Growth Inhibition Of Lemna Research Articles

Биотестирование меламина с использованием многокомпонентной тест-системы

In recent decades, halogen-containing flame retardants have been gradually replaced by safer flame retardants, including nitrogen-containing compounds. However, their ecotoxicity is poorly studied. The ecotoxicity of melamine, a widely used nitrogen flame retardant, at concentrations equal to MPC in water (4 mg/L), 5 MPC (20 mg/L) and 10 MPC (40 mg/L) was assessed in this study using a complex of test organisms. The assessment of ecotoxicity using the dehydrogenase activity of Dietzia maris AM3 as a test microorganism revealed a stimulating effect of melamine at a concentration equivalent to the MPC; concentrations of 5 and 10 MPC inhibited the activity of dehydrogenases by 19.3% and 10.5%, respectively, indicating low toxicity. No toxic effects were observed on protococcal algae Chlorella vulgaris Beijer at any of the tested concentrations. The effect of melamine solutions on the mortality of crustaceans Daphnia magna Straus was noted only at a concentration of 10 MPC, and the mortality rate was 25%. Lemna growth inhibition test showed that melamine at concentrations equal to the MPC and 5 MPC had an inhibitory effect on the growth of Lemna minor L. It also caused a significant decrease (by 47–52%) in the total chlorophyll content in fronds when exposed to all studied concentrations of melamine.

Ecotoxicity and Essential Properties of Fine-Recycled Aggregate.

This article deals with the possibility of utilization of secondary-raw materials as a natural sand replacement in concrete. Four types of waste construction materials were examined—recycled aggregate from four different sources. The natural aggregate was examined as well as used as the reference sample. All the samples were tested to evaluate the water absorption, particle size distribution, and particle density. The basic chemical reactions in the view of ecotoxicology are investigated and measured based on Czech standards. Chemical analysis, Lemna growth inhibition test, freshwater algae, daphnia acute, and mustard germination toxicity test were made and discussed in this paper. Based on the physical and geometrical properties and ecotoxicology of examined waste materials, this work evaluated them as suitable for utilization in concrete as a sand replacement.

Evaluating the ecotoxicity of nitrification inhibitors using terrestrial and aquatic test organisms

BackgroundThe increasing demand for food and animal fodder worldwide has led to an intensified agriculture with an increasing use of nitrogen fertilizers. More recently, nitrate leaching and gaseous nitrogen emissions have become the focus of environmental discussions and climate politics. One approach to reduce such negative impacts is the use of nitrification inhibitors (NIs) that have shown to effectively reduce nitrogen losses to the groundwater and the air. However, ecotoxic effects of NIs have been studied to a limited extent only. Therefore, two commercial NIs (Piadin and Vizura) and an active ingredient of another NI, dicyandiamide (DCD), were assayed using various ecotoxicological biotests and test species: the Lemna Growth Inhibition Test (Lemna gibba), the Seed Germination/Root Elongation Toxicity Test (Agrostemma githago, Fagopyrum esculentum, Glycine max, Hordeum vulgare, Lunaria annua, Zea mays), the Seedling Emergence and Seedling Growth Test (A. githago, F. esculentum, Z. mays) and the marine Luminescent Bacteria Test (Aliivibrio fischeri). The fresh water L. gibba and the bacterium A. fischeri were exposed to different test concentrations in liquid growth media, whereas the terrestrial plants were exposed to the test substances diluted/dissolved in deionized water and added to the solid growth medium.ResultsDicyandiamide did not show ecotoxic effects in any test conducted. Piadin and Vizura showed ecotoxic effects throughout all experiments. Frond number and frond area of L. gibba were inhibited with increasing concentrations of both substances with Piadin leading to an earlier inhibition and therefore lower EC50 values. In the Seed Germination Test, Vizura generally inhibited seed germination and root development more effectively than Piadin. Regarding both substances, the endpoint root length was much more sensitive than the endpoint germination. In the Seedling Emergence Test, Z. mays was the least sensitive and the rare weed species A. githago the most sensitive species with regard to the tested endpoints and both substances. A. fischeri was strongly inhibited by Vizura, whereas Piadin had barely effects on the bacteria.ConclusionAll findings indicate ecotoxic effects of Piadin and Vizura, especially on the aquatic species L. gibba and on the root development of several terrestrial plant species. However, the origins of the ecotoxic properties remain unclear as both substances contain a mixture of—to some extent unknown—chemical compounds.

Potential toxic effects of aircraft de-icers and wastewater samples containing these compounds

One of the major problems of airport operation is the impact of pollution caused by runoff waters. Runoff waters at an airport may contain high concentrations of different contaminants resulting from various activities of its operation. High quantities of aircraft de-icing/anti-icing fluids are used annually at airports worldwide. Aircraft de-icers and anti-icers may have negative environmental impacts, but their effects on aquatic organisms are virtually unknown. In order to address this issue, aircraft de-icers, pavement de-icers and wastewater samples were obtained from a regional airport. To evaluate the toxicity of wastewater samples and aircraft de-icing/anti-icing fluids (ADAFs), two bio-tests were performed: the Lemna growth inhibition test according to OECD guideline 221 and the luminescent bacteria test according to ISO guideline 11348-2. In the Lemna growth inhibition test, phytotoxicity was assessed using the endpoints frond number and frond area. The luminescent bacteria test involved the marine bacterium Vibrio fischeri. The estimates of effective concentrations (EC50) values were determined using the free software R and the "drc" library. Aquatic plants and marine bacteria showed a higher sensitivity towards ADAFs than to wastewater samples. Experiments showed that aircraft de-icing/anti-icing fluids and wastewater samples were relatively more toxic towards Lemna gibba L. in comparison to V. fischeri.

Mechanistic TK/TD-model simulating the effect of growth inhibitors on Lemna populations

A mechanistic combined toxicokinetic–toxicodynamic (TK/TD) and growth model for the aquatic macrophytes Lemna spp. has been developed. This model simulates the development of Lemna biomass under laboratory and environmental conditions. Growth of the Lemna population is simulated on basis of photosynthesis and respiration rates which are functions of environmental conditions, i.e., temperature, global radiation, N- and P-concentrations. The toxicodynamic sub-model describes the effects of growth-inhibiting substances by a respective reduction in the photosynthesis rate based on the Lemna spp. internal concentrations. Internal concentrations are calculated using a simple, one-compartment toxicokinetic model that considers the uptake of substances through the plant surface.The growth model was parameterised based on literature data while toxicokinetic and toxicodynamic parameters were determined by calibrating the model using substance specific effect data. Both the growth model and the toxicokinetic model were independently tested by comparing model predictions to observed data.In an exemplary case study, the model was applied to a risk assessment for the sulfonyl urea herbicide metsulfuron-methyl. This assessment was carried out for two standard scenarios used in European regulatory risk assessments for pesticides. Thereby, it was shown that the effect of transient concentration peaks of metsulfuron-methyl on Lemna populations is much lower than estimated in a low tier assessment considering the maximum surface water concentration and the EC50 obtained from the standard Lemna growth inhibition test. The model also predicts moderate effects for longer lasting exposures resulting from calculated drainage entries into the water body if the majority of the entry occurs during the cold season with no or slow growth of the plants.

Growth inhibition of aquatic plant caused by silver and titanium oxide nanoparticles

Emerging nanomaterials are of great concern to aquatic environment. The inhibitory effects of silver nanoparticles (Ag-NP) and titanium oxide nanoparticles (TiO2-NP) on the growth of aquatic plant duckweed were evaluated. Lemna paucicostata was used as a test organism, and the test method was followed by the OECD test guideline 221. Ag-NP (50 nm) and TiO2-NP (2–3 nm) inhibited the growth of Lemna in different manner and the EC50s were calculated as 13.8 and 538.5 ppm, respectively. The LOECs of Ag-NP and TiO2-NP were calculated to be 1 and 125 ppm, respectively. The results showed that Ag-NP could cause growth inhibition of Lemna in low concentration range (≥1 ppm), but TiO2-NP appeared toxic effect to the growth of Lemna in the concentration range of ≥250 ppm, which was over two orders higher than the previously reported concentration of TiO2-NP determined in the aquatic environment.

Strong growth limitation of a floating plant (Lemna gibba) by the submerged macrophyte (Elodea nuttallii) under laboratory conditions

Summary1. The asymmetric competition for light and nutrients between floating and submerged aquatic plants is thought to be key in explaining why dominance by either of these groups can be stable and difficult to change.2. Although the shading effect of floating plants on submerged plants has been well documented, the impact of submerged plants on floating plants has been poorly explored hitherto.3. Here, we used laboratory experiments to examine how submerged plant (Elodea nuttallii) alter nutrient conditions in the water column and how this affects the growth of floating plants (Lemna gibba).4. We demonstrate that, at higher nutrient concentrations, Lemna is increasingly likely to outcompete Elodea.5. Under low nutrient concentrations (0.1–2 mg N L−1) Elodea can strongly reduce the growth of Lemna. Growth of floating plants virtually stopped in some of the experiments with Elodea.6. Extremely reduced tissue N, Mn, chlorophyll and elongated roots indicated that the growth inhibition of Lemna by Elodea was predominantly caused by the latter’s impact on the nutrient conditions for floating plants.7. These results strengthen the hypothesis that submerged plants can prevent colonization of a lake by floating plants.

Effects of phenanthrene on lemna minor in a sediment-water system and the impacts of UVB.

The objective of this study was to evaluate if the Lemna-bioassay is appropriate to test contaminated sediments. A mixture of sand was spiked with phenanthrene to investigate whether sediment-bound pollutants can affect the plants via direct contact of the roots or the underside of the leaves. After 24h of equilibration for sorption/desorption processes, the test was carried out in the sediment-water mixture, and another test was performed with the aqueous phase which was separated from the sediment. The growth inhibition of Lemna was nearly the same in both tests. Hence it follows that the toxicant is adsorbed from the aqueous phase via the underside of the leaves and sediment bound phenanthrene is not bioavailable. Polycyclic aromatic hydrocarbons are known to show photoinduced toxicity to plants in the presence of UV which is a result of photosensitization reactions in the plant and photomodification to more toxic and better soluble photoproducts. Photoinduced toxicity could be observed in the water phase during UVB treatment, whereas the presence of suspended sediment probably lowered the UV intensity, resulting in a lower growth inhibition.

Biodegradation in laboratory activated sludge plants and aquatic toxicity of herbicides

The biodegradation and the aquatic toxicity of four herbicides (isoproturon, terbuthylazine, mecoprop, metamitron) were investigated. Laboratory activated sludge plants were used for biodegradation experiments. The biodegradation of mecoprop reached nearly 100%, the other herbicides were not eliminated by biodegradation. The acute Daphnia magna 24-h assay, the algal 72-h inhibition test, and the recently developed lemna growth inhibition 7-d test were applied to evaluate the biological effects of herbicides as original substances. EC 50 and EC 10 values were determined. Algal and lemna test show that isoproturon and terbuthylazine are both much more toxic than mecoprop and metamitron. Daphnids are generally less sensitive against herbicides than plants. Biodegradation and toxicity test were coupled for mecoprop to assess biological long-term effects of possible biodegradation products of this herbicide. The effluents of the laboratory activated sludge units were used in toxicity tests ( Daphnia magna 21-d reproduction test, lemna growth inhibition 7-d test). No inhibiting effect on the tested organisms was observed.

Methionine Biosynthesis in Lemna: Inhibitor Studies

A search was made for compounds that would inhibit methionine biosynthesis in Lemna paucicostata Hegelm. 6746. dl-Propargylglycine (0.15 micromolar) produced growth inhibition and morphological changes which were prevented by exogenous methionine. Also, dl-propargylglycine inhibits cystathionine gamma-synthase activity. l-Aminoethoxyvinylglycine (0.05 micromolar) produced growth inhibition and morphological changes partially preventable by exogenous methionine. l-Aminoethoxyvinylglycine impairs the cleavage of cystathionine to homocysteine. Lysine and threonine, at concentrations which individually had little effect on growth or morphology of Lemna, together produced growth inhibition and morphological changes preventable by exogenous methionine. The resulting metabolic block prevented conversion of cysteine to cystathionine, presumably secondary to depletion of the supply of O-phosphohomoserine.Inhibition of Lemna growth resulted when the molybdate:sulfate ratio in the medium was increased to 20:1 or more. Such inhibition was prevented by lowering this ratio to 0.3 or less. A non-steady-state experiment (molybdate:sulfate, 20:1) showed that molybdate inhibited sulfate uptake, but it provided no evidence of a further impairment in the organification of sulfate. Molybdate-induced growth inhibition of Lemna was prevented by cystine but not by cystathionine or methionine. Cystathionine is not converted by Lemna to cysteine rapidly enough to sustain growth.