The Role of H2O2-Scavenging Enzymes (Ascorbate Peroxidase and Catalase) in the Tolerance of Lemna minor to Antibiotics: Implications for Phytoremediation

We investigated the individual and combined contributions of two distinct heme proteins namely, ascorbate peroxidase (APX) and catalase (CAT) on the tolerance of Lemna minor plants to antibiotics. For our investigation, we used specific inhibitors of these two H2O2-scavenging enzymes (p-aminophenol, 3-amino,1,2,4-triazole, and salicylic acid). APX activity was central for the tolerance of this aquatic plant to amoxicillin (AMX), whereas CAT activity was important for avoiding oxidative damage when exposed to ciprofloxacin (CIP). Both monitored enzymes had important roles in the tolerance of Lemna minor to erythromycin (ERY). The use of molecular kinetic approaches to detect and increase APX and/or CAT scavenging activities could enhance tolerance, and, therefore, improve the use of L. minor plants to reclaim antibiotics from water bodies.

Duckweed roots are dispensable and are on a trajectory toward vestigiality

Duckweeds are morphologically simplified, free floating aquatic monocots comprising both rooted and rootless genera. This has led to the idea that roots in these species may be vestigial, but empirical evidence supporting this is lacking. Here we show that duckweed roots are no longer required for their ancestral role of nutrient uptake. Comparative analyses of nearly all rooted duckweed species revealed a highly reduced anatomy, with greater simplification in the more recently diverged genus Lemna. A series of root excision experiments demonstrated that roots are dispensable for normal growth in Spirodela polyrhiza and Lemna minor. Furthermore, ionomic analyses of fronds in these two species showed little difference in the elemental composition of plants in rooted versus root-excised samples. In comparison, another free-floating member of the Araceae, Pistia stratiotes, which colonized the aquatic environment independently of duckweeds, has retained a more complex root anatomy. Whilst Pistia roots were not absolutely required for growth, their removal inhibited plant growth and resulted in a broad change in the mineral profile of aerial tissues. Collectively, these observations suggest that duckweeds and Pistia may be different stages along a trajectory towards root vestigialisation Given this, along with the striking diversity of root phenotypes, culminating in total loss in the most derived species, we propose that duckweed roots are a powerful system with which to understand organ loss and vestigiality.

In-Vivo Neuropharmacological and Anti-Nutrient Study of Methanolic Extract of Lemna Minor

Medicinal plants constitute an important natural wealth of a country. They play a significant role in providing primary health care services to rural people. They serve as therapeutic agents as well as important raw materials for the manufacture of traditional and modern medicine. Lemna minor, the common duckweed is an aquatic freshwater aquatic plant of the genus Lemna. They belong to the family of Lemnaceae, which is monophyletic to the Araceae family. The study assesses In-vivo Neuropharmacological and Anti Nutrient Study of methanolic extract of Lemna minor. The plants were collected from Chandpur were extracted in methanol solvents using soxhlet apparatus. Chemical tests to identify different anti nutrients, total phenolic and flavonids were carried out using specific reagents. Several test such as open field test, hole cross test, hole board test and phenobarbital induced sleeping time test are performed to check possible neurological activity.The study of anti-nutrient properties showed a very high amount of tannin (5.625gm/kg) but a low amount of phytic acid (0.03gm/kg) & alkaloids (0.526gm/kg) comparison with standard value. Total phenolic (19.22 GAE/g dry weight) and flavonoids (7.68 QE/g dry weight) content determine that Lemna minor have a very good amount of phenolic and flavanoids content and which may act as good anti-oxidant. In the study of in-vivo neurological activity the efficacy of Lemna minorextract was compared with standard anxiolytic drug diazepam (1 mg/kg b.w.) showed limited sedation as well as anxiolytic properties in mice. The present study of in-vivo & anti-nutrient is biological evaluation of this plant forms a primary platform for further phytochemical, anti-nutrient & pharmacological studies.

Comparison of Pistia Stratiotes and Lemna Minor Plants Potentials in Bioremediation of Domestic Wastewater

Phytoremediation is an eco-friendly and cost-effective biotechnological method of wastewater treatment that involves the use of plants. In this research work, the potentials of Pistia stratiotes and Lemna minor aquatic plants in treatment of wastewater was examined. The two plants were cultivated in the wastewater sample for a period of 10 days. Water quality parameters (turbidity, chemical oxygen demand (COD), phosphate, ammoniacal nitrogen and nitrate) tests was subjected on the untreated (influent) and treated water (effluent) samples at a detention time of 24 hours. The outcome of the analysis demonstrates that P. stratiotes effluent achieved a reduction efficiency of up to 91.9%, 68%, 79.6%, and 71% for turbidity, phosphate, ammoniacal nitrogen and nitrate, respectively. Whereas for L. minor treated water samples, the highest reduction efficiency for turbidity, COD, phosphate, ammoniacal nitrogen and nitrate was found to be 87.2%, 46%, 48.7%, 83% and 56%, respectively. Hence, the overall outcome obtained indicate that P. stratiotes performed better in improving the quality of domestic wastewater compared to L. minor plants.

Biogas Potential Assessment of the Composite Mixture from Duckweed Biomass

The article presents the research results of anaerobic digestion processes in bioreactors of composite mixtures based on initial and residual biomass of Lemna minor duckweed and additives: inoculum (manure), food waste, and spent sorbents to determine biogas potential (biogas volume, methane content). Duckweed Lemna minor, which is widespread in freshwater reservoirs, is one of the promising aquatic vegetation species for energy use. Residual biomass is obtained by chemically extracting valuable components from the primary product. The purpose of the research was to evaluate the possibility of the energy potential of residual biomass of Lemna minor to reduce the consumption of fossil fuels and reduce greenhouse gas emissions. This is in line with the International Energy Agency (IEA) scenarios for the reduction of environmental impact. The obtained results confirm the feasibility of using this type of waste for biogas/biomethane production. The recommendations on the optimal composition of the mixture based on the residual biomass of Lemna minor, which will allow for an increase in biogas production, are given. The obtained data can be used in the design of bioreactors.

Interlaboratory Validation of Toxicity Testing Using the Duckweed Lemna minor Root-Regrowth Test

The common duckweed (Lemna minor), a freshwater monocot that floats on the surfaces of slow-moving streams and ponds, is commonly used in toxicity testing. The novel Lemna root- regrowth test is a toxicity test performed in replicate test vessels (24-well plates), each containing 3 mL test solution and a 2–3 frond colony. Prior to exposure, roots are excised from the plant, and newly developed roots are measured after 3 days of regrowth. Compared to the three internationally standardized methods, this bioassay is faster (72 h), simpler, more convenient (requiring only a 3-mL) and cheaper. The sensitivity of root regrowth to 3,5-dichlorophenol was statistically the same as using the conventional ISO test method. The results of interlaboratory comparison tests conducted by 10 international institutes showed 21.3% repeatability and 27.2% reproducibility for CuSO4 and 21.28% repeatability and 18.6% reproducibility for wastewater. These validity criteria are well within the generally accepted levels of <30% to 40%, confirming that this test method is acceptable as a standardized biological test and can be used as a regulatory tool. The Lemna root regrowth test complements the lengthier conventional protocols and is suitable for rapid screening of wastewater and priority substances spikes in natural waters.

The Dynamics of NO3− and NH4+ Uptake in Duckweed Are Coordinated with the Expression of Major Nitrogen Assimilation Genes

Duckweed plants play important roles in aquatic ecosystems worldwide. They rapidly accumulate biomass and have potential uses in bioremediation of water polluted by fertilizer runoff or other chemicals. Here we studied the assimilation of two major sources of inorganic nitrogen, nitrate (NO3−) and ammonium (NH4+), in six duckweed species: Spirodela polyrhiza, Landoltia punctata, Lemna aequinoctialis, Lemna turionifera, Lemna minor, and Wolffia globosa. All six duckweed species preferred NH4+ over NO3− and started using NO3− only when NH4+ was depleted. Using the available genome sequence, we analyzed the molecular structure and expression of eight key nitrogen assimilation genes in S. polyrhiza. The expression of genes encoding nitrate reductase and nitrite reductase increased about 10-fold when NO3− was supplied and decreased when NH4+ was supplied. NO3− and NH4+ induced the glutamine synthetase (GS) genes GS1;2 and the GS2 by 2- to 5-fold, respectively, but repressed GS1;1 and GS1;3. NH4+ and NO3− upregulated the genes encoding ferredoxin- and NADH-dependent glutamate synthases (Fd-GOGAT and NADH-GOGAT). A survey of nitrogen assimilation gene promoters suggested complex regulation, with major roles for NRE-like and GAATC/GATTC cis-elements, TATA-based enhancers, GA/CTn repeats, and G-quadruplex structures. These results will inform efforts to improve bioremediation and nitrogen use efficiency.