Growth Of Duckweed Research Articles

Effects of a rhizobacterium on the growth of and chromium remediation by Lemna minor.

Duckweed has shown great potential for both energy and environmental applications, particularly in wastewater treatment and fuel ethanol production. A rhizobacterium, Exiguobacterium sp. MH3, has been reported to associate with the duckweed Lemna minor for symbiotic growth. The aim of this work is to study the effects of rhizobacterium MH3 on L. minor growth and chromium (Cr) remediation. It appeared to have a synergism between the rhizobacterium MH3 and duckweed; the presence of strain MH3 promoted the growth of duckweeds by increasing both the frond number and dry weight of duckweed by more than 30%, while duckweed in turn provided essential carbon source and energy for the growth of rhizobacterium MH3. Under Cr(VI) exposure, particularly at higher Cr(VI) concentrations, Exiguobacterium sp. MH3 significantly alleviated the harmful effects of the stress on the duckweed by promoting duckweed growth and preventing duckweed from excessive uptake of Cr. Potential mechanisms were also discussed in light of the genome sequence of strain MH3, and it was speculated that siderophores and indole-3-acetic acid (IAA) secreted by strain MH3 might contribute to promoting duckweed growth.

Regeneration and Transformation of Gene Encoding the Hemagglutinin Antigen of the H5N1 Virus in Frond of Duckweed (Spirodela polyrhiza L.)

H5N1 (Avian influenza virus) has caused economic loss and remained a serious human health risk in many countries, including Vietnam. Plant-derived vaccines have offered the advantages over tradition subunit vaccine with low-cost production potential. Duckweed (Sprirodela polyrhiza L.) has found a valuable target plant for various application. In this study, we have attempted to re-generate and transform the gene encoding the hemagglutinin antigen of H5N1 virus in frond of S. polyrhiza, a widely great duckweed grown in Vietnam. The results have shown that the culture medium for S. polyrhiza duckweed is Hutner medium with reduced mineral concentration ½ (H/2) supplemented with 10g/l sucrose at pH 6. This medium showed appropriate for the best growth and development of duckweed. Results of PCR analysis of S. polyrhiza lines from 14 transformation experiments that has obtained 4 duckweed lines carrying HA1 gene. This prelinary results will be provide the basis for transgenic research in the dukweed species and be useful for further generate the producing enable vaccine via the transgenic plants

Microbial community and removal of nitrogen via the addition of a carrier in a pilot-scale duckweed-based wastewater treatment system

Carriers were added to a pilot-scale duckweed-based (Lemna japonica 0223) wastewater treatment system to immobilize and enhance microorganisms. This system and another parallel duckweed system without carriers were operated for 1.5years. The results indicated the addition of the carrier did not significantly affect the growth and composition of duckweed, the recovery of total nitrogen (TN), total phosphorus (TP) and CO2 or the removal of TP. However, it significantly improved the removal efficiency of TN and NH4+-N (by 19.97% and 15.02%, respectively). The use of 454 pyrosequencing revealed large differences of the microbial communities between the different components within a system and similarities within the same components between the two systems. The carrier biofilm had the highest bacterial diversity and relative abundance of nitrifying bacteria (3%) and denitrifying bacteria (24% of Rhodocyclaceae), which improved nitrogen removal of the system. An efficient N-removal duckweed system with enhanced microorganisms was established.

Assessment of overall herbicide effects on growth ofduckweed in a flowthrough aquarium carrying pesticide polluted river water

Assessment of overall herbicide effects on growth ofduckweed in a flowthrough aquarium carrying pesticide polluted river water

Reproducibility of effects of homeopathically potentised gibberellic acid on the growth of Lemna gibba L. in a randomised and blinded bioassay

Reproducibility of basic research investigations in homeopathy is challenging. This study investigated if formerly observed effects of homeopathically potentised gibberellic acid (GA3) on growth of duckweed (Lemna gibba L.) were reproducible. Duckweed was grown in potencies (14x-30x) of GA3and one time succussed and unsuccussed water controls. Outcome parameter area-related growth rate was determined by a computerised image analysis system. Three series including five independent blinded and randomised potency experiments (PE) each were carried out. System stability was controlled by three series of five systematic negative control (SNC) experiments. Gibbosity (a specific growth state of L. gibba) was investigated as possibly essential factor for reactivity of L. gibba towards potentised GA3 in one series of potency and SNC experiments, respectively. Only in the third series with gibbous L. gibba L. we observed a significant effect (p=0.009, F-test) of the homeopathic treatment. However, growth rate increased in contrast to the former study, and most biologically active potency levels differed. Variability in PE was lower than in SNC experiments. The stability of the experimental system was verified by the SNC experiments. Gibbosity seems to be a necessary condition for reactivity of L. gibba to potentised GA3. Further still unknown conditions seem to govern effect direction and the pattern of active and inactive potency levels. When designing new reproducibility studies, the physiological state of the test organism must be considered. Variability might be an interesting parameter to investigate effects of homeopathic remedies in basic research.

The influence of barley straw extract addition on the growth of duckweed (Lemna valdivianaPhil.) under laboratory conditions

Due to its ability to forming dense mats in small waterbodies, duckweeds are often considered as nuisance plants in some freshwaters. Up to now, few techniques had been tested aiming towards managing duckweeds, but all of them had appeared to have some disadvantages. As an attempt to find a new effective management tool, a laboratory experiment assessing the influence of barley straw (BS) extract addition – a substance used in algal bloom control, upon the growth of the duckweed Lemna valdiviana, was performed. Reaction on two various concentrations of BS extract were quantified by measurements of changes in duckweed biomass and root length. The results showed that plants which have received the extract increased their biomass slower than that of the control, however only those with the addition of smaller amounts of BS differed significantly from the controls. Furthermore, BS addition stimulated the root growth in both experimental tanks. This implies that the mean roots length was higher, although the statistical differences were insignificant. As possible explanation for the observed changes we suggest that: (1) the growth inhibition of Lemna valvidiana under exposition to BS extract might be induced by an uptake of organic compounds from which some (phenolic substances) are (probably) toxic; (2) competitive interactions with the microbial communities developed upon the duckweed roots might play a role as well.

The logistic growth of duckweed (Lemna minor) and kinetics of ammonium uptake

Mathematical models have been developed to describe nitrogen uptake and duckweed growth experimentally to study the kinetics of ammonium uptake under various concentrations. The kinetics of duckweed ammonium uptake was investigated using the modified depletion method after plants were grown for two weeks at different ammonium concentrations (0.5–14 mg/L) in the culture medium. The maximum uptake rate and Michaelis–Menten constant for ammonium were estimated as 0.082 mg/(g fresh weight·h) and 1.877 mg/L, respectively. Duckweed growth was assessed when supplied at different total nitrogen (TN) concentrations (1–5 mg/L) in the culture medium. The results showed that the intrinsic growth rate was from 0.22 to 0.26 d−1, and TN concentrations had no significant influence on the duckweed growth rate.

Ammonium-induced oxidative stress on plant growth and antioxidative response of duckweed (Lemna minor L.)

This study investigates ammonium (NH4+) uptake kinetics, growth characteristics, and antioxidative response of Lemna minor L. to NH4+ exposure. L. minor was exposed to different NH4+ levels (0.5, 1, 2, 3, and 4mM) for various contact durations (1, 3, 5, 9, and 14d). L. minor grew well in 0.5–3.0mM NH4+, with a relative growth rate of 0.046–0.048d−1. The maximum uptake velocity was achieved at 0.066mgg−1FWh−1, and the growth velocity could be fitted well with the Michaelis–Menten function (R2=0.90507). Plant growth was suppressed, and the chlorophyll and carotenoid contents decreased after “14”-day of exposure on 4mM NH4+. 4mM NH4+ induced oxidative stress and heated the antioxidative response in L. minor after “5”-day of exposure. Superoxide dismutase activity increased in contrast to the peroxidase activity decreasing compared with control. The increased malondialdehyde indicated membrane lipid peroxidation because of incomplete antioxidative reactions.

Phytotoxicity of Sodium Chloride Towards Common Duckweed (Lemna Minor L.) and Yellow Lupin (Lupinus Luteus L.)

Abstract Salinity has adverse effects on plants and is one of the causes of environment degradation. Plants have developed many defensive mechanisms, protecting them from sodium chloride (NaCl), including accumulation of osmoprotective compounds, which maintain osmotic balance, protect cell structure and enzymes. In the current study, we investigated the effects of salinity resulting from a range of sodium chloride concentrations (from 0 to 400 mM) on the growth of common duckweed (Lemna minor L.) and yellow lupin (Lupinus luteus L.). Increasing concentration of sodium chloride decreased the area of common duckweed leaves. At the highest applied salt concentration, the decrease of leaf area was associated with leaf chlorosis. In yellow lupin, the increasing sodium chloride concentration inhibited root and stem elongation. The highest tested NaCl concentration of 400 mM completely stopped elongation of yellow lupin shoots. The content of cyclitols and soluble carbohydrates in plant tissues was evaluated as well. Cyclitols (D -chiro -inositol and D -pinitol), as well as soluble carbohydrates (glucose, fructose and sucrose) were detected in common duckweed tissues. Yellow lupin seedlings also contained cyclitols - D -pinitol, myo -inositol and D -chiro -inositol - and soluble carbohydrates - glucose, galactose and sucrose. The content of osmoprotectants in plant tissues, especially sucrose and cyclitols, increased with increasing concentration of sodium chloride in the soil. The results indicate that the content of cyclitols and soluble carbohydrates in plant tissues can be an indicator of plant response to salinity stress.

Culturing duckweed in the field for starch accumulation

Duckweed, a small floating aquatic plant, is a novel bioenergy crop with great potential to accumulate starch. Three factors involved in the growth and starch accumulation of duckweed were investigated in the field: population, harvesting frequency and nutrient supply. Under identical conditions, Landoltia S3 had the highest maximum growth rate at 30.35g/m2/week; Lemna P1 had the highest N and P absorption rates at 0.622gN/m2/week and 0.135gP/m2/week, respectively; Landoltia OT had the highest starch accumulation rate at 3.88g/m2/week. The protein and P contents in each population decreased as the growth rate slowed. Different harvesting frequencies resulted in different growth rates. However, their biomass had almost the same composition. The addition of 15, 30 and 45ppm NH4+-N inhibited the growth of duckweed. The addition of CaO or microelements dramatically increased duckweed growth. By adding microelements, duckweed could grow in cold weather for an increased time period. With pond water and no sediment supply, duckweed reached the highest starch content of 52.9% with the lowest growth rate, which was the highest starch content in duckweed in the field in literatures. Starch content was negatively correlated with the growth rate, protein and P contents, which suggests that a high growth rate and high starch content in duckweed could hardly be acquired simultaneously. According to this systemic study, an operation process for harvesting high starch duckweed was proposed, paving the way for the large scale exploitation and application of duckweed in bioenergy and feed.

Influence of Salinity on Duckweed Growth and Duckweed Based Wastewater Treatment System

The growth of duckweed (Spirodela polyrrhiza) was investigated in an outdoor batch system under 15 different conductivities ranging from 200 μS/cm to 3000 μS/cm with average 110 μmol/m2 daylight intensity. The growth was performed in an anaerobically treated domestic wastewater using an initial plants population of 50 fronds. Increase in Relative Growth Rate—RGR—(in terms of fresh weight and number of fronds) had a significant non-linear (polynomial) relationship with the conductivity. The maximum RGR related to fresh weight of 0.176 was observed at the conductiviity of 1200 μS/cm while the maximum RGR related to fronds number was 0.193 at the conductivity of 800 μS/cm. The optimum range for duckweeds growth was found to be between conductivities of 600 μS/cm and 1400 μS/cm. The maximal rates of removal of COD of 14.5 mg/day, of 0.65 mg/day, NTK of 15.68 mg/day, faecal coliforms of 100% and turbidity of 80.8% were observed in this range. The COD and PO42- removal rates were highly correlated to the growth rate, with the correlation factor of up to 0.783 and, then to the conductivity. The NTK reduction was positively related to the conductivity.

Responses and toxin bioaccumulation in duckweed (Lemna minor) under microcystin-LR, linear alkybenzene sulfonate and their joint stress

Microcystin-LR (MCLR) and linear alkylbenzene sulfonate (LAS) are commonly found in eutrophic lakes due to toxic cyanobacterial blooms and exogenous organic compounds pollution. However, the ecotoxicological risk of their combination in the aquatic environment is unknown. This study investigated the effects of MCLR, LAS and their mixture on duckweed (Lemna minor) growth and physiological responses. MCLR accumulation in duckweed, with or without LAS, was also examined. Growth of duckweed and chlorophyll-a contents were significantly reduced after 8d exposure to high concentrations of MCLR (≥3μg/ml), LAS (≥20μg/ml) and their mixture (≥3+10μg/ml). After 2d of exposure, superoxide dismutase activity and glutathione content in duckweed increased with increasing concentrations of MCLR, LAS and their mixture, with a significant difference observable after 8d of exposure. When MCLR and LAS concentrations were lower (≤0.1+1μg/ml), the interaction of them is synergistic, but when the concentrations were higher, the synergy was weak. MC accumulation was much higher at 2d than at 8d when duckweed was exposed to lower concentrations of MCLR (≤3μg/ml) or MCLR–LAS (≤3+10μg/ml). Furthermore, LAS significantly enhanced the accumulation of MCLR in duckweed, even with LAS concentrations as low as 0.3μg/ml (environmental concentration), indicating that greater negative ecological risks and higher MCLR phytoremediation potentials of duckweed might occur in MCLR–LAS-concomitant water.

Effects of Injury by a Pyralid Insect Pest on Duckweed Growth and Productivity in Minipond Ecosystem

The strategic points of a pyralid insect, Synclita occidentalis (Pylralidae, Lepidoptera) on duckweed productivity, life cycle and its association with duckweed (host-plant) in pond ecosystem was studied. A total of 16 samples were used to study the infestation intensity and the impact of pest on duckweed production. The insect was found deeply associated with duckweed to complete its life cycle. The pyralid insect attains its pest status at larval stage and continues up-to the pupal stage. Larval and pupal case-making and feeding adaptations were noted as the characteristic nature of injury. The larvae build case with duckweed fronds and roots and use duckweed fronds that failed to multiply further. The crop of larva was the largest and widest part of the alimentary canal and varied exceedingly along with larval category. The experimental result indicated that pest impact in two different experimental miniponds was different in quantities but similar in mode of action. DOI: http://dx.doi.org/10.3329/jbas.v36i1.10920 Journal of Bangladesh Academy of Sciences, Vol. 36, No. 1, 53-59, 2012

Oxidative effects and metabolic changes following exposure of greater duckweed (Spirodela polyrhiza) to diethyl phthalate

The toxicity and effects of diethyl phthalate (DEP), a potent allelochemical, on the growth of greater duckweed were studied. Biochemical analyses and physiological methods were combined to investigate oxidative stress, adverse effects and their mechanisms in greater duckweeds grown in 0–2mM of diethyl phthalate (DEP) after cultivation for 7 days. The results showed that J-shaped concentration response curves were displayed in hydrogen peroxide (H2O2), ascorbic acid (ASA) and dehydroascorbate (DHA) levels, and ascorbate peroxidase (APX) and gualacol peroxidase (POD) activities, indicating reduced oxidative stress and toxic effect. The inverted U-shaped curves were exhibited in relative growth rate (RGR), fresh weight/dry weight (FW/DW) ratio, total chlorophyll content, total soluble thiols, and glutathione reductase (GR) activity, revealing beneficial effect in plant growth. The inverted U-shaped curves were also found in malondialdehyde (MAD) and superoxide radical (O2−) contents with the increasing concentration of DEP, indicative of enhanced oxidative stress. The results suggest that DEP is toxic to the greater duckweed by inducing oxidative stress and antioxidative enzymes may play important roles in the defense strategy against DEP toxicity.

Waste water treatment and metal (Pb2+, Zn2+) removal by microalgal based stabilization pond system

A case study was undertaken for the treatment of domestic wastewater generated at village of Sanghol, Distt. Fatehgarh Sahib, Punjab (India), using a schematic designed algal and duckweed based stabilization pond system, which is discussed here for winter months only (November to March) as there was no growth of duckweeds and only algae dominated the whole system. A proficient increase in pH and dissolved oxygen was observed after the treatment with reduction in chemical oxygen demand and biochemical oxygen demand by 93% and 79% respectively. Chlorella sp. was the dominating algal species in the stabilization pond water during entire period and was studied for its Zn(2+) and Pb(2+) metal removal efficiency. 60-70% removal of Zn(2+) was observed from culture medium containing 5-20 mg L(-1) Zn(2+), which declined to 42% at 50 mg L(-1). A constant decline in cell number from 538 × 10(5) to 8 × 10(5) cells ml(-1) was observed indicating zinc toxicity to Chlorella. Lead was maximally removed by 66.3% from culture medium containing 1 mg L(-1). The lead removal efficiency was 45 50 % at higher 5 to 20 mg L(-1) of external lead concentrations. The increase in cell number indicated no signs of Pb(2+) toxicity up to 20 mg L(-1). The maximum uptake (q(max)) by live Chlorella biomass for both Zn(2+) and Pb(2+) was 34.4 and 41.8 mg/g respectively.

Zinc reduces copper toxicity induced oxidative stress by promoting antioxidant defense in freshly grown aquatic duckweed Spirodela polyrhiza L.

The mechanism by which Zn promotes Cu toxicity in duckweed Spirodela polyrhiza L. was investigated in order to understand the possible interaction between these two metals. Cu uptake was gradually declined by Zn. The induction of oxidative stress is shown by increased levels of lipid peroxidation, total peroxide, superoxide anion and lipoxygenase activity. Zn interaction reduced the oxidative damage. However, only Zn-treated plants did not show alteration in the above observed parameters. The activities of antioxidant enzymes catalase, ascorbate peroxidase and peroxidase showed a very high increase in activity in Cu + Zn treatment as compared to Cu or Zn alone-treated plants. Thus, this study demonstrates that zinc reversed the effect of copper, combating against Cu induced oxidative damage and improvement of duckweed's growth and toxicity under natural condition.

Measurement of the Effects of Liquid Fertilizers at the Different Levels on Duckweed (Lemna Minor L.) Growth Using Image Analysis Technique

ABSTRACTThis study aims the measurement of the effects of liquid fertilizers at different levels on the growth of duckweed (Lemna minor) and to investigate the relationship between the weight and surface area covered by duckweed via image analysis technique. A linear correlation was found between these values (R2=0.972). The equation is indicated as Y=5.10975+0.199898X where X is the surface area covered by duckweed (mm) and Y is the duckweed weight (mg). It can be emphasized that the results calculated by image analysis technique were at par with the results obtained by weighing.

The suitable phosphorus concentration level for restoration by duckweed

The suitable level of phosphorus concentration in waterbody was determined for the growth of duckweed. Lemna minor and Spirodela polyrhiza were cultured in medium containing five different phosphorus concentrations (0.01, 0.2, 0.5, 5 and 50 mg l−1). The increase of frond number, fresh weight, soluble protein, root length, peroxidase, catalase and malondialdehyde were measured. The two species of duckweed can survive under all circumstances. They grew better when phosphorus concentrations were 0.5-5 mg l−1 than other phosphorus concentrations. This study indicated that the two species of duckweed are suitable for recovering the eutrophicated natural waterbodies in China.

Variable toxicity of ionic liquid–forming chemicals to Lemna mino and the influence of dissolved organic matter

Ionic liquids (ILs) are nonvolatile organic salts that remain liquid over a wide range of temperatures. Ionic liquids are promoted as environmentally friendly alternatives to the volatile organic solvents that are currently in widespread industrial usage. Although ILs are unlikely to contribute to air pollution, their potential effects on aquatic ecosystems are largely unknown. Furthermore, information is lacking on how ILs will interact with common features of aquatic environments, such as dissolved organic matter (DOM). We assessed the effect of five IL-forming chemicals on the growth of duckweed, Lemna minor, a common aquatic vascular plant. In general, 1-alkyl-3-methylimidazolium chemicals with longer alkyl chains were more toxic to L. minor than those with short alkyl chain lengths. The concentration that produced a 50% reduction (the EC50) in root growth was 8.56 ppm when a butyl chain was present but was 0.25 ppm (i.e., much more toxic) when an octyl chain was substituted. Butyl-substituted 3-methylpyridinium (root growth EC50 of 7.49 ppm) and 3-methylimidazolium cations had similar toxicity, whereas a tetrabutyl ammonium cation was considerably less toxic (root growth EC50 of 32.71 ppm). When we tested whether DOM reduced the toxicity of these cations, we saw no effect of a low-molecular-weight organic acid or commercial humic matter. In contrast, natural DOM reduced the toxicity of imidazolium, but only at low concentrations. Design and use of ILs and other new chemicals should incorporate not only standard toxicity tests but also information on how such chemicals will interact with other components of aquatic ecosystems.

Effects of artificial ultraviolet‐B radiation on growth and fatty acid composition of duckweed (Lemna minor)

Summary1. Duckweed (Lemna minor), collected either in summer or early fall was exposed under laboratory conditions to control (photosynthetically active and UV‐A radiation) or experimental (control plus UV‐B radiation) conditions.2. Growth and survival were determined by counting the number of green, and brown/white fronds following 1–5 or 11 days of irradiation. Growth of duckweed was impaired by exposure to UV‐B radiation in the fall experiment but not in the summer.3. Fatty acid compositions were analysed following 5 or 11 days of irradiation and a recovery period of 0, 5, 29 or 40 h. Concentrations of the major fatty acids, palmitic, linoleic (LA) and α‐linolenic (ALA) acids were similar in the summer and fall duckweed collections, but the summer samples had higher concentrations of the desaturation products of LA and ALA.4. UV‐B exposure had small, but significant, and contrasting effects on duckweed fatty acid concentrations. In the summer experiment, duckweed exposed to UV‐B had slightly lower concentrations of major fatty acids than control duckweed, while the reverse was true in the fall experiments.5. These minor effects of UV‐B on concentrations of LA and ALA would be unlikely to have a major impact on the supply of these essential fatty acids from duckweed to freshwater food webs.