Validation of photosynthetic-fluorescence parameters as biomarkers for isoproturon toxic effect on alga Scenedesmus obliquus

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.     

Effects of chitosan on oxidative stress and metallothioneins in aquatic worm Tubifex tubifex (Oligochaeta, Tubificidae)

Chitosan is a natural polymer which has the property to elicit the natural defenses mechanism in plant and which can be an interesting biopesticides. It is then necessary to investigate the potential toxicity of chitosan for aquatic animal health. Metallothioneins (MTs) are low molecular weight proteins, mainly implicated in metal ion detoxification. Increase in MTs contents had been considered as a specific biomarker of metal exposure. However recently it has been demonstrated that MTs participate in several cellular functions such as regulation of growth and anti-oxidative defenses. Therefore, the induction of MTs has been investigated in the aquatic worms Tubifex tubifex exposed to chitosan. MTs levels in exposed worm increased significantly (p > 0.05) after 2, 4, and 7 days of exposure to different concentrations of chitosan (maximum + 158.19 +/- 10.2% after 2 days of exposure to 125 mgl(-1) of chitosan). Several antioxidant parameters including glutathione (GSH), glutathione-S-transferase (GST), glutathione reductase (GR), and catalase (CAT) were quantified in T. tubifex after 2, 4, and 7 days of exposure to chitosan. Exposure to chitosan had a negative effect on T. tubifex growth (maximum effect -6.11 +/- 1.6% after 7 days with 125 mgl(-1)) demonstrating the toxic effect of the pesticide. This growth rate decrease was accompanied by a reduction in protein contents. The activity of catalase (CAT), glutathione-S-transferase (GST), and glutathione reductase (GR) increased in response to the chitosan demonstrating an oxidative stress in the worms.     

用水生生物对重金属污染土壤进行生态毒理评价

应用斜生栅藻（Scenedesmus obliquus）和明亮发光杆菌T3（Photobacterium phosphoreum）急性毒性实验方法对重金属污染土壤的进行生态毒理评价，结果表明，斜生栅藻的生长繁殖率和发光菌的相对发光度与土壤中的重金属含量明显相关，并且随重金属投加量的增加，其生长繁殖率和发光度逐渐降低。对3种测试参数进行比较可知，斜生栅藻细胞数增长率是最敏感的土壤毒性检测指标。土壤的毒性在复合污染的条件下比在单一污染的条件下高很多。本研究的结果可以为污染土壤的优先修复提供理论依据。     

用水生生物对重金属污染土壤进行生态毒理评价

应用斜生栅藻(Scenedesmusobliquus)和明亮发光杆菌T3(Photobacteriumphosphoreum)急性毒性实验方法对重金属污染土壤的进行生态毒理评价,结果表明,斜生栅藻的生长繁殖率和发光菌的相对发光度与土壤中的重金属含量明显相关,并且随重金属投加量的增加,其生长繁殖率和发光度逐渐降低。对3种测试参数进行比较可知,斜生栅藻细胞数增长率是最敏感的土壤毒性检测指标。土壤的毒性在复合污染的条件下比在单一污染的条件下高很多。本研究的结果可以为污染土壤的优先修复提供理论依据。     

Toxicity of copper excess on the lichen Dermatocarpon luridum: antioxidant enzyme activities

The aim of this study was to investigate the toxicity of copper on the aquatic lichen Dermatocarpon luridum focusing on the activities of some antioxidant enzymes. Investigations were conducted using increasing copper concentrations (0.00, 0.25, 0.50, 0.75 and 1.00 mM CuSO(4) x 5H(2)O) in synthetic freshwater that emulated the major ion compositions of its natural water biota; time course measurement was 0, 3, 6, 12, 24 and 48 h. The copper concentration in thalli increased with its increase in the medium and the duration of treatment. Copper induced lipid peroxidation, measured using the hydroperoxi-conjugated dienes (HPCD) concentration. The decrease in the protein concentrations was similar in thalli exposed to copper concentrations above 0.50 mM and the decrease was twice lower in thalli exposed to 0.25 mM copper. The activities of antioxidant enzymes measured were differently affected by copper excess. For 0.25 mM copper, the activities of SOD (superoxide dismutase) and APX (ascorbate peroxidase) were unchanged when compared with unstressed thalli whereas the CAT (catalase) activity increased and the GR (glutathione reductase) activity decreased. The activities of SOD and APX increased in thalli exposed to concentrations above 0.50mM copper. The CAT activity increased after the first 3h of experiments at these concentrations and then decreased with the duration of treatment at an activity lower than in the unstressed plant. Whereas the APX activity increased, the GR activity similarly decreased for the copper concentration tested whatever the duration of the experiment.     

Enantioselectivity in toxicity and degradation of dichlorprop-methyl in algal cultures

Enantioselectivity in the toxicity and degradation of the herbicide dichlorprop-methyl (2,4-DCPPM) in algal cultures was studied. Enantioselectivity was clearly observed in the toxicity of racemic 2,4-DCPPM and its two enantiomers. R-2,4-DCPPM showed low toxicity to Chlorella pyrenoidosa and Chlorella vulgaris, but higher toxicity to Scenedesmus obliquus. The observed toxicity was ranked: R-2,4-DCPPM>S-2,4-DCPPM>Rac-2,4-DCPPM; the toxicity of R-2,4-DCPPM was about 8-fold higher than that of Rac-2,4-DCPPM. Additionally, 2,4-DCPPM was quickly degraded, in the initial 12 h, and different algae cultures had different enantioselectivity for the 2,4-DCPPM enantiomers. There was no significant enantioselectivity for 2,4-DCPPM in Chlorella vulgaris in the initial 7 h. However, racemic 2,4-DCPPM was degraded by Scenedesmus obliquus quickly, in the initial 4 h, much quicker, in fact, than the S- or R-enantiomers (racemate>R->S-), indicating that the herbicide 2,4-DCPPM was absorbed enantioselectively by Scenedesmus obliquus. The rapid formation of 2,4-DCPP suggested that 2,4-DCPPM adsorbed by algal cells was catalytically hydrolyzed to the free acid, a toxic metabolite. The production rates of 2,4-DCPP were as follows: Scenedesmus obliquus>Chlorella pyrenoidosa>Chlorella vulgaris, consistent with the degradability of 2,4-DCPPM. Scenedesmus obliquus had quick, but different, degradative and uptake abilities for R-, S-, and Rac-2,4-DCPPM. The R- and S- enantiomers were not hydrolyzed in the first 12 h, while both enantiomers were hydrolyzed slowly after that. These results indicate that some physical and chemical properties of compounds are of importance in determining their enantioselective toxicity and degradation. The ester and its metabolite likely played an important role in enantioselective toxicity to the three algae.     

Effects of phenanthrene on the mortality, growth, and anti-oxidant system of earthworms (Eisenia fetida) under laboratory conditions

To assess the toxic effects of phenanthrene on earthworms, we exposed Eisenia fetida to artificial soils supplemented with different concentrations (0.5, 2.5, 12.5, mgkg(-1) soil) of phenanthrene. The residual phenanthrene in the soil, the bioaccumulation of phenanthrene in earthworms, and the subsequent effects of phenanthrene on growth, anti-oxidant enzyme activities, and lipid peroxidation (LPO) were determined. The degradation rate of low concentrations of phenanthrene was faster than it was for higher concentrations, and the degradation half-life was 7.3d (0.5 mgkg(-1)). Bioaccumulation of phenanthrene in the earthworms decreased the phenanthrene concentration in soils, and phenanthrene content in the earthworms significantly increased with increasing initial soil concentrations. Phenanthrene had a significant effect on E. fetida growth, and the 14-d LC(50) was calculated as 40.67 mgkg(-1). Statistical analysis of the growth inhibition rate showed that the concentration and duration of exposure had significant effects on growth inhibition (p<0.001). Superoxide dismutase (SOD) activity increased at the beginning (2 and 7d) and decreased in the end (14 and 28 d). Catalase (CAT) activity in all treatments was inhibited from 1 to 14 d of exposure. However, no significant perturbations in malondialdehyde (MDA) content were noted between control and phenanthrene-treated earthworms except after 2d of exposure. These results revealed that bioaccumulation of phenanthrene in E. fetida caused concentration-dependent, sub-lethal toxicity. Growth and superoxide dismutase activity can be regarded as sensitive parameters for evaluating the toxicity of phenanthrene to earthworms.     

Atrazine promotes biochemical changes and DNA damage in a Neotropical fish species

The effects of Atrazine, an herbicide used worldwide and considered as a potential contaminant in aquatic environments, were assessed on the Neotropical fish Prochilodus lineatus acutely (24 and 48 h) exposed to 2 or 10 μg L⁻¹ of atrazine by using a set of biochemical and genetic biomarkers. The following parameters were measured in the liver: activity of the biotransformation enzymes ethoxyresorufin-O-deethylase (EROD) and glutathione S transferase (GST), antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), content of reduced glutathione (GSH), generation of reactive oxygen species (ROS) and occurrence of lipid peroxidation (LPO); in brain and muscle the activity of acetylcholinesterase (AChE) and DNA damage (comet assay) on erythrocytes, gills and liver cells. A general decreasing trend on the biotransformation and antioxidant enzymes was observed in the liver of P. lineatus exposed to atrazine; except for GR, all the other antioxidant enzymes (SOD, CAT and GPx) and biotransformation enzymes (EROD and GST) showed inhibited activity. Changes in muscle or brain AChE were not detected. DNA damage was observed in the different cell types of fish exposed to the herbicide, and it was probably not from oxidative origin, since no increase in ROS generation and LPO was detected in the liver. These results show that atrazine behaves as enzyme inhibitor, impairing hepatic metabolism, and produces genotoxic damage to different cell types of P. lineatus.     

Influence of toxicity and dissipation of racemic fenoxaprop and its R-enantiomer in Scenedesmus obliquus suspension by cyclodextrins

Cyclodextrins (CDs), a class of cyclic oligosaccharide molecules containing a variety of chiral centre, are capable of recognizing enantiomeric molecules through the formation of inclusion complexes. In this work, we selected three types of CDs, beta-CD and its two derivatives, randomly methylated beta-CD (RAMEB) and hydroxypropyl beta-CD (HP-beta-CD), to evaluate effects on toxicity of racemic fenoxaprop (rac-FA) and its R-enantiomer (R-FA) to freshwater alga Scenedesmus obliquus (S. obliquus) and their dissipation in S. obliquus suspension with and without CDs addition, respectively, in an attempt to get more detail about enantioselective behavior of fenoxaprop acid (FA) in the environment, using CDs as a remediation agent for FA and formulation additive for fenoxaprop-p-ethyl (FE). The significant difference between rac-FA and R-FA was not observed in their acute toxicity to S. obliquus and dissipation in S. obliquus suspension. RAMEB had no effect on either toxicity of FA to S. obliquus or dissipation of FA in S. obliquus suspension, and it also didn't change the extent of enantioselectivity in toxicity of FA to S. obliquus. But the addition of a certain amount of beta -CD and HP-beta -CD reduced the toxicity of FA to S. obliquus and increased dissipation of FA in S. obliquus suspension, as well as changed the enantioselectivity in toxicity of FA to S. obliquus. The results indicated beta-CD and HP-beta-CD could be used as a promising agent for remediation of aquatic contamination produced by FA, and RAMEB might be used as potential formulation additives for FE, the parent compound of FA, as RAMEB didn't decrease activity of R-FA and might be environmentally safer than the conventional additives.     

Glutathione levels and enzyme activity in the tissues of bank vole Clethrionomys glareolus chronically exposed to a mixture of metal contaminants

The biochemical response to chronic heavy metal exposure was studied in tissues of bank voles Clethrionomys glareolus. Animals were collected from three sites located 4, 8 and 30km from a zinc-lead smelter, the area's main source of metal contamination. Concentrations of Cd, Pb, Zn and Fe were measured in the liver, kidneys and gonads to assess the level of metal intoxication. In response to intoxication, organisms activate detoxification mechanisms which can protect animals from metals' toxicity. Glutathione plays an important role in toxic substance detoxification. Total glutathione (tGSH) and glutathione disulfide (GSSG) were measured in the tissues. Also, the activity of glutathione reductase (GR), glutathione peroxidase (GPX), and glutathione-S-transferase (GST) was measured in the studied tissues. Results indicate that levels of all studied parameters were tissue and site-dependent. Evidence indicates that the most sensitive parameter of metal toxicity for animals living in a chronically contaminated environment is the GSH/GSSG ratio. In our study, the GSH/GSSG ratio was decreased in the liver of animals with high Cd levels. However, the relationship between Pb and the GSH/GSSG ratio was positive in the gonads. Cadmium and lead negatively influenced GPX activity in the liver; this was probably connected with inhibition of the Se-dependent fraction. The relationship between iron and GR activity in the kidney was also negative, but other correlations for iron both in liver and kidney were not significant. Positive correlations between Zn levels and GST and GR activity were found in the gonads of bank voles.     

Short term recovery of periphyton photosynthesis after pulse exposition to the photosystem II inhibitors atrazine and isoproturon

Aquatic organisms are exposed to fluctuating concentrations of herbicides which contaminate rivers following their use for agricultural or domestic purposes. The development of sensitive bioanalytical tests enabling us not only to detect the effects of those pollutants but to take into account this pattern of exposure should improve the ecological relevance of river toxicity assessment. In this respect, the use of chlorophyll fluorescence measurements is a convenient way to probe the effect of photosystem II (PSII) inhibitors on primary producers. This study was devoted to validate the combined use of two fluorescence parameters, the effective and the optimal quantum yields of PSII photochemistry (Φ_PSII and F_v/F_m), as reliable biomarkers of initial isoproturon (IPU) or atrazine (ATZ) toxicity to natural periphyton in a pulse exposition scenario. Φ_PSII and F_v/F_m were regularly estimated during a 7 h-exposure to each pollutant (0-100 μM) and also later after being transferred in herbicide-free water (up to 36 h). Our results showed that IPU was more toxic than ATZ, but with effects reversible within 12 h. Moreover, these two similarly acting herbicides (i.e. same target site) presented contrasted short term recovery patterns, regarding the previous exposure duration.     

Brassinosteroid alleviates phenanthrene and pyrene phytotoxicity by increasing detoxification activity and photosynthesis in tomato

The present study was carried out to investigate the effects of exogenously applied 24-epibrassinolide (BR) on growth, gas exchange, chlorophyll fluorescence characteristics, lipid peroxidation and antioxidant systems of tomato seedlings grown under different levels (0, 10, 30, 100 and 300 μM) of phenanthrene (PHE) and pyrene (PYR) in hydroponics. A concentration-dependent decrease in growth, photosynthetic pigment contents, net photosynthetic rate (Pn), stomatal conductance (Gs), maximal quantum yield of PSII (Fv/Fm), effective quantum yield of PSII (Φ_PSII), photochemical quenching coefficient (qP) has been observed following PHE and PYR exposure. By contrast, non-photochemical quenching coefficient (NPQ) was increased. PHE was found to induce higher stress than PYR. However, foliar or root application of BR (50 nM and 5 nM, respectively) alleviated all those depressions with a sharp improvement in the activity of photosynthetic machinery. The activities of guaicol peroxidase (GPOD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR) as well as content of malondialdehyde (MDA) were increased in a dose-dependent manner under PHE or PYR treatments. Compared with control the highest increments of GPOD, CAT, APX, GR and MDA by PHE/PYR alone treatments were observed following 300 μM concentration, which were 67%, 87%, 53%, 95% and 74% by PHE and 42%, 53%, 30%, 86% and 62% by PYR, respectively. In addition, both reduced glutathione (GSH) and oxidized glutathione (GSSG) were induced by PHE or PYR. Interestingly, BR application in either form further increased enzymatic and non enzymatic antioxidants in tomato roots treated with PHE or PYR. Our results suggest that BR has an anti-stress effect on tomato seedlings contaminated with PHE or PYR and this effect is mainly attributed by increased detoxification activity.     

Acute toxicity of excess mercury on the photosynthetic performance of cyanobacterium, S. platensis--assessment by chlorophyll fluorescence analysis

Measurement of chlorophyll fluorescence has been shown to be a rapid, non-invasive, and reliable method to assess photosynthetic performance in a changing environment. In this study, acute toxicity of excess Hg on the photosynthetic performance of the cyanobacterium S. platensis, was investigated by use of chlorophyll fluorescence analysis after cells were exposed to excess Hg (up to 20 microM) for 2 h. The results determined from the fast fluorescence kinetics showed that Hg induced a significant increase in the proportion of the Q(B)-non-reducing PSII reaction centers. The fluorescence parameters measured under the steady state of photosynthesis demonstrated that the increase of Hg concentration led to a decrease in the maximal efficiency of PSII photochemistry, the efficiency of excitation energy capture by the open PSII reaction centers, and the quantum yield of PSII electron transport. Mercury also resulted in a decrease in the coefficients of photochemical and non-photochemical quenching. Mercury may have an acute toxicity on cyanobacteria by inhibiting the quantum yield of photosynthesis sensitively and rapidly. Such changes occurred before any other visible damages that may be evaluated by other conventional measurements. Our results also demonstrated that chlorophyll fluorescence analysis can be used as a useful physiological tool to assess early stages of change in photosynthetic performance of algae in response to heavy metal pollution.     

Lead induced changes in antioxidant metabolism of horsegram (Macrotyloma uniflorum (Lam.) Verdc.) and bengalgram (Cicer arietinum L.)

One-month old horsegram (Macrotyloma uniflorum (Lam.) Verdc. cv VZM1) and bengalgram (Cicer arietinum L. cv Annogiri) were exposed to different regimes of lead stress as Pb(NO3)2 at 0, 200, 500 and 800 ppm concentrations. The extent of oxidative damage as the rate of lipid peroxidation, antioxidative response and the accumulation of lead in roots and shoots of both plants were evaluated after 12 days of lead stress. Lead (Pb) treated plants showed increased levels of lipid peroxidation as evidenced from the increased malondialdehyde content coupled with the increase in the activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), glutathione reductase (GR), glutathione S-transferase (GST) compared to control (untreated) plants. Lead stress caused significant changes in the activity of antioxidative enzymes. The effect of lead was found to be concentration dependent. Higher concentration of lead (800 ppm) resulted 2- to 3-fold increase in SOD, catalase and peroxidase activities, 3- to 5-fold increase in GR activity and 3- to 4-fold increase in GST activity in roots and leaves of both horsegram and bengalgram plants. Lead stress caused a significant increase in the rate of peroxidation as showed in the levels of malondialdehyde content in roots and leaves of both plant species. Horsegram registered lower Pb accumulation than bengalgram, however localization of Pb was greater in roots than leaves in both plants. In general, lipid peroxide levels and antioxidative enzyme activities were higher in horsegram than bengalgram and also more in roots than leaves which best concordance with the lead contents of both the plants and organs. These results suggest that Pb toxicity causes oxidative stress in plants and the antioxidative enzymes SOD, CAT, POD, GR, GST could play a pivotal role against oxidative injury.     

Physiological and molecular responses of the earthworm <Emphasis Type="Italic">Eisenia fetida</Emphasis> to polychlorinated biphenyl contamination in soil

Polychlorinated biphenyls (PCBs) are a class of man-made organic compounds ubiquitously present in the biosphere. In this study, we evaluated the toxic effects of different concentrations of PCBs in two natural soils (i.e. red soil and fluvo-aquic soil) on the earthworm Eisenia fetida. The parameters investigated included anti-oxidative response, genotoxic potential, weight variation and biochemical responses of the earthworm exposed to two different types of soils spiked with PCBs after 7 or 14 days of exposure. Earthworms had significantly lower weights in both soils after PCB exposure. PCBs significantly increased catalase (CAT), superoxide dismutase (SOD), and guaiacol peroxidase (POD) activity in earthworms exposed to either soil type for 7 or 14 days and decreased the malondialdehyde (MDA) content in earthworms exposed to red soil for 14 days. Of the enzymes examined, SOD activity was the most sensitive to PCB stress. In addition, PCB exposure triggered dose-dependent coelomocyte DNA damage, even at the lowest concentration tested. This response was relatively stable between different soils. Three-way analysis of variance (ANOVA) showed that the weight variation, anti-oxidant enzyme activities, and MDA contents were significantly correlated with exposure concentration or exposure duration (P < 0.01). Furthermore, weight variation, CAT activity, and SOD activity were significantly affected by soil type (P < 0.01). Therefore, the soil type and exposure time influence the toxic effects of PCBs, and these factors should be considered when selecting responsive biomarkers.     

Multiple effects of chromate on the photosynthetic apparatus of Spirodela polyrhiza as probed by OJIP chlorophyll a fluorescence measurements

Chromate (Cr) decreases the growth of Spirodela polyrhiza. The fronds lost their pigments. The O2 evolution was also decreased. The Cr effect was found to be dose dependent. The toxic effects of Cr have further been studied on the photosynthetic activity of Spirodela polyrhiza by means of the chlorophyll a (Chl a) fluorescence transient O-J-I-P. The Chl a fluorescence transients were recorded in vivo with high time resolution and analyzed according to the JIP-test which can quantify the photosystem II behavior. Cr treated plants show a decrease in yield for primary photochemistry, phi Po. The performance index of PSII, PIABS, which is the combination of the indexes of three independent parameters, (1) the total number of active reaction centers per absorption (RC/ABS), (2) yield of primary photochemistry (phi Po) and (3) efficiency with which a trapped exciton can move an electron into the electron transport chain (psi 0), decreased due to Cr treatment. Chromate sensitivity varies within plant populations. In summary Cr affects several targets of PSII. More specifically, the main targets of Cr, according to the JIP-test, can be listed as a decrease in the number of active reaction centers and damage to the oxygen-evolving complex.     

Effect of the herbicide flumioxazin on photosynthetic performance of grapevine (Vitis vinifera L.)

Among the herbicides used in vineyards, the pre-emergence soil-applied flumioxazin (fmx) is a recently used molecule that inhibits chlorophyll biosynthesis in weed species. The aim of this work is to further characterize the effects of fmx on the non-target grapevine (Vitis vinifera L. cv. Chardonnay) using cutting as a model. Several photosynthesis parameters were estimated during 25 days after treatment with various fmx concentrations (from 0.5mM to 50mM). Measuring chlorophyll fluorescence it appeared that fmx or a by-product penetrated the plant throughout roots and spread throughout vessels. Besides the initial target, protox, fmx affected other functions related to photosynthesis. Fmx induced a simultaneous drop of both P(n), g(s) and T. Fmx caused stomatal closure, which partially explains the decrease of the net photosynthesis. The decline in F(v)/F(m) indicates that the photochemistry of PSII and its ability to reduce the primary acceptor Q(A) are also affected by fmx in grapevine. Fmx leads to a decrease in the coefficients of both photochemical and non-photochemical quenching. Simultaneous stomatal closure and decrease in the quantum yield of CO(2) assimilation indicate a change in energy metabolism following fmx stress. After ten days of fmx treatment, analyses of the response of net carbon assimilation in leaves to different intercellular CO(2) concentrations have shown a decrease of the maximum carboxylation velocity of RuBP. Stomatal closure, PSII photochemistry, change in energy metabolism and RuBP activity were affected by fmx treatment.     

Ultrasonic vibration seeds showed improved resistance to cadmium and lead in wheat seedling

Heavy metals have long-term adverse impacts on the health of soil ecosystems and even exhibit hazardous influences on human health. Literatures have shown that heavy metals could result in the reduction of crops growth and development and finally result in crops production decline. To determine whether or not ultrasonic vibration alleviate damage induced by cadmium and lead in crops, the wheat seeds, which is one of the most important agriculture crops in China and other countries in the world, were exposed to 10 min ultrasonic vibration and then the toxicological effects were investigated. Wheat seeds were soaked for 3 h with water and then the seeds were placed in clean beaker with some water, the beaker were placed in ultrasonic apparatus to vibrate (model, KQ-200VDV; frequency, 45 KHz; power, 160 W). Pretreatment seeds of 80 were sown in dishes (Ø 15 cm). After seeds emergence, the seedlings were thinned to 60 per dish. The dishes with seedlings were placed in a growth chamber maintained at 25 °C, 70 % relative humidity and 380 μmol?mol^?1 CO₂ under dark condition. A 400 μmol?m^?2?s^?1 photosynthetically active radiation was provided for 8 h (dark for 16 h) after the seed germination. When the seedlings were 2 days old, the seedlings were subjected to cadmium and lead for 4 days and then some selective biochemical and physiological parameters were measured. (1) Although each doses of ultrasonic vibration could improve seed germination, enhance biosynthesis of protein and chlorophyll and seedlings growth, the optimum dosage of ultrasonic vibration was 10 min. (2) Compared with the controls, cadmium and lead stress led to significant increase in the concentrations of malondialdehyde (MDA) and O^?2 and in the conductivity of electrolyte leakage, but the activities of catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR), the glutathione concentration, and the shoot weight were decreased by Cd and Pb stress. In the case of the seeds exposed to ultrasonic vibration and the seedlings followed by cadmium lead stress, the concentrations of MDA and O^?2, and the conductivity of electrolyte leakage were significantly lower than those in cadmium and lead stress; the activities of CAT, SOD, and GR and the shoot weight were significantly higher (except for glutathione (GSH) concentration) than those in cadmium and lead stress seedlings. The membrane is responsible for the selective inflow and outflow of molecules, ions, and water, and is a dynamic structure that performs a variety of functions. Cellular membrane systems play an important role in the compartmentalization of cells and maintaining intercellular homeostasis. Abiotic and biotic stress can induce functional impairments to the cellular membrane systems through triggering an increased formation of reactive oxygen species (ROS), such as superoxide (O₂ ^?), hydrogen peroxide (H₂O₂), and hydroxyl radicals. There are several pathways that can be utilized to eliminate ROS in plants, e.g., CAT, SOD, and GR and GSH, etc. compared with controls, cadmium, and lead enhanced the concentrations of ROS; decreased the SOD, CAT, and GR activities; the GSH concentration, and the seedling growth. In the case of ultrasonic pretreatment followed by cadmium and lead stresses, the activities of CAT, SOD, and GR were significant higher, and the conductivity of electrolyte leakage and the concentrations of MDA and O₂ ^? were significant lower than that of those subjected by cadmium and lead stress. This phenomenon demonstrated ultrasonic pretreatment can help plant eliminate the ROS by enhance the activities of antioxidant enzymes. These results suggested that ultrasonic vibration can alleviate the toxicological effect induced by heavy mental.     

Measurement of movement patterns of Caenorhabditis elegans (Nematoda) with the Multispecies Freshwater Biomonitor® (MFB)—a potential new method to study a behavioral toxicity parameter of nematodes in sediments

The nematode Caenorhabditis elegans receives increasing attention in sediment ecotoxicology and new toxicity tests with sensitive test parameters are under development. In this study, the motility of C. elegans could be measured for the first time online in sediment, using the Multispecies Freshwater Biomonitor. Whereas single nematodes could not be recorded, groups of 10 nematodes gave typical locomotive signals in different media (water, agar, sediment) with comparable precision and accuracy. The results of this study encourage to develop a new rapid online whole-sediment toxicity test with behaviour as sensitive test parameter.     

The fate of herbicide acetochlor and its toxicity to Eisenia fetida under laboratory conditions

To assess the toxic effects of the herbicide acetochlor on earthworms, we exposed Eisenia fetida (Savigny) to artificial soils (OECD soil) supplemented with different concentrations (5, 10, 20, 40 and 80 mg kg-1 soil) of acetochlor. The residues of acetochlor in soil and the effect of the herbicide on growth, reproduction, glutathione-S-transferases (GST) activity and cellulase activity of earthworms were determined. The degradation half-life of acetochlor in soil of acetochlor was between 9.3 and 15.6 days under laboratory condition; the degradation rate with low concentrations was faster than it was with higher concentrations. At 5 and 10 mg kg-1, acetochlor had not significant effect on growth of E. fetida except after 15 and 30 days of exposure. When concentration>20 mg kg-1, growth rates and numbers of juveniles per cocoon decreased significantly compared to the control in all treatments. However, cellulase activity decreased significantly in all treatments (5-80 mg kg-1). This study showed that acetochlor had no long-term effect on the growth and reproduction of E. fetida at field dose (5-10 mg kg-1). At higher concentrations of acetochlor (20-80 mg kg-1), acetochlor revealed sublethal toxicity to E. fetida. Growth, numbers of juveniles per cocoon and cellulase activity can be regarded as sensitive parameters to evaluate the toxicity of acetochlor on earthworms.