Wolffia Globosa Research Articles

Effect of green-Mediterranean diet on intrahepatic fat: the DIRECT PLUS randomised controlled trial

ObjectiveTo examine the effectiveness of green-Mediterranean (MED) diet, further restricted in red/processed meat, and enriched with green plants and polyphenols on non-alcoholic fatty liver disease (NAFLD), reflected by intrahepatic fat...

Lamellidens and Wolffia canopy improves growth, feed utilization and welfare of Labeo rohita (Hamilton,1822) in integrated multi-trophic freshwater aquaculture system

A 90 days' trial on integrated multi-trophic aquaculture (IMTA) incorporating floating weed Wolffia globosa as inorganic extractive and a bivalve Lamellidens marginalis as organic extractive was conducted to assess the growth, survival, yield, water quality and welfare of Labeo rohita (Rohu) in an outdoor tank culture system. Twelve cement tanks (20 m3) were randomly allocated into four treatments (in triplicate) where L. rohita was used as fed species. The treatments were assigned as control (C) only rohu, T1: Rohu and partitioned Wolffia canopy, T2: Rohu, L. marginalis and T3: Rohu, Wolffia and L. marginalis. The stocking densities for rohu and L marginalis were 30,000 fingerlings ha−1 and 750 kg ha−1 while Wolffia was transplanted to cover 30% of the tank surface area, and fish to mussel biomass ratio maintained was 2:1. The fish were fed with a sinking pelleted feed (30% Crude Protein) at the rate of 4% body weight. It is observed that total biomass, survival, net fish yield (NFY) was significantly highest in T3 as compared to T1, control and T2. The total protein and lipid content of rohu (whole-body) differ significantly between the treatments. Among the welfare parameters, the nitroblue tetrazolium (NBT) activity was significantly higher in T1 and T3 while superoxide dismutase (SOD) was highest in T1. The catalase (CAT) activity lowest in T3 among all the treatment groups. The water quality parameters like NH4-N, NO3-N, PO4-P were significantly lower in T3 among all treatment groups. Higher water transparency was observed with no algal bloom in T3 and T1. The results suggest that co-culture of L. rohita with W. globosa and L. marginalis can improve water quality, welfare parameters, enhancing fish survival and productivity.

The effect of green Mediterranean diet on cardiometabolic risk; a randomised controlled trial

BackgroundA Mediterranean diet is favourable for cardiometabolic risk.ObjectiveTo examine the residual effect of a green Mediterranean diet, further enriched with green plant-based foods and lower meat intake, on cardiometabolic risk.MethodsFor...

Research and application in duckweeds: A review

<p indent=0mm>The free-floating aquatic duckweeds consist of the five genera, <italic>Spirodela</italic>, <italic>Landoltia</italic>, <italic>Lemna</italic>, <italic>Wolffiella</italic> and <italic>Wolffia</italic>, comprising 36 species within the monocot order of Alismatales. They are strongly adaptable to various environments and are widely distributed in a variety of climates all over the world except that <italic>Wolffiella</italic> species are restricted to the Americas and Africa. Among them, <italic>Spirodela</italic> species have large a flattened frond with 5−11 rhizoids while the rootless<italic> Wolffia </italic>species form an oval-shaped frond and<italic> </italic>are the smallest flowering plants. Duckweeds seldom flower and their rapid asexual propagation allows them to accumulate biomass quickly. They usually bud new generations (daughter fronds) from their reproductive pouches at the base of the mother fronds and the frond number almost doubles within <sc>24 h</sc>under good growth conditions yielding the fastest-growing flowering plants. They tend to be associated with nutrient-rich or eutrophic freshwater environments with slow-moving flow such as ponds, lakes, ditches, and paddy fields. While duckweeds become more reduced from <italic>Spirodela</italic> to <italic>Wolffia</italic>, their genome size varies 13-fold, ranging from 150 Mb in <italic>Spirodela polyrhiza</italic> to 1881 Mb in <italic>Wolffia arrhiza</italic>. With the development of long-read sequencing technology, the genomes of common duckweed species including <italic>S. </italic><italic>polyrhiza</italic>, <italic>Lemna minor</italic>,<italic> Lemna gibba</italic> and <italic>Wolffia australiana</italic> have been sequenced and assembled. The underlying molecular mechanisms and regulatory networks in duckweeds under different treatments such as starvation, salt stress, heavy metal and radiation have also been revealed by transcriptome, proteome and metabolome analyses for the genera <italic>Spirodela</italic>, <italic>Landoltia</italic>, and <italic>Lemna </italic>enhancing their potential applications in the fields of phytoremediation and bioenergy. Furthermore, genetic transformation systems for some common duckweeds such as <italic>L. minor</italic>,<italic> Lemna aequinoctialis</italic>, <italic>S. </italic><italic>polyrhiza</italic> and <italic>Wolffia globosa </italic>have been established, and especially the frond transformation systems have significantly improved transformation efficiencies (more than 90%). These characteristics have made duckweeds model systems for several decades for the study of plant physiology, biochemistry, ecotoxicology, and have contributed to knowledge of auxin biosynthesis, plant flowering and the circadian system. Duckweeds have also been widely used for the treatment of agricultural, municipal, and even industrial wastewater because they can uptake nitrogen and phosphorus as well as quickly accumulate heavy metals and organic pollutants. Besides, their accumulated biomass is rich in starch and protein and therefore can be used for feed applications and biofuels. In this review, we introduce the origin, classification and evolution of duckweeds, as well as research in morphology and anatomy, physiology, genetic transformation and omics studies. We further discuss the application of duckweeds in food, feed, bioenergy, and bioremediation. Finally, we highlight the challenges and future directions of duckweed research, providing a reference for basic biological research and resource utilization.

Effects of Diet-Modulated Autologous Fecal Microbiota Transplantation on Weight Regain

We evaluated the efficacy and safety of diet-modulated autologous fecal microbiota transplantation (aFMT) for treatment of weight regain after the weight-loss phase. In the DIRECT PLUS (Dietary Intervention Randomized Controlled Trial Polyphenols-Unprocessed) weight-loss trial (May 2017 through July 2018), abdominally obese or dyslipidemic participants in Israel were randomly assigned to healthy dietary guidelines, Mediterranean diet, andgreen-Mediterranean diet weight-loss groups. All groupsreceived free gym membership and physical activity guidelines. Both isocaloric Mediterranean groups consumed 28 g/d walnuts (+440 mg/d polyphenols provided). The green-Mediterranean dieters also consumed green tea (3-4 cups/d) and a Wolffia globosa (Mankai strain, 100 g/d) green shake (+800 mg/d polyphenols provided). After 6 months (weight-loss phase), 90 eligible participants (mean age, 52 years; mean weight loss, 8.3 kg) provided a fecal sample that was processed into aFMT by frozen, opaque, and odorless capsules. The participants were then randomly assigned to groups that received 100 capsules containing their own fecal microbiota or placebo until month 14. The primary outcome was regain of the lost weight over the expected weight-regain phase (months 6-14). Secondary outcomes were gastrointestinal symptoms, waist circumference, glycemic status, and changes in the gut microbiome, as measured by metagenomic sequencing and 16s ribosomal RNA. We validated the results in a parallel invivo study of mice specifically fed with Mankai compared with control chow diet. Of the 90 participants in the aFMT trial, 96% ingested at least 80 of 100 oral aFMT or placebo frozen capsules during the transplantation period. No aFMT-related adverse events or symptoms were observed. For the primary outcome, although no significant differences in weight regain were observed among the participants in the different lifestyle interventions during months 6-14 (aFMT, 30.4% vs placebo, 40.6%; P= .28), aFMT significantly attenuated weight regain in the green-Mediterranean group (aFMT, 17.1%, vs placebo, 50%; P= .02), but not in the dietary guidelines (P= .57) or Mediterranean diet (P= .64) groups (P for the interaction= .03). Accordingly, aFMT attenuated waist circumference gain (aFMT, 1.89 cm vs placebo, 5.05 cm; P= .01) and insulin rebound (aFMT, -1.46 ± 3.6 μIU/mL vs placebo, 1.64 ± 4.7 μIU/mL; P= .04) in the green-Mediterranean group but not in the dietary guidelines or Mediterranean diet (P for the interaction= .04 and .03, respectively). The green-Mediterranean diet was the only intervention to induce a significant change in microbiome composition during the weight-loss phase, and to prompt preservation of weight-loss-associated specific bacteria and microbial metabolic pathways (mainly microbial sugar transport) after the aFMT. In mice, Mankai-modulated aFMT in the weight-loss phase compared with control diet aFMT, significantly prevented weight regain and resulted in better glucose tolerance during a high-fat diet-induced regain phase (all, P < .05). Autologous FMT, collected during the weight-loss phase and administrated in the regain phase, might preserve weight loss and glycemic control, and is associated with specific microbiome signatures. A high-polyphenols, green plant-based or Mankai diet better optimizes the microbiome for an aFMT procedure. ClinicalTrials.gov number, NCT03020186.

Expression of LamB Vaccine Antigen in Wolffia globosa (Duck Weed) Against Fish Vibriosis.

Vibriosis is a commonly found bacterial disease identified among fish and shellfish cultured in saline waters. A multitude of Vibrio species have been identified as the causative agents. LamB, a member of outer membrane protein (OMPs) family of these bacteria is conserved among all Vibrio species and has been identified as an efficient vaccine candidate against vibriosis. Rootless duckweed (Wolffia) is a tiny, edible aquatic plant possessing characteristics suitable for the utilization as a bioreactor. Thus, we attempted to express a protective edible vaccine antigen against fish vibriosis in nuclear-transformed Wolffia. We amplified LamB gene from virulent Vibrio alginolyticus and it was modified to maximize the protein expression level and translocate the protein to the endoplasmic reticulum (ER) in plants. It was cloned into binary vector pMYC under the control of CaMV 35S promoter and introduced into Wolffia globosa by Agrobacterium-mediated transformation. Integration and expression of the LamB gene was confirmed by genomic PCR and RT-PCR. Western blot analysis revealed accumulation of the LamB protein in 8 transgenic lines. The cross-protective property of transgenic Wolffia was evaluated by orally vaccinating zebrafish through feeding fresh transgenic Wolffia and subsequently challenging with virulent V. alginolyticus. High relative percent survival (RPS) of the vaccinated fish (63.3%) confirmed that fish immunized with transgenic Wolffia were well-protected from Vibrio infection. These findings suggest that Wolffia expressed LamB could serve as an edible plant-based candidate vaccine model for fish vibriosis and feasibility of utilizing Wolffia as bioreactor to produce edible vaccines.

Characterization of the complete chloroplast genome sequence of Wolffia globosa (Lemnoideae) and its phylogenetic relationships to other Araceae family

Wolffia globosa is the smallest angiosperm in the world and can be found in Asia and parts of America. Also, it is commonly used as food in Southeast Asia. In this study, the complete chloroplast genome of the Wolffia globosa was assembled from the whole genome Illumina sequencing data. The assembled genome size is 169,405 bp in length, which composed of a large single copy region (LSC) of 92,171 bp, a small single copy (SSC) regions of 13,570 bp and separated by a pair of inverted repeat (IR) regions of 31,810 bp each. It encodes a total of 113 genes, including 78 protein-coding genes, 31 tRNA genes, and 4 rRNA genes. There are 22 duplicated genes in the predicted gene catalog. The overall GC content is 35.9% while the GC content of the LSC, SSC, and IR regions are 33.8%, 31.1%, and 40.0%, separately. Based on Bayesian phylogenetic analysis, it represents that Wolffia globosa was closely related to Wolffia australiana.

Effects of Wolffia Globosa (Mankai) in Patients Undergoing Bariatric Surgery.

Effects of Wolffia Globosa (Mankai) in Patients Undergoing Bariatric Surgery.

The Effect of Wolffia globosa Mankai, a Green Aquatic Plant, on Postprandial Glycemic Response: A Randomized Crossover Controlled Trial.

To compare the postprandial and overnight glycemic response using a novel green aquatic plant thought to provide a dietary source for high-quality protein, with an iso-carbohydrate/protein/caloric dairy shake. This is a randomized controlled crossover trial among 20 abdominally obese participants (age 51.4 years; fasting plasma glucose 110.9 mg/dL), who were allocated to replace dinner with either, first, a green shake containing Wolffia globosa duckweed (Mankai: specific-strain) or an iso-carbohydrate/protein/calorie yogurt shake. A 2-week flash glucose-monitoring system was used to assess postmeal glucose dynamics (6 net administration days; 97 observation days in total). We further obtained from each participant dietary/daily activity/satiety scale/sleep logs. Participants were recruited from the green-Mediterranean diet arm of the 18-month Dietary Intervention Randomized Controlled Trial-Polyphenols Unprocessed (DIRECT-PLUS) study. Wolffia globosa Mankai elicited a lower postprandial glucose peak compared with yogurt (∆peak = 13.4 ± 9.2 vs. 19.3 ± 15.1 mg/dL; P = 0.044), which occurred later (77.5 ± 29.2 vs. 59.2 ± 28.4 min; P = 0.037) and returned faster to baseline glucose levels (135.8 ± 53.1 vs. 197.5 ± 70.2 min; P = 0.012). The mean post-net incremental area under the curve (netAUC) was lower with Wolffia globosa up to 60 and 180 min (netAUC 60 min: 185.1 ± 340.1 vs. 441.4 ± 336.5 mg/dL/min, P = 0.005; netAUC 180 min: 707.9 ± 1,428.5 vs. 1,576.6 ± 1,810.1 mg/dL/min, P = 0.037). A Wolffia globosa-based shake replacing dinner resulted in lower next-morning fasting glucose levels (83.2 ± 0.8 vs. 86.6 ± 13 mg/dL; P = 0.041). Overall, postprandial glucose levels from the shake administration until the next morning were lower in the Wolffia globosa Mankai green shake compared with the yogurt shake (P < 0.001). Overnight sleep duration was similar (378.2 ± 22.4 vs. 375.9 ± 28.4 min; P = 0.72), and satiety rank was slightly higher for the Wolffia globosa shake compared with the yogurt shake (7.5 vs. 6.5; P = 0.035). Wolffia globosa Mankai duckweed may serve as an emerging alternative plant protein source with potential beneficial postprandial glycemic effects.

Evaluation of live duckweed, Wolffia globosa as an allochthonous feed for Labeo rohita fry during nursery rearing

A 40 days feeding trial with Labeo rohita (rohu) fry was conducted in six outdoor cemented tanks (5m × 4m × 1 m; 6–8 cm soil base) to establish the relative impact of on‐farm grown live Wolffia globosa (a duckweed with crude protein of 28.57%) and a formulated iso‐nitrogenous feed (crude protein 28.37%) on growth performance, survival, health and overall quality of fingerlings. The experimental tanks were dried, limed at 250 kg/ha, filled with ground water and subsequently applied with cow dung (soaked overnight) and mustard oil cake at 1,000 kg/ha and 50 kg/ha respectively. The fry were stocked at 0.3 millions/ha in six prepared tanks, and fed live Wolffia (T1) and formulated feed (T2). Results of the study indicate better performance (p < 0.05) of fry in terms of final mean weight (7.83 g), length (8.82 cm), daily growth index (6.51 g %/day) and survival (89.5%) than those fed on formulated feed. Furthermore, significantly improved (p < 0.05) feed utilization parameters viz. apparent feed conversion ratio (AFCR), apparent protein conversion efficiency (APCE), apparent protein efficiency ratio (APER); haematological parameters viz. total erythrocyte count (TEC), total leucocyte count (TLC), packed cell volume (PCV), plasma glucose and protein of fry were also observed in T1 (live Wolffia). Overall findings from this study hints towards the possible utilization of on‐farm grown live Wolffia as a suitable nutrient source for fry rearing of L. rohita.

Duckweed for Human Nutrition: No Cytotoxic and No Anti-Proliferative Effects on Human Cell Lines.

Duckweeds (Lemnaceae) possess good qualitative and quantitative profiles of nutritional components for its use as human food. However, no studies have been conducted on the probable presence or absence of any adverse effects. The extracts from seven duckweed species (Spirodela polyrhiza, Landoltia punctata, Lemna gibba, Lemna minor, Wolffiella hyalina, Wolffia globosa, and Wolffia microscopica) covering all five genera of the plant family were herewith tested for cytotoxic effects on the human cell lines HUVEC, K-562, and HeLa and for anti-proliferative activity on HUVEC and K-562 cell lines. From these assays, it is evident that duckweeds do not possess any detectable anti-proliferative or cytotoxic effects, thus, the high nutritional value is not diminished by such detrimental factors. The present result is a first step to exclude any harmful effects of highly nutritious duckweed for human.

Development of Efficient Protocols for Stable and Transient Gene Transformation for Wolffia Globosa Using Agrobacterium.

Members of the Wolffia genus are fascinating plants for many biologists as they are the smallest flowering plants on Earth and exhibit a reduced body plan that is of great interest to developmental biologists. There has also been recent interest in the use of these species for bioenergy or biorefining. Molecular and developmental studies have been limited in Wolffia species due to the high genome complexity and uncertainties regarding the stable genetic transformation. In this manuscript we present new protocols for both stable and transient genetic transformation for Wolffia globosa using Agrobacterium tumefaciens. For the transient transformation, we used Wolffia fronds whereas we used clusters for the stable transformation. As proof of concept we transformed two synthetic promoter constructs driving expression of the GUS marker gene, that have previously been used to monitor auxin and cytokinin output in a variety of species. Using these approaches we obtained a Transformation Efficiency (TE) of 0.14% for the stable transformation and 21.8% for the transient transformation. The efficiency of these two methods of transformation are sufficient to allow future studies to investigate gene function. This is the first report for successful stable transformation of W. globosa.

The Bioactivity Study of Active Compounds in Wolffia globosa Extract for an Alternative Source of Bioactive Substances

Wolffia globosa is a small plant found in the lagoons in tropical zones. The aim of our study was to examine the biological compounds found in W. globosa and their activities. The substances in W. globosa were extracted, isolated, and their chemical structures ascertained by Fourier transform infrared (FT-IR) spectroscopy and proton nuclear magnetic resonance (1H-NMR) spectroscopy. The extract was tested for bioactivity, including antioxidant, anti-inflammatory, and cytotoxic activities. The results showed that the isolated compounds in fraction two were mainly β-sitosterol and stigmasterol. The sterols found in the extract were able to inhibit nitric oxide production in RAW 264.7 macrophage cells, which implied an anti-inflammatory activity. The extract was found to be non-toxic to human dermal fibroblast cells with an IC50 of 106.38 ± 37.0 µg/mL.

Surface coating-modulated toxic responses to silver nanoparticles in Wolffia globosa

With the omnipresence of silver nanoparticles (AgNPs) in our daily consumer products, their release has raised serious concerns. However, the biochemical mechanisms by which plants counteract the toxicity of nanoparticles are largely unknown. This study investigated the exposure of aquatic Wolffia globosa to ATP-nAg (AgNPs coated with adenosine triphosphate), cit-nAg (AgNPs coated with citrate), and Ag+. Hill reaction activity was basically lost in W. globosa treated with 10mg/L ATP-nAg and Ag+, while the activity was still maintained at 38.7%–38.9% of the respective controls at 10mg/L cit-nAg. The reduction of amounts of chlorophyll and soluble protein were shown in response to the Ag stresses. This was accompanied by the accumulation of sugar in W. globosa treated with cit-nAg. By contrast, the depletion of sugar was recorded after 10mg/L ATP-nAg and Ag+ treatments. The superoxide dismutase and peroxidase activities were significantly increased after exposure to 10mg/L ATP-nAg and Ag+, which did not occurred in W. globosa treated with cit-nAg. The ratio between NADPH/NADP+ was higher after cit-nAg and Ag+ stresses than the respective controls. The accumulation of Ag was found to increase in a concentration-dependent manner. Ag+ and ATP-nAg inhibited the uptake of P and K, and promoted the uptake of Fe and Cu. In contrast, cit-nAg only promoted the uptake of Cu. Our results implied that surface coating induced different physiological responses of W. globosa to AgNPs. Based on above results, we speculated that after exposure to cit-nAg, citrate possibly could serve as the substrate for the tricarboxylic acid cycle and accumulated sugar may promote pentose phosphate pathways. For ATP-nAg treatments, ATP would act as an exogenous energy source of plant metabolisms. Our findings demonstrate that surface coating regulates the physiological responses of plants to AgNPs through distinct mechanisms.

Effects of simulated microgravity on the performance of the duckweeds Lemna aequinoctialis and Wolffia globosa

Duckweed is considered to be one of the most attractive higher plants to provide the life support requirements of the crew in long-duration space missions. Two species of duckweed, Lemna aequinoctialis and Wolffia globosa, were comparatively studied with focus on the effects of simulated microgravity conditions. A significant enhancement of plant relative growth rate (RGR) was observed under simulated microgravity conditions. The mean RGR of L. aequinoctialis was 32% increased, and W. globosa was 12% increased compared to control. Light and electron microscope analyses showed that the mesophyll cells of duckweed fronds were loosely arranged and many intercellular air spaces enclosed by mesophyll cells were observed in reaction to simulated microgravity, and few starch grains were detected in root tip cells in L. aequinoctialis under simulated microgravity conditions. For L. aequinoctialis, the starch content was significantly increased under simulated microgravity conditions. Thus, the starch content of W. globosa under simulated microgravity conditions was kept stable during all growth periods. This pattern might be associated with the different expression change of the rate-limiting gene APL in regulating starch levels. Taking into consideration of the duckweed growth, ultra-structure and starch content changes, we considered that simulated microgravity conditions do not have a significant adversely affect on the duckweed growth.

Duckweed biomass as a renewable biorefinery feedstock: Ethanol and succinate production from Wolffia globosa

For evaluating duckweed biomass as a bioresource, the specific growth rate and the chemical constituents of duckweed of four kinds were investigated. Spirodela polyrrhiza, Lemna minor, Wolffia arrhiza, and Wolffia globosa commonly showed high specific growth rates of 0.22–0.30 d−1 with initial concentrations of nitrogen >3.0 kg m−3 and phosphorus >5.0 kg m−3. All duckweeds had high sugar contents greater than 300 g kg−1 of dry mass. Especially, vegetative fronds of W. globosa showed the highest sugar content of 410 g kg−1 of dry mass. The duckweed biomass was pretreated easily by heating at 121 °C for saccharification using α-amylase and amyloglucosidase. The ethanol yield of W. globosa biomass in the simultaneous saccharification and fermentation (SSF) using the enzymes and dry yeast was 170 g kg−1 of dry mass, whereas the succinate yield in the SSF using the enzymes and Actinobacillus succinogenes was 200 g kg−1 of dry mass. The production rates of ethanol and succinate from the W. globosa biomass were estimated as 0.58 kg m−2 y−1 and 0.68 kg m−2 y−1, respectively. The biomass of duckweed, with its high growth rate and high starch content, can be an excellent renewable feedstock for the production of ethanol and succinate as building block chemicals for the replacement of petrochemicals.

Survey of duckweed diversity in Lake Chao and total fatty acid, triacylglycerol, profiles of representative strains.

Lemnaceae (duckweeds) are widely distributed aquatic flowering plants. Their high growth rate, starch content and suitability for bioremediation make them potential feedstock for biofuels. However, few natural duckweed resources have been investigated in China, and there is no information about total fatty acid (TFA) and triacylglycerol (TAG) composition of duckweeds from China. Here, the genetic diversity of a natural duckweed population collected from Lake Chao, China, was investigated using multilocus sequence typing (MLST). The 54 strains were categorised into four species in four genera, representing 12 distinct sequence types. Strains representing Lemna aequinoctialis and Spirodela polyrhiza were predominant. Interestingly, a surprisingly high degree of genetic diversification within L. aequinoctialis was observed. The four duckweed species revealed a uniform fatty acid composition, with three fatty acids, palmitic acid, linoleic acid and linolenic acid, accounting for more than 80% of the TFA. The TFA in biomass varied among species, ranging from 1.05% (of dry weight, DW) for L. punctata and S. polyrhiza to 1.62% for Wolffia globosa. The four duckweed species contained similar TAG contents, 0.02% mg · DW(-1). The fatty acid profiles of TAG were different from those of TFA, and also varied among the four species. The survey investigated the genetic diversity of duckweeds from Lake Chao, and provides an initial insight into TFA and TAG of four duckweed species, indicating that intraspecific and interspecific variations exist in the content and composition of both TFA and TAG in comparison with other studies.

Potential of some aquatic plants for removal of arsenic from wastewater by green technology

Abstract Phytoremediation or green technology is counted among the successful and effective biological contaminated water treatment techniques. Basically, the concept of this green, cost-effective, simple, environmentally nondisruptive method consists in using plants and microbiological processes to reduce contaminants in the ecosystem. Different species from aquatic plants (emerged, free-floating, and submerged) have been studied to mitigate toxic contaminants such as arsenic, cadmium, chromium, copper, lead, mercury, zinc, etc. Arsenic is one of the most severe toxic elements; it is widely distributed in the environment, usually found in combination with chloride, oxygen, sulphur and metal ions as a result of mineral dissolution from sedimentary or volcanic rocks and the dilution of geothermal water. The effluents from both industrial and agricultural sectors are also regarded as sources to contaminate water. From the accumulation point of view, several aquatic plants have been mentioned as good arsenic accumulators and their performance is evaluated using the green technology method. These include Spirodela polyrhiza, Wolffia globosa, Lemna gibba, L. minor, Eichhornia crassipes, Azolla caroliniana, Azolla filiculoides, Azolla pinnata, Ceratophyllum demersum and Pistia stratiotes. The up-to-date information illustrated in this review paper generates knowledge about the ability of some common aquatic plants around the globe to remediate arsenic from contaminated water.

Species distribution, genetic diversity and barcoding in the duckweed family (Lemnaceae)

Duckweeds are a family of aquatic flowering plants that have a high potential for environmental remediation and biofuel manufacture. Two hundred and twenty clones of duckweeds were collected in Hainan Island, China. Based on morphological and phylogenetic analyses of the chloroplast ribosomal protein S16 intron (rps16) and atpF-atpH intergenic spacer sequences, these clones were classified into four species belonging to four genera: Lemna aequinoctialis, Spirodela polyrhiza, Wolffia globosa, and Landoltia punctata. Eight community types including single-, bi-, and/or tri-species communities were observed. L. aequinoctialis was the most widely distributed of the four species. W. globosa has the highest genetic diversity followed by L. aequinoctialis, whereas S. polyrhiza and L. punctata did not show any significant diversity. Duckweeds collected from the south of Hainan had higher diversity than those from the north. Moreover, very high rates of transversional nucleotide substitutions were found in the rps16 sequences of L. aequinoctialis and W. globosa, which make these duckweeds special with respect to nucleotide substitutions.

WOLFFIA GLOBOSA (ROXBURGH) HARTOG ET PLAS (LEMNACEAE): A NEW SPECIES IN BULGARIAN FLORA

Wolffia globosa is one of the smallest flowering plants on the Earth. We discovered Wolffia globosa in a vegetation season unusual for our latitudes - the winter of 2010. The species was discovered in a little pond near the town of Hisar - Plovdiv district, Bulgaria. The plant was together with two other species of Lemnaceae - Lemna gibba and L. minutа in a community with the following aquatic plants: Typha latifolia, Ranunculus aquatilis , Alisma plantago - aquati ca and algae - Spirogyra sp. ster., Tribonema sp.