Presence Of Atrazine Research Articles

Effects of atrazine and paraquat on nitrifying bacteria

The influence of atrazine and paraquat on a mixed culture of nitrifying bacteria was studied in an aqueous system. At a concentration as low as 1 μg/mL paraquat exerted a complete inhibition of ammonium and nitrite oxidation for 40 days. Atrazine (1 μg/mL and 2 μg/mL), however, caused only an inhibition of ammonium oxidation for a short period. After 16–18 days of inhibition the ammonium oxidizing activity was resumed. In the presence of atrazine (1 μg/mL), however, the rate of nitrite oxidation was increased. Within a period of 28 days, in culture media a partial degradation of atrazine occurred.

Effect of some photosynthesis‐inhibiting herbicides on growth and nitrogenase activity of a new isolate of cyanobacteria, Nostoc G3

AbstractThe effect of the photosynthesis‐inhibiting herbicides Goltix, Sencor, Tycor, Arelon, DCMU, paraquat and atrazine on growth and nitrogenase activity of a new isolate of cyanobacteria, Nostoc G3 was studied. Nostoc G 3 was cultivated under N2‐fixing photoautotrophic conditions. The used herbicide concentrations were in the range or recommended field rates. In the presence of Goltix (50 mg/l and 100mg/l), Arelon (15 mg/l und 30 mg/l), paraquat (10 mg/l and 20 mg/l) and DCMU (1 μM) the growth and nitrogenase activity of Nostoc G3 was almost completely inhibited. The most severe inhibitory effect was observed in the presence of paraquat. Even 1 h treatment of 1 mg/l paraquat caused a total inhibition of growth for 4 weeks. In contrast, the herbicides Sencor (10 mg/l and 20 mg/l) and Tycor (10 mg/l and 50 mg/l) did not cause inhibition of growth and nitrogenase activity. In the presence of atrazine (1 mg/l and 2 mg/l) the nitrogenase activity and the growth were partially inhibited. The results obtained in this study show that cyanobacteria occurring in natural environments are resistant against some of the photosynthesis‐inhibiting herbicides.

Fluorescence polarization of trypsin digested photosystem II membranes

Fluorescence polarization of photosystem II particles treated with trypsin and incubated with high salt-medium (2M NaCl) was investigated. The presence of atrazine and TMPD in normal and salt-washed particles induced a decrease in the polarization ratios. Similar results were obtained at low concentrations of trypsin. On the basis of our observations we suggest that the presence of these perturbing agents causes a reorganisation of the membrane components and alters pigment-pigment and pigment-protein interactions. The results of fluorescence polarization demonstrate trypsin entry into the membrane after the digestion of the peripheral proteins.

Effects of herbicides on binary oscillations of ultraviolet flash-induced absorption changes in chloroplasts

The competition between various herbicides and plastoquinone, at the Q B site of Photosystem II, has been studied by measuring absorption changes between 300 and 360 nm in spinach and chenopod chloroplasts, in response to a train of saturating short xenon flashes. A complex pattern was observable without addition of chemicals interfering with electron flow. The effect of potassium ferricyanide, of hydroxylamine and of valinomycine-K + permitted to simplify the pattern and, in particular, to observe binary oscillations with flash number, attributable to the functioning of the two-electron gate Q B. Herbicides belonging to different classes block electron transfer when added at high concentration. At low concentration, however, inverted binary oscillations become observable. When the chloroplasts have been first oxidized with ferricyanide, this behaviour develops progressively in response to illumination. Varying the herbicide concentration, it appears that the concentration inducing maximum binary oscillations correlates with inhibition of linear electron transfer, within each class of herbicides. Phenolic herbicides induce the largest oscillations and ureas the smallest. The binary oscillations have the spectrum of the plastoquinone anion. The results clearly show that the studied herbicides compete efficiently with Q B, but not with Q − B, at the Q B binding site. Atrazine-resistant chenopod chloroplasts still display normal binary oscillations in the absence of herbicide, or in the presence of atrazine alone. They are highly sensitive to DCMU and to i-dinoseb, but no inverted binary oscillations could be observed with these herbicides.

Influence of Atrazine on Denitrification in Soil Columns

AbstractThe effects of the herbicide atrazine (2‐chloro‐4(ethylamino)‐6‐(iso‐propylamino)‐s‐triazine) on denitrification was evaluated during steady transport of 15N‐nitrate through 0.15 m long columns of San Cataldo silt loam (Fluvisol, according to the FAO world map legend) and Yolo loam soil (Typic Xerorthents). The soil atmosphere was maintained at a small O2 partial pressure by flowing a gas mixture of 70% He and 30% N2 through plastic jackets surrounding the plastic soil columns, which had many holes (1 mm diam) drilled through the column sides. This column design allowed evolved N2 and N2O gases to be measured in the effluent gas of each column. The nitrate (NO3−) concentration in the solution effluent and the evolved gases from columns with added atrazine (3 mg kg−1) were compared with that from columns without atrazine. Nitrate reduction rates were determined from a mathematical solution of transport and transformation of nitrate according to first‐order kinetics. The presence of atrazine in the soils resulted in slightly increased nitrate reduction rates over that of the controls. Atrazine caused a decrease in the N2/N2O ratio of the evolved gases. A small amount of NO was also detectable in San Cataldo column without atrazine. The apparent inhibition of N2O reduction by atrazine may have environmental implications in relation to N2O release from the soil to the atmosphere.

Effets physiologiques de ľ atrazine à doses sublétales sur Lemna minor, VII. Incorporation ?acétate‐l,2‐[14C] dans les groupes de lipides et leurs acides gras

Physiological effects of sublethal doses of atrazine on Lemna minor. VII. 1,2‐[14C] acetate incorporation into the groups of lipids and their fatty acids.The lipids and the fatty acids of ten‐day old duckweed (Lemna minor L.), cultivated aseptically in mineral solution containing sublethal concentrations of 0,10 and 0,50 ppm (0.46 and 2.3 μM, respectively) of atrazine, were analyzed by thin‐layer chromatography and gas‐liquid radiochromatography after 1,2‐[14C] acetate feeding. Sublethal concentrations of atrazine increased the incorporation of radioactivity in total lipids, diacylgalactosylglycerol (DGG), diacyldigalactosylglycerol (DDG), sul‐folipids (SL), phosphatidylglycerol (PG), diacylglycerol (DAG) and triacylglycerol + steroll esters (TAG+SE). The incorporation of acetate‐1,2‐[14C] decreased in phos‐phatidylcholine (PC) and in phosphatidylethanolamine (PE) in the presence of atrazine. The radioactivity increased in total Transic‐hexadecenoic, linoleic and α ‐linolenic acids while it decreased in the other fatty acids. This indicates that the sublethal concentrations of atrazine stimulate the desaturation of fatty acids of L. minor. The radioactivity was strongly incorporated in the α ‐linolenic acid of DGG in the presence of atrazine. The specific radioactivity of α‐linolenic acid was greater in DAG than in PG > TAG + SE > PC > PE > DGG > SL > DDG and it increased in all groupd of lipids analyzed under the influence of sublethal doses of atrazine. The labelling of Translchexadecenoic acid of PG and its specific radioactivity increased in the presence of atrazine. These changes suggest that the sublethal concentrations of atrazine stimulate especially the lipid metabolism of the chloroplasts of L. minor and they could explain the increase in the number of grana per chloroplast in treated L. minor. The results are discussed in relation to the biosynthesis of galactolipids.

Response of light- and dark-grown callus of atrazine-resistant and susceptible rapeseed (Brassica napus) to varying concentrations of atrizine

Callus cultures initiated with tissue of triazine-resistant and susceptible lines of Brassica napus L. were cultured in the presence of atrazine (10-5 to 10-4 M) under a 16-h photoperiod or in continuous darkness. On atrazine-free media callus growth was characteristically greater for the light-grown cultures. On media containing atrazine, growth of callus from triazine-resistant and susceptible rapeseed cultured in the dark did not differ significantly. Addition of atrazine to the culture medium resulted in a significant reduction in the growth of light-grown callus of the susceptible genotype to a level equivalent to that of the dark-grown cultures. Atrazine had no effect on the growth of light-grown callus initiated with triazine-resistant rapeseed.

Geographical variation in populations of Chenopodium album resistant and susceptible to atrazine. I. Between- and within-population variation in growth and response to atrazine

Between- and within-population variation in growth characteristics, isoenzyme patterns, and response to atrazine were studied in individuals from four atrazine-resistant (R) and four susceptible (S) populations of Chenopodium album L. collected from sites of contrasting climate in southern Ontario. In both the R and S types, population differences in growth characteristics were correlated with geographical location and climatic differences. The more northerly R and S populations had a greater rate of development, earlier maturation, lower biomass at maturity, and greater reproductive effort compared, respectively, with the more southerly R and S populations.Estimates of within-population variation were obtained statistically for a number of growth characters and from the electrophoretic patterns of five enzyme systems (PGM, PGI, GOT, MPI, and LAP). These indicated marked homogeneity in the four R populations as compared with the more variable S populations. Populations from the two disjunct areas of resistance were different for two of the enzymes studied and would appear to represent two different genotypes. This would suggest that mutation for resistance in populations of C. album has occurred independently in the two areas. Coupled with the evidence for differential growth characteristics of these two genotypes in response to climate, we would suggest that resistance has developed in individuals already established in each of the two separate areas, rather than spreading from a single recent introduction of the R type in Ontario.As expected, distinct differences between the R and S types were obtained in response to postemergence treatments with atrazine. The four R populations either showed no effect or exhibited increased growth. S populations all showed marked decreases in growth and production of biomass. Significant between-population differences in growth features were apparent for both types in the control and were maintained in the presence of atrazine. Although small differences in relative susceptibility were obtained for the susceptible populations, statistically significant population by treatment interactions were not evident.

Effect of Atrazine on Soil Transformations of Nitrogen and Uptake by Corn

AbstractThe influence of different rates of atrazine (2‐chloro‐4‐[ethylamino]‐6‐[isopropylamino]‐s‐triazine) (0,2, and 6 kg ha−1) on nitrogen balance and soil urease following 15N‐urea fertilization (200 kg ha−1) was investigated in corn (Zea mays L.) plots by emission spectrometry. Urease activity was affected by both urea and atrazine applications. Concentrations of NH4+‐N and NO3−‐N in soil were greater at the highest herbicide rate. Organic N buildup was slower in plots that received atrazine at the highest rate, but at the end of the cropping season the total amount of organic N was similar for all treatments.Nitrogen losses, as determined by an N balance sheet, were 51, 32, and 22% of added N in the plots treated with 0, 2, and 6 kg ha−1 of atrazine, respectively.The main role of organic N in the N cycle of the soil‐plant environment in the presence of atrazine is suggested.

Effects of atrazine on the toxicity, penetration and metabolism of carbofuran in the house fly.

Experiments were conducted to obtain additional information relative to the effects of the herbicide atrazine on the toxicity, penetration, and metabolism of 14C-carbofuran in Musca domestica L. Topically applied carbofuran yielded, after 24h, an LD-50 at 0.16 μg/fly but dropped to 0.08 μg/fly when a nontoxic dose of 15 μg of atrazine also had been applied. In the presence of atrazine, twice as much 14C-carbofuran was left on the outside of the flies as compared to controls. Conversely, amounts of the less toxic metabolite 3-hydroxy-carbofuran in the chloroform extraction phase of fly excreta were only 30% of those excreted by control flies. Amounts of the major metabolite 3-hydroxycarbofuran in the water extraction phase of fly excreta were 2.57% of the applied radiocarbon after 14C-carbofuran plus atrazine treatment and 4.14% in excreta from control flies, thus indicating a reduction in the formation of this carbofuran metabolite due to atrazine. The respective figures were 0.38 and 0.97% for 3-hydroxycarbofuran phenol and 0.12 and 0.31% for carbofuran phenol. Data indicated that the herbicide atrazine inhibited the penetration of 14C-carbofuran into houseflies or stabilized it on the cuticle, thus making its biological activity available over longer time periods. In addition, it inhibited the metabolic detoxication of the insecticide into less insecticidal compounds, whose toxicity in turn also could be enhanced by atrazine. The increased stability of 14C-carbofuran, both outside and inside the insect body, resulted in an increased toxicity of the insecticide, thus explaining to some extent the synergism of carbofuran with atrazine in house flies.

Atrazine Inhibition of Carbofuran Metabolism in the House Cricket1

The metabolism of ring-labeled [14C] carbofuran was studied in Acheta domesticus (L.) which has been pre-exposed to 10, 20, and 30 ppm of atrazine for a month. Most of the carbofuran could be extracted from the cricket body. Excretion of carbofuran is not an important defense mechanism in the cricket. Degradation of carbofuran was inhibited in the presence of atrazine, especially when the concentration of atrazine was 30 ppm. The inhibition occurred at the level of the hydroxylation of cabofuran at its carbon-3 position. The results support the hypothesis that compounds capable of blocking the microsomal electron flow can potentate the toxicity of certain insecticides, possibly by inhibition of the microsomal detoxification process.

Mutagenicity of atrazine: A maize-microbe bioassay

A water-soluble extract from maize plants grown in the presence of atrazine contained a mutagenic agent(s) when tested on strains of yeast. Atrazine alone or control plants not treated with atrazine did not express mutagenic properties. The reversion frequency at the waxy locus in pollen grains from plants grown in atrazine was higher than in control plants. We suggest that atrazine may be degraded by the plant into environmental mutagenic agents.

Effect of Atrazine on Chromatin Activity in Corn and Soybean

Applications of 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine) at 10−4, 10−5, and 10−6M to 4-day-old etiolated soybean [Glycine max(L.) Merr. ‘Mark’] seedlings 6 hr before the isolation of chromatin enhanced the chromatin directed ribonucleic acid (RNA) synthesis by 16, 65, and 40%, respectively. The magnitude of this inductive effect increased with an increasing interval of time from 6 to 24 hr between application and chromatin isolation. The basis for the effect appeared to be an atrazine-mediated increase in chromatin template availability. The presence of atrazine during extraction and the assay was sufficient to evoke the response. This effect on chromatin activity was not observed for 2-hydroxy-4-(ethylamino)-6-isopropylamino)-s-triazine (hydroxyatrazine) or for atrazine on corn(Zea maysL. ‘Michigan 400′).