chlorophyll-a and isoproturon

Phenylurea herbicides are often present in the aquatic ecosystems and may be accumulated by the non-targeted organisms and impose a negative effect on the organism and the community. This study aims to investigate and compare the effects of two different isoproturon (IPU) pulse exposure scenarios on the non-targeted aquatic plant Lemna minor with effects observed in the standard test with continuous exposure. The obtained results showed that continuous IPU treatment causes significant reduction of photosynthetic pigment concentration and proteins as well as inhibition of L. minor growth. The activities of CAT, G-POX, and APX were significantly induced to diminish the accumulation of ROS under IPU treatment, but the induction of antioxidant enzymes was not sufficient to protect the plants from herbicide-induced oxidative stress. The growth of L. minor under pulse exposure to IPU recovers fast, but pulse treatment results in significant physiological changes in treated plants. The accumulation of H

Topics: Antioxidants; Araceae; Carotenoids; Chlorophyll; Hydrogen Peroxide; Oxidative Stress; Phenylurea Compounds; Photosynthesis; Plant Proteins; Thiobarbituric Acid Reactive Substances; Time Factors; Toxicity Tests; Water Pollutants, Chemical

Jasmonic acid (JA) [or methyl-jasmonic acid (MeJA)] is one of the important regulators of plant growth, development, and defense with respect to environmental stresses, but how JA is involved in mediation of pesticide accumulation and degradation in plants is largely unknown. This study investigated the contribution of MeJA to detoxification and degradation of isoproturon (IPU) residues in wheat ( Triticum aestivum). Wheat plants were exposed to 4 mg of isoproturon kg

Topics: Biomarkers; Chlorophyll; Chromatography, High Pressure Liquid; Crops, Agricultural; Cyclopentanes; Enzymes; Herbicides; Inactivation, Metabolic; Oxylipins; Phenylurea Compounds; Plant Growth Regulators; Soil Pollutants; Triticum

The effects of short-term treatment with phenylurea (DCMU, isoproturon) and phenol-type (ioxynil) herbicides on the green alga Chlorella kessleri and the cyanobacterium Synechocystis salina with different organizations of photosystem II (PSII) were investigated using pulse amplitude modulated (PAM) chlorophyll fluorescence and photosynthetic oxygen evolution measured by polarographic oxygen electrodes (Clark-type and Joliot-type). The photosynthetic oxygen evolution showed stronger inhibition than the PSII photochemistry. The effects of the studied herbicides on both algal and cyanobacterial cells decreased in the following order: DCMU>isoproturon>ioxynil. Furthermore, we observed that the number of blocked PSII centers increased significantly after DCMU treatment (204-250 times) and slightly after ioxynil treatment (19-35 times) in comparison with the control cells. This study suggests that the herbicides affect not only the acceptor side but also the donor side of PSII by modifications of the Mn cluster of the oxygen-evolving complex. We propose that one of the reasons for the different PSII inhibitions caused by herbicides is their influence, in different extents, on the kinetic parameters of the oxygen-evolving reactions (the initial S0-S1 state distribution, the number of blocked centers SB, the turnover time of Si states, misses and double hits). The relationship between the herbicide-induced inhibition and the changes in the kinetic parameters is discussed.

Topics: Chlorella; Chlorophyll; Diuron; Dose-Response Relationship, Drug; Electron Transport; Herbicides; Iodobenzenes; Nitriles; Oxygen; Phenylurea Compounds; Photosynthesis; Photosystem II Protein Complex; Synechocystis

Treatment with the recommended field dose of isoproturon to 7-d-old wheat seedlings significantly decreased shoot height, fresh and dry weights during the subsequent 15days. Meanwhile contents of carotenoids, chlorophylls and anthocyanin as well as activities of δ-aminolevulinate dehydratase (ALA-D), phenylalanine ammonia lyase (PAL) and tyrosine ammonia lyase (TAL) were significantly inhibited. On the other hand, the herbicide significantly increased malondialdehyde (MDA), a naturally occurring product of lipid peroxidation and H2O2, while it significantly decreased the contents of glutathione (GSH) and ascorbic acid (AsA) and reduced the activities of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX). These findings indicate an induction of a stress status in wheat seedlings following isoproturon treatment. However, exogenous GSH appeared to limit the toxic effects of isoproturon and seemed to overcome this stress status. Most likely, contents of pigment and activities of enzymes were raised to approximate control levels. Moreover, antioxidants were elevated and the oxidative stress indices seemed to be alleviated by GSH application. These results indicate that exogenous GSH enhances enzymatic and nonenzymatic antioxidants to alleviate the effects of isoproturon.

Topics: Ascorbate Peroxidases; Ascorbic Acid; Carotenoids; Catalase; Chlorophyll; Glutathione; Hydrogen Peroxide; Lipid Peroxidation; Malondialdehyde; Oxidative Stress; Phenylurea Compounds; Plant Proteins; Porphobilinogen Synthase; Seedlings; Superoxide Dismutase; Time Factors; Triticum

A mesocosm study with three photosystem-II inhibitors and an equipotent mixture was performed to address the value of functional and structural endpoints in evaluating the impact of herbicides on aquatic systems. The herbicides atrazine, diuron, and isoproturon were dosed in the ratio of their relative potencies as HC30 for the single substance treatments and as 1/3 HC30 for the mixture treatment to obtain comparable effect concentrations. To investigate the effects of the three herbicides and their mixture on photosynthesis of the whole system, the physical-chemical parameters pH, dissolved oxygen, and conductivity were monitored. To address effects on photosynthesis more specifically, the photosynthetic efficiency of phytoplankton and three submersed macrophytes (Elodea canadensis, Myriophyllum spicatum, and Potamogeton lucens) were investigated applying in vivo chlorophyll fluorescence as an indicator for their activity. As a structural endpoint, the species abundance and community structure of the phytoplankton community was determined. Effects were continuously monitored over a five week period of constant exposure, and during a 3 month post-exposure period. The sensitivity, expressed as maximum effect during constant exposure, was higher for the structural parameters (total and single species abundances and PRC) than for the functional parameters. The mean coefficient of variation (CV) for the physical-chemical parameters was below 10%, for the photosynthesis measurement of the phytoplankton and macrophytes below 10 and 30%, respectively. Structural parameters, however, yielded higher variability with mean CVs for phytoplankton abundance data and single sensitive species reaching up to 96%. Effects on the phytoplankton photosynthesis measured via in vivo chlorophyll fluorescence were constant during the exposure period; whereas macrophytes recovered quickly from photosynthesis inhibition despite constant exposure. Effects on total system photosynthesis, determined via physical-chemical parameters, lasted for a shorter period than for the phytoplankton photosynthesis demonstrating the importance of the macrophytes for total primary production. Thus, the evaluation of effects on communities in model ecosystems such as micro- and mesocosms should not be based on structural endpoints only due to their comparably high inherent variability. Instead, we recommend complementing the risk assessment with data obtained from sensitive functional endpoints addre

Topics: Atrazine; Chlorophyll; Diuron; Ecosystem; Herbicides; Hydrocharitaceae; Phenylurea Compounds; Photosynthesis; Phytoplankton; Potamogetonaceae; Risk Assessment; Water Pollutants, Chemical

Isoproturon, a herbicide belonging to the phenylurea family, is widely used to kill weeds in soils. Recent study indicated that isoproturon has become a contaminant in ecosystems due to its intensive use, thus bringing environmental risks to crop production safety. Salicylic acid (SA) is one of the components in plant defense signaling pathways and regulates diverse physiological responses to biotic and environmental stresses. The purpose of the study is to help to understand how SA mediates the biological process in wheat under isoproturon stress.. Wheat seeds (Triticum aestivum, cv. Yangmai 13) were surface-sterilized and placed on moist filter paper for germination. After 24 h, the germinating seeds were placed on a plastic pot (1 L) containing 1,120 g soil mixed with isoproturon at 4 mg kg(-1) soil. After 4 days, wheat leaves were sprayed with 5 mg L(-1) SA. The SA treatment was undertaken once a day and lasted for 6 days, when the third true leaf was well developed. For control seedlings, only water was sprayed. Seedlings were grown under a light intensity of 300 µmol m(-2) s(-1) with a light/dark cycle of 12/12 h at 25°C, and watered to keep 70% relative water content in soils.. We investigated the role of SA in alleviating isoproturon-induced toxicity in the food crop wheat (T. aestivum). Plants exposed to 4 mg kg(-1) isoproturon showed growth stunt and oxidative damage, but concomitant treatment with 5 mg L(-1) SA was able to attenuate the toxic effect. Isoproturon in soils was readily accumulated by wheat, but such accumulation can be blocked significantly by SA application. Treatment with SA decreased the abundance of O(2) (.-) and H(2)O(2), as well as activities of antioxidant enzymes, and increased activities of catalase in isoproturon-exposed plants. The enzyme activities were confirmed by the native polyacrylamide gel electrophoresis. Further, an RT-PCR-based assay was performed to show that several transcripts coding antioxidant enzymes were increased with isoproturon but decreased by SA.. The present results indicate that exogenous SA is able to improve the wheat tolerance to isoproturon toxicity.

Topics: Chlorophyll; Herbicides; Lipid Peroxidation; Oxidative Stress; Phenylurea Compounds; Plant Leaves; Reverse Transcriptase Polymerase Chain Reaction; Salicylic Acid; Triticum

Isoproturon (IPU) is a pesticide used for protection of land crops from weed or pathogen attack. Recent survey shows that IPU has been detected as a contaminant in aquatic systems and may have negative impact on aquatic organisms. To understand the phytotoxicity and potential accumulation and degradation of IPU in algae, a comprehensive study was performed with the green alga Chlamydomonas reinhardtii. Algae exposed to 5-50 μg L(-1) IPU for 3d displayed progressive inhibition of cell growth and reduced chlorophyll fluorescence. Time-course experiments with 25 μg L(-1) IPU for 6d showed similar growth responses. The 72 h EC50 value for IPU was 43.25 μg L(-1), NOEC was 5 μg L(-1) and LOEC was 15 μg L(-1). Treatment with IPU induced oxidative stress. This was validated by a group of antioxidant enzymes, whose activities were promoted by IPU exposure. The up-regulation of several genes coding for the enzymes confirmed the observation. IPU was shown to be readily accumulated by C. reinhardtii. However, the alga showed a weak ability to degrade IPU accumulated in its cells, which was best presented at the lower concentration (5 μg L(-1)) of IPU in the medium. The imbalance of accumulation and degradation of IPU may be the cause that resulted in the detrimental growth and cellular damage.

Topics: Biodegradation, Environmental; Biomass; Cell Proliferation; Chlamydomonas reinhardtii; Chlorophyll; Culture Media; Fluorescence; Free Radical Scavengers; Gene Expression Regulation; Herbicides; Hydrogen Peroxide; Oxidative Stress; Phenylurea Compounds; Real-Time Polymerase Chain Reaction; Superoxide Dismutase

Pesticides are being detected in water bodies on an increasingly frequent basis. The present study focused on toxicity and phytoremediation potential of aquatic plants to remove phytosanitary products from contaminated water. We investigated the capacity of Lemna minor (L. minor) to eliminate two herbicides isoproturon and glyphosate from their medium. Since phytoremediation relies on healthy plants, pesticide toxicity was evaluated by exposing plants to 5 concentrations (0-20 microg L(-1) for isoproturon and 0-120 microg L(-1) for glyphosate) in culture media for 4 d using growth rate and chlorophyll a fluorescence as endpoints. At exposure concentrations of 10 microg x L(-1) for isoproturon and 80 microg x L(-1) for glyphosate, effects on growth rate and chlorophyll fluorescence were minor (< 25%), so that this initial concentration was selected to study herbicide removal After a 4-d incubation, removal yields were 25% and 8% for isoproturon and glyphosate, respectively.

Topics: Araceae; Biodegradation, Environmental; Chlorophyll; Chlorophyll A; Fluorescence; Glycine; Glyphosate; Herbicides; Phenylurea Compounds; Time Factors; Water Pollutants, Chemical

This study tested if a variation in light intensity, in comparison to constant light required in well-designed toxicity test, could have measurable consequences on the sensitivity of phototrophic biofilms (periphyton) to isoproturon. Two independent experiments were carried out to investigate the combined effects of light and isoproturon on the photochemical behavior of intact natural biofilms by measurements of chlorophyll fluorescence and pigment composition. Experiment 1 consisted of exposing biofilms to series of isoproturon concentrations (0-2 mg L(-1)) for 7 h under constant light at different irradiance levels (25-300 micromol m(-2) s(-1)). In experiment 2, biofilms were exposed using more environmentally realistic conditions to three selected concentrations of isoproturon (2, 6 and 20 microg L(-1)) during a 7-h-simulated daily light cycle. Our results demonstrated that light, considered here as a direct physical stressor, slightly modulated the acute toxicity of isoproturon on these diatom dominated communities. This was attributed to the fact that these two factors act specifically on the photosynthetic activity. Furthermore, it was shown that a dynamic light regime increased periphyton sensitivity to isoproturon by challenging its photoprotective mechanisms such as the xanthophyll cycle, therefore implying that traditional ecotoxicological bioassays lead to underestimate the effect of isoproturon.

Topics: Biofilms; Chlorophyll; Diatoms; Environmental Monitoring; Fluorometry; Herbicides; Phenylurea Compounds; Photoperiod; Photosynthesis; Rivers; Water Pollutants, Chemical

The biomonitoring of pesticide pollution in streams and rivers using algae such as diatoms remains difficult. The responses of diatom communities to toxic stress in stream water are disturbed by the variations of environmental parameters. In this study, periphytic algae collected in situ were exposed under controlled conditions to two major herbicides used in French agriculture (isoproturon and s-metolachlor). Three exposure regimes were tested: 5 and 30 microg L(-1) for 6 days and 30 microg L(-1) for 3 days followed by a recovery period of 3 days. The algal biomasses were assessed from pigment concentrations (chlorophyll a and c) and from live cell density. The highest concentration (30 microg L(-1)) of isoproturon inhibited the biomass increase statistically significantly. In periphyton exposed to 5 and 30 microg L(-1) of s-metolachlor, chlorophyll c concentration and live cell density were also statistically significantly lower than in the control. Periphyton left to recover after reduced exposure duration (3 days) showed higher growth rates after treatment with s-metolachlor than with isoproturon. Taxonomic identifications showed that species like Melosira varians, Nitzschia dissipata and Cocconeis placentula were not affected by the herbicide exposure. Other species like Eolimna minima and Navicula reichardtiana were more sensitive. Studying diatoms according to their trophic mode showed that facultative heterotroph species were statistically significantly favoured by isoproturon exposure at the highest concentration. Results obtained with s-metolachlor exposure showed a disturbance of cell multiplication rather than that of photosynthesis. These results suggest that photosynthesis inhibitors like isoproturon favour species able to survive when the autotroph mode is inhibited.

Topics: Acetamides; Biomass; Cell Count; Chlorophyll; Chlorophyll A; Chromatography, High Pressure Liquid; Diatoms; Environmental Monitoring; Fresh Water; Herbicides; Phenylurea Compounds; Rivers; Solid Phase Extraction; Statistics, Nonparametric; Temperature; Water Pollutants, Chemical

The herbicide isoproturon is widely used for controlling weed/grass in agricultural practice. However, the side effect of isoproturon as contaminants on crops is unknown. In this study, we investigated isoproturon-induced oxidative stress in wheat ( Triticum aestivum). The plants were grown in soils with isoproturon at 0-20 mg/kg and showed negative biological responses. The growth of wheat seedlings with isoproturon was inhibited. Chlorophyll content significantly decreased at the low concentration of isoproturon (2 mg/kg), suggesting that chlorophyll was rather sensitive to isoproturon exposure. The level of thiobarbituric acid reactive substances (TBARS), an indicator of cellular peroxidation, showed an increase, indicating oxidative damage to plants. The isoproturon-induced oxidative stress resulted in a substantial change in activities of the majority of antioxidant enzymes, including superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX). Activities of the antioxidant enzymes showed a general increase at low isoproturon concentrations and a decrease at high isoproturon concentrations. Activities of CAT in leaves showed progressive suppression under the isoproturon exposure. Analysis of nondenaturing polyacrylamide gel electrophoresis (PAGE) confirmed these results. We also tested the activity of glutathione S-transferase (GST) and observed the activity stimulated by isoproturon at 2-10 mg/kg.

Topics: Antioxidants; Catalase; Chlorophyll; Herbicides; Oxidative Stress; Peroxidase; Phenylurea Compounds; Seedlings; Superoxide Dismutase; Thiobarbituric Acid Reactive Substances; Triticum

Photosynthetic-fluorescence parameters were investigated to be used as valid biomarkers of toxicity when alga Scenedesmus obliquus was exposed to isoproturon [3-(4-isopropylphenyl)-1,1-dimethylurea] effect. Chlorophyll fluorescence induction of algal cells treated with isoproturon showed inactivation of photosystem II (PSII) reaction centers and strong inhibition of PSII electron transport. A linear correlation was found (R2>or=0.861) between the change of cells density affected by isoproturon and the change of effective PSII quantum yield (PhiM'), photochemical quenching (qP) and relative photochemical quenching (qP(rel)) values. The cells density was also linearly dependent (R2=0.838) on the relative unquenched fluorescence parameter (UQF(rel)). Non-linear correlation was found (R2=0.937) only between cells density and the energy transfer efficiency from absorbed light to PSII reaction center (ABS/RC). The order of sensitivity determined by the EC-50% was: UQF(rel)>PhiM'>qP>qP(rel)>ABS/RC. Correlations between cells density and those photosynthetic-fluorescence parameters provide supporting evidence to use them as biomarkers of toxicity for environmental pollutants.

Topics: Chlorophyll; Environmental Monitoring; Fluorescence; Herbicides; Linear Models; Phenylurea Compounds; Photosynthesis; Photosystem II Protein Complex; Scenedesmus; Toxicity Tests; Water Pollutants, Chemical

Bioassays with unicellular algae are frequently used as ecotoxicological test systems to evaluate the toxicity of contaminated environmental samples or chemicals. In contrast, aquatic macrophyte test systems are still rarely used as they are laborious to handle because species exhibit distinct ecological requirements. The aim of this study was to establish a fast and reproducible measuring system for aquatic macrophyte species to overcome those limitations for use. Thus, a newly developed pulse-amplitude modulated chlorophyll fluorometer (Imaging-PAM) was applied as an effect detection in short-term bioassays with aquatic macrophyte species. This multiwell-plate-based measuring device enables the incubation and measurement of up to 24 samples in parallel. The Imaging-PAM was used (i) to establish and validate the sensitivity of the test systems to three Photosystem II (PSII) inhibitors (atrazine, prometryn, isoproturon), (ii) to compare the test systems with established biotests for macrophytes and (iii) to define necessary time scales in aquatic macrophyte testing. The results showed that fluorescence-based measurements with the Imaging-PAM allow rapid and parallel analysis of large amounts of aquatic macrophyte samples and of toxicants effects of the PSII inhibitors tested on aquatic macrophytes. Measurements revealed a good correlation between obtained median effective concentrations (EC50s) for the new and the established biotest systems. Hence, the Imaging-PAM measuring device is a promising tool to allow fast chemical effect screening for high amounts of samples with little time and material and thus offers scope for high-throughput biotesting using aquatic macrophyte species.

Topics: Atrazine; Chlorophyll; Environmental Monitoring; Fluorescence; Herbicides; Magnoliopsida; Phenylurea Compounds; Prometryne; Reproducibility of Results; Toxicity Tests; Water Pollution

The acute toxicity was determined for soil algae Chlorella kesslerei and Anabaena inaequalis, exposed to pesticides lindane, pentachlorophenol (PCP), isoproturon (IPU), and methyl parathion (MP). Toxicity markers included growth inhibition, chlorophyll biosynthesis, and total carbohydrate content, as a function of dose and time. Concentration response functions (EC50) were estimated by probit data transformation and weighted linear regression analyses. Lindane's toxicity to Chlorella increased sharply with time (EC50 = 7490, 10.3, 0.09 mg L(-1); 24, 48, 72 h), but remained nearly constant through 72 h with Anabaena (8.7-6.7 mg L(-1); 24-72 h). PCP at low concentrations stimulated algal growth and chlorophyll a production, an effect reversed at higher doses. Anabaena was less tolerant of PCP and MP than was Chlorella. The 96-h static EC50 values for Chlorella were: 0.003, 34, 0.05, and 291 mg L(-1) for lindane, PCP, isoproturon, and MP, respectively; for Anabaena, these were 4.2, 0.13, 0.21, and 19 mg L(-1). Carbohydrate production responses were similar to those of cell density (growth) and chlorophyll biosynthesis, with MP having the lowest adverse impact. The overall relative toxicity among the four tested pesticides was: for Chlorella, lindane > IPU >> PCP >> MP; and for Anabaena, PCP > IPU > lindane > MP. The results confirm that toxicants such as these pesticides may affect individual (though related) species to significantly different degrees.

Topics: Anabaena; Biomass; Chlorella; Chlorophyll; Chlorophyll A; Dose-Response Relationship, Drug; Hexachlorocyclohexane; Methyl Parathion; Methylurea Compounds; Pentachlorophenol; Pesticides; Phenylurea Compounds; Photosynthesis; Regression Analysis; Soil Pollutants; Toxicity Tests, Acute

The experimental approach to the effects of the phenylurea herbicide Isoproturon (IPU), on the photosynthesis activity of leaf cells of the freshwater macrophyte Elodea densa was based on the fast induction kinetics of the PSII chlorophyll a in vivo fluorescence. FI/FP ratios determined on the induction curves exhibited a noticeable effect at 5 micrograms IPU.liter-1. They appeared to be the most reliable parameter for the quantitative evaluation of the dissociation constant of the complex "IPU/D1 protein" (Kd = 1.2 x 10(-7) M) and of the concentration of free IPU either at the thylakoid level or in the surrounding medium of the leaf epithelial cells. Total IPU bioaccumulation at the whole plant level as a function of [IPU] in the medium indicated that the D1 protein represented the main binding site for IPU in this aquatic plant species.

Topics: Binding Sites; Chlorophyll; Dose-Response Relationship, Drug; Fresh Water; Herbicides; Light-Harvesting Protein Complexes; Methylurea Compounds; Models, Theoretical; Phenylurea Compounds; Photosynthesis; Photosynthetic Reaction Center Complex Proteins; Photosystem II Protein Complex; Plant Leaves; Spectrometry, Fluorescence; Water Pollutants, Chemical