Biochemical Responses of Wheat Seedlings on the Introduction of Selected Chiral Ionic Liquids to the Soils

Ionic Liquids as Environmental Pollutants-Analysis of the Effect of Tetrabutylammonium Chloride on the Growth and Development of Wheat and Cucumber

Ionic liquids are a huge group of chemical compounds that have found, or may, in the future, find, applications in various industries. These compounds are characterized by excellent physical, chemical, and biological properties, but a big problem is their environmental impact. One of the representatives of this group of compounds is tetrabutylammonium chloride ([TBA][Cl]). In this present study, the effects of [TBA][Cl] were evaluated on two popular plant species-a monocotyledonous plant-wheat (Triticum aestivum L.) and a dicotyledonous plant-cucumber (Cucumis sativus L.). The results showed that the compound caused a pronounced inhibition of plant growth and roots, as well as plant fresh weight yield. An increase in plant dry weight was observed at the same time. Despite the decrease in the content of photosynthetic pigments, no major changes were observed in chlorophyll fluorescence. All observed changes were strongly related to the applied concentration of the compound.

Plant species compositions alleviate toxicological effects of bisphenol A by enhancing growth, antioxidant defense system, and detoxification

Bisphenol A (BPA), a broadly disseminated endocrine disturbing chemicals in environment, is harmful to creatures and plants. Plants can uptake and metabolize BPA, but a single plant species ability is limited. Undeniably, plant species compositions have a more vital ability to remove pollutants than a single plant species. However, the mechanisms of plant species compositions alleviating toxicological effects of bisphenol A are poorly understood. Here, we administered plant species compositions, which based on a full-factorial design of Phragmites australis (A), Typha latifolia (B), and Arundo donax (C), to unveil their role in BPA exposure. The results illustrated that the root activity, biomass, and photosynthetic pigment contents of the mixed hydroponic group (e.g., sp(ABC)) were significantly increased under concentration of BPA(1.5, 5, and 10 mg L^-1), which showed that the root activity, fresh weight, dry weight, chlorophyll a, and total chlorophyll contents of shoots were increased. While mixed-hydroponic culture groups (e.g., sp(AB), sp(ABC)) significantly increased antioxidant enzyme activity and antioxidant substances under concentration of BPA(5 and 10 mg L^-1), it astoundingly diminished responsive oxygen species (ROS) and malondialdehyde (MDA) substance, proposing that mixed-hydroponic culture groups calmed oxidative stress. Further analysis revealed that mixed-hydroponic culture groups (e.g., sp(AB), sp(AC), sp(ABC)) of 1.5, 5, and 10 mg L^-1 BPA exposure significantly increased detoxification enzyme activity of NADPH-cytochrome P450 reductase (CPR), glutathione S-transferase (GST), and glycosyltransferase (GT). Moreover, mixed-hydroponic culture groups (e.g., sp(AB), sp(AC), sp(ABC)) decreased the BPA substance in leaves, proposing that mixed-hydroponic culture groups advanced BPA metabolism by improving CPR, GST, and GT enzyme activities. These results demonstrated that a mixed-hydroponic culture strategy can alleviate BPA phytotoxicity and possibly offer natural and potential phytoremediation methods for BPA.

Molecular response mechanisms of silkworm (Bombyx mori L.) to the toxicity of 1-octyl-3-methylimidazole chloride based on transcriptome analysis of midguts and silk glands

In a previous study, silkworm larvae were used as a novel model to assess the biotoxicity of ILs, which showed that ILs could cause significant physiological and biochemical changes in midguts and silk glands of the larvae, and result in the death of larvae. In order to investigate the toxicity of 1-octyl-3-methylimidazole chloride ([C₈mim]Cl) to the larvae at molecular level, RNA-sequencing technology was used to construct transcriptomic profiles of midguts and silk glands in this work. Results showed that a lot of differentially expressed genes (DEGs) were effectively screened out through bioinformatics software based on the transcriptome data and reference genome. To give more detail, 5118 and 2211 DEGs (926 and 822 DEGs) were obtained in the midguts (silk glands) when the larvae were exposed to [C₈mim]Cl for 6 and 12 h, respectively, relative to the controls. In addition, gene ontology (GO) analysis suggested that the DEGs could be divided into three categories (i.e., biological process, cellular component, and molecular function), and were involved in multiple organelle functions and complex biological processes. Kyoto encyclopedia of genes and genomes (KEGG) analysis showed that the DEGs were enriched in a variety of pathways, such as signal transduction, apoptosis, glycolysis, peroxisome, autophagy, hippo signaling pathway, arginine and proline metabolism. Results of quantitative real-time PCR and histopathological observation indicated that molecular mechanism of the larvae against [C₈mim]Cl toxicology may be attributed to cell apoptosis regulation via both the mitochondrial pathway and the death receptor-initiated pathway. Thus, these results provided useful data for exploring the toxicity of ILs to insects at molecular level.

Effect of diclofenac and naproxen and their mixture on spring barley seedlings and Heterocypris incongruens

Nonsteroidal anti-inflammatory drugs (NSAIDs) are a popular group of drugs used worldwide. These drugs are also available over the counter, which implies that their consumption is not strictly regulated. They are released through wastewater and feces and can have adverse effects on the environment. The present study aimed to evaluate the effect of two NSAIDs, diclofenac (DCF) and naproxen (NAP), and their mixture (DCF + NAP) on spring barley seedlings and ostracods Heterocypris incongruens. The tested drugs had a negative impact on bivalve ostracods and the studied plants. DCF was the most toxic toward ostracods, while spring barley seedlings were affected the most by NAP. The application of the tested compounds and their mixture resulted in a decrease in fresh weight yield and the content of photosynthetic pigments. In addition, an increase in H₂O₂ and proline content and changes in the activity of antioxidant enzymes (POD, APX, CAT, and SOD) were observed.

Review of the toxic effects of ionic liquids

Interest in ionic liquids (ILs), called green or designer solvents, has been increasing because of their excellent properties such as thermal stability and low vapor pressure; thus, they can replace harmful organic chemicals and help several industrial fields e.g., energy-storage materials production and biomaterial pretreatment. However, the claim that ILs are green solvents should be carefully considered from an environmental perspective. ILs, given their minimal vapor pressure, may not directly cause atmospheric pollution. However, they have the potential to cause adverse effects if leaked into the environment, for instance if they are spilled due to human mistakes or technical errors. To estimate the risks of ILs, numerous ILs have had their toxicity assessed toward several micro- and macro-organisms over the past few decades. Since the toxic effects of ILs depend on the method of estimating toxicity, it is necessary to briefly summarize and comprehensively discuss the biological effects of ILs according to their structure and toxicity testing levels. This can help simplify our understanding of the toxicity of ILs. Therefore, in this review, we discuss the key findings of toxicological information of ILs, collect some toxicity data of ILs to different species, and explain the influence of IL structure on their toxic properties. In the discussion, we estimated two different sensitivity values of toxicity testing levels depending on the experiment condition, which are theoretical magnitudes of the inherent sensitivity of toxicity testing levels in various conditions and their changes in biological response according to the change in IL structure. Finally, some perspectives, future research directions, and limitations to toxicological research of ILs, presented so far, are discussed.

Phytotoxicity and Effect of Ionic Liquids on Antioxidant Parameters in Spring Barley Seedlings: The Impact of Exposure Time

The influence of the ionic liquids (ILs) tetrabutylammonium bromide [TBA][Br], 1-butyl-3-methylimidazole bromide [BMIM][Br], and tetrabutylphosphonium bromide [TBP][Br] added at different concentrations to the soil were studied for the growth and development of spring barley seedlings. Samples were harvested at three different time points: day 7, 14, and 21 after addition of ILs. The results show that [TBP][Br] was the most toxic. The introduction of this IL at the dose of 100 mg kg−1 of soil DM decreased the growth of seedlings at all test dates. The addition of the studied ILs to the soil in higher doses resulted in an increase in peroxidase and catalase activity, which may indicate the occurrence of oxidative stress in plants. An increase in the content of plant dry matter weight, contents of H2O2 and proline and a decrease in the content of photosynthetic pigments in barley seedlings were also observed. The malondialdehyde content and superoxide dismutase activity fluctuated randomly during the experiment. As a result, it was found that the phytotoxicity of ILs and the magnitude of oxidative stress in seedlings depended more on the added doses of these compounds than on the measurement date.

The reaction of cucumber to the introduction of ionic liquids into the soil

This paper presents the influence of two bromides, tetrabutylammonium and tetrabutylphosphonium, on the growth and development of cucumber seedlings. The tests were performed at two dates, i.e. 10 and 20 days, after the introduction of increasing amounts of ionic liquids (ILs) into the soil. The applied ILs showed phytotoxicity dependent mainly on the concentration of the substance, which is proved by the inhibition of the length of aboveground parts and their roots and the yield of cucumber fresh mass, from which EC50 values were calculated. The phytotoxicity symptoms were the result of oxidative stress, one of the manifestations of which was a decrease in assimilative pigments, linearly correlated with an increase in bromide concentration in the medium. The stress is also proven by the large increase in hydrogen peroxide, malondialdehyde and free proline in cucumber leaves. The reaction of this plant to oxidative stress was an increase in the activity of antioxidative enzymes such as catalase and peroxidase. As a result of statistical analysis, it was proved that all changes of biomarkers of phytotoxicity of examined ILs and oxidative stress indicators in cucumber seedlings depended more on the applied concentration of these salts than on the date of the study.

Effects of ketoprofen on rice seedlings: Insights from photosynthesis, antioxidative stress, gene expression patterns, and integrated biomarker response analysis

Pharmacologically active compounds found in reclaimed wastewater irrigation or animal manure fertilizers pose potential risks for agriculture. The mechanism underlying the effects of ketoprofen on rice (Oryza sativa L.) seedlings was investigated. The results showed that low concentrations (0.5 mg L^-1) of ketoprofen slightly stimulate growth of rice seedlings, while high concentrations can significantly inhibit growth by reducing biomass and causing damage to roots. Ketoprofen affects photosynthetic pigment content (Chla, Chlb, and carotenoids) and chlorophyll synthesis gene (HEMA, HEMG, CHLD, CHLG, CHLM, and CAO) expression. Fluorescence parameters such as minimum fluorescence (F₀), maximum fluorescence (F_m), variable fluorescence (F_v), potential photosynthetic capacity (F_v/F₀), maximum quantum efficiency of PSII photochemistry (F_v/F_m), electron transfer rate (ETR), and Y(II), Y(NPQ), Y(NO) values were affected, showing photosynthetic electron transfer was blocked. Active oxygen radical (O₂^•-and H₂O₂), malondialdehyde and proline content increased. Superoxide dismutase, catalase and ascorbate peroxidase activities, glutathione content and antioxidant-related gene (FSD1, MSD1, CSD1, CSD2, CAT1, CAT2, CAT3, APX1, APX2) expression were induced. Higher integrated biomarker response values of eight oxidative stress response indexes were obtained at higher ketoprofen concentrations. Ultrastructure observation showed that ketoprofen causes cell structure damage, chloroplast swelling, increase in starch granules, and reduction in organelles. This study provides some suggested toxicological mechanisms and biological response indicators in rice due to stress from pharmacologically active compounds.

Oxidative stress response and proteomic analysis reveal the mechanisms of toxicity of imidazolium-based ionic liquids against Arabidopsis thaliana

Ionic liquids (ILs) are extensively used in various fields, posing a potential threat in the ecosystem because of their high stability, excellent solubility, and biological toxicity. In this study, the toxicity mechanism of three ILs, 1-octyl-3-methylimidazolium chloride ([C₈MIM]Cl), 1-decyl-3-methylimidazolium chloride ([C₁₀MIM]Cl), and 1-dodecyl-3-methylimidazolium chloride ([C₁₂MIM]Cl) on Arabidopsis thaliana were revealed. Reactive oxygen species (ROS) level increased with higher concentration and longer carbon chain length of ILs, which led to the increase of malondialdehyde (MDA) content and antioxidase activity, including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX) and peroxidase (POD) activities. SOD, CAT, and GPX activities decreased in high ILs concentration due to the excessive ROS. Differentially expressed protein was analyzed based on Gene ontology (GO) and KEGG pathways analysis. 70, 45, 84 up-regulated proteins, and 72, 104, 79 down-regulated proteins were identified in [C₈MIM]Cl, [C₁₀MIM]Cl, and [C₁₂MIM]Cl treatment, respectively (fold change ≥ 1.5 with ≥95% confidence). Cellular aldehyde metabolic process, mitochondrial and mitochondrial respiratory chains, glutathione transferase and oxidoreductase activity were enriched as up-regulated proteins as the defense mechanism of A. thaliana to resist external stresses. Chloroplast, photosynthetic membrane and thylakoid, structural constituent of ribosome, and transmembrane transport were enriched as the down-regulated protein. Compared with the control, 8 and 14 KEGG pathways were identified forup-regulated and down-regulated proteins, respectively, in three IL treatments. Metabolic pathways, carbon metabolism, biosynthesis of amino acids, porphyrin and chlorophyll metabolism were significantly down-regulated. The GO terms annotation demonstrated the oxidative stress response and effects on photosynthesis of A. thaliana in ILs treatment from biological process, cellular component, and molecular function categories.

Transcriptomic analysis of the phytotoxic effects of 1-allyl-3-methylimidazolium chloride on the growth and plant hormone metabolic pathways of maize (Zea mays L.) seedlings

In this study, we investigated the phytotoxicity of an imidazolium-based ionic liquid, 1-allyl-3-methylimidazolium chloride ([Amim]Cl), against maize seedlings. It was found that in response to an increase in [Amim]Cl treatment concentrations, there were significant decreases in growth parameters (fresh weights and lengths) and the photosynthetic pigment contents of maize plants, whereas in contrast, the malondialdehyde content increased. In order to determine the molecular basis of [Amim]Cl-induced plant growth inhibition, an RNA-Seq analysis to examine the gene expression profiles of selected central biological pathways was performed. And a total of 4024 genes that were differentially expressed between control and 400 mg/L [Amim]Cl-treated plants were accordingly identified. Pathway enrichment analysis for the differentially expressed genes revealed that 12 of 15 genes in the porphyrin and chlorophyll metabolic pathways were down-regulated in response to [Amim]Cl treatment. Moreover, all six genes encoding key chlorophyll synthetic enzymes were down-regulated by [Amim]Cl. With regards to plant hormone metabolic pathways, the genes encoding key enzymes involved in ethybilene and abscisic acid (ABA) biosynthesis were up-regulated in response to [Amim]Cl treatment. Genes responsible for gibberellin (GA) inactivation were also stimulated by [Amim]Cl. These observations indicate that [Amim]Cl may promote the biosynthesis of senescence-related hormones (ethylene and ABA) as well as inactivation of growth-promoting hormones (GAs). It might be concluded that the observed [Amim]Cl-induced inhibition of maize seedling growth could be associated with changes in the gene expression profiles of these metabolic pathways.

Phytotoxicity of ionic liquids

Ionic liquids (ILs) have been one of the most interesting chemical entities over the last two decades and have been investigated by numerous scientists all over the world. However, during IL research, it has been shown that these compounds present toxicity to both terrestrial and aquatic plants, among others. The phytotoxicity of ILs depends on the type of cation, the length of the alkyl chain in the substituent or enantioselectivity, on the concentration used, and, it appears that the type of anion may also have an impact on toxicity. The toxic effects of ILs on plants also depend on the conditions under which such tests are conducted. The results may help facilitate the development of protective environmental measures against IL-induced negative effects, but they may also be used in various landscape-related areas, such as herbology, to design new substances with weed killing properties.

Protic Ionic Liquids as Efficient Solvents in Microwave-Assisted Extraction of Rhein and Emodin from Rheum palmatum L

Rheum palmatum L. (R. palmatum L.) is a traditional Chinese herb and food, in which rhein and emodin are the main bioactive components. The extraction of the two compounds from R. palmatum L. is, thus, of great importance. In this work, protic ionic liquids (PILs) were applied in the microwave-assisted extraction (MAE) of rhein and emodin from R. palmatum L., which avoids the toxicity of organic solvents. The results of the present study indicate that PILs possessing higher polarity exhibit higher extraction ability due to their stronger absorption ability for microwave irradiation. Compared with conventional solvents, such as methanol, trichloromethane, and deep eutectic solvents (DESs), the PIL, 1-butyl-3-himidazolium methanesulfonate ([BHim]MeSO3) reported herein is more efficient. The selected extraction conditions of liquid-solid ratio, microwave irradiation time, microwave irradiation power, and PIL concentration were 40 g·g-1, 50 s, 280 W, and 80%, respectively. Under the selected conditions, the extraction yields of rhein and emodin were 7.8 and 4.0 mg·g-1, respectively. These results suggest that PILs are efficient extraction solvents for the separation of active components from natural products.