts of various dosages of glyphosate on rabbits. A total of 30 rabbits were divided into four groups: one control group and three treatment groups, with three concentrations of glyphosate selected as D1 (200 mg/kg/bw). The treatment groups were administered glyphosate at a dosage of 1 mL/day for 6 days per week over 4 weeks. The findings substantially reduced several hematological parameters, including hemoglobin, erythrocytes, leukocytes, hematocrit, and platelets. At the same time, the levels of white blood cells and lymphocytes increased significantly in all glyphosate-treated groups compared to the control group. Additionally, changes were observed in the liver, thymus, and kidney tissues, including alterations in hepatocyte cells, portal blood vessel congestion, inflammatory cell infiltration, and necrosis of sporadic hepatocytes.

The combined effect of environmentally relevant doses of glyphosate and high temperature: An integrated and multibiomarker approach to delineate redox status and behavior in Danio rerio.

Glyphosate, a pesticide commonly found in aquatic ecosystems, affects this habitat and nontarget organisms such as fish. The increase in water temperature, linked to factors such as climate change, poses a considerable threat. Despite extensive ecotoxicological research, we still do not know the real individual and specific consequences of continued exposure to glyphosate and high temperatures, simulating a scenario where the aquatic environment remains contaminated and temperatures continue to rise. Therefore, in this study, we examined the effects of exposure to environmentally relevant concentrations of glyphosate, active ingredient glyphosate (GAI), and glyphosate-based herbicide (GBH) in combination with high temperature (34 °C) in adult zebrafish (Danio rerio). The fish were acclimated to 28 or 34 °C for 96 h. The exposure to 225 and 450 μg L-1 (GBH or GAI) at 28 or 34 °C for 7 days. We analyzed behavioral endpoints (anxiety-like response, sociability, and aggressivity) and biochemical biomarkers of the brain and muscle (oxidative stress). Anxiety-like responses and decreased sociability were disrupted by the combination of glyphosate and high temperature. Furthermore, there is a decrease in Acetylcholinesterase activity in the brain, and an increase in Lipid Peroxidation, Protein Carbonylation, Acetylcholinesterase activity, and Glutathione S-Transferase activity in the muscle. These results demonstrated oxidative stress, anxiety-like behavior and decreased sociability caused by glyphosate and high temperature. We concluded that the combined effects of glyphosate and high temperature affected redox homeostasis and behavior, emphasizing that the field of glyphosate pollution should be carefully considered when evaluating the effects of climate change.

Effect of Different Doses of Glyphosate on Soil Physical Parameters in the Prefecture of N'Zérékoré, Guinea

This study examines the effect of different glyphosate doses on the soil texture in four rural communes of the N'Zérékoré prefecture in Guinea. A complete randomized block design was used to assess the impact of glyphosate doses on several soil parameters, including granulometry, aggregate stability, bulk density, and porosity. The analysis of variance (ANOVA) revealed that glyphosate doses significantly influence Granulometry A (p = 0.02881) and show a trend toward affecting soil aggregate stability (SI) and overall stability (Sg), although these effects are not significant at the 0.05 threshold. Conversely, glyphosate doses had no significant effect on Granulometry Lf, Granulometry Lg, bulk density, and soil porosity, as these parameters were more influenced by soil type and year. These results suggest that higher doses of glyphosate can alter soil structure, but the effect varies depending on specific environmental conditions, particularly soil type and annual variations. Careful management of glyphosate doses is therefore recommended to preserve soil quality and support sustainable agricultural practices. Keywords: Glyphosate, granulometry, aggregate stability, bulk density, porosity, Guinea.

Emergence of multiple resistance to EPSPS and ALS herbicides in smooth pigweed (Amaranthus hybridus): a growing concern in Brazil

Abstract Recently, farmers in Brazil have observed a decline in efficacy of glyphosate, chlorimuron, and imazethapyr control of smooth pigweed (Amaranthus hybridus L.). The objectives of this study were to quantify the resistance of Amaranthus in Brazil to glyphosate and acetolactate synthase (ALS)-inhibiting herbicides, elucidate the mechanism of resistance, and assess the frequency of sensitivity shifts to glyphosate and chlorimuron in Brazil. Dose–response assays were conducted in a greenhouse with glyphosate, chlorimuron, and imazethapyr. This was followed by sequencing of the EPSPS and ALS genes. Additionally , 740 Amaranthus populations across several Brazilian states were monitored over 4 yr, subjected to a single discriminatory dose of glyphosate and chlorimuron. The populations BR18Asp051 and BR21Asp205 were resistant to glyphosate, chlorimuron, and imazethapyr. The elevated resistance level to glyphosate in these populations is attributed to multiple amino acid substitutions (TAP-IVS) in the EPSPS gene; and cross-resistance to sulfonylureas and imidazolinones is conferred by the Trp-574-Leu substitution in the ALS gene in both populations. Overall, resistance distribution indicated that 88% of the sampled populations were considered sensitive to glyphosate, while 66% were sensitive to chlorimuron. Furthermore, 10% of the samples demonstrated multiple resistance to both active ingredients. A shift in glyphosate sensitivity was observed in four states in Brazil; however, sensitivity shifts to chlorimuron were more widely dispersed in Brazilian agricultural regions.

Glyphosate contact alters the expression of genes in the head of africanized Apis mellifera bees

The increase in the world population results in a greater demand for food, intensifying the dependence on pesticides use. Glyphosate, a pesticide widely used in crops, can contaminate resources collected by bees. In this context, this study aimed to analyze the transcriptome of the head of Africanized Apis mellifera bees during the foraging phase to determine whether contact with the herbicide glyphosate, in lethal and sublethal doses, causes changes in the gene expression profile. For this, 180 marked bees were collected from their hives, aged 21 days, and distributed into three treatment groups: 1) bees in contact with the lethal dose of glyphosate (255.73 µg/bee); 2) bees in contact with the sublethal dose of glyphosate (2.5573 µg/bee); 3) control group with distilled water. Transcriptome analysis was performed on 12 bees from each treatment after one and four hours of exposure. The results show that one hour of contact with glyphosate resulted in 57 genes presenting differential expression in relation to the control (11 lethal and 53 sublethal), interfering in the signaling, communication and metabolism processes, while four hours of exposure, 38 genes (32 lethal and 11 sublethal) related, mainly, to the stimulation of the immune response. In summary, glyphosate affects the gene expression of honey bees during the foraging phase, at both doses, resulting in negative effects on behavior, metabolism and immune system, which compromises the health, activity and development of the colonies, also compromising the process of pollination.

Root exudation of glyphosate in Eucalyptus urophylla S.T. Blake

Glyphosate stands out in the eucalyptus management, which makes it essential to know its behavior, its effects on the plant, and possible environmental impacts. This study aimed to identify and quantify the root exudation of glyphosate and aminomethylphosphonic acid (AMPA) by Eucalyptus urophylla with chromatographic and biological methods. The five glyphosate doses were tested (0, 360, 720, 1080 and 1440 g a.e ha−1) on E. urophylla plants. The physiological and intoxication evaluations were performed after herbicide application. Water samples remaining from the pots were used for chemical quantification of root exudation of glyphosate and AMPA in high-performance liquid chromatography. Cucurbita pepo plants were used as bioindicators of glyphosate in the water remaining in the pots after applying herbicide. The increase in glyphosate doses promoted linear growth in E. urophylla intoxication and significantly reduced total dry mass and root production. E. urophylla plants had their photosynthetic, transpiratory, and stomatal conductance rates reduced as the herbicide doses increased. The AMPA root exudation was not detected, but it was possible to identify the presence of glyphosate by bioassay and chemical methods. Root exudation of glyphosate by eucalyptus can result in lesser herbicide action in plant control and cause contamination of deeper soil layers.

Glyphosate application may influence the transfer of trace elements from soils to both soil solutions and plants

Trace element dynamics in the soil-plant system depends on multiple parameters, including chelating organic compounds from natural or synthetic organic matters. In this study, we evaluated the influence of one of the most common pesticides—glyphosate—on the mobility of trace elements considering contrasted soils (uncontaminated, anthropogenically contaminated, and naturally-enriched) in a greenhouse experiment. Four modalities have been tested: one control without any application, two with different glyphosate doses (1 and 3 times the authorised field dose), and one with compost addition to evaluate its potential ability to mitigate the impact of glyphosate on trace element mobility. Both, trace element and glyphosate concentrations were measured in the soil solutions and trace element contents were determined in plants at the end of the experiment. The results showed that, although glyphosate concentrations rapidly decreased in soil solutions, glyphosate application still influenced the transfer of trace elements to both soil solution (up to 12-times higher) and plant (up to 5.2-times higher). This influence was highly dependent on both the specific elements and the type of soils considered. For instance, in uncontaminated soils, glyphosate especially increased the mobilization of Mn, Co, Zn, Mo, and Pb to soil solution. This effect diminished of 2.5 times on average with increasing soil contamination. A similar trend was observed for the transfer of trace elements from soil to plant (i.e., on average 2.2-times lower in the most contaminated compared to the uncontaminated soil). However, in the naturally-enriched soil, opposing trends were noticed between soil solution and plant. The impact of compost addition on the transfer of trace elements to plants remains unclear: compost enhanced the transfer of trace elements to soil solution in uncontaminated and naturally-enriched soils likely due to trace element input through the compost, but decreased the transfer in anthropogenically-contaminated soils likely due to adsorption processes. Therefore, glyphosate could potentially increase the exposure of trace elements through food consumption and their transfer to the ecosystem, particularly in uncontaminated and weakly contaminated soils. In highly contaminated soils, compost could mitigate the glyphosate-induced enhancement of trace element mobility to soil solution.

In vitro impacts of glyphosate on manatee lymphocytes

Exposure to contaminants, such as the herbicide glyphosate, can suppress protective immune functions. Glyphosate is the herbicide most used worldwide and has been found in the plasma of more than 50 % of the Florida manatees (Trichechus manatus latirostris) and all-year-round in their aquatic environment. Our objectives were to analyze the consequences of glyphosate exposure on their immune responses via T-lymphocyte proliferation assays and transcriptomics. We isolated peripheral blood mononuclear cells (mainly lymphocytes) of free-ranging manatees and performed T-cell proliferation assays. We used transcriptomics to understand the consequences of glyphosate in vitro exposure. The three doses chosen ranged from environmentally relevant concentrations at 10 to 10,000 µg.L−1 that is considered an environmental contamination scenario. Glyphosate caused a dose-dependent reduction in T-lymphocyte proliferation, with a significant mean reduction of 27.3 % at 10,000 µg.L−1 and up to 51.5 % in some individuals. Additionally, T-lymphocyte proliferation was significantly reduced in mid-winter compared to early winter. Transcriptomic analysis of peripheral blood mononuclear cells indicated that all doses of glyphosate (10, 1,000, and 10,000 µg.L−1) resulted in up-regulation of genes related to acute phase inflammation and inhibition of the T-lymphocyte proliferation pathway. Exposure to this contaminant along with other environmental stressors, such as extreme winters and red tide, might further affect the adaptive immune response of this threatened species.

Potential Protective Effect of Hesperidin (Vitamin P) against Glyphosate-Induced Spermatogenesis Damage in Male Rats: Biochemical and Histopathological Findings on Reproductive Parameters.

The aim of this study was to investigate the effectiveness of hesperidin (HES) on testicular histopathological changes, biochemical changes, and semen characteristics in rats exposed to glyphosate (GLP). The control group was given a normal diet devoid of GLP and HES, the HES group was given 100 mg/kg/day HES with the normal diet, the GLP group was given GLP at the LD50/10 dose of normal feed, which was 787.85 mg/kg/day, and the GLP + HES group was given normal feed containing 787.85 mg/kg/day LD50/10 dose of GLP in addition to 100 mg/kg/day HES. GLP administration reduced sperm motility, sperm plasma membrane integrity, glutathione levels, and total antioxidant levels in the testicular tissues of rats. Moreover, it caused an increase in right testis and left epididymis weights, abnormal sperm counts, malondialdehyde levels, total oxidant status, and DNA damage. The HES treatment showed curative effects on these parameters. Furthermore, HES was effective in lessening the histopathological damage that was caused by GLP. The results showedthat HES protects spermatological parameters and DNA integrity, improves antioxidant defenses, and lowers the damage and lipid peroxidation caused by GLP in testicular tissue.

P25-14 Renal disturbances after prenatal and postnatal exposure to a very low dose of glyphosate and its mixture with dicamba and 2-4-D

P25-14 Renal disturbances after prenatal and postnatal exposure to a very low dose of glyphosate and its mixture with dicamba and 2-4-D

The light intensity in the cultivation environment and the impact of glyphosate on plants of the Urochloa genus

The variation in light within the environment triggers morphophysiological changes in plants and can lead to distinct responses in sun-exposed or shaded plants to glyphosate. The response of Urochloa genotypes subjected to desiccation with 2160, 1622.4, 1080, 524.4, 273.6, and 0.0 g ha−1 of glyphosate was evaluated in full sun and shade conditions. Cayana grass, mulato II grass, and sabiá grass – hybrids recently launched on the market, in addition to palisade grass and congo grass were evaluated. Under full sun, we achieved control of congo grass using 1080 g ha−1 of glyphosate, while the other grasses required 2160 g ha−1. In the low-light environment, sabiá grass was effectively controlled with 524.4 g ha−1 of glyphosate, but the other grasses needed 273.6 g ha−1. In shading, compared to full sun, the savings with glyphosate were 75 and 76% for the control of congo grass and sabiá grass, respectively, and 87% for palisade grass, mulato II grass and cayana grass. Increasing glyphosate doses leads to a decline in the quantum efficiency of photosystem II and in the electron transport rate, especially in the shade. Urochloa genotypes are more sensitive to glyphosate in the shade, which must be considered when determining the herbicide dose.

Changes in the proteome of Apis mellifera acutely exposed to sublethal dosage of glyphosate and imidacloprid

Uncontrolled use of pesticides has caused a dramatic reduction in the number of pollinators, including bees. Studies on the effects of pesticides on bees have reported effects on both metabolic and neurological levels under chronic exposure. In this study, variations in the differential expression of head and thorax–abdomen proteins in Africanized A. mellifera bees treated acutely with sublethal doses of glyphosate and imidacloprid were studied using a proteomic approach. A total of 92 proteins were detected, 49 of which were differentially expressed compared to those in the control group (47 downregulated and 2 upregulated). Protein interaction networks with differential protein expression ratios suggested that acute exposure of A. mellifera to sublethal doses of glyphosate could cause head damage, which is mainly associated with behavior and metabolism. Simultaneously, imidacloprid can cause damage associated with metabolism as well as, neuronal damage, cellular stress, and impairment of the detoxification system. Regarding the thorax–abdomen fractions, glyphosate could lead to cytoskeleton reorganization and a reduction in defense mechanisms, whereas imidacloprid could affect the coordination and impairment of the oxidative stress response.

Влияние фосфорсодержащих пестицидов на ферментативную активность и множественные формы кислой фосфатазы живородки речной (Viviparus viviparus L.)

Organophosphate pesticides are used in agriculture and for treating landscape and park areas due to their high efficiency and economic availability, and therefore they are potential toxicants in water bodies. Broad-spectrum systemic herbicide (Glyphosate) and an organophosphorus insecticide (Malathion) have been studied against the freshwater mollusks (Viviparus viviparus L.), widespread in permanent water bodies of the European part of Russia and Siberia. Changes in the activity and composition of multiple forms of acid phosphatase (AcP) were revealed in the hepatopan creas of mollusks under the influence of high doses of glyphosate and malathion in an acute toxicological experiment (96 hours). In both cases, an increase in enzyme activity is observed, but the cholinomimetic malathion is significantly more active than glyphosate, the neurotropic activity of which is unknown. It was shown that the increase in activity in the experimental groups of mollusks is associated with the appearance of new multiple forms of acid phosphatase, which persist throughout the experiment. Multiple form of AсP with low relative electrophoretic mobility revealed as an effect of glyphosate and malathion. In addition, in mollusks exposed to malathion, a multiple form of the enzyme with an average electrophoretic mobility was detected. The composition of multiple forms of acid phosphatase in mollusks of the control group did not change during the exposure. The results indicate the formation of nonspecific adaptations in response to organophosphate pesticides and confirm that acid phosphatase can be an indicator of toxic effects in environmental and biochemical monitoring of freshwater pollution.

Effect of glyphosate on germination and seedling development of four native plants of dunes in Spain

Using glyphosate is easier than manually controlling the invasive plant Carpobrotus in dune ecosystems. However, before it is used its effect on native species in this ecosystem needs to be determined. This study reports the effects in the laboratory of different concentrations of glyphosate (1.0, 0.5, 0.3, 0.1, 0.05, 0.01, and 0.005 g/m2 ) on germination and seedling emergence of four species of Mediterranean dune plants, Lotus creticus, Medicago marina, Ononis ramosissima and Ammophila arenaria, used in the restoration of this natural ecosystem. Germination was completely inhibited when glyphosate was applied at 0.5, and 1.0 g/m2. The recommended dose (0.3 g/m2 ) also inhibited the germination of L. creticus and M. marina. The percentage germination of O. ramosissima and A. arenaria was around 40% and 30% respectively when a dose of glyphosate of 0.1 g/m2 was used, whereas for seeds of L. creticus and M. marina it was lower than 5%. The T50 at germination of seed incubated with glyphosate increased in all species independently of the dose of glyphosate. Seedling emergence from seeds previously germinated in the presence of glyphosate was only recorded for O. ramosissima and A. arenaria. The results indicate that seeds of O. ramosissima are more tolerant of glyphosate, followed by those of A. arenaria and those of L. creticus and M. marina are the most sensitive.

Effect of soil drainage on Peruvian watergrass biochemical response and control by glyphosate

AbstractPeruvian watergrass (Luziola peruviana J.F. Gmel.) is a perennial weed often found in paddy fields in the southern region of Brazil. Its chemical control is performed mainly by herbicides such as glyphosate in burndown, whose efficacy depends on soil moisture. Under excess‐water soil conditions, glyphosate efficacy is reduced, probably due to reduced translocation and the involvement of photoassimilates partition. Furthermore, little is known about the stress tolerance of these plants subjected to water deficit. Based on that, we performed experiments to verify the effect of soil moisture on the biochemical parameters of Peruvian watergrass and glyphosate translocation to the stolon and roots. Total soluble sugars, sucrose, starch, and glyphosate concentrations in leaves, culms, roots, and glyphosate partitioning were quantified. The malondialdehyde content and the lipid peroxidation increased with the drainage. Under drainage conditions, superoxide production was higher in roots than leaves, while peroxide production was lower in roots than leaves. The electrolyte leakage increased with the drainage and glyphosate application. The total soluble sugar content varied in each organ with a significant increase in the culm 14 days after application in the draining treatment. Sucrose varied considerably and reached its maximum concentration at 21 days after herbicide application. The starch accumulation in the culm was 7 days after applying the highest glyphosate dose. The presence of glyphosate in the roots subjected to soil drainage indicates the movement of this herbicide. In conclusion, soil drainage profoundly impacts Peruvian watergrass physiology, increasing the photoassimilates and glyphosate translocation to the stolon and root. This explains why glyphosate efficacy is higher under drainage conditions.

Glyphosate-induced changes in the expression of galanin and GALR1, GALR2 and GALR3 receptors in the porcine small intestine wall

Glyphosate is the active ingredient of glyphosate-based herbicides and the most commonly used pesticide in the world. The goal of the present study was to verify whether low doses of glyphosate (equivalent to the environmental exposure) evoke changes in galanin expression in intramural neurons in the small intestine in pigs and to quantitatively determine changes in the level of galanin receptor encoding mRNA (GALR1, GALR2, GALR3) in the small intestine wall. The experiment was conducted on 15 sexually immature gilts divided into three study groups: control (C)—animals receiving empty gelatin capsules; experimental 1 (G1)—animals receiving a low dose of glyphosate (0.05 mg/kg b.w./day); experimental 2 (G2)—animals receiving a higher dose of glyphosate (0.5 mg/kg b.w./day) orally in gelatine capsules for 28 days. Glyphosate ingestion led to an increase in the number of GAL-like immunoreactive intramural neurons in the porcine small intestine. The results of RT-PCR showed a significant increase in the expression of mRNA, which encodes the GAL-receptors in the ileum, a decreased expression in the duodenum and no significant changes in the jejunum. Additionally, intoxication with glyphosate increased the expression of SOD2-encoding mRNA in the duodenum and decreased it in the jejunum and ileum, but it did not affect SOD1 expression. The results suggest that it may be a consequence of the cytotoxic and/or neurotoxic properties of glyphosate and/or its ability to induce oxidative stress.

Glyphosate hormesis stimulates tomato (Solanum lycopersicum L.) plant growth and enhances tolerance against environmental abiotic stress by triggering nonphotochemical quenching.

Glyphosate is the most widely applied herbicide in the world. Hormesis caused by low glyphosate doses has been widely documented in many plant species. However, the specific adaptative mechanism of plants responding to glyphosate hormesis stimulation remains unclear. This study focused on the biphasic relationship between glyphosate dose and tomato plant growth, and how glyphosate hormesis stimulates plant growth and enhances tolerance to environmental stress. We constructed a hormesis model to describe the biphasic relationship with a maximal stimulation (MAX) of 162% above control by glyphosate at 0.063 g ha-1. Low-dose glyphosate increased photosynthetic pigment contents and improve photosynthetic efficiency, leading to plant growth stimulation. We also found that glyphosate hormesis enhanced plant tolerance to diuron (DCMU; a representative photosynthesis inhibitor) by triggering the nonphotochemical chlorophyll fluorescence quenching (NPQ) reaction to dissipate excess energy stress from photosystem II (PSII). Transcriptomic analysis and quantitative real-time polymerase chain reaction results revealed that the photosynthesis-antenna proteins pathway was the most sensitive to glyphosate hormesis, and PsbS (encoding photosystem II subunit S), ZEP (encoding zeaxanthin epoxidase) and VDE (encoding violaxanthin de-epoxidase) involved in NPQ played crucial roles in the plant response to glyphosate hormesis. These results provide novel insights into the mechanisms of plant hormesis and is meaningful to the application of glyphosate hormesis in agriculture. © 2024 Society of Chemical Industry.

Confirmation of a four-way herbicide-resistant Palmer amaranth (Amaranthus palmeri) population in Iowa

Abstract Palmer amaranth (Amaranthus palmeri S. Watson) was first reported in Iowa in 2013 and has continued to spread across the state over the last decade. Importantly, A. palmeri is widely recognized as one of the more economically important weeds in production agriculture. The presence of A. palmeri in Iowa is concerning as the species has evolved resistance to nine herbicide sites of action, however, no formal characterization has been conducted on Iowa populations. Therefore, herbicide assays were conducted on an A. palmeri population collected in Harrison County, Iowa in 2023 (Southwest Palmer Amaranth, SWPA) and a known herbicide-susceptible population collected from Nebraska in 2001 (Palmer Amaranth Susceptible, PAS). The two populations were treated with preemergence and postemergence herbicides commonly used in Iowa. The treatments included preemergence applications of atrazine, metribuzin, and mesotrione and postemergence applications of atrazine, imazethapyr, glyphosate, lactofen, mesotrione, glufosinate, 2,4-D and dicamba at 1x and 4x the labeled rates. Survival frequency of SWPA was >90% when treated postemergence with 1x rates of imazethapyr, atrazine, glyphosate, and mesotrione compared to ≤6% for PAS. Both SWPA and PAS had 0% survival when treated with lactofen, glufosinate, 2,4-D, and dicamba at the 1x or 4x rates. Plant population density reduction for SWPA was 53% and 40% in response to 1x rates of preemergence-applied mesotrione and atrazine, respectively. Metribuzin applied preemergence reduced SWPA plant population density by >90% at both rates. Dose-response experiments revealed the 50% effective doses (ED50) of mesotrione, glyphosate, imazethapyr, and atrazine for SWPA were 9.5-,8.5-, 71- and 40-fold greater than for PAS, respectively. The results confirm that SWPA is four-way multiple herbicide-resistant. Amaranthus palmeri infestations are likely to continue to spread within Iowa, therefore diversified weed management programs that include early detection, rapid response, and effective multi-tactic management strategies will be required for control.

Both acute glyphosate and the aminomethylphosphonic acid intoxication decreased the acetylcholinesterase activity in rat hippocampus, prefrontal cortex and gastrocnemius muscle

It has been reported that glyphosate, one of the most common herbicides used in agriculture, impairs locomotion and cognition. Glyphosate has a variable half-life in soil up to biotic and/or abiotic factors transform the molecule in metabolites such as the aminomethylphosphonic acid (AMPA) that has a longer half-life. In this study, female Sprague Dawley rats were acutely exposed to different doses of glyphosate or AMPA (i.e. 10, 56 or 100 mg/kg) and, subsequently, the acetylcholinesterase (AChE) activity was measured in the hippocampus, prefrontal cortex (PFC) and the gastrocnemius muscle. Both glyphosate and AMPA produced a similar decrease in the AChE activity in all the tissues tested. These results suggest that interference with normal cholinergic neurotransmission may be one of the mechanisms involved in glyphosate-induced motor alterations in rats. Moreover, our results highlight the biological importance of AMPA as a molecule with anticholinesterase action in brain and skeletal muscle. To our knowledge, this is the first report showing in vivo that AMPA, the major metabolite of glyphosate, behaves as an organophosphate.

Role of glutathione S-transferases in the mode of action of herbicides that inhibit amino acid synthesis in Amaranthus palmeri

Acetolactate synthase inhibitors (ALS inhibitors) and glyphosate are two classes of herbicides that act by inhibiting an enzyme in the biosynthetic pathway of branched-chain or aromatic amino acids, respectively. Besides amino acid synthesis inhibition, both herbicides trigger similar physiological effects in plants. The main aim of this study was to evaluate the role of glutathione metabolism, with special emphasis on glutathione S-transferases (GSTs), in the mode of action of glyphosate and ALS inhibitors in Amaranthus palmeri. For that purpose, plants belonging to a glyphosate-sensitive (GLS) and a glyphosate-resistant (GLR) population were treated with different doses of glyphosate, and plants belonging to an ALS-inhibitor sensitive (AIS) and an ALS-inhibitor resistant (AIR) population were treated with different doses of the ALS inhibitor nicosulfuron. Glutathione-related contents, GST activity, and related gene expressions (glutamate-cysteine ligase, glutathione reductase, Phi GST and Tau GST) were analysed in leaves. According to the results of the analytical determinations, there were virtually no basal differences between GLS and GLR plants or between AIS and AIR plants. Glutathione synthesis and turnover did not follow a clear pattern in response to herbicides, but GST activity and gene expression (especially Phi GSTs) increased with both herbicides in treated sensitive plants, possibly related to the rocketing H2O2 accumulation. As GSTs offered the clearest results, these were further investigated with a multiple resistant (MR) population, compressing target-site resistance to both glyphosate and the ALS inhibitor pyrithiobac. As in single-resistant plants, measured parameters in the MR population were unaffected by herbicides, meaning that the increase in GST activity and expression occurs due to herbicide interactions with the target enzymes.