Doses Of Atrazine Research Articles

Mixture of glufosinate and atrazine for ryegrass (Lolium multiflorum Lam.) control and its effect on seeds’ quality

Ryegrass management has been difficult by the occurrence of resistant biotypes to several herbicides with different action mechanisms. Since herbicides mixes and rotations are an important alternative for resistant weed management, the objective of this work was to evaluate the interaction of the dose of the herbicides glufosinate and atrazine on ryegrass control and its seeds’ quality exposed to their association. For this study, three experiments were carried out using factorial design in field, laboratory, and greenhouse conditions. Two factors (A and B) were evaluated in each experiment, where factor A and B represented the doses of glufosinate and atrazine, respectively. Ryegrass control was evaluated in field experiment, while germination percentage and Emergence Speed Index (ESI), were obtained in laboratory and greenhouse analyses, respectively. The data were submitted to variance analysis (P≤0.05) and the significant results were analyzed through response surface graphs. For ryegrass control data, the effect of the interaction was analyzed by the Colby method; glufosinate provides efficient ryegrass control, but its association with atrazine reduces the efficiency, being characterized as an antagonism between molecules. Glufosinate herbicide application, independent of atrazine presence, reduced the ryegrass seeds quality at the post-flowering stage.

Influence of glyphosate underdoses on the suppression of Panicum maximum cultivars

ABSTRACT: The use of herbicide underdoses allows minimizing the competition of grasses on annual crops, enabling simultaneous cultivation. In this context, the objective of this study was to investigate glyphosate underdoses on the suppression of the initial growth of three Panicum maximum cultivars aiming at the integrated cultivation, in addition to the effects of forage species on the incidence and development of weeds. Three field experiments were conducted. The experimental design was a randomized block design with four replications and eight treatments consisting of increasing glyphosate doses (0, 54, 108, 270, 378, 540, 756, and 1,080 g a.e. ha−1). An atrazine dose of 1,200 g a.i. ha−1 was added to each treatment. Plant phytotoxicity assessments were performed at 7, 14, 21, and 28 days after application. At 80 and 125 days after sowing, the assessments of total dry matter production, leaf dry matter, stem dry matter, and leaf to stem ratio were carried out, in addition to density and dry matter production of weed community. Glyphosate underdoses below 215, 65, and 90 g a.e. ha-1 have a potential to be investigated aiming at the management of P. maximum cv. Atlas, P. maximum cv. Mombasa, and P. maximum cv. Tanzania under intercropping. The three forage species are effective in suppressing weeds.

Nanosorbent of hydroxyapatite for atrazine: A new approach for combating agricultural runoffs

The attention of current work was on the fabrication of effective nanoadsorbent of hydroxyapatite (HAp) for the controlled release of atrazine (ATZ) formulation. The ATZ-HAp complex (ATZ@HAp) was able to inhibit the growth of Brassica sp. under in situ conditions. This developed methodology aspires to cease the agricultural runoffs of ATZ applied with the HAp adjuvant and ensure their effective functioning. The efficacy of the protocol was mainly accomplished by adsorbing ATZ over the surface of HAp NPs that restricted its premature runoff and promoted the prolonged herbicidal efficiency. The influence of fundamental parameters i.e., HAp dose, ATZ dose and initial pH on the adsorption process was investigated systematically. The suitability of ATZ@HAp complex for real world application was adjudged after proofing its toxicological behaviour and its role in Zea mays plantations. The complex was found to be non-toxic and nurturing due to its phosphate rich nature. Further investigations of ATZ@HAp complex and its effect on the non-target species will help in establishing an effective framework for their commercial use in agricultural practices.

Oxidative stress in triazine pesticide toxicity: a review of the main biomarker findings

This review article provides a summary of the studies relying on oxidative stress biomarkers (lipid peroxidation and antioxidant enzymes in particular) to investigate the effects of atrazine and terbuthylazine exposure in experimental animals and humans published since 2010. In general, experimental animals showed that atrazine and terbuthylazine exposure mostly affected their antioxidant defences and, to a lesser extent, lipid peroxidation, but the effects varied by the species, sex, age, herbicide concentration, and duration of exposure. Most of the studies involved aquatic organisms as useful and sensitive bio-indicators of environmental pollution and important part of the food chain. In laboratory mice and rats changes in oxidative stress markers were visible only with exposure to high doses of atrazine. Recently, our group reported that low-dose terbuthylazine could also induce oxidative stress in Wistar rats. It is evident that any experimental assessment of pesticide toxic effects should take into account a combination of several oxidative stress and antioxidant defence biomarkers in various tissues and cell compartments. The identified effects in experimental models should then be complemented and validated by epidemiological studies. This is important if we wish to understand the impact of pesticides on human health and to establish safe limits.

Post-Emergence Herbicidal Activity of Nanoatrazine Against Susceptible Weeds

Poly(ɛ-caprolactone) (PCL) nanocapsules have been previously developed as a carrier system for atrazine. However, the efficacy of this nanoformulation against weeds commonly found in crop cultures has not been tested yet. Here, we evaluated the post-emergence herbicidal activity of PCL nanocapsules containing atrazine against Amaranthus viridis (slender amaranth) and Bidens pilosa (hairy beggarticks), in comparison with a commercial formulation of atrazine. For both species, treatment with atrazine-loaded nanocapsules (at 2000 g ha-1) led to a greater decrease in the photosystem II activity (above 50% inhibition relative to the control) than the commercial atrazine formulation at the same concentration (around 40% inhibition). The growth of A. viridis plants was equally reduced by nanoatrazine and commercial formulation (above 64% for root and 75% for shoot). In the case of B. pilosa, atrazine-loaded nanocapsules decreased more effectively the root and shoot growth than the commercial formulation, leading to a loss of plant biomass. Moreover, for both species, the use of ten-fold diluted atrazine-loaded PCL nanocapsules (200 g ha-1) resulted in the same inhibitory effect in root and shoot growth as the commercial formulation at the standard atrazine dose. These results suggest that the utilization of atrazine-containing PCL nanocapsules potentiated the post-emergence control of A. viridis and B. pilosa by the herbicide. Thus, this nanoformulation emerges as an efficient alternative for weed control.

Acute and chronic toxicity of pesticides on tadpoles of Physalaemus cuvieri (Anura, Leptodactylidae)

Brazil is the largest consumer of pesticides in the world. However, knowledge on how these pesticides affect wildlife is scarce. Among the vertebrates, amphibians are particularly important in research to assess the impact of pesticides because of the correlation between pesticide and the decline of these species. This study aimed to evaluate the acute and chronic toxicity of commercial formulations of pesticides, i.e., atrazine (herbicide), cypermethrin (insecticide), and tebuconazole (fungicide) in Physalaemus cuvieri tadpoles. Eggs were collected in nature and cultivated under controlled conditions in the laboratory. Toxicity tests were carried out under standard conditions to determine the lethal concentration (LC50) after 96 h of exposure and to determine the effect of sublethal concentrations after 7 days. In addition, we performed swimming activity tests on tadpoles exposed to sublethal concentrations. The lethal concentration (LC50) was 19.69 mg/L for atrazine, 0.24 mg/L for cypermethrin and 0.98 mg/L for tebuconazole. In the acute test, atrazine showed lower toxicity than cypermethrin and tebuconazole for P. cuvieri. Swimming activity was affected at sublethal doses of atrazine and cypermethrin, but was not after exposure to tebuconazole. Cypermethrin was the insecticide that most altered the swimming activity of the individuals tested. The risk evaluation analysis indicated risks for tadpoles exposed to three tested pesticides, specially cypermethrin.

Crecimiento de oocitos biderianos en machos adultos de Rhinella marina (Linnaeus, 1758) mediante el uso de hormonas y disruptores endócrinos

En la región anterior de los testículos de los machos de ciertos taxa de la familia Bufonidae se localiza el órgano de Bidder (OB), un ovario rudimentario no funcional que crece y se desarrolla parcialmente si los testículos son removidos. En esta investigación se analizó el efecto de hormonas y disruptores endócrinos sobre el crecimiento de los oocitos del OB de machos adultos orquidectomizados de la especie Rhinella marina. Machos adultos fueron orquidectomizados y sometidos a dosis diarias de una solución salina, atrazina y progesterona durante un periodo de dos meses y el efecto de dichas substancias fue analizado mediante observaciones en la morfología interna y externa y mediciones del diámetro máximo de los oocitos biderianos de los machos oquidectomizados.
 
 Todos los tratamientos exhibieron un incremento en el diámetro máximo de los oocitos biderianos. Los tratamientos que presentaron oocitos de mayor tamaño y con características correspondientes a estadios de la oogénesis posteriores, fueron el tratamiento con progesterona seguido por el tratamiento con atrazina + progesterona; sin embargo, se obtuvo una baja cantidad de oocitos crecidos. Los resultados sugieren que la hormona progesterona fue la que promovió un mayor crecimiento de los oocitos biderianos de machos orquidectomizados de la especie Rhinella marina.

Lack of immunotoxic effects of repeated exposure to atrazine associated with the adaptation of adrenal gland activation

T cell-dependent IgM antibody production and natural killer cell (NKC) activity were assessed in SD rats orally administered atrazine for 28 days to males (0, 6.5, 25, or 100 mg/kg/day) or females (0, 3, 6, or 50 mg/kg/day), or 30 or 500 ppm in diet (3 or 51 mg/kg/day). Anti-asialo GM1 antibodies (NKC) and cyclophosphamide (antibody-forming cell assay [AFC]) served as positive controls. Pituitary (ACTH, prolactin), adrenal (corticosterone, progesterone, aldosterone), and gonadal (androgens, estrogens) hormones were assessed after 1, 7, and/or 28 days of treatment. Food intake and body weights were significantly reduced in the highest dosed males, and transiently affected in females. Urinary corticosterone levels were not increased in atrazine-treated groups in either sex at any time point measured (10, 22, or 24 days). Corticosterone and progesterone were elevated in males after a single atrazine dose ≥6.5 mg/kg/day, but not after 7, 14, or 28 doses. There were no effects on adrenal, pituitary, or gonadal hormones in females. Atrazine did not suppress the AFC response or decrease NKC function after 28 days in males or females. Atrazine had no effect on spleen weights or spleen cell numbers in males or females, although thymus weights were elevated in males receiving the highest dose. The lack of immunotoxic effect of atrazine was associated with diminished adrenal activation over time in males, and no effects on adrenal hormones in females.

Assessing the phytoremediation potential of crop and grass plants for atrazine-spiked soils

Pollution of soil and groundwater by atrazine has become an increasing environmental concern in the last decade. A phytoremediation test using plastic pots was conducted in order to assess the ability of several crops and grasses to remove atrazine from a soil of low permeability spiked with this herbicide. Four plant species were assessed for their ability to degrade or accumulate atrazine from soils: two grasses, i.e., ryegrass (Lolium perenne) and tall fescue (Festuca arundinacea), and two crops, i.e., barley (Hordeum vulgare) and maize (Zea mays). Three different doses of atrazine were used for the contamination of the pots: 2, 5 and 10 mg kg−1. 16 days after spiking, the initial amount of atrazine was reduced by 88.6–99.6% in planted pots, while a decrease of only 63.1–78.2% was found for the unplanted pots, thus showing the contribution of plants to soil decontamination. All the plant species were capable of accumulating atrazine and its N-dealkylated metabolites, i.e., deethylatrazine and deisopropylatrazine, in their tissues. Some toxic responses, such as biomass decreases and/or chlorosis, were observed in plants to a greater or lesser extent for initial soil doses of atrazine above 2 mg kg−1. Maize was the plant species with the highest ability to accumulate atrazine derivatives, reaching up to 38.4% of the initial atrazine added to the soil. Rhizosphere degradation/mineralization by microorganisms or plant enzymes, together with degradation inside the plants, have been proposed as the mechanisms that contributed to a higher extent than plant accumulation to explain the removal of atrazine from soils.

Germination of Seeds and Seedling Growth of Amaranthus retroflexus L. Following Sublethal Exposure of Parent Plants to Herbicides

Herbicides have long-term effects on the vegetative parts and reproduction of plants; however, the carry-over effects of herbicides on the F1 generation of invasive plants remain unclear. The objectives of this work were to investigate the germination and growth of the F1 generation of A. retroflexus, an invasion plant, treated by sublethal herbicides. The results demonstrated that atrazine or tribenuron-methyl had carry-over effects on the F1 generation of A. retroflexus. Atrazine or tribenuron-methyl exposure during the vegetative and reproductive periods significantly inhibited the germination and growth of the F1 generation; a lower sublethal dose of atrazine or tribenuron-methyl did not weaken the inhibition of germination or growth of the F1 generation. Our results suggest that although herbicides have a carry-over inhibition effect on the F1 generation of invasive plants, they may have a more serious carry-over effect on native plants and cause changes in weed species composition and weed diversity.

Lichen microalgae are sensitive to environmental concentrations of atrazine

ABSTRACTThe identification of new organisms for environmental toxicology bioassays is currently a priority, since these tools are strongly limited by the ecological relevance of taxa used to study global change. Lichens are sensitive bioindicators of air quality and their microalgae are an untapped source for new low-cost miniaturized bioassays with ecological importance. In order to increase the availability of a wider range of taxa for bioassays, the sensitivity of two symbiotic lichen microalgae, Asterochloris erici and Trebouxia sp. TR9, to atrazine was evaluated. To achieve this goal, axenic cultures of these phycobionts in suspension were exposed to a range of environmental concentrations of the herbicide atrazine, a common water pollutant. Optical density and chlorophyll autofluorescence were used as endpoints of ecotoxicity and ecophysiology on cell suspensions. Results show that lichen microalgae show high sensitivity to very low doses of atrazine, being higher in Asterochloris erici than in Trebouxia sp. TR9. We conclude that environmental concentrations of atrazine could modify population dynamics probably through a shift in reproduction strategies of these organisms. This seminal work is a breakthrough in the use of lichen microalgae in the assessment of micropollution effects on biodiversity.

Effects of co-exposure to atrazine and ethanol on the oxidative damage of kidney and liver in Wistar rats

Both ethanol (EtoH) and atrazine (ATZ) have hepatic and nephro-toxic effects in rats. In the present study, the toxicity of EtoH (5 g kg−1) on the kidney and liver in the absence or in the presence of different doses of ATZ (50, 100, 300 mg kg−1) was evaluated after 21 days in rats. Results showed that the mixture effects on catalase and superoxide dismutase activities were more severe in both tissues compared to EtoH alone, especially as the dose of ATZ was increased. Hepatic malondialdehyde level (an index of lipid peroxidation) was increased from 20.32% in the EtoH +50 mg kg−1 ATZ-treated rats to 34% in the EtoH +300 mg kg−1 ATZ-treated rats compared to the EtoH values. Renal malondialdehyde values remain as high as 81% in the EtoH-treated rats and the different combine exposure groups. Furthermore, as the dose of ATZ in the mixture was increased, serum uric acid level increased compared to the EtoH values. When the EtoH +300 mg kg−1 ATZ-animals were pretreated with curcumin (an antioxidant), the histopathological changes and peroxidative damages in both tissues were blocked. The exposure of EtoH-treated rats to ATZ enhanced renal and hepatic peroxidative damages in rats.

Effect of atrazine on immunocompetence of red-eared slider turtle(Trachemys scripta)

The impact of agrichemicals on aquatic vertebrate species has been a matter of increasing concern to researchers and environmentalist. The present study aimed to evaluate the effect of atrazine (ATZ), a worldwide used herbicide, on some immune parameters of red-eared slider (Trachemys scripta). Twenty-four turtles (2 years old) were randomly distributed in four groups. Three groups were intraperitoneally injected once with one of three different doses of atrazine (0.01, 0.1 or 1.0 ng/g body mass), while one was maintained as control (saline injected). Blood samples were taken 1- and 2-week post-treatment. A positive correlation was found between atrazine (high dose) concentration and immunosuppressive effects as evidenced by lowered serum complement and lysozyme activities, reduced leucocyte number as well as their phagocytic activity and increased heterophil/lymphocyte ratio. These data demonstrate that turtles with elevated atrazine exposure exhibit immunomodulation.

Effect of Age, Duration of Exposure, and Dose of Atrazine on Sexual Maturation and the Luteinizing Hormone Surge in the Female Sprague-Dawley Rat.

Atrazine (ATZ) was administered daily by gavage to pregnant female Sprague Dawley rats at doses of 0, 6.25, 25 or 50 mg/kg/day, either during gestation, lactation and post‐weaning (G/L/PW cohort) to F1 generation female offspring or only from postnatal day (PND 21) until five days after sexual maturation (vaginal opening) when the estrogen‐primed, luteinizing hormone (LH) surge was evaluated (PW cohort). Additional subgroups of F1 females received the vehicle or ATZ from PND 21–133 or from PND 120–133. Slight reductions in fertility and the percentage of F1 generation pups surviving to PND 21 in the gestationally exposed 50 mg/kg dose group were accompanied by decreased food intake and body weight of dams and F1 generation offspring. The onset of puberty was delayed in of the F1 generation G/L/PW females at doses of 25 and 50 mg/kg/day. F1 generation females in the PW high‐dose ATZ group also experienced a delay in the onset of puberty. ATZ had no effect on peak LH or LH AUC in ovariectomized rats 5 days after sexual maturation, irrespective of whether the F1 generation females were treated from gestation onward or only peripubertally. There was no effect of ATZ treatment on the estrous cycle, peak LH or LH AUC of F1 generation females exposed from gestation through to PND 133 or only for two weeks from PND 120–133. These results indicate that developing females exposed to ATZ are not more sensitive compared to animals exposed to ATZ as young adults

Field evaluation of allelopathic plant extracts alongside herbicides on weed management indices and weed–crop regression analysis in maize

Synthetic herbicides are posing problems owing to the development of weed resistance and emerging debate on their associated health hazards and ecological threats. Allelopathic manipulations are evolving as applicable substitutes for weed management in agroecosystems. In order to assess the efficacy of potential allelopathic water extracts from different plant species, field experiments were conducted during 2010 and 2011. Sorghum bicolor L., Helianthus annuus L., Brassica napus L., Oryza sativa L., Zea mays L. and Morus alba L. aqueous extracts in different combinations alone or along with a reduced dose of herbicide were evaluated for weed suppression in a maize crop. A weedy check and two herbicidal treatments, S‐metolachlor + atrazine (pre‐emergence) and atrazine alone (early postemergence), were included for comparison. Sorghum, brassica or sunflower tank‐mixed with 25% of the recommended dose of atrazine significantly suppressed the total weed density and dry biomass, along with a concomitant decrease in the crop resistance indices and treatment efficacy indices over the control. The weed density and dry biomass that were recorded at 60 days after sowing showed a strong negative correlation, while the leaf area index, crop growth rate, dry matter accumulation and net assimilation rate predicted a strong positive correlation, with the stover and grain yield of maize.

Estimation of weed dry biomass and grain yield as a function of growth and yield traits under allelopathic weed management in maize

Growing concerns about toxicity and development of resistance against synthetic herbicides have demanded looking for alternative weed management approaches. Allelopathy has gained sufficient support and potential for sustainable weed management. Aqueous extracts of six plant species (sunflower, rice, mulberry, maize, brassica and sorghum) in different combinations alone or in mixture with 75% reduced dose of herbicides were evaluated for two consecutive years under field conditions. A weedy check and S-metolachlor with atrazine (pre emergence) and atrazine alone (post emergence) at recommended rates was included for comparison. Weed dynamics, maize growth indices and yield estimation were done by following standard procedures. All aqueous plant extract combinations suppressed weed growth and biomass. Moreover, the suppressive effect was more pronounced when aqueous plant extracts were supplemented with reduced doses of herbicides. Brassica-sunflower-sorghum combination suppressed weeds by 74-80, 78-70, 65-68% during both years of study that was similar with S-metolachlor along half dose of atrazine and full dose of atrazine alone. Crop growth rate and dry matter accumulation attained peak values of 32.68 and 1,502 g m-2 d-1 for brassica-sunflower-sorghum combination at 60 and 75 days after sowing. Curve fitting regression for growth and yield traits predicted strong positive correlation to grain yield and negative correlation to weed dry biomass under allelopathic weed management in maize crop.

Atrazine Genotoxicity on Human Placental Cells

Atrazine is one of the most commonly used herbicides. After exposure to Atrazine during pregnancy, it can be found in placental tissue. We investigated the toxic effects of different Atrazine concentrations on human cytotrophoblasts. These cells were isolated from fresh placenta and were exposed to Atrazine for 24 hours. Our results showed that very low doses of Atrazine induced apoptotic placental cell death. It decreased the relative survival of human cytotrophoblastsup to 50% of control. It significantly decreased P53 and TNF- alpha genes expression while Bcl2 gene expression was increased insignificantly. Our findings suggested that exposure of placental cells to Atrazine even in low doses causes harmful effects, leading to adverse pregnancy outcomes such as preeclampsia, intrauterine growth restriction, prematurity and pregnancy loss.

Allelopathic Effects of Some Botanical Extracts, Compared to the Herbicide Atrazine, against Germination of Selected Weeds

This study was conducted to evaluate the herbicidal activity of some plant extracts against three selected weeds (Amaranthus retroflexus, Cichorium intybus and Echinochloa crus-galli.) and also to be compared with the herbicide atrazine (gesaprim®, 80% WP). The plant extracts included: Allium cepa (Onion) lamina, Allium sativum (Garlic) lamina, Cichorium intybus (Chicory) (whole plant), Citrus aurantium (Sour orange) peel, Conyza aegyptiaca (Fleabane) (whole plant), Oryza sativa (Rice) straw, Triticum aestivum (Wheat) straw, and Zea mays (Corn) straw. Three sets of laboratory experiments were conducted. First, the plant species were water extracted and bioassayed using radish as a bioindicator plant. Then these plants were tested against the chosen weeds in six different concentrations (1%, 4%, 7%, 10%, 15%, and 20% w/v). Finally, weeds were subjected to the herbicide atrazine in four concentrations (3.75%, 1.875%, 0.9375%, and 0.46875% w/v). The results showed that the majority of screened plants inhibited germination of radish seeds in a percentage ca 40% or more. The concentration 25% of the recommended dose of atrazine (0.9375% w/v) was the most effective against germination of all target weeds. The herbicide atrazine was found to be more potent than all the tested plant extracts against all target weeds. As for the effect on Amaranthus retroflexus and Cichorium intybus, extracts of Citrus aurantium peel and Cichorium intybus, respectively were considered more promising since atrazine exceeded their potency with only 0.6 times. It was noticed also that the relative potency of atrazine and Oryza sativa extract (against Cichorium intybus) were nearly the same (1.1 time). Most the tested plant extracts were very weak as compared with atrazine against Echinochloa crus-galli.

Effects of Atrazine on Reproductive Health of Nondiabetic and Diabetic Male Rats.

The aim of the present study was to investigate the effects of low dose of atrazine on reproductive system of male Wistar rats. 16 rats were divided into four groups of four animals each. Group I (nondiabetic) and group III (diabetic) animals served as controls that received safflower oil (300 μL/kg bw/day), respectively. Group II (nondiabetic) and group IV (diabetic) animals received atrazine (300 μg/kg bw/day). Nonsignificant decrease in the activities of antioxidant and steroidogenic enzymes and sperm parameters suggests that atrazine did not produce any effect on reproductive system of rats. Histological findings also revealed that atrazine at a dose of 300 μg/kg bw did not produce any testicular toxic effects in nondiabetic and diabetic atrazine treated rats. Low dose of atrazine did not show reproductive toxicity in rats. To know the effects of atrazine in diabetic rats further studies have to be carried out with increased concentration of atrazine.

Transcriptional profiles of glutathione-S-Transferase isoforms, Cyp, and AOE genes in atrazine-exposed zebrafish embryos.

Glutathione-S-transferase (GST) superfamily consists of multiple members involved in xenobiotic metabolism. Expressional pattern of the GST isoforms in adult fish has been used as a biomarker of exposure to environmental chemicals. However, GST transcriptional responses vary across organs, thus requiring a cross-tissue examination of multiple mRNAs for GST profiling in an animal after chemical exposure. Zebrafish embryos express all GST isoforms as adult fish and could therefore represent an alternative model for identification of biomarkers of exposure. To evaluate such a possibility, we studied a set of cytosolic and microsomal GST isoform-specific expression profiles in the zebrafish embryos after exposure to atrazine, a widely used herbicide. Expression of the GST isoforms was compared with that of CYP genes involved in the phase I of xenobiotic metabolism and antioxidant enzyme (AOE) genes. Using quantitative real-time PCR, we showed dynamic changes in the expressional pattern of twenty GST isoforms, cyp1a, cyp3a65, ahr2, and four AOEs in early development of zebrafish. Acute (48 and 72 h) exposure of 24 h-old embryos to atrazine, from environmentally relevant (0.005 mg/L) to high (40 mg/L) concentrations, caused a variety of transient, albeit minor changes (<2.5-fold) in the GST isoforms, ahr2 and AOE genes response. However, expression of cyp1a and cyp3a65 mRNA was markedly and consistently induced by high doses of atrazine (5 and 40 mg/L). In summary, an analysis of the response of multiple systems in the zebrafish embryos provided a comprehensive understanding of atrazine toxicity and its potential impact on biological processes.