Characterization of copper speciation on waste biomass of phytofiltration systems using energy dispersive Inelastic X-ray scattering.

BACKGROUND: Remediation of heavy metal-contaminated water using phytoremediation with accumulator aquatic plants is a promising low-cost emerging technology that adapts very well to the surrounding ecosystem. For the system to work efficiently, metal-saturated plants must be replaced, producing a potentially toxic amount of biomass that is usually stored dry to reduce its volume. The speciation of the high metal content in this biomass is crucial to define its final destination. This work explores the application of synchrotron-based EDIXS (Energy Dispersive Inelastic X-ray Scattering) to monitor the speciation of copper in regional aquatic plants from a laboratory-scale phytoremediation system. RESULTS: The phytofiltration system utilized Lemna minor L. and Salvinia biloba Raddi species grown under controlled conditions of light and nutrient availability. Both species are known hyperaccumulators of copper and are prevalent in lakes and rivers across South America. The validation of EDIXS was previously carried out by comparing the results of copper standard samples with those obtained by XANES. The findings revealed that both plant species retained copper in chemical complexes exhibiting octahedral coordination with a Cu valence of 2. Notably, differences emerged between the leaves and roots of Lemna minor L., suggesting a more pronounced adsorption of copper in its leaves, a trend that intensified with exposure. In opposite, for Salvinia the differences between leaves and roots suggests the presence of specific protective mechanisms to cope the copper exposure. Surprisingly, no significant dependence on copper concentration of the aqueous media was observed for either species. SIGNIFICANCE AND NOVELTY: These promising results endorse the viability of the proposed methodology in identifying the most effective fate of biomass generated in phytoremediation systems. EDIXS provides a valid tool for performing local copper speciation in aquatic plants with sufficient selectivity to identify subtle differences in various biological tissues. The simplicity of this methodology renders it a valuable tool for advancing our comprehension of metal speciation within waste biomass, thereby holding significant implications for the development of environmental remediation strategies.

Genetic Evidence of SpGH9A3 in Leaf Morphology Variation of Spathiphyllum 'Mojo'.

Leaves play a crucial role as ornamental organs in Spathiphyllum, exhibiting distinct differences across various Spathiphyllum varieties. Leaf development is intricately linked to processes of cell proliferation and expansion, with cell morphology often regulated by plant cell walls, primarily composed of cellulose. Alterations in cellulose content can impact cell morphology, subsequently influencing the overall shape of plant organs. Although cellulases have been shown to affect cellulose levels in plant cells, genetic evidence linking them to the regulation of leaf shape remains limited. This study took the leaves of Spathiphyllum 'Mojo' and its somatic variants as the research objects. We screened four cellulase gene family members from the transcriptome and then measured the leaf cellulose content, cellulase activity, and expression levels of cellulase-related genes. Correlation analysis pinpointed the gene SpGH9A3 as closely associated with leaf shape variations in the mutant. Green fluorescent fusion protein assays revealed that the SpGH9A3 protein was localized to the cell membrane. Notably, the expression of the SpGH9A3 gene in mutant leaves peaked during the early spread stage, resulting in smaller overall leaf size and reduced cellulose content upon overexpression in Arabidopsis.

Utilizing Morphological and Physiological Parameters of Lemna minor for Assessing Tetracyclines' Removal.

Antibiotics with significant environmental toxicity, e.g., tetracyclines (TCs), are often used in large quantities worldwide, with 50-80% of the applied dose ending up in the environment. This study aimed to investigate the effects of exposure to tetracycline hydrochloride (TC) and minocycline hydrochloride (MIN) on L. minor. Our research evaluated the phytotoxicity of the TCs by analyzing plant growth and biomass and evaluating assimilation pigment levels and fluorescence. The research was extended with the ability potential of duckweed as a tool for removing TCs from water/wastewater. The results demonstrated that both TCs influenced Ir, Iy, biomass, and photosynthetic efficiency. The uptake of TC and MIN by duckweed was proportional to the concentration in the growth medium. The TC was absorbed more readily, reaching up to 8.09 mg × g-1 of dry weight (DW) at the highest concentration (19.2 mg × L-1), while MIN reached 6.01 mg × g-1 of DW. As indicated, the consequences of the influence of TC on plants were slightly smaller, in comparison to MIN, while the plants could biosorb this drug, even at the lowest tested concentration. This study has shown that using plants for drug biosorption can be an effective standalone or complementary method for water and wastewater treatment.

The immediate metabolomic effects of whole-genome duplication in the greater duckweed, Spirodela polyrhiza.

PREMISE: In plants, whole-genome duplication (WGD) is a common mutation with profound evolutionary potential. Given the costs associated with a superfluous genome copy, polyploid establishment is enigmatic. However, in the right environment, immediate phenotypic changes following WGD can facilitate establishment. Metabolite abundances are the direct output of the cell's regulatory network and determine much of the impact of environmental and genetic change on the phenotype. While it is well known that an increase in the bulk amount of genetic material can increase cell size, the impact of gene dosage multiplication on the metabolome remains largely unknown. METHODS: We used untargeted metabolomics on four genetically distinct diploid-neoautotetraploid pairs of the greater duckweed, Spirodela polyrhiza, to investigate how WGD affects metabolite abundances per cell and per biomass. RESULTS: Autopolyploidy increased metabolite levels per cell, but the response of individual metabolites varied considerably. However, the impact on metabolite level per biomass was restricted because the increased cell size reduced the metabolite concentration per cell. Nevertheless, we detected both quantitative and qualitative effects of WGD on the metabolome. Many effects were strain-specific, but some were shared by all four strains. CONCLUSIONS: The nature and impact of metabolic changes after WGD depended strongly on the genotype. Dosage effects have the potential to alter the plant metabolome qualitatively and quantitatively, but were largely balanced out by the reduction in metabolite concentration due to an increase in cell size in this species.

Streamlined spatial and environmental expression signatures characterize the minimalist duckweed Wolffia australiana.

Single-cell genomics permits a new resolution in the examination of molecular and cellular dynamics, allowing global, parallel assessments of cell types and cellular behaviors through development and in response to environmental circumstances, such as interaction with water and the light-dark cycle of the Earth. Here, we leverage the smallest, and possibly most structurally reduced, plant, the semiaquatic Wolffia australiana, to understand dynamics of cell expression in these contexts at the whole-plant level. We examined single-cell-resolution RNA-sequencing data and found Wolffia cells divide into four principal clusters representing the above- and below-water-situated parenchyma and epidermis. Although these tissues share transcriptomic similarity with model plants, they display distinct adaptations that Wolffia has made for the aquatic environment. Within this broad classification, discrete subspecializations are evident, with select cells showing unique transcriptomic signatures associated with developmental maturation and specialized physiologies. Assessing this simplified biological system temporally at two key time-of-day (TOD) transitions, we identify additional TOD-responsive genes previously overlooked in whole-plant transcriptomic approaches and demonstrate that the core circadian clock machinery and its downstream responses can vary in cell-specific manners, even in this simplified system. Distinctions between cell types and their responses to submergence and/or TOD are driven by expression changes of unexpectedly few genes, characterizing Wolffia as a highly streamlined organism with the majority of genes dedicated to fundamental cellular processes. Wolffia provides a unique opportunity to apply reductionist biology to elucidate signaling functions at the organismal level, for which this work provides a powerful resource.

Influence of humic acid on the p-tert-Butylphenol removal efficiency by Spirodela polyrhiza-Tas13 association.

Plant-microbe remediation technique is considered as a promising technology in removal of organic pollutants and its remediation efficiency is largely affected by a variety of surrounding environmental factors. Humic acid (HA) is the complex organic substance ubiquitous in environment, which characterized by its surfactant-like micelle microstructure and various reaction activity. In our study, a plant-microbe association with high p-tert-Butylphenol (PTBP) degradation potential constructed by Spirodela polyrhiza and Sphingobium phenoxybenzoativorans Tas13 has been used, and the influence of HA on the PTBP degradation efficiency of S. polyrhiza-Tas13 association was investigated. The result showed that the presence of HA greatly improved PTBP removal efficiency of S. polyrhiza-Tas13. The reason accounted for this may be due to the presence of HA promoted bacterial cell propagation, altered bacterial cell wall permeability, increased catechol 2,3-dioxygenase (C23O) enzyme activity of strain Tas13, rather than increasing the colonization ability of strain Tas13 on to the root surface. This study will greatly facilitate the application of aquatic plant-microbe association in environmental remediation.

Exploring the defense strategies of benzalkonium chloride exposures on the antioxidant system, photosynthesis and ROS accumulation in Lemna minor.

With the advent of technological advancements post the industrial revolution, thousands of chemicals are introduced into the market annually to enhance different facets of human life. Among these, pharmaceutical and personal care products (PPCPs), including antibiotics and disinfectants, such as benzalkonium chlorides (BACs), are prominent. BACs, often used for surface and hand disinfection in high concentrations or as preservatives in health products such as nasal sprays and eye drops, may present environmental risks if they seep into irrigation water through prolonged exposure or improper application. The primary objective of this study is to elucidate the tolerance mechanisms that may arise in Lemna minor plants, known for their remarkable capability to accumulate substances efficiently, in response to exogenously applied BACs at varying concentrations. The study applied six different concentrations of BACs, ranging from 0.25 to 10 mg L-1. The experimental period spanned seven days, during which the treatments were conducted in triplicate to ensure reliability and reproducibility of the results. It was observed that low concentrations of BACs (0.25, 0.5 and 1 mg L-1) did not elicit any statistically significant changes in growth parameters. However, higher concentrations of BACs (2.5, 5, and 10 mg L-1) resulted in a reduction in RGR by 20%, 28%, and 36%, respectively. Chlorophyll fluorescence declined significantly at BAC doses of 5 and 10 mg L-1, with Fv/Fm ratios decreasing by 9% and 15%, and Fv/Fo ratios by 40% and 39%, respectively. Proline content decreased in all treatment groups, with a 46% reduction at 10 mg L-1 BAC. TBARS and H2O2 contents increased proportionally with BAC dosage, showing the highest increases of 30% and 40% at 10 mg L-1, respectively. The noticeable increase in SOD enzyme activity at BAC concentrations of 0.5, 1, and 2.5 mg L-1, with increases of 2.7-fold, 2.2-fold, and 1.7-fold respectively, along with minimal accumulation of H2O2, suggests that L. minor plants have a strong tolerance to BAC. This is supported by the efficient functioning of the CAT and GST enzymes, especially evident at the same concentrations, where increased activities effectively reduce the buildup of H2O2. In the AsA-GSH cycle, although variations were observed between groups, the contribution of the GR enzyme to the preservation of GSH content by recycling GSSG likely maintained redox homeostasis in the plant, especially at low concentrations of BACs. The study revealed that L. minor effectively accumulates BAC alongside its tolerance mechanisms and high antioxidant activity. These results underscore the potential for environmental cleanup efforts through phytoremediation.

A P1-like MYB transcription factor boosts biosynthesis and transport of C-glycosylated flavones in duckweed.

C-glycosylated flavones (CGFs) are the main flavonoids in duckweed (Lemna turionifera), known for their diverse pharmacological activities and nutritional values. However, the molecular mechanisms underlying flavonoid metabolism in duckweed remain poorly understood. This study identified a P1-Like R2R3-MYB transcription factor, LtP1L, as a crucial regulator of CGF biosynthesis and transport in L. turionifera. Over-expression of LtP1L led to a six-fold increase in CGF levels, whereas the CRISPR-mediated knockdown of LtP1L caused a drastic 74.3 % decrease in CGF contents compared with the wild type. LtP1L specifically activated the expression of genes encoding key enzymes involved in the biosynthesis of CGFs, including flavanone 3'-hydroxylases (F3'H), flavanone 2-hydroxylases (F2H), and C-glycosyltransferase (CGT). Meanwhile, LtP1L activated genes associated with phenylalanine and phenylpropanoid biosynthesis pathways, such as 3-deoxy-7-phosphoheptulonate synthase (DHS), phenylalanine ammonia-lyase (PAL), cinnamate 4-hydroxylase (C4H), and 4-coumarate: CoA ligase (4CL), redirecting carbon metabolic flux towards flavonoid pathway at the early stages of phenylalanine synthesis. In addition, LtP1L directly bound to a novel AC-like cis-element in the promoter of a tonoplast-localized ATP-binding cassette (ABC) transporter LtABCC4 and activated its expression. Furthermore, the preference of LtABCC4 for isoorientin over orientin during vacuolar transport was evidenced by the significant reduction of isoorientin compared to orientin in the Ltabcc4crispr lines. Altogether, LtP1L acts as a crucial transcriptional orchestrator in coordinating the biosynthesis and intracellular transport of CGFs in duckweed.

Removal of contaminants of emerging concern by Wolffia arrhiza and Lemna minor depending on the process conditions, pollutants concentration, and matrix type.

Research was carried out on the removal of a group of six contaminants of emerging concern: bisphenol A, N,N-diethyl-m-toluamide, diethylstilbestrol, triclosan, estrone and estradiol from the water matrix during contact with small floating macrophytes Wolffia arrhiza and Lemna minor. The optimal conditions for the process, such as pH, light exposure per day, and plant mass, were determined using the design of experiments chemometric approach based on central composite design. Experiments conducted under the designated optimal conditions showed that after 7 days, the removal efficiency equals 88-98% in the case of W. arrhiza and 87-97% in the case of L. minor, while after 14 days of the experiment, these values are 93-99.6% and 89-98%, respectively. The primary mechanism responsible for removing CECs is the plant uptake, with the mean uptake rate constant equal to 0.299 day-1 and 0.277 day-1 for W. arrhiza and L. minor, respectively. Experiments conducted using municipal wastewater as a sample matrix showed that the treatment efficiency remains high (the average values 84% and 75%; in the case of raw wastewater, 93% and 89%, and in the case of treated wastewater, for W. arrhiza and L. minor, respectively). Landfill leachate significantly reduces plants' ability to remove pollutants (the average removal efficiency equals 59% and 56%, for W. arrhiza and L. minor, respectively).

Regulation and microbial response mechanism of nitric oxide to copper-containing swine wastewater treated by Pistia stratiotes.

As a signaling molecule, Nitric oxide (NO) has been widely used in abiotic stress mitigation studies.Pistia stratiotes showed a good synergistic removal effect on heavy metals, nitrogen and phosphorus, but the high concentration of copper(Cu) in swine wastewater inhibited the comprehensive removal ability of Pistia stratiotes. At present, it is not clear how the addition of NO regulates the stress resistance mechanism of Pistia stratiotes to copper in swine wastewater, and the microbial response mechanism accompanying this process is not yet clear. Therefore, in the concentration range of 0.31∼4 mg·L-1Cu2+ and NO concentration of 0,0.05 and 0.1 mg L-1, the removal effect of Pistia stratiotes on copper from swine wastewater was studied. The results showed as follows: The treatment of non-available copper in groups M and H increased by 10.67% and 22.31%, respectively, compared with that in group L. The critical point of inhibiting effect of NO on growth rate was 2.03 mg·L-1Cu. By measuring three-dimensional fluorescence spectrum, combined with parallel factor analysis and principal component analysis, it was confirmed that exogenous addition of NO affected the humification degree of dissolved organic matter(DOM) and promoted the chelation of organic matter with copper. With the increase of Cu concentration, the Reyranella and Prosthecobacter with certain copper resistance gradually gained advantages. Redundancy analysis(RDA) showed that Emiticicia had a strong correlation with the removal rates of ammonia nitrogen, total phosphorus and copper in swine wastewater, while hgcI_clade had a strong correlation with the removal rates of total nitrogen. In conclusion, controlling the dosage of NO can effectively improve the tolerance and removal effect of Pistia stratiotes on copper in swine wastewater, which is of great significance for promoting the treatment and resource transformation of swine wastewater.

Preliminary studies of selected Lemna species on the oxygen production potential in relation to some ecological factors.

Dissolved oxygen is fundamental for chemical and biochemical processes occurring in natural waters and critical for the life of aquatic organisms. Many organisms are responsible for altering organic matter and oxygen transfers across ecosystem or habitat boundaries and, thus, engineering the oxygen balance of the system. Due to such Lemna features as small size, simple structure, vegetative reproduction and rapid growth, as well as frequent mass occurrence in the form of thick mats, they make them very effective in oxygenating water. The research was undertaken to assess the impact of various species of duckweed (L. minor and L. trisulca) on dissolved oxygen content and detritus production in water and the role of ecological factors (light, atmospheric pressure, conductivity, and temperature) in this process. For this purpose, experiments were carried out with combinations of L. minor and L. trisulca. On this basis, the content of oxygen dissolved in water was determined depending on the growth of duckweed. Linear regression models were developed to assess the dynamics of changes in oxygen content and, consequently, organic matter produced by the Lemna. The research showed that the presence of L. trisulca causes an increase in dissolved oxygen content in water. It was also shown that an increase in atmospheric pressure had a positive effect on the ability of duckweed to produce oxygen, regardless of its type. The negative correlation between conductivity and water oxygenation, obtained in conditions of limited light access, allows us to assume that higher water conductivity limits oxygen production by all combinations of duckweeds when the light supply is low. Based on the developed models, it was shown that the highest increase in organic matter would be observed in the case of mixed duckweed and the lowest in the presence of the L. minor species, regardless of light conditions. Moreover, it was shown that pleustophytes have different heat capacities, and L. trisulca has the highest ability to accumulate heat in water for the tested duckweed combinations. The provided knowledge may help determine the good habitat conditions of duckweed, indicating its role in purifying water reservoirs as an effect of producing organic matter and shaping oxygen conditions with the participation of various Lemna species.

Sulfamethoxazole removal and fuel-feedstock biomass production from wastewater in a phyto-Fenton process using duckweed culture.

The phyto-Fenton process, which generates hydroxyl radicals through Fenton and Fenton-like reactions using plant-derived hydrogen peroxide (H2O2) and ferrous iron (Fe (II)) can degrade organic pollutants. Duckweed, an aquatic plant, is promising for a co-beneficial phytoremediation process that combines wastewater treatment and biomass production for biofuel feedstock. However, the phyto-Fenton process using duckweed has not been extensively studied. Because sulfamethoxazole (SMX), a major antibiotic, is distributed widely and is an emerging contaminant, its effective removal from contaminated water is necessary. The present study investigated the possibility of the simultaneous efficient removal of SMX from polluted water and biomass production for fuel feedstock by the phyto-Fenton process using duckweed. This is the first attempt to demonstrate the co-benefits of SMX removal and biomass production using duckweed. Intracellular H2O2 was produced using four duckweeds, Lemna aequinoctialis, L. minor, Landolina punctata, and Spirodela polyrhiza, in the range of 16.7-24.6 µ mol g-1 fresh weight, and extracellular H2O2 was released into the water phase. Consequently, duckweed could be used as an H2O2 supply source for the phyto-Fenton process. Specifically, 0.5 g fresh duckweed almost completely eliminated 1 mg L-1 SMX after 5 d in 50 mL sterile modified Hoagland solution containing 10 mM Fe (II). Fe (II)-dependent elimination of SMX indicated the occurrence of phyto-Fenton reaction. The phyto-Fenton process using duckweed effectively removed SMX. S. polyrhiza duckweed similarly removed 1 mg L-1 SMX even in sewage effluent containing other organic contaminants. During this treatment, duckweed biomass was generated at 7.95 g dry weight m-2 d-1, which was converted into methane at 353 normal liters CH4 kg-1 volatile solids by anaerobic digestion. For the first time, this study clearly demonstrates the potential for simultaneous SMX removal and biomass production from SMX-contaminated wastewater using duckweed.

Optimizing biochar, vermicompost, and duckweed amendments to mitigate arsenic uptake and accumulation in rice (Oryza sativa L.) cultivated on arsenic-contaminated soil.

The accumulation of arsenic (As) in rice (Oryza sativa L.) grain poses a significant health concern in Bangladesh. To address this, we investigated the efficacy of various organic amendments and phytoremediation techniques in reducing As buildup in O. sativa. We evaluated the impact of five doses of biochar (BC; BC0.1: 0.1%, BC0.28: 0.28%, BC0.55: 0.55%, BC0.82: 0.82% and BC1.0: 1.0%, w/w), vermicompost (VC; VC1.0: 1.0%, VC1.8: 1.8%, VC3.0: 3.0%, VC4.2: 4.2% and VC5.0: 5.0%, w/w), and floating duckweed (DW; DW100: 100, DW160: 160, DW250: 250, DW340: 340 and DW400: 400 g m- 2) on O. sativa cultivated in As-contaminated soil. Employing a three-factor five-level central composite design and response surface methodology (RSM), we optimized the application rates of BC-VC-DW. Our findings revealed that As contamination in the soil negatively impacted O. sativa growth. However, the addition of BC, VC, and DW significantly enhanced plant morphological parameters, SPAD value, and grain yield per pot. Notably, a combination of moderate BC-DW and high VC (BC0.55VC5DW250) increased grain yield by 44.4% compared to the control (BC0VC0DW0). As contamination increased root, straw, and grain As levels, and oxidative stress in O. sativa leaves. However, treatment BC0.82VC4.2DW340 significantly reduced grain As (G-As) by 56%, leaf hydrogen peroxide by 71%, and malondialdehyde by 50% compared to the control. Lower doses of BC-VC-DW (BC0.28VC1.8DW160) increased antioxidant enzyme activities, while moderate to high doses resulted in a decline in these activities. Bioconcentration and translocation factors below 1 indicated limited As uptake and translocation in plant tissues. Through RSM optimization, we determined that optimal doses of BC (0.76%), VC (4.62%), and DW (290.0 g m- 2) could maximize grain yield (32.96 g pot- 1, 44% higher than control) and minimize G-As content (0.189 mg kg- 1, 54% lower than control). These findings underscore effective strategies for enhancing yield and reducing As accumulation in grains from contaminated areas, thereby ensuring agricultural productivity, human health, and long-term sustainability. Overall, our study contributes to safer food production and improved public health in As-affected regions.

Chiral Herbicide 2,4-D Ethylhexyl Ester: Absolute Configuration, Stereoselective Herbicidal Activity, Crop Safety, and Metabolic Behavior on Maize and Flixweed.

This study represents the initial examination of the herbicidal efficacy, crop safety, and degradation patterns of 2,4-D ethylhexyl ester (2,4-D EHE) at the enantiomeric level. Baseline separation of 2,4-D EHE enantiomers was achieved using a superchiral R-AD column, with their absolute configurations determined through chemical reaction techniques. Evaluation of weed control efficacy against sensitive species such as sun spurge and flixweed demonstrated significantly higher inhibition rates for S-2,4-D EHE compared to R-2,4-D EHE. Conversely, no stereoselectivity was observed in the fresh-weight inhibition rates of both enantiomers on crops or nonsensitive weeds. A sensitive HPLC-MS/MS method was developed to simultaneously detect two enantiomers and the metabolite 2,4-D in plants. Investigation into degradation kinetics revealed no substantial difference in the half-lives of R- and S-2,4-D EHE in maize and flixweed. Notably, the metabolite 2,4-D exhibited prolonged persistence at elevated levels on flixweed, while it degraded rapidly on maize.

Duckweed: Beyond an Efficient Plant Model System.

Duckweed (Lemnaceae) rises as a crucial model system due to its unique characteristics and wide-ranging utility. The significance of physiological research and phytoremediation highlights the intricate potential of duckweed in the current era of plant biology. Special attention to duckweed has been brought due to its distinctive features of nutrient uptake, ion transport dynamics, detoxification, intricate signaling, and stress tolerance. In addition, duckweed can alleviate environmental pollutants and enhance sustainability by participating in bioremediation processes and wastewater treatment. Furthermore, insights into the genomic complexity of Lemnaceae species and the flourishing field of transgenic development highlight the opportunities for genetic manipulation and biotechnological innovations. Novel methods for the germplasm conservation of duckweed can be adopted to preserve genetic diversity for future research endeavors and breeding programs. This review centers around prospects in duckweed research promoting interdisciplinary collaborations and technological advancements to drive its full potential as a model organism.

In situ phytoextraction of Mn and NH4+-N from aqueous electrolytic manganese residue solution by Pistia stratiotes: Effects of Fe/Co presence and rhizospheric microbe synergistic involvement.

The electrolytic manganese industry produces a large amount of electrolytic manganese residue (EMR). Soluble Mn, NH4+-N, and other pollutants may be released from the open-air stacked EMR and transported to the environment along with rainfall or surface runoff. Aqueous EMR solution (AES) generally contains various elements required for plant growth, and phytoremediation can be applied to remove these pollutants from AES. Since the contents of Fe and Co vary greatly in AES depending on the ore sources as well as the pre-treatment processes, the presence of bioavailable Fe and Co at different levels may affect plant growth, the rhizosphere microbes, and pollutant removal. The present study investigated the in-situ removal of Mn(II) and NH4+-N from AES solution using free floating aquatic plant Pistia stratiotes, focusing especially on the effects of Fe/Co presence and rhizospheric microbe synergistic involvement on contaminant removal. The results showed that 69.08% of Mn and 94.99% of NH4+-N were removed by P. stratiotes in 24 d. Both the presence of Fe(II) and Co(II) facilitated the Mn(II) immobilization and increased Mn(II) removal by 19-31% due to the enhanced peroxidase activity and the increased Mn accumulating in roots The complete removal of Mn from AES was found in the presence of Fe(II) at 2 mg L-1 or Co(II) at 0.5 mg L-1 and more than 51% accumulated Mn in the roots was stored in the vacuole and cytoplasm. BioMnOx was found on the surface of the roots, revealing that rhizofiltration, rhizospheric plaque/biofilm formation, and Mn biogeochemical cycle exert synergic effects on Mn(II) immobilization. The findings of the present study demonstrate the feasibility of using P. stratiotes in the treatment of aqueous EMR solutions and the presence of an appropriate amount of bio-available Fe and Co can promote the removal of Mn(II) and NH4+-N.

Comparison of mercury (Hg) bioaccumulation with mono- and mixed Lemna minor and Spirodela polyrhiza cultures.

Mercury (Hg) is a prevalent and harmful contaminant that persists in the environment. For phytoremediation, it is important to discover which plants can bioaccumulate meaningful amounts of Hg while also tolerating its toxicity. Additionally, increasing biodiversity could create a more resilient and self-sustaining system for remediation. This study explores whether mixed populations of Lemna minor and Spirodela polyrhiza can better bioaccumulate and tolerate Hg than monocultures. Mono- and mixed cultures of L. minor and S. polyrhiza were grown in mesocosms of 0.5 µg/L or 100 µg/L Hg (HgCl2) spiked water for 96 h. Change in weight of duckweed was used to assess Hg tolerance. Diffusive gradients in thin-films (DGTs) were used as surrogate monitoring devices for bioavailable levels of Hg. For biomass growth, the mixed culture of the L. minor was greater than the monoculture at the high dose. The L. minor accumulated more Hg in the mixed culture at the low dose while the S. polyrhiza was higher in the mixed at the high dose. Hg speciation in water was modeled using Windermere Humic Aqueous Model 7 (WHAM7) to compare the bioavailable species indicated by the DGTs.  Potentially due to the controlled conditions, the WHAM7 output of bioavailable Hg was almost 1:1 to that estimated by the DGTs, indicating good predictive capability of geochemical modeling and passive sampler DGT on metal bioavailability. Overall, the mixed cultures statistically performed as well as or better than the monocultures when tolerating and bioaccumulating Hg. However, there needs to be further work to see if the significant differences translate into practical differences worth the extra resources to maintain multiple species.

Optimization of Hoagland solution macro-elements as a culture media, for increasing protein content of duckweeds (Lemna minor).

This study aimed to increase the protein content of duckweed, a promising alternative to animal proteins and a sustainable source of plant protein cultivated via soilless agriculture, by manipulating the culture medium conditions (Hoagland solution). The contribution percentages of KH2PO4 and Ca(NO3)2, pivotal macro-elements in Hoagland solution affecting duckweed protein content, were determined using Plackett-Burman factorial design as 33.06 % and 36.61 %, respectively. Additionally, optimization was conducted employing response surface methodology, incorporating pH alongside KH2PO4 and Ca(NO3)2. Under optimal conditions of 3.92 mM KH2PO4, 7.95 mM Ca(NO3)2, and 7.22 pH, the protein content of duckweed increased significantly, reaching 51.09 % from 39.81 %. The duckweed cultivated in modified Hoagland solution exhibited protein content of 41.74 %, while duckweed grown in commercial Hoagland solution displayed protein content of 33.01 %. This study showed protein content of duckweed could significantly increase according to the growth medium and showcasing its potential as a sustainable source of plant protein.

Changes in Metabolism and Content of Chlorophyll in Common Duckweed (Lemna minor L.) Caused by Environmental Contamination with Fluorides.

The impact of fluorine on plants remains poorly understood. We examined duckweed growth in extracts of soil contaminated with fluorine leached from chicken manure. Additionally, fluorine levels were analyzed in fresh manure, outdoor-stored manure, and soil samples at varying distances from the manure pile. Fresh manure contained 37-48 mg F- × kg-1, while soil extracts contained 2.1 to 4.9 mg F- × kg-1. We evaluated the physiological effects of fluorine on duckweed cultured on soil extracts or in 50% Murashige-Skoog (MS) medium supplemented with fluorine concentrations matching those in soil samples (2.1 to 4.9 mg F- × L-1), as well as at 0, 4, and 210 mg × L-1. Duckweed exposed to fluorine displayed similar toxicity symptoms whether in soil extracts or supplemented medium. Fluoride at concentrations of 2.1 to 4.9 mg F- × L-1 reduced the intact chlorophyll content, binding the porphyrin ring at position 32 without affecting Mg2+. This reaction resulted in chlorophyll a absorption peak shifted towards shorter wavelengths and formation of a new band of the F--chlorophyll a complex at λ = 421 nm. Moreover, plants exposed to low concentrations of fluorine exhibited increased activities of aminolevulinic acid dehydratase and chlorophyllase, whereas the activities of both enzymes sharply declined when the fluoride concentration exceeded 4.9 mg × L-1. Consequently, fluorine damages chlorophyll a, disrupts the activity of chlorophyll-metabolizing enzymes, and diminishes the plant growth rate, even when the effects of these disruptions are too subtle to be discerned by the naked human eye.

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.