Spatio-Temporal Study of Galactolipid Biosynthesis in Duckweed Using Mass Spectrometry Imaging and in vivo Isotope Labeling.

Isotope labeling coupled with mass spectrometry imaging (MSI) presents a potent strategy for elucidating the dynamics of metabolism at cellular resolution, yet its application to plant systems is scarce. It has the potential to reveal the spatio-temporal dynamics of lipid biosynthesis during plant development. In this study, we explore its application to galactolipid biosynthesis of an aquatic plant, Lemna minor, with D2O labeling. Specifically, matrix-assisted laser desorption/ionization-MSI data of two major galactolipids in L. minor, monogalactosyldiacylglycerol and digalactosyldiacylglycerol, were studied after growing in 50% D2O media over a 15-day time period. When they were partially labeled after 5 d, three distinct binomial isotopologue distributions were observed corresponding to the labeling of partial structural moieties: galactose only, galactose and a fatty acyl chain and the entire molecule. The temporal change in the relative abundance of these distributions follows the expected linear pathway of galactolipid biosynthesis. Notably, their mass spectrometry images revealed the localization of each isotopologue group to the old parent frond, the intermediate tissues and the newly grown daughter fronds. Besides, two additional labeling experiments, (i) 13CO2 labeling and (ii) backward labeling of completely 50% D2O-labeled L. minor in H2O media, confirm the observations in forward labeling. Furthermore, these experiments unveiled hidden isotopologue distributions indicative of membrane lipid restructuring. This study suggests the potential of isotope labeling using MSI to provide spatio-temporal details in lipid biosynthesis in plant development.

Characterization of the cryptic interspecific hybrid Lemna×mediterranea by an integrated approach provides new insights into duckweed diversity.

Lemnaceae taxonomy is challenged by the particular morphology of these tiny free-floating angiosperms. Although molecular taxonomy has helped clarify the phylogenetic history of this family, some inconsistency with morphological data leads to frequent misclassifications in the genus Lemna. Recently, the finding that Lemna japonica is an interspecific hybrid between Lemna minor and Lemna turionifera provided a clear explanation for one such taxonomic question. Here we demonstrated that L. minor is also capable of hybridizing with Lemna gibba, generating a cryptic but widespread taxon in the Mediterranean area. The nothotaxon Lemna ×mediterranea is described and compared with clones of the putative parental species L. minor and L. gibba. Genetic analysis by nuclear and plastid markers, as well as genome size measurement, revealed that two different cytotypes, diploid and triploid, originated by at least two independent hybridization events. Despite high overall similarity, morphometrical, physiological, and biochemical analyses showed an intermediate position of L. ×mediterranea between its parental species in most qualitative and quantitative characters, and also separation of the two hybrid cytotypes by some criteria. These data provide evidence that hybridization and polyploidization, driving forces of terrestrial plant evolution, contribute to duckweed genetic diversity and may have shaped the phylogenetic history of these mainly asexual, aquatic plants.

Engineering triacylglycerol accumulation in duckweed (Lemna japonica).

Duckweeds are amongst the fastest growing of higher plants, making them attractive high-biomass targets for biofuel feedstock production. Their fronds have high rates of fatty acid synthesis to meet the demand for new membranes, but triacylglycerols (TAG) only accumulate to very low levels. Here we report on the engineering of Lemna japonica for the synthesis and accumulation of TAG in its fronds. This was achieved by expression of an estradiol-inducible cyan fluorescent protein-Arabidopsis WRINKLED1 fusion protein (CFP-AtWRI1), strong constitutive expression of a mouse diacylglycerol:acyl-CoA acyltransferase2 (MmDGAT), and a sesame oleosin variant (SiOLE(*)). Individual expression of each gene increased TAG accumulation by 1- to 7-fold relative to controls, while expression of pairs of these genes increased TAG by 7- to 45-fold. In uninduced transgenics containing all three genes, TAG accumulation increased by 45-fold to 3.6% of dry weight (DW) without severely impacting growth, and by 108-fold to 8.7% of DW after incubation on medium containing 100 µm estradiol for 4 days. TAG accumulation was accompanied by an increase in total fatty acids of up to three-fold to approximately 15% of DW. Lipid droplets from fronds of all transgenic lines were visible by confocal microscopy of BODIPY-stained fronds. At a conservative 12 tonnes (dry matter) per acre and 10% (DW) TAG, duckweed could produce 350 gallons of oil/acre/year, approximately seven-fold the yield of soybean, and similar to that of oil palm. These findings provide the foundation for optimizing TAG accumulation in duckweed and present a new opportunity for producing biofuels and lipidic bioproducts.

DNA methylation in clonal duckweed (Lemna minor L.) lineages reflects current and historical environmental exposures.

Environmentally induced DNA methylation variants may mediate gene expression responses to environmental changes. If such induced variants are transgenerationally stable, there is potential for expression responses to persist over multiple generations. Our current knowledge in plants, however, is almost exclusively based on studies conducted in sexually reproducing species where the majority of DNA methylation changes are subject to resetting in germlines, limiting the potential for transgenerational epigenetics stress memory. Asexual reproduction circumvents germlines, and may therefore be more conducive to long-term inheritance of epigenetic marks. Taking advantage of the rapid clonal reproduction of the common duckweed Lemna minor, we hypothesize that long-term, transgenerational stress memory from exposure to high temperature can be detected in DNA methylation profiles. Using a reduced representation bisulphite sequencing approach (epiGBS), we show that temperature stress induces DNA hypermethylation at many CG and CHG cytosine contexts but not CHH. Additionally, differential methylation in CHG context that was observed was still detected in a subset of cytosines, even after 3-12 generations of culturing in a common environment. This demonstrates a memory effect of stress reflected in the methylome and that persists over multiple clonal generations. Structural annotation revealed that this memory effect in CHG methylation was enriched in transposable elements. The observed epigenetic stress memory is probably caused by stable transgenerational persistence of temperature-induced DNA methylation variants across clonal generations. To the extent that such epigenetic memory has functional consequences for gene expression and phenotypes, this result suggests potential for long-term modulation of stress responses in asexual plants.

Physical and chemical effects of conventional microplastic glitter versus alternative glitter particles on a freshwater plant (Lemnaceae: Lemna minor).

Glitters are primary microplastics which are directly littered into the environment, yet the ecological effects have seldom been tested. When microplastics enter the environment, their physical presence and chemical leachate may alter the physiology of primary producers. Glitter can be composed of plastic or natural and/or biodegradable materials, often with additives. Three experiments were run for 14 days to separate chemical and physical effects of different types of glitter: polyethylene terephthalate (PET), biodegradable modified regenerated cellulose (MRC), synthetic mica, and a natural particle control (kaolinite) on several physical characteristics of Lemna minor (common duckweed). L. minor was exposed to either fresh (chemical and physical effects), leachate from glitter (chemical) or aged glitter (physical). Overall, there was little effect of PET, synthetic mica, kaolinite or of any aged glitter. High concentrations of fresh MRC glitters, however, decreased root length, biomass and chlorophyll content of L. minor. Some of these effects were also present when exposed to leachate from MRC glitters, but were less pronounced. Elemental analysis revealed the presence of metals in MRC glitters which may explain these responses. Short-term ecotoxicity of biodegradable glitters can arise due to their physical and chemical properties, but may lessen over time as their surface coating degrades.

Rate enhancement of plant growth using Ormus solution: optimization of operating factors by response surface methodology.

Phytoremediation is an economical technique for the biological treatment of soil and water contamination. Improving the growth of plants used in this technique leads to greater efficiency of the process. Herein, Lemna minor plant used in phytoremediation was collected from Sarab-e Nilufar region of Kermanshah province, Iran, and maintained in a culture medium. This study focused on the preparation of Ormus solution based on crystalline salt extracted from the salt mountains of Karmowstaj region in Fars province, Iran, to increase the proliferation of Lemna minor. The optimal growth conditions, including the pH of the medium, the residence time in the Ormus preparation process, and the concentration of Ormus solution were analyzed using the response surface methodology (RSM) based on a Box-Behnken design (BBD) model. Numerical optimization based on the quadratic model was carried out to achieve the maximum growth percentage. The percentage of the proliferation of Lemna minor varied from 34.6% to 117.3%, while growth was highest at a medium pH value of 10.75, a residence time of 72 h in the Ormus preparation process, and an Ormus concentration of 17 g.L-1. The results revealed that Ormus, as a supplemental fertilizer, under optimal conditions can significantly increase the rate of plant reproduction.

Herein, the Ormus solution was applied for the first time to increase plant growth. In addition, the operating factors, including the pH of the medium, the residence time in the Ormus preparation process, and the concentration of Ormus solution, were optimized using the RSM based on a BBD model. In this study, Ormus was introduced under optimal conditions as a suitable additive to increase the proliferation rate of plants.

Ecotoxicity of Diazinon and Atrazine Mixtures after Ozonation Catalyzed by Na+ and Fe2+ Exchanged Montmorillonites on Lemna minor.

The toxicity of two pesticides, diazinon (DAZ) and atrazine (ATR), before and after montmorillonite-catalyzed ozonation was comparatively investigated on the duckweed Lemna minor. The results allowed demonstrating the role of clay-containing media in the evolution in time of pesticide negative impact on L. minor plants. Pesticides conversion exceeded 94% after 30 min of ozonation in the presence of both Na+ and Fe2+ exchanged montmorillonites. Toxicity testing using L. minor permitted us to evaluate the change in pesticide ecotoxicity. The plant growth inhibition involved excessive oxidative stress depending on the pesticide concentration, molecular structure, and degradation degree. Pesticide adsorption and/or conversion by ozonation on clay surfaces significantly reduced the toxicity towards L. minor plants, more particularly in the presence of Fe(II)-exchanged montmorillonite. The results showed a strong correlation between the pesticide toxicity towards L. minor and the level of reactive oxygen species, which was found to depend on the catalytic activity of the clay minerals, pesticide exposure time to ozone, and formation of harmful derivatives. These findings open promising prospects for developing a method to monitor pesticide ecotoxicity according to clay-containing host-media and exposure time to ambient factors.

An endogenous basis for synchronisation characteristics of the circadian rhythm in proliferating Lemna minor plants.

The circadian clock is a cell-autonomous system that functions through the coordination of time information in the plant body. Synchronisation of cellular clocks is based on coordination mechanisms; the synchronisation characteristics of proliferating plants remain unclear. The bioluminescence circadian rhythms of fronds (leaf-like plant units) of proliferating Lemna minor plants carrying a circadian bioluminescence reporter, AtCCA1:LUC, were spatiotemporally analysed at a cell-level resolution. We focused on spontaneous circadian organisation under constant light conditions for plants with light : dark treatment (LD grown) or without it (LL grown). Fronds developing even from an LL-grown parental frond showed coherent circadian rhythms among them. This allowed the maintenance of circadian rhythmicity in proliferating plants. Inside a frond, a centrifugal phase/period pattern was observed in LD-grown plants, whereas various phase patterns with travelling waves were formed in LL-grown plants. These patterns were model simulated by local coupling of heterogeneous cellular circadian oscillators with different initial synchronous states in fronds. Spatiotemporal analysis of the circadian rhythms in proliferating plants reveals spontaneous synchronisation manners that are associated with local cell-cell coupling, spatial phase patterns and developmental stages.

Short-Term Test for Toxicogenomic Analysis of Ecotoxic Modes of Action in Lemna minor.

In the environmental risk assessment of substances, toxicity to aquatic plants is evaluated using, among other methods, the 7 dayLemna sp. growth inhibition test following the OECD TG 221. So far, the test is not applicable for short-term screening of toxicity, nor does it allow evaluation of toxic modes of action (MoA). The latter is also complicated by the lack of knowledge of gene functions in the test species. Using ecotoxicogenomics, we developed a time-shortened 3 day assay inLemna minor which allows discrimination of ecotoxic MoA. By examining the changes in gene expression induced by low effect concentrations of the pharmaceutical atorvastatin and the herbicide bentazon at the transcriptome and proteome levels, we were able to identify candidate biomarkers for the respective MoA. We developed a homology-based functional annotation pipeline for the reference genome ofL. minor, which allowed overrepresentation analysis of the gene ontologies affected by both test compounds. Genes affected by atorvastatin mainly influenced lipid synthesis and metabolism, whereas the bentazon-responsive genes were mainly involved in light response. Our approach is therefore less time-consuming but sensitive and allows assessment of MoA in L. minor. Using this shortened assay, investigation of expression changes of the identified candidate biomarkers may allow the development of MoA-specific screening approaches in the future.

Assessment of the Effects of Chitosan, Chitooligosaccharides and Their Derivatives on Lemna minor.

Chitosan, chitooligosaccharides and their derivatives' production and use in many fields may result in their release to the environment, possibly affecting aquatic organisms. Both an experimental and a computational approach were considered for evaluating the effects of these compounds on Lemna minor. Based on the determined EC50 values against L. minor, only D-glucosamine hydrochloride (EC50 = 11.55 mg/L) was considered as "slightly toxic" for aquatic environments, while all the other investigated compounds, having EC50 > 100 mg/L, were considered as "practically non-toxic". The results obtained in the experimental approach were in good agreement with the predictions obtained using the admetSAR2.0 computational tool, revealing that the investigated compounds were not considered toxic for crustacean, fish and Tetrahymena pyriformis aquatic microorganisms. The ADMETLab2.0 computational tool predicted the values of IGC50 for Tetrahymena pyriformis and the LC50 for fathead minnow and Daphnia magna, with the lowest values of these parameters being revealed by totally acetylated chitooligosaccharides in correlation with their lowest solubility. The effects of the chitooligosaccharides and chitosan on L. minor decreased with increased molecular weight, increased with the degree of deacetylation and were reliant on acetylation patterns. Furthermore, the solubility mainly influenced the effects on the aqueous environment, with a higher solubility conducted to lower toxicity.

Clay-Catalyzed Ozonation of Organic Pollutants in Water and Toxicity on Lemna minor: Effects of Molecular Structure and Interactions.

The use of clays as adsorbents and catalysts in the ozonation of organic pollutants (Atrazine, bis-Phenol A, Diazinon, and Diclofenac sodium) allowed simulating their natural oxidative degradation in clay soils and to evaluate the ecotoxicity of mixtures partially oxidized on the species Lemna minor, a biodiversity representative of plants in the aquatic environment. Kinetic data showed that the adsorption of organic pollutants on clay particles obeys the pseudo-second-order model, while the adsorption isotherms satisfactorily fit the Langmuir model. Adsorption reduces the dispersion of the organic pollutant in the environment and prolongs its persistence and its natural degradation probability. Measurements of the Zeta potential and particle size as a function of pH demonstrate that the catalytic activity of clay depends on its cation, its silica/alumina ratio, and therefore on its permanent and temporary ion exchange capacities. These factors seem to govern its delamination and dispersion in aqueous media, its hydrophilic-hydrophobic character, and its porosity. Tests conducted on Lemna minor in contact with ozonation mixtures revealed that the toxicity could be due to pH decrease and to the toxicity of the intermediates yielded. Ecotoxicity would depend on the structure of the organic molecules, the chemical composition of the clay surface and ozonation time, which determines the oxidation progress. These results are of great importance for further research because they allow concluding that the negative impact of the persistence of an organic molecule in clay-containing media depends on the type and composition of the very clay mineral.

Potential of Lemna minor and Eichhornia crassipes for the phytoremediation of water contaminated with Nickel (II).

Phytoextraction of Nickel (II) in water by two types of aquatic macrophytes (Lemna minor and Eichhornia crassipes) was investigated using synthetic aqueous solutions of NiSO4 at concentrations of 0.5, 1.5 and 2.5 mg/L. The toxic effects of nickel salt in plants were evaluated through the presence of necrosis and chlorosis. The bioconcentration factor, Nickel (II) removal efficiency and kinetics of removal were also calculated. Results of this study show bioconcentration factors higher than 1000, which categorize L. minor and E. crassipes as hyperaccumulators. Besides, L. minor presented a removal percentage higher than 68%, compared to E. crassipes that did not exceed 50% in any of the three concentrations studied. However, E. crassipes showed better resistance to the effects of nickel and obtained a greater removal capacity during the phytoremediation process that lasted for 10 days. In contrast, L. minor suffered necrosis and chlorosis in a concentration-dependent way. Consequently, both macrophytes are sustainable alternatives for nickel removal from contaminated water.

Duckweed Potential for the Phytoremediation of Linear Alkylbenzene Sulfonate (LAS): Identification of Some Intermediate Biodegradation Products and Evaluation of Antioxidant System.

Duckweed (Lemna minor L.) has a high potential for wastewater treatment. Here, its capability for bioremoval of linear alkylbenzene sulfonate (LAS) as one of the primary contaminants of water resources was evaluated. The effect of some operational parameters on surfactant removal efficiency was determined. Also, the impact of LAS on several physiological responses of Lemna was investigated. LAS remediation efficiency of L. minor was elevated with increasing LAS concentration, duckweed weight, and temperature. Furthermore, the optimal pH for removal was 7-8.5. The benzenesulfonate ring and five homologs of sulfophenyl carboxylate were identified as intermediates in the LAS degradation pathway. A decrease in relative growth rate and pigment contents was observed by increasing LAS concentration. In contrast, an increase in hydrogen peroxide content and electrolyte leakage indicated oxidative stress by LAS. Induction of enzymatic/non-enzymatic antioxidants was observed during the surfactant remediation process, indicating their role in overcoming free radicals generated under surfactant stress.

Detection of Uncoupled Circadian Rhythms in Individual Cells of Lemna minor using a Dual-Color Bioluminescence Monitoring System.

The plant circadian oscillation system is based on the circadian clock of individual cells. Circadian behavior of cells has been observed by monitoring the circadian reporter activity, such as bioluminescence of AtCCA1::LUC+. To deeply analyze different circadian behaviors in individual cells, we developed the dual-color bioluminescence monitoring system that automatically measured the luminescence of two luciferase reporters simultaneously at a single-cell level. We selected a yellow-green-emitting firefly luciferase (LUC+) and a red-emitting luciferase (PtRLUC) that is a mutant form of Brazilian click beetle ELUC. We used AtCCA1::LUC+ and CaMV35S::PtRLUC. CaMV35S::LUC+ was previously reported as a circadian reporter with a low-amplitude rhythm. These bioluminescent reporters were introduced into the cells of a duckweed, Lemna minor, by particle bombardment. Time series of the bioluminescence of individual cells in a frond were obtained using a dual-color bioluminescence monitoring system with a green-pass- and red-pass filter. Luminescence intensities from the LUC+ and PtRLUC of each cell were calculated from the filtered luminescence intensities. We succeeded in reconstructing the bioluminescence behaviors of AtCCA1::LUC+ and CaMV35S::PtRLUC in the same cells. Under prolonged constant light conditions, AtCCA1::LUC+ showed a robust circadian rhythm in individual cells in an asynchronous state in the frond, as previously reported. By contrast, CaMV35S::PtRLUC stochastically showed circadian rhythms in a synchronous state. These results strongly suggested the uncoupling of cellular behavior between these circadian reporters. This dual-color bioluminescence monitoring system is a powerful tool to analyze various stochastic phenomena accompanying large cell-to-cell variation in gene expression.

Flowering and Seed Production across the Lemnaceae.

Plants in the family Lemnaceae are aquatic monocots and the smallest, simplest, and fastest growing angiosperms. Their small size, the smallest family member is 0.5 mm and the largest is 2.0 cm, as well as their diverse morphologies make these plants ideal for laboratory studies. Their rapid growth rate is partially due to the family's neotenous lifestyle, where instead of maturing and producing flowers, the plants remain in a juvenile state and continuously bud asexually. Maturation and flowering in the wild are rare in most family members. To promote further research on these unique plants, we have optimized laboratory flowering protocols for 3 of the 5 genera: Spirodela; Lemna; and Wolffia in the Lemnaceae. Duckweeds were widely used in the past for research on flowering, hormone and amino acid biosynthesis, the photosynthetic apparatus, and phytoremediation due to their aqueous lifestyle and ease of aseptic culture. There is a recent renaissance in interest in growing these plants as non-lignified biomass sources for fuel production, and as a resource-efficient complete protein source. The genome sequences of several Lemnaceae family members have become available, providing a foundation for genetic improvement of these plants as crops. The protocols for maximizing flowering described herein are based on screens testing daylength, a variety of media, supplementation with salicylic acid or ethylenediamine-N,N'-bis(2-hydroxyphenylacetic acid) (EDDHA), as well as various culture vessels for effects on flowering of verified Lemnaceae strains available from the Rutgers Duckweed Stock Cooperative.

Effects of environmental parameters on Lemna minor growth: An integrated experimental and modelling approach.

Pollution of surface waters is a worldwide problem for people and wildlife. Remediation and phytoremediation approaches can offer a solution to deal with specific scenarios. Lemna minor, commonly known as duckweed, can absorb and accumulate pollutants in its biomass. To evaluate if L. minor could be applied for phytoremediation purposes, it is necessary to further investigate its remediation capability and to identify which parameters affect the remediation process. Such a model must include both plant growth and pollutant exchange. A remediation model based on a robust experimental study can help to evaluate L. minor as a proper remediation strategy and to predict the outcome of a L. minor based remediation system. To set up this model, this paper focusses on a detailed experimental study and a comprehensive mathematical modelling approach to represent L. minor growth as a function of biomass, temperature, light irradiation and variable nutrient concentrations. The influence of environmental conditions on L. minor growth was studied, by composing 7 days growth curves. Plants were grown under predefined environmental conditions (25°C, 14h photoperiod, 220 µmol m-2 s-1 light intensity and a modified Hoagland solution with 23.94 mg N L-1 and 3.10 mg P L-1 (N:P ratio of 7.73)) as standard for all experiments. The influence of different temperatures (6, 10, 15, 20, 25, 30 and 35°C), light intensities (63, 118, 170, 220 and 262 µmol m-2 s-1), photoperiods (12h and 14h) and N:P ratios (1.18, 3.36, 7.73 and 29.57) were tested in the model. As a result, a growth model was optimised using separate datasets for temperature, light intensity, photoperiod and nutrients and validated by further integrated testing. The growth model is a stable platform for application in phytoremediation of radionuclides in contaminated water, to be extended in future studies with information of pollutant uptake, pollutant-nutrient interactions and transfer to the biomass.

Resilience to multiple stressors in an aquatic plant and its microbiome.

PREMISE: Outcomes of species interactions, especially mutualisms, are notoriously dependent on environmental context, and environments are changing rapidly. Studies have investigated how mutualisms respond to or ameliorate anthropogenic environmental changes, but most have focused on nutrient pollution or climate change and tested stressors one at a time. Relatively little is known about how mutualisms may be altered by or buffer the effects of multiple chemical contaminants, which differ fundamentally from nutrient or climate stressors and are especially widespread in aquatic habitats. METHODS: We investigated the impacts of two contaminants on interactions between the duckweed Lemna minor and its microbiome. Sodium chloride (salt) and benzotriazole (a corrosion inhibitor) often co-occur in runoff to water bodies where duckweeds reside. We tested three L. minor genotypes with and without the culturable portion of their microbiome across field-realistic gradients of salt (3 levels) and benzotriazole (4 levels) in a fully factorial experiment (24 treatments, tested on each genotype) and measured plant and microbial growth. RESULTS: Stressors had conditional effects. Salt decreased both plant and microbial growth and decreased plant survival more as benzotriazole concentrations increased. In contrast, benzotriazole did not affect microbial abundance and even benefited plants when salt and microbes were absent, perhaps due to biotransformation into growth-promoting compounds. Microbes did not ameliorate duckweed stressors; microbial inoculation increased plant growth, but not at high salt concentrations. CONCLUSIONS: Our results suggest that multiple stressors matter when predicting responses of mutualisms to global change and that beneficial microbes may not always buffer hosts against stress.

Growth inhibition and recovery patterns of common duckweed Lemna minor L. after repeated exposure to isoproturon.

Aquatic non-targeted organisms are more likely to be exposed to herbicides in multiple pulse events then long continuous exposure. The potential of an organism to recover between exposures has an important role in the overall effects of the toxicant. Common duckweeds show high potential for recovery after a single exposure to isoproturon. To evaluate the growth patterns and recovery potential between multiple exposures, L. minor plants were exposed to isoproturon in three repetitive 7-day treatment cycles in three time-variable exposure scenarios with equivalent time-weighted average concentrations. The growth was significantly inhibited during each exposure phase with significant cumulative effects in every subsequent treatment cycle resulting in a cumulative decrease in biomass production. However, inhibitory effects were reversible upon transferring plants to a herbicide-free nutrient solution. These results indicate that L. minor plants have a high recovery potential even after multiple exposures to isoproturon. Observed cumulative decrease in biomass production, as well as the potential for fast and efficient recovery from repeated herbicide exposure, might affect the competitiveness of L. minor in surface water communities. The observations made during each exposure period, recovery patterns, and the resulting cumulative effects over time may contribute to further development, calibration and validation of mechanistic toxicokinetic/toxicodynamic models for simulating the effects of pesticides on aquatic plants populations in the laboratory and environmental conditions.

Growth and digestive enzyme activities of rohu labeo rohita fed diets containing macrophytes and almond oil-cake.

The impact of plant-based diets on the digestive physiology of rohu Labeo rohita fingerlings (10.66 ±â€¯0.53 g) was evaluated. A diet with all protein supplied by fishmeal was included as a control (F). Four test diets containing 300 g/kg protein were formulated using the following plant ingredients and fishmeal in a 1:1 blend: almond oil-cake Terminalia catappa (FTC), duckweed Lemna minor (FLM), water fern Salvania molesta (FSM) and combination of these three ingredients (FTCLMSM). The final body weight and specific growth rate were significantly higher in rohu fed diet FLM compared to the other treatments. Significantly lower feed conversion ratio in rohu fed diet FLM showed that diet was utilized efficiently in this feeding regime compared to the other diets. The composition of diets also influenced the digestive enzyme activities of the fish. Thus, amylase, trypsin and chymotrypsin activities were significantly higher in rohu fed diet FLM compared to the rohu fed the other diets. Protease activity was significantly higher in rohu fed diets FTC and F and lipase activity was significantly higher in rohu fed diet FTC compared to the rohu fed the other diets. The inclusion of raw duckweed in feed replaced 300 g/kg of dietary fishmeal without affecting growth.

Effect of Gold Nanoparticles and Ions Exposure on the Aquatic Organisms.

An increase in the production and usage of gold nanoparticles (AuNPs) triggers the necessity to focus on their impact on ecosystems. Therefore, the purpose of this study was to investigate the acute toxicity of AuNPs and ionic gold (Au (III)) to organisms representing all trophic levels of the aquatic ecosystem, namely producers (duckweed Lemna minor), consumers (crustacean Daphnia magna, embryos of Danio rerio) and decomposers (bacteria Vibrio fischeri). The organisms were exposed according to a standardized protocol for each species and endpoints. The AuNPs (1.16 and 11.6 d.nm) were synthesized using citrate (CIT) and polyvinylpyrrolidone (PVP) as capping agents, respectively. It was found, that Au (III) was significantly more toxic than AuNPs PVP and AuNPs CIT. AuNPs showed significant toxicity only at high concentrations (mg/L), which are not environmentally relevant in the present time, but a cautious approach is advised, due to the possibility of interactions with other contaminants.