Growth Of Duckweed Research Articles

Comprehensive modeling of mat density effect on duckweed ( Lemna minor) growth under controlled eutrophication

The effect of mat density on duckweed (Lemna minor) growth was studied under controlled conditions: 12.5 h a day light exposure and 342 mol m −2 s −1 light intensity at 20 °C. The plant growth was carried out in Hoagland medium for 7 days without harvesting. The results revealed a maximal biomass growth rate of 88 g-dry m −2 (1470 g-wet m −2) at an optimal initial mat density of 45 g-dry m −2 (750 g-wet m −2), with removal rates for nitrogen (N) and phosphorus (P) of 483 mg-N m −2 d −1 and 128 mg-P m −2 d −1, respectively. A mathematical model that takes into account the mat density was developed in order to simulate the growth of Lemna minor under controlled eutrophication. Based on experiments carried out, the model exhibits a reliability of 89% . The model remains to be validated at the full-scale level.

The strength of limiting factors for duckweed during algal competition

Duckweed (Lemna gibba) growth was found to be strongly reduced by unicellular green algae (Scenedesmus conspicua, Chlorella sp., Chlamydomonas sp.) in indoor experiments. These algae reduced N, P, Fe and Mn concentrations of the medium drastically, moreover they increased the pH beyond 10. Subsequent additions of nutrients and pH neutralisation removed the growth inhibition of duckweed. This growth inhibition is, therefore, concluded to be due to pH increase and N, P and trace element (Fe, Mn) removal. Of the five factors significantly inhibiting duckweed growth, depletion of N was strongest, increase in pH was second, followed by reduction of P > Fe > Mn.

Chemical constituents of rice (Oryza sativa) hulls and their herbicidal activity against duckweed (Lemna paucicostata Hegelm 381)

Four new compounds, stigmastanol-3beta-p-glyceroxydihydrocoumaroate (1), stigmastanol-3beta-p-butanoxydihydrocoumaroate (2), lanast-7,9(11)-dien-3alpha,15alpha-diol-3alpha-D-glucofuranoside (3) and 1-phenyl-2-hydroxy-3,7-dimethyl-11-aldehydic-tetradecane-2-beta-D-glucopyranoside (4), along with several known compounds were isolated from the methanol extract of hulls of Oryza sativa. The new structures were established by one- and two-dimensional NMR and in combination with IR, EI/MS, FAB/MS and HR-FAB/ MS. Compound (3) strongly inhibited the growth of duckweed (Lemna paucicostata Hegelm 381), whilst compounds (2) and (4) exhibited weak inhibition.

Effects of stagnating sulphate-rich groundwater on the mobility of phosphate in freshwater wetlands: a field experiment

Water tables in the Netherlands have been greatly lowered in recent decades, largely in order to favour agricultural activities. Drought and increased nitrate (NO3-) leaching from agricultural land lead to oxidation of iron-sulphide (FeSx) in the subsoil, resulting in increased sulphate (SO42-) concentrations in the groundwater. In addition, increased atmospheric sulphur (S) deposition and leaching of SO42- from agricultural land have increased SO42- concentrations in the groundwater. Attempts to retain groundwater in desiccated wetlands by simply damming drainage ditches have resulted in greatly increased retention times of the water, die-back of the original vegetation and massive development of algae and lemnids in summer. In order to determine whether stagnation of SO42--rich groundwater plays an important role in eutrophication, nine bottomless enclosures were placed in the sediment of an open water body to block the supply of groundwater. Na2SO4 was added to three enclosures twice a year to simulate a minimised input of SO42--rich groundwater. In addition NaCl was added to three enclosures, while three enclosures were left untreated. (Pore) water quality and vegetation development were compared with those at seepage-fed sites outside the enclosures. The results show that stagnating SO42--rich groundwater led to increased SO42- reduction in the sediment, resulting in phosphate (o-PO43-) mobilisation from the sediment and eutrophication of the water layer, due to the interference of S2- with the iron-phosphorous cycle. This was accompanied by massive growth of common duckweed (Lemna minor) and filamentous algae and a decreased growth of broad-leaved pondweed (Potamogeton natans). The consistently high input of SO(4)2- via seepage did not lead to eutrophication. The results indicated that SO42- reduction rates at sites fed by seepage were very low. This was probably caused by the consistently high input of Fe and NO3- via the groundwater, which prevents reduction of SO42- by providing energetically more favourable electron acceptors. In fens with stagnating groundwater, Fe and NO3- will be rapidly depleted, stimulating SO42- reduction resulting in development of toxic S2- concentrations and eutrophication of the water layer.

INTERLABORATORY STUDY CEN-METHODS FOR THE ANALYSIS OF GROWING MEDIA AND SOIL IMPROVERS

For testing phytotoxicity many methods have been developed. In this experiment some methods are compared. Tests with development of cucumber cotyledons, luminescence of bacteria, growth of duckweed and root growth of germinating seeds of kohlrabi and garden cress are compared. All tests were suitable but the bioassay where development of cucumber cotyledons is determined and the luminescence of bacteria were the most practicable. The different bioassays give comparable results but they cannot always be converted directly. The different bioassays can be used when in a short time results are needed or when experience has learned that e.g. phytotoxic substances can be expected from a certain production process. For a more robust general bioassay an adapted version of ISO 11269-2 (1995) standard for testing the soil quality looks promising, although the adaptations still have to be tested.

Ciliate populations in temporary freshwater ponds: seasonal dynamics and influential factors.

SUMMARY 1. The ciliate populations of two temporary ponds in southern Ontario were studied throughout their aquatic phases in 2001. Pond I (∼1 ha) held water for 98 days, whereas Pond II (∼0.25 ha) held water for 34 days. Populations were assessed both within the ponds themselves and within a series of enclosures in which invertebrate predator pressure was manipulated.2. In the natural pond water, total ciliate abundance in Pond II rose rapidly from day 1 increasing two orders of magnitude by day 7. In contrast, total abundance in Pond I began at the same level as in Pond II but increased much more slowly, reached a plateau of around 500 individuals L−1, and increased again late in the hydroperiod.3. Despite being only 500 m apart, the two ponds were fairly dissimilar in terms of their species richness and species composition. Pond I contained 50 species compared with 70 species for Pond II, with only 24 species shared. Additional species occurred within the enclosures raising the total species richness to 145 species; 88 from Pond I, 104 from Pond II, with 47 species (30%) in common. Pond II contained more mid‐sized ciliates (50–200 μm), whereas Pond I was dominated by smaller ciliates, especially in mid‐May and early June. In Pond I, cumulative species richness throughout the hydroperiod was highest in the predator addition enclosures (65 ± 4 species), followed by the partial‐predator exclusion enclosures (50 ± 4). Lowest species richness was found in the control enclosures (39 ± 2) and in the pondwater controls (39 ± 0). Differences between the ciliates in the natural pond water and the enclosures appeared to be related to a greater concentration of phytoplankton within the enclosures (perhaps resulting from extensive growth of duckweed, Lemna, outside), and higher densities of zooplankters in the pond.4. The physicochemical environment influenced species richness, total abundance and the number of rare species (27 in Pond II versus 13 in Pond I). Variation in ciliate abundance in Pond I could be explained by the number of days after filling (39%) and enclosure treatment (23%). These two parameters also explained 72% of the variation in species richness in Pond I (46 and 26%, respectively). Sixty‐five per cent of the variation in abundance in Pond II could be explained by the measured parameters: number of days after filling 27%, pH 19%, and nitrate levels 12%. Fifty‐two per cent of the variation in species richness was explained by the environmental parameters, of which pH was the most influential. Species succession was a strong feature of both ponds and its relationship to environmental variables and the presence of other organisms is discussed.5. Addition of invertebrate predators resulted in higher abundance and higher species richness for a limited time period in one of the ponds – suggesting that differences in foodweb dynamics may influence ciliate community composition.

Does Spirodela punctata break P-C bonds?

Spirodela punctata was cultivated on phosphate-deficient medium (-Pi) with racemic 1-amino-2-phenylethylphosphonic acid (PheP) as a source of Pi. The growth of duckweed was inversely correlated with PheP concentration. The growth of plants on medium -Pi with 0.1 M PheP was accelerated whereas with 0.001 mM PheP was slower than in -Pi control. PheP at low concentrations decreased loss of chlorophyll in comparison with -Pi plants. Content of anthocyanins decreased but activity of the extractable constitutive phosphatases of pH 6.0 and pH 7.5 increased along with increasing concentration of PheP in the medium. We suggest that S. punctata does not break P-C bonds but probably PheP interrupts processes involved in the regulation of Pi-starvation response.

Phytotoxicity of coloured substances: is Lemna duckweed an alternative to the algal growth inhibition test?

Coloured substances cause problems when interpreting algal tests, because effects due to light absorption can interact with potential toxicity. The Lemna Duckweed growth inhibition test can complement the algal test, on condition that the test is performed on a black, not reflecting surface. On white surfaces, test solution colour can strongly impact Lemna growth. For example, average control sample growth rate of is much higher on white surfaces (0.362 d(-1)) than on black surfaces (0.284 d(-1)). We found that 10 mg l(-1) of the dyestuff "Brilliant Blue R spezial" inhibited average Lemna growth rate about 22% on white surfaces but did not inhibit growth on black surfaces. The reason for this difference stems from the difference in amount of light reflected from below the test beakers. With Brilliant Blue on white surfaces, the test solution colour reduces utilizable light and causes a deterioration of light conditions, whereas on a black surfaces, reflected light is absent a priori, and thus no inhibiting effect was measured. Of particular importance is the choice of test parameter. With Brilliant Blue, a LOEC for average growth rate, based on frond numbers, of 320 mg l(-1) was determined. However, when average growth rate was calculated using dry weights of the plants, the LOEC decreased clearly to 1.0 mg l(-1). In this study, the Lemna test was much more sensitive than the algal test. We recommend Lemna tests be used in addition to algal tests, because doing so may significantly improve the assessment of phytotoxicity of chemicals and sewage.

Elemental flux between algae and duckweeds (Lemna gibba) during competition

Axenic Lemna gibba fronds were co-cultured with five green algal, three diatom and three cyanobacterial species and were grown separately and in mixed combination on autoclaved communal wastewater. These species were obtained from a local minipond containing wastewater covered by duckweeds. The impact of selected algal species on bioproduction of Lemna cultures was measured. The flux of elements during competition for nutrients between algae and duckweeds was examined. When the duckweed cover was incomplete, duckweeds had no impact on the multiplication of algae. Under this condition, algae showed a much stronger competitive effect for nutrients against Lemna, because algal nutrient removal was much more intensive than the nutrient removal of the fronds. The elemental composition of the water was mainly determined by algae. In Lemna-alga cocultures, the elemental concentration of the water was lowered to below 0.01 mg/l for phosphorus and for iron due to the algal activity. They were below the minimal concentrations for growth of duckweeds. Algae increased the pH of the water to above 10, which resulted in 5.5 mg/l NH 3 -N in the medium. The elemental concentration of the algal treated fronds decreased by 87 % for phosphorus and by 90 % for iron. Results suggested that during competition with algae, iron and phosphorus became a potential minimum factor for duckweeds.

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

Growth-Retarding Effect of 2-Aminoindan-2-phosphonic Acid on Spirodela punctata

2-Aminoindan-2-phosphonic acid (AIP) retarded the growth of duckweed, Spirodela punctata, and increased its dry mass. The accumulation of starch was observed at all concentrations of AIP at 8 days after treatment. The increase in starch was inversely proportional to the growth. The retarded growth of Spirodela by AIP was not limited only by excessive starch accumulation.

Use of Duckweed ( Lemna minor L.) growth inhibition test to evaluate the toxicity of acrylonitrile, sulphocyanic sodium and acetonitrile in China

This study was designed to evaluate the acute toxicity of three major pollutants (acrylonitrile, sulphocyanic sodium and acetonitrile) in acrylonitrile-acrylic effluents to Lemna minor using the growth inhibition test. As well, the study wanted to determine if L. minor can be used as an effective bioassay organism in China. The experimental approach involved exposure of L. minor under standard laboratory conditions to the three chemicals. The results indicated that the 96 h–IC 50s of the three chemicals to L. minor were 27.08 mg litre −1, 3663 mg litre −1 and 3685 mg litre −1, respectively, while using the relative growth rate as the IC 50 endpoint. L. minor proved to be a practical bioassay organism because the L. minor toxicity test is simple, sensitive, and cost-effective.

The influence of coins on the growth of duckweed

The influences of a British one-pence coin and a Japanese ten-yen coin on the growth of duckweed were studied. These coins inhibited the growth of duckweed It is well known that copper inhibits the growth of plants, but there are few good materials to demonstrate this fact to students. We used a British one-pence and a Japanese ten-yen coin instead of copper, because they are made mainly of copper. Duckweed serves as an indicator plant, for it could easily be collected and its frond number would increase over a short period, i.e. one or two weeks. The growth could be evaluated by counting the number of fronds. Both coins inhibited the growth of duckweed. Spirodela died in a solution containing a penny after 10 days' culture, and after nine days with a ten-yen coin. The growth curve of Lemna is very similar to Spirodela. From these results, the coin and duckweed investigations were considered to be suitable materials for use in environmental education.

Effects of rodeo® and garlon® 3A on nontarget wetland species in central Washington

AbstractPurple loosestrife (Lythrum salicaria) is an invasive wetland perennial that became established in northeastern North America in the early 1800s. Despite its designation as a noxious weed, its distribution has continued to expand. Treatment with herbicides is the most widely used means of controlling purple loosestrife. This study examined the nontarget effects of two herbicides, Rodeo® and Garlon® 3A, currently used or being considered for use in controlling purple loosestrife in Washington State, respectively. Growth and/or survival of duckweed, Daphnia, and rainbow trout were monitored for at least 24 h following an application of each herbicide. Free‐living water column and benthic invertebrates were monitored 24 h and 7 d post‐spray using activity traps and sediment cores. Neither chemical was associated with significant decreases in survival or growth of the bioassay organisms, with the exception that growth of duckweed was reduced 48 h after exposure to Rodeo. Nor were significant decreases in the abundance of free‐living aquatic invertebrates detected following the herbicide applications. Results suggest that neither herbicide, at the application rates used, poses a hazard to aquatic invertebrates in wetlands in central Washington. However, Rodeo, because it is a broad‐spectrum herbicide, may pose a greater hazard to nontarget aquatic vegetation.

EFFECTS OF RODEO® AND GARLON® 3A ON NONTARGET WETLAND SPECIES IN CENTRAL WASHINGTON

Purple loosestrife (Lythrum salicaria) is an invasive wetland perennial that became established in northeastern North America in the early 1800s. Despite its designation as a noxious weed, its distribution has continued to expand. Treatment with herbicides is the most widely used means of controlling purple loosestrife. This study examined the nontarget effects of two herbicides, Rodeo® and Garlon® 3A, currently used or being considered for use in controlling purple loosestrife in Washington State, respectively. Growth and/or survival of duckweed, Daphnia, and rainbow trout were monitored for at least 24 h following an application of each herbicide. Free-living water column and benthic invertebrates were monitored 24 h and 7 d post-spray using activity traps and sediment cores. Neither chemical was associated with significant decreases in survival or growth of the bioassay organisms, with the exception that growth of duckweed was reduced 48 h after exposure to Rodeo. Nor were significant decreases in the abundance of free-living aquatic invertebrates detected following the herbicide applications. Results suggest that neither herbicide, at the application rates used, poses a hazard to aquatic invertebrates in wetlands in central Washington. However, Rodeo, because it is a broad-spectrum herbicide, may pose a greater hazard to nontarget aquatic vegetation.

Effects of zinc and copper on growth and metal accumulation in duckweed, Lemna minor

Heavy metal pollutants are known to be quite toxic to a wide variety of aquatic plants. Lemna (duckweed), due to its special feature, is sought as a test organism for aquatic pollutant studies and for wastewater treatment. Lemna grows rapidly and reproduces vegetatively; its biomass is measured easily. It is adaptable to various aquatic conditions; it extacts and also accumulates metals in its frond bodies. Among the metals, Cu is classified as extremely toxic and Zn is classified as moderately toxic to Lemna. It is reported that both Cu and Zn concentrations in the medium have a great impact on the growth responses and the physiological processes in Lemna. Deficiencies in Cu and Zn resulted in chlorosis of L.minor fronds and low concentrations of CU interfered with the floral induction in L.minor and L.gibba. Excess Cu inhibited both frond growth and frond multiplication of L. paucicostata and it decreased the content of chlorophyll [alpha] and photosynthetic CO[sub 2] uptake in L.minor. In water bodies, metals always are present in combination. Consequently, metal pair interaction is a factor to be considered. However, there are few studies on the effects of metal pair interactions on duckweed growth and metal accumulation. The purposemore » of this study was to investigate the effects of increased concentrations of Zn and Cu in combination on growth and metal accumulation by Lemna minor L. under controlled laboratory conditions. Zn and Cu were chosen since they are known as essential trace elements for duckweed up to a certain concentration; above that growth inhibition might occur. 16 refs., 3 figs., 6 tabs.« less

Metabolism of allenic analogues of abscisic acid

We have already reported that some allenic analogues of abscisic acid inhibited growth of duckweed ( Lemna gibba and L. paucicostata) in axenic

Cultivation of duckweeds in septage-loaded earthen ponds

A series of three experiments was conducted on the cultivation of duckweeds ( Spirodela polyrrhiza, Lemna perpusilla ) and Wolffia arrhiza ) in 200 m 2 septage-fed earthen ponds. Mean short- and long-term (27 and 182 days) extrapolated yields of Spirodela were 21·4 and 9·2 t dry wt/ha/year in Experiments 1 and 2, respectively. In the 90 days of Experiment 3, extrapolated yields of Spirodela and Lemna were 20·4 and 10·9 t dry wt/ha/year, respectively. Growth of Lemna continued for 160 days, but it was contaminated with Wolffia which reduced the yield. Mean crude protein contents of Spirodela and Lemna were 24·1 and 28·0% dry matter, respectively. Duckweed nitrogen and phosphorus contents increased significantly with an increase in nitrogen and phosphorus concentrations of pond water. Algal blooms, insect infestation, wind, low temperature, and loss of pigments and decay of duckweeds had noticeable effects on the growth and productivity of duckweeds.

Ammonia toxicity to macrophytes (common duckweed and rice) using static and renewal methods

AbstractAmmonia is a widespread contaminant that occurs in municipal wastewaters, industrial wastewaters, and agricultural wastes. Most ammonia toxicity studies deal with species of fish and macroinvertebrates, but very little information is available on ammonia phytotoxicity. The objectives of this study were to compare ammonia toxicity by using static and renewal methods and to compare phytotoxicity tests by using the vascular plants common duckweed and rice. Un‐ionized ammonia‐N at the rate of 8.85 mg/L inhibited rice seedling growth by 27%, using the renewal method, whereas the same amount caused insignificant effects on rice growth, using the static method. Ammonia‐N at up to 8.85 mg/L did not inhibit duckweed growth, using the static method. By using the renewal method, un‐ionized ammonia‐N at concentrations greater than 3.0 mg/L depressed duckweed growth noticeably (20% or more). The increased ammonia concentration inhibited duckweed growth correspondingly, producing a linear relation for the concentration‐inhibition effect. An un‐ionized ammonia‐N concentration of 7.16 mg/L was calculated to cause 50% duckweed growth inhibition (IC50), and 95% confidence limits ranged from 6.33 to 8.47 mg/L.

The effect of various aquatic bacteria on the growth and senescence of duckweed (Lemna minor)

Five different species of freshwater bacteria (Pseudomonas sp., Vibrio sp., Klebsiella sp., Enterobacter sp., Serratia sp.) and a mixed natural population were used separately to inoculate cultures of axenic duckweed (Lemna minor). Inoculation with Vibrio sp. caused the final population density of Lemna plants to be significantly greater after 52 d than that of either axenic controls or Lemna inoculated with a mixed bacterial community. Inoculation with Pseudomonas sp. caused the final population density of Lemna to be significantly higher than with the mixed bacterial treatment. Inoculation of Lemna with Klebsiella sp., Enterobacter sp. or Serratia sp. resulted in higher plant populations compared with controls, but these differences were not statistically significant. The presence of a mixed community of bacteria did not significantly affect the final population density of Lemna compared with the controls. However, Lemna plants inoculated with a natural population of bacteria showed significantly higher levels of senescence compared with the other five treatments and the controls. None of the five single bacterial taxa used appeared to have any significant effect of the sensescence of duckweed.