Cepa Root Cells Research Articles

Phytotoxicity of Tridax procumbens L.

Phytotoxicity is the term used to describe the toxic effect of chemical compounds on growth and development of plants. Phytotoxic compounds vary in their chemical composition, and may be found in natural environments due to their biosynthesis and active release (allelochemicals). These compounds have the potential to be used as natural pesticides for the control of agricultural plagues. Therefore, this study aimed to evaluate the phytotoxic potential of different extracts and fractions of Tridax procumbens, using pre and post-emergence bioassays of Lactuca sativa L. seeds and mitotic index of Allium cepa L. root cells. Furthermore, the chemical compounds present in the extracts were phytochemically elucidated and the most bioactive fraction determined. Germination and development of tested seedlings were inhibited by the different extracts and ethyl acetate fraction of the ethanolic extract. There were notable alterations in the mitotic index of exposed A. cepa root cells compared to those of the negative control. Phytochemical identification was performed by HPLC-PAD, which showed that a considerable amount of flavonoid compounds were present in the ethanolic extract and its ethyl acetate fraction. According to the results obtained, it can be concluded that T. procumbens possesses phytotoxic compounds that are probably of flavonoid origin. The possession of these bioactive compounds may be related to its invasive nature and weed capacity.

Chromosomal aberrations induced by <i>Markhamia tomentosa</i> (Benth.) K. Schum. Ex Engl. ethanolic leaf extract on <i>Allium cepa</i> root cells

Markhamia tomentosa (Benth.) K. Schum. Ex Engl. (Bignoniaceae) is used traditionally in the treatment of pain, oedema, pulmonary troubles and cancer. The genotoxic and cytotoxic effects of the ethanolic extract of the leaves of M. tomentosa was investigated using the Allium cepa root chromosomal aberration assay. The mitotic index, chromosomal aberrations and mean root length effects of the plant extract on onion bulbs were determined using 50, 100, 200, 400 and 1000 μg/ml concentrations of the plant extract. Tap water was used as the negative control. The result showed a significant (p<0.05) decrease in mitotic index of the onion root tip cells with increased concentration. The plant extract induced stickiness, c-mitosis, bridges and fragments, vagrant, bi-nucleus, multipolar anaphase and laggard chromosomal aberrations in the tested concentrations with no observable chromosome aberrations in the control group. A significant difference (p<0.05) in the mean root length of onions treated with 400 and 1000 μg/ml concentrations and the control group was recorded. Thus, Markhamia tomentosa ethanol extract exerted mito-depressive, genotoxic and cytotoxic effects on Allium cepa root cells.

MWCNT uptake in Allium cepa root cells induces cytotoxic and genotoxic responses and results in DNA hyper-methylation

Advances in nanotechnology have led to the large-scale production of nanoparticles, which, in turn, increases the chances of environmental exposure. While humans (consumers/workers) are primarily at risk of being exposed to the adverse effect of nanoparticles, the effect on plants and other components of the environment cannot be ignored. The present work investigates the cytotoxic, genotoxic, and epigenetic (DNA methylation) effect of MWCNT on the plant system- Allium cepa. MWCNT uptake in root cells significantly altered cellular morphology. Membrane integrity and mitochondrial function were also compromised. The nanotubes induced significant DNA damage, micronucleus formation and chromosome aberration. DNA laddering assay revealed the formation of internucleosomal fragments, which is indicative of apoptotic cell death. This finding was confirmed by an accumulation of cells in the sub-G0 phase of the cell cycle. An increase in CpG methylation was observed using the isoschizomers MspI/HpaII. HPLC analysis of DNA samples revealed a significant increase in the levels of 5-methyl-deoxy-cytidine (5mdC). These results confirm the cyto-genotoxic effect of MWCNT in the plant system and simultaneously highlight the importance of this epigenetic study in nanoparticle toxicity.

Determination of genotoxic effects of Imazethapyr herbicide in Allium cepa root cells by mitotic activity, chromosome aberration, and comet assay

Imazethapyr (IM) is an imidazolinone herbicide that is currently used for broad-spectrum weed control in soybean and other legume crops. In this study, cytotoxic and genotoxic effects of IM were investigated by using mitotic index (MI), mitotic phases, chromosomal abnormalities (CAs) and DNA damage on the root meristem cells of Allium cepa. In Allium root growth inhibition test, EC50 value was determined as 20 ppm, and 0.5xEC50, EC50 and 2xEC50 concentrations of IM herbicide were introduced to onion tuber roots. Distilled water and methyl methane sulfonate (MMS, 10 mg/L) were used as a negative and positive control, respectively. As A. cepa cell cycle is 24 hours, so, application process was carried out for 24, 48, 72 and 96 hours. All the applied doses decreased MIs compared to control group and these declines were found to be statistically meaningful. Analysis of the chromosomes showed that 10 ppm IM except for 48 h induced CAs but 40 ppm IM except for 72 h decreased CAs. DNA damage was found significantly higher in 20 and 40 ppm of IM compared to the control in comet assay. These results indicated that IM herbicide exhibits cytotoxic activity but not genotoxic activity (except 10 ppm) and induced DNA damage in a dose dependent manner in A. cepa root meristematic cells.

Determination of Pb genotoxic effects in Allium cepa root cells by fluorescent probe, microtubular immunofluorescence and comet assay

In order to further understand the toxic effects of Pb on root tip cells of Allium cepa var. agrogarum, root growth, Pb uptake, cell division, DNA damage and MT cytoskeleton were investigated. Fluorescence labeling; Carbol Fuchsin-staining; indirect immunofluorescent microscopy; comet assay. Pb ions entered A. cepa root meristem cells within hours of exposure. The mitotic index (MI) decreased progressively with increasing of Pb concentration. Chromosomal segregation and motility are inhibited, which is directly correlated with the disorganization of the corresponding MT arrays. Pb may interact with tubulin and hinder the polymerization process, resulting in defective mitotic spindles. Pb induced DNA damage in A. cepa root nuclei. Root tips of plants are the most sensitive organ to environmental stresses. Root apical meristems play a key role in the immediate reaction to stress factors by activating signal cascades to the other plant organs. The data presented above can be used as valuable and early markers in cellular changes induced by metals for the evaluation of metal contamination and can be used as early warning signals for general or particular stress.

English

&nbsp; Increased pesticides application in agriculture and public health has contributed to the pollution of the environment. This study evaluates the cytogenotoxic effects of emulsifiable concentrate of cypermethrin, deltamethrin, lambdacyhalothrin and endosulfan on&nbsp;Allium cepa&nbsp;root cells. Five concentrations (1.0, 5.0, 10.0, 20.0 and 40.0 ppm) of each pesticide were used&nbsp;for microscopic (48 h) and macroscopic (72 h) evaluations with distilled water as the control.&nbsp;Data&nbsp;were&nbsp;analyzed&nbsp;by Student&#39;s t-test. A dose dependent reduction in&nbsp;A. cepa&nbsp;root length was observed for the pesticides. Significant reduction in treated root length was observed at 10.0&nbsp;ppm of deltamethrin, cypermethrin and lambdacyhalothrin,&nbsp;and at 20.0 and 40.0 ppm of&nbsp;all the pesticides&nbsp;compared to the control&nbsp;(P&lt;0.05). The&nbsp;EC50&nbsp;values&nbsp;showed growth inhibition in the order of&nbsp;lambdacyhalothrin&nbsp;&gt;&nbsp;cypermethrin&nbsp;&gt;&nbsp;deltamethrin&nbsp;&gt;endosulfan,&nbsp;while that of total aberrant cells was&nbsp;cypermethrin &gt; lambdacyhalothrin &gt; deltamethrin &gt; endosulfan.&nbsp;Microscopic aberrations observed in the pesticide-treated onions include&nbsp;sticky chromosomes, disturbed spindle&nbsp;and&nbsp;chromosome bridges.Dose dependent reduction was observed in the total mitotic dividing cells and mitotic index of the pesticide-treated&nbsp;A. cepa,&nbsp;except for 5.0 ppm of endosulfan. The pesticides induced growth inhibition and caused cytogenotoxic effects on the meristematic cells of&nbsp;Allium cepa.&nbsp;The data herein provide more information on the pesticides of which exposure to substantial concentration might constitute health risk to non-target organisms. &nbsp; Key words:&nbsp;Pesticides, mitotic aberration, pyrethroid, organochlorine, growth.

Toxicological evaluation of landfill leachate using plant (Allium cepa) and fish (Leporinus obtusidens) bioassays

The disposal of municipal waste in landfills may pose an environmental problem because the product of the decomposition of these residues generates large volumes of leachate, which may present high toxicity. The aim of this study was to assess the toxic and genotoxic effects of a sample of untreated leachate in fish (Leporinus obtusidens) and onions (Allium cepa). The leachate was collected in a landfill located in the region of Vale do Rio dos Sinos, southern Brazil. The fish were exposed to raw leachate, at concentrations of 0.5%, 1.0%, 5%, 10% and 20% for 6 days, while the bulbs of A. cepa were exposed to concentrations of 5%, 10%, 25%, 50% and 100% for 48 h. For fish, the concentrations of 5%, 10% and 20% were lethal, thus indicating high toxicity; however, sublethal concentrations (0.5% and 1.0%) showed no genotoxicity by micronucleus test when compared with the control group. In the bioassays involving onions, high toxicity was observed, with significant reduction of root growth and mitotic index in bulbs exposed to the 100% concentration of the leachate. An increase in the frequency of chromosome abnormalities in the A. cepa root cells in anaphase-telophase was observed in accordance with the increase in the concentration of leachate (5%, 10%, 25% and 50%), with values significantly greater than the control, at the highest concentration. The results showed that the leachate contains toxic and genotoxic substances, thus representing a major source of environmental pollution if not handled properly.

DNA integrity of onion root cells under catechol influence

Catechol is a highly toxic organic pollutant, usually abundant in the waste effluents of industrial processes and agricultural activities. The environmental sources of catechol include pesticides, wood preservatives, tanning lotion, cosmetic creams, dyes, and synthetic intermediates. Genotoxicity of catechol at a concentration range 5 × 10(-1)-5 mM was evaluated by applying random amplified polymorphic DNA (RAPD) and time-lapse DNA laddering tests using onion (Allium cepa) root cells as the assay system. RAPD analysis revealed polymorphisms in the nucleotidic sequence of DNA that reflected the genotoxic potential of catechol to provoke point mutations, or deletions, or chromosomal rearrangements. Time-lapse DNA laddering test provided evidence that catechol provoked DNA necrosis and apoptosis. Acridine orange/ethidium bromide staining could distinguish apoptotic from necrotic cells in root cells of A. cepa.

Biodecolorization of Azo Dye Remazol Orange by Pseudomonas aeruginosa BCH and Toxicity (Oxidative Stress) Reduction in Allium cepa Root Cells

In this report a textile azo dye Remazol orange was degraded and detoxified by bacterium Pseudomonas aeruginosa BCH in plain distilled water. This bacterial decolorization performance was found to be pH and temperature dependent with maximum decolorization observed at pH8 and temperature 30°C. Bacterium tolerated higher dye concentrations up to 400mg l(-1). Effect of initial cell mass showed that higher cell mass concentration can accelerate decolorization process with maximum of 92% decolorization observed at 2.5g l(-1) cell mass within 6.5h. Effect of various metal ions showed Mn has inducing effect whereas Zn strongly inhibited the decolorization process at 5mM concentration. Analysis of biodegradation products carried out with UV-vis spectroscopy, HPTLC and FTIR confirmed the decolorization and degradation of Remazol orange. Possible route for the degradation of dye was proposed based on GC-MS analysis. During toxicological scrutiny in Allium cepa root cells, induction in the activities of superoxide dismutase (SOD), guaiacol peroxidase (GPX) and inhibition of catalase (CAT) along with raised levels of lipid peroxidation and protein oxidation in dye treated samples were detected which conclusively indicated the generation of oxidative stress. Less toxic nature of the dye degraded products was observed after bacterial treatment.

Biodegradability, toxicity and mutagenicity of detergents: Integrated experimental evaluations

The widespread use of detergents has raised concern with regard to the environmental pollution caused by their active ingredients, which are biorefractory, toxic and persistent. Since detergents are complex mixtures of different substances, in which synergistic effects may occur, we aimed to assess the mutagenicity of different detergent formulations, taking into account aquatic toxicity and ready biodegradability. We performed a ready biodegradability test (OECD 301 F), Daphnia magna and Vibrio fischeri toxicity tests, and mutagenicity tests (Salmonella/microsome test, Allium cepa test and comet assay). Six detergent formulations were examined, 3 pre-manufacture and 3 commercially available. All detergents presented ready biodegradability. EC50 values varied for all products, according to the marker organism used, but were always higher than the more stringent value considered for aquatic toxicity assessment (V. fischeri 10–60mg/L; D. magna 25–300mg/L; A. cepa 250–2000mg/L). None of the detergents caused mutations in bacteria. However, one commercial ecolabelled product induced an increase in micronucleus frequency in A. cepa root cells. All pre-manufacture detergents and one commercial one, which gave negative results in the Ames and A. cepa tests, induced DNA damage in human leukocytes. A more accurate evaluation of the environmental impact of complex mixtures such as detergents requires a battery of tests to describe degradation, as well as toxicological and mutagenic features.

Biodegradation of Rubine GFL by Galactomyces geotrichum MTCC 1360 and subsequent toxicological analysis by using cytotoxicity, genotoxicity and oxidative stress studies

Galactomyces geotrichum MTCC 1360 showed 87 % decolorization of the azo dye Rubine GFL (50 mg l(-1)) within 96 h at 30 °C and pH 7.0 under static conditions, with significant reduction of chemical oxygen demand (67 %) and total organic carbon (59 %). Examination of oxidoreductive enzymes, namely laccase, tyrosinase and azo reductase, confirmed their role in decolorization and degradation of Rubine GFL. Biodegradation of Rubine GFL into different metabolites was confirmed using high-performance TLC, HPLC, Fourier transform IR spectroscopy and GC-MS analysis. During toxicological studies, cell death was observed in Rubine GFL-treated Allium cepa root cells. Toxicological studies before and after microbial treatment were done with respect to cytotoxicity, genotoxicity, oxidative stress, antioxidant enzyme status, protein oxidation and lipid peroxidation using root cells of A. cepa. The analysis with A. cepa showed that the dye exerts oxidative stress and subsequently has a toxic effect on the root cells, whereas its metabolites are less toxic. Phytotoxicity studies revealed the less toxic nature of the metabolites as compared with Rubine GFL.

Determination of genotoxic effects of chlorfenvinphos and fenbuconazole in Allium cepa root cells by mitotic activity, chromosome aberration, DNA content, and comet assay

Genotoxic effects of Chlorfenvinphos and fenbuconazole were examined by using mitotic index, mitotic phase, chromosomal abnormalities, 2C DNA content and Comet assay on the root meristem cells of Allium cepa. The roots were treated with 10, 20, 40, 60, 80, and 100ppm concentrations for 24 and 48h. The results indicated that Chlorfenvinphos and fenbuconazole significantly decreased the mitotic index in all treatments when compared with their controls. The percentages of mitotic phases have changed. Chlorfenvinphos and fenbuconazole significantly increased the abnormal cell frequency at all concentrations and treatment periods when compared with their controls. Different abnormal mitotic figures were observed in all mitotic phases. Among these abnormalities were stickiness, anaphase bridges, c-mitosis, laggards, and micronucleus. These pesticides remarkably depressed the 2C DNA content in the root meristems of A. cepa. The genotoxicity of chlorfenvinphos and fenbuconazole in A. cepa root cells was analyzed using comet assay, which allows the detection of single strand breaks. In all concentrations, chlorfenvinphos and fenbuconazole induced a significant increase in DNA damage. Additionally, it was also researched to determine if there is a relation between the amount of DNA and the DNA damage and a regression analyses was conducted. When the data that was accumulated via comet analysis from A. cepa root tip cells that are treated with type chlorfenvinphos and fenbuconazole, was compared to the data that was acquired as the result of the measurement of 2C DNA amount, a relation with negative correlation was found, (respectively, r=−0.80 and r=−0.82). This relation factor is statistically important and strong (p<0.05).

Biochemical degradation pathway of textile dye Remazol red and subsequent toxicological evaluation by cytotoxicity, genotoxicity and oxidative stress studies

Remazol red (RR), a monochloro sulphonated azo dye was degraded up to 97% within 20 min at 40 °C and pH 7 at dye concentration 50 mg l −1 by Pseudomonas aeruginosa BCH. Examination of enzyme status exposed the involvement of various oxidoreductive enzymes viz. laccase, veratryl alcohol oxidase and NADH-DCIP reductase. Analytical studies viz. HPTLC, HPLC, FTIR and GC-MS carried out with dye and dye metabolites formed after dye decolorization confirmed that the decolorization was due to degradation. Based on enzymatic status and GC-MS analysis the possible metabolic pathway followed by bacterial strain for the degradation of RR was proposed. During toxicological scrutiny, cell death was observed in RR treated Allium cepa ( A. cepa) root cells. The observed inhibition of catalase (CAT) activity and induction in enzyme activities of sulfur oxide dismutase (SOD) and ascorbate peroxidase (APX) along with raised protein oxidation and lipid peroxidation signified that RR generated the oxidative stress in A. cepa roots. These toxicological studies along with genotoxicity studies using A. cepa roots and phytotoxicity studies using Phaseolus mungo ( P. mungo) and Sorghum vulgare ( S. vulgare) conclusively designated the toxicity of RR and comparatively less toxic nature of metabolites formed after dye degradation by P. aeruginosa BCH.

Development of a Non-Scanning Vibrational Sum-Frequency Generation Detected Infrared Super-Resolution Microscope and its Application to Biological Cells

We report single-cell infrared (IR) imaging of onion (Allium cepa) root cells using an IR super-resolution microscope based on vibrational sum-frequency generation (VSFG). The resolution of recorded IR images was less than 2 microm and IR super-resolution was achieved by virtue of the VSFG detection. In addition, IR spectra measurements were successfully performed on distinct intra-cellular assemblies. The IR absorption intensity of the cell nuclear edge and the nucleolus in the 3055-3130 cm(-1) region was stronger than that from the cytoplasmic part. This is because the cell nucleus and nucleolus contain larger amounts of nucleic acid. Thus, the obtained IR spectra reflect differences in chemical composition among different cellular structures. In addition, the ability of our novel IR super-resolution microscope to obtain distinct information on both VSFG and two-photon fluorescence is demonstrated.

Cytotoxicity testing of aqueous extract of bitter leaf (Vernonia amygdalina Del.) using the Allium cepa chromosome aberration assay.

Mitotic studies were carried out on Allium cepa (onion) root cells treated with different concentrations of aqueous leaf extract of Vernonia amygdalina (bitter leaf). The onion root cells showed reduced mitotic indices with corresponding increase in concentration of the bitter leaf extract [200 g/L (C2), 400 g/L (C3) and 500 g/L (C4)]. Chromosomal aberrations, such as endopolyploidization, lagging of chromo-somes and cells with giant chromosomes, were also observed in onion roots treated with same. No chromosomal aberration was observed in the control and in onion roots treated with 100 g/L (C1) of the leaf extract. These observations indicate that abnormal use of this medicinal herb could cause genetic damage. Low concentration and wide spacing of dosage are, therefore, suggested for its dietary intake or use in herbal medicine. Key words: Vernonia amygdalina, Allium cepa, chromosome aberration, cytotoxicity, herbal medicine.

Determination of genotoxic effects of copper sulphate and cobalt chloride in Allium cepa root cells by chromosome aberration and comet assays

We used the anaphase–telophase chromosome aberration and comet (Single Cell Gel Electrophoresis, SCGE) assays to evaluate the genotoxic effects of copper sulphate (CS) and cobalt chloride (CC) chemicals prepared in two concentrations (EC 50, 2xEC 50), using methyl methanesulfonate (MMS) as a positive control and untreated cells as a negative control. In Allium root growth inhibition test, EC 50 values for CS and CC are 1.5 and 5.5 ppm, respectively. Mitotic index (MI) decreased in all concentrations tested of CS and CC compared to the control at each exposure time. The bridge, stickiness, vagrant chromosomes, fragments, c-anaphase and multipolarity chromosome aberrations were observed in anaphase–telophase cells. The total chromosome aberrations were more frequent with an increasing in the exposure time and the concentrations of both chemicals. The genotoxicity of CS and CC in Allium cepa root cells was analyzed using a mild alkaline comet assay at pH 12.3, which allows the detection of single strand breaks. In all the concentrations, CS and CC induced a significant increase ( P < 0.05) in DNA damage. No significant difference was found between positive control (300 ± 5.81) and 3 ppm CS (280 ± 4.61). The methods used are applicable for biological monitoring of environmental pollutants.

Toxicity and genotoxicity of wastewater from gasoline stations

The toxicity and genotoxicity of wastewater from eight gasoline stations in Brasília, Brazil's capital city, was studied by assessing chromosomal aberrations, chromosomal malsegregation and the mitotic index in Alliumcepa root cells, and the occurrence of micronucleus and nuclear abnormalities in peripheral erythrocytes of tilapia fish (Oreochromis niloticus). The content of gasoline station effluents was also analyzed based on several physico-chemical parameters. None of the wastewater samples was genotoxic to A. cepa root cells, although cell proliferation was significantly inhibited, especially at the highest concentrations. Likewise, no micronuclei were observed in O. niloticus peripheral erythrocytes, even after exposure to high concentrations, but there was an increase in the number of nuclear abnormalities and fish mortality. These results show that although the effluent from gasoline stations is processed by an oil/water separation system before being discharged into the main sewage system, the wastewater still contains toxic compounds.

Cytotoxic and Genotoxic Effects of cis-Tetraammine(oxalato)Ruthenium(III) Dithionate on the Root Meristem Cells of Allium cepa

Ruthenium complexes have attracted much attention as possible building blocks for new transition-metal-based antitumor agents. The present study examines the mitotoxic and clastogenic effects induced in the root tips of Allium cepa by cis-tetraammine(oxalato)ruthenium(III) dithionate {cis-[Ru(C(2)O(2))(NH(3))(4)](2)(S(2)O(6))} at different exposure durations and concentrations. Correlation tests were performed to determine the effects of the time of exposure and concentration of ruthenium complex on mitotic index (MI) and mitotic aberration index. A comparison of MI results of cis-[Ru(C(2)O(2))(NH(3))(4)](2)(S(2)O(6)) to those of lead nitrate reveals that the ruthenium complex demonstrates an average mitotic inhibition eightfold higher than lead, with the frequency of cellular abnormalities almost fourfold lower and mitotic aberration threefold lower. A. cepa root cells exposed to a range of ruthenium complex concentrations did not display significant clastogenic effects. Cis-tetraammine(oxalato)ruthenium(III) dithionate therefore exhibits a remarkable capacity to inhibit mitosis, perhaps by inhibiting DNA synthesis or blocking the cell cycle in the G2 phase. Further investigation of the mechanisms of action of this ruthenium complex will be important to define its clinical potential and to contribute to a novel and rational approach to developing a new metal-based drug with antitumor properties complementary to those exhibited by the drugs already in clinical use.

Evaluation of genotoxicity of coal fly ash in Allium cepa root cells by combining comet assay with the Allium test

Fly ash is a by-product of coal-fired electricity generation plants. Its utilization and disposal is of utmost importance. Using onion (Allium cepa) root tip system, the present study was carried out to evaluate the potential toxic and genotoxic effects of fly ash, collected from a thermal power plant in West Bengal, India. Prior to testing, the collected fly ash sample was mixed with sand in different proportions. Allium bulbs were allowed to germinate directly in fly ash and after five days the germinating roots were processed for the Allium test. Additionally, the Allium test was adapted for detecting DNA damage through comet assay. The results from the Allium test indicate that fly ash at 100% concentration inhibits root growth and mitotic indices; induces binucleated cells as a function of the proportion, but is not toxic at very low concentration. In the comet assay, a statistical increase for DNA strand breaks was found only at higher concentrations. The sample was analyzed by flame atomic absorption spectrometer for Zn, Pb, Cu, Ni, Cd and As, whose presence could partly be responsible for the toxicity of fly ash. The study concludes that the classical Allium test can give a more comprehensive data when done in combination with the comet assay, which is faster, simpler and independent of mitosis. Also when fly ash is used for other purposes in combination with soils, it should be judiciously used at very low concentrations in order to protect the ecosystem health from any potential adverse effects.

Action mechanisms of petroleum hydrocarbons present in waters impacted by an oil spill on the genetic material of Allium cepa root cells

Chromosomal aberration (CA) assays have been widely used, not only to assess the genotoxic effects of chemical agents, but also to evaluate their action mechanisms on the genetic material of exposed organisms. This is of particular interest, since such analyses provide a better knowledge related to the action of these agents on DNA. Among test organisms, Allium cepa is an outstanding species due to its sensitivity and suitable chromosomal features, which are essential for studies on chromosomal damage or disturbances in cell cycle. The goal of the present study was to analyze the action mechanisms of chemical agents present in petroleum polluted waters. Therefore, CA assay was carried out in A. cepa meristematic cells exposed to the Guaecá river waters, located in the city of São Sebastião, SP, Brazil, which had its waters impacted by an oil pipeline leak. Analyses of the aberration types showed clastogenic and aneugenic effects for the roots exposed to the polluted waters from Guaecá river, besides the induction of cell death. Probably all the observed effects were induced by the petroleum hydrocarbons derived from the oil leakage.