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{{Taxobox
{{Taxobox
|image = dickweeds.jpg
|image = Duckweeds.jpg
|image_caption = Close up of two different dickweeds: ''[[Spirodela polyrrhiza]]'' and ''[[Wolffia globosa]]''. The latter are less than 2 mm long.
|image_caption = Close up of two different duckweeds: ''[[Spirodela polyrrhiza]]'' and ''[[Wolffia globosa]]''. The latter are less than 2 mm long.
|regnum = [[Plantae]]
|regnum = [[Plantae]]
|unranked_divisio = [[Angiosperms]]
|unranked_divisio = [[Angiosperms]]
Line 16: Line 16:
*''[[Wolffia]]''
*''[[Wolffia]]''
}}
}}
'''dickweeds''', or water lentils, are aquatic plants which float on or just beneath the surface of still or slow-moving fresh water bodies. They arose from within the arum or aroid family, ([[Araceae]]),<ref name="tam">{{citation | journal = American Journal of Botany | year = 2004 | volume = 91 | pages = 490–498 | title = Intergeneric and infrafamilial phylogeny of subfamily Monsteroideae (Araceae) revealed by chloroplast <011>trnL-F sequences | author = Sheh-May Tam, Peter C. Boyce, Tim M. Upson, Denis Barabé, Anne Bruneau, Felix Forest and John S. Parker | doi = 10.3732/ajb.91.3.490 }}</ref> and therefore, often are classified as the subfamily '''Lemnoideae''' within the Araceae. Classifications created prior to the approximate end of the twentieth century tend to classify them as a separate family, '''Lemnaceae'''.
'''Duckweeds''', or water lentils, are aquatic plants which float on or just beneath the surface of still or slow-moving fresh water bodies. They arose from within the arum or aroid family, ([[Araceae]]),<ref name="tam">{{citation | journal = American Journal of Botany | year = 2004 | volume = 91 | pages = 490–498 | title = Intergeneric and infrafamilial phylogeny of subfamily Monsteroideae (Araceae) revealed by chloroplast <011>trnL-F sequences | author = Sheh-May Tam, Peter C. Boyce, Tim M. Upson, Denis Barabé, Anne Bruneau, Felix Forest and John S. Parker | doi = 10.3732/ajb.91.3.490 }}</ref> and therefore, often are classified as the subfamily '''Lemnoideae''' within the Araceae. Classifications created prior to the approximate end of the twentieth century tend to classify them as a separate family, '''Lemnaceae'''.


These plants are very simple, lacking an obvious stem or leaves. They consist of a small 'thalloid' or plate-like structure that floats on or just under the water surface, with or without simple rootlets. The plants are highly reduced from their earlier relatives in [[Araceae]].
These plants are very simple, lacking an obvious stem or leaves. They consist of a small 'thalloid' or plate-like structure that floats on or just under the water surface, with or without simple rootlets. The plants are highly reduced from their earlier relatives in [[Araceae]].


Reproduction is mostly by [[asexual reproduction|asexual]] budding, but occasionally three tiny '[[flower]]s' consisting of two [[stamens]] and a [[pistil]] are produced and [[sexual reproduction]] occurs. Some view this 'flower' as a [[pseudanthium]], or reduced [[inflorescence]], with three flowers that are distinctly either female or male and which are derived from the [[spadix]] in [[Araceae]]. The flower of ''Wolffia'' is the smallest known flower in the world, measuring merely 0.3&nbsp;mm long.<ref>Landolt, E. (1986) Biosystematic investigations in the family of dickweeds (Lemnaceae). Vol. 2. The family of Lemnaceae - A monographic study. Part 1 of the monograph: Morphology; karyology; ecology; geographic distribution; systematic position; nomenclature; descriptions. Veröff. Geobot. Inst., Stiftung Rübel, ETH, Zurich.</ref>
Reproduction is mostly by [[asexual reproduction|asexual]] budding, but occasionally three tiny '[[flower]]s' consisting of two [[stamens]] and a [[pistil]] are produced and [[sexual reproduction]] occurs. Some view this 'flower' as a [[pseudanthium]], or reduced [[inflorescence]], with three flowers that are distinctly either female or male and which are derived from the [[spadix]] in [[Araceae]]. The flower of ''Wolffia'' is the smallest known flower in the world, measuring merely 0.3&nbsp;mm long.<ref>Landolt, E. (1986) Biosystematic investigations in the family of duckweeds (Lemnaceae). Vol. 2. The family of Lemnaceae - A monographic study. Part 1 of the monograph: Morphology; karyology; ecology; geographic distribution; systematic position; nomenclature; descriptions. Veröff. Geobot. Inst., Stiftung Rübel, ETH, Zurich.</ref>
The [[fruit]] produced through this occasional sexual reproduction is a ''[[utricle (fruit)|utricle]]'', and a [[seed]] is produced in a sac containing air that facilitates flotation.
The [[fruit]] produced through this occasional sexual reproduction is a ''[[utricle (fruit)|utricle]]'', and a [[seed]] is produced in a sac containing air that facilitates flotation.


==dickweed in various environments around the world==
==Duckweed in various environments around the world==


dickweed is an important high-[[Protein (nutrient)|protein]] [[food]] source for [[waterfowl]] and also is eaten by humans in some parts of [[Southeast Asia]] (as ''khai-nam''). Sometimes it is cited as an overlooked source for application as a food for a hungry world that produces more protein than soybeans.[http://www.journeytoforever.org/edu_pond.html] [http://www.geocities.com/RainForest/Canopy/3631/]
Duckweed is an important high-[[Protein (nutrient)|protein]] [[food]] source for [[waterfowl]] and also is eaten by humans in some parts of [[Southeast Asia]] (as ''khai-nam''). Sometimes it is cited as an overlooked source for application as a food for a hungry world that produces more protein than soybeans.[http://www.journeytoforever.org/edu_pond.html] [http://www.geocities.com/RainForest/Canopy/3631/]
Some dickweeds are introduced into freshwater [[aquarium]]s and ponds where they may spread rapidly. This introduction may be deliberate or unintended and once established in a large pond, may be difficult to eradicate. Occurring naturally by being carried on the feathers, shells, and coats of native species, the plant is introduced readily by birds, turtles, reptiles, and aquatic mammals visiting multiple ponds, rivers, and lakes. In water bodies with constant currents or overflow, the plants are carried down the water channels and do not proliferate greatly. In some locations a cyclical pattern driven by weather patterns exists in which the plants proliferate greatly during low water flow periods, yet are carried away as rainy periods ensue.
Some duckweeds are introduced into freshwater [[aquarium]]s and ponds where they may spread rapidly. This introduction may be deliberate or unintended and once established in a large pond, may be difficult to eradicate. Occurring naturally by being carried on the feathers, shells, and coats of native species, the plant is introduced readily by birds, turtles, reptiles, and aquatic mammals visiting multiple ponds, rivers, and lakes. In water bodies with constant currents or overflow, the plants are carried down the water channels and do not proliferate greatly. In some locations a cyclical pattern driven by weather patterns exists in which the plants proliferate greatly during low water flow periods, yet are carried away as rainy periods ensue.


The tiny plants provide cover for [[Spawn_(biology)#Fry|fry]] of many aquatic species. The plants are used as shelter by pond water species such as [[bullfrog]]s and [[bluegill]]s. They also provide shade and, although frequently confused with them, can reduce certain light-generated growths of [[photoautotrophic]] [[algae]].
The tiny plants provide cover for [[Spawn_(biology)#Fry|fry]] of many aquatic species. The plants are used as shelter by pond water species such as [[bullfrog]]s and [[bluegill]]s. They also provide shade and, although frequently confused with them, can reduce certain light-generated growths of [[photoautotrophic]] [[algae]].


The plants can provide [[nitrate]] removal, if cropped, and the dickweeds are important in the process of [[bioremediation]] because they grow rapidly, absorbing excess mineral nutrients, particularly [[nitrogen]] and [[phosphates]]. For these reasons they are touted as water purifiers of untapped value.<ref>[http://www.idrc.ca/es/ev-6314-201-1-DO_TOPIC.html dickweed Wastewater Treatment and Reuse for Fodder (West Bank)]</ref>
The plants can provide [[nitrate]] removal, if cropped, and the duckweeds are important in the process of [[bioremediation]] because they grow rapidly, absorbing excess mineral nutrients, particularly [[nitrogen]] and [[phosphates]]. For these reasons they are touted as water purifiers of untapped value.<ref>[http://www.idrc.ca/es/ev-6314-201-1-DO_TOPIC.html Duckweed Wastewater Treatment and Reuse for Fodder (West Bank)]</ref>


The Swiss ''Department of Water and Sanitation in Developing Countries'', SANDEC, associated with the Swiss Federal Institute for Environmental Science and Technology, asserts that as well as the food and agricultural values, dickweed also may be used for [[waste water treatment]] to capture toxins and for odor control, and, that if a mat of dickweed is maintained during harvesting for removal of the toxins captured thereby, it prevents the development of algae and controls the breeding of [[mosquitoes]]. [http://www.eawag.ch/organisation/abteilungen/sandec/publikationen/publications_wra/downloads_wra/dickweed.pdf] The same publication provides an extensive list of references for many dickweed-related topics.
The Swiss ''Department of Water and Sanitation in Developing Countries'', SANDEC, associated with the Swiss Federal Institute for Environmental Science and Technology, asserts that as well as the food and agricultural values, duckweed also may be used for [[waste water treatment]] to capture toxins and for odor control, and, that if a mat of duckweed is maintained during harvesting for removal of the toxins captured thereby, it prevents the development of algae and controls the breeding of [[mosquitoes]]. [http://www.eawag.ch/organisation/abteilungen/sandec/publikationen/publications_wra/downloads_wra/duckweed.pdf] The same publication provides an extensive list of references for many duckweed-related topics.


These plants also may play a role in conservation of water because a cover of dickweed will reduce [[evaporation]] of water when compared to the rate of a similar size water body with a clear surface.
These plants also may play a role in conservation of water because a cover of duckweed will reduce [[evaporation]] of water when compared to the rate of a similar size water body with a clear surface.
==Taxonomy==
==Taxonomy==
The dickweeds long have been a taxonomic mystery, and usually have been considered to be their own family, Lemnaceae. They primarily reproduce asexually. Flowers, if present at all, are small. Roots are either very much reduced, or absent entirely. They were suspected of being related to the Araceae as long ago as 1876, but until the advent of [[molecular phylogeny]] it was difficult to test this hypothesis. Starting in 1995 studies began to confirm their placement in the Araceae and since then, most systematists consider them to be part of that family.<ref name="cabrera"/>
The duckweeds long have been a taxonomic mystery, and usually have been considered to be their own family, Lemnaceae. They primarily reproduce asexually. Flowers, if present at all, are small. Roots are either very much reduced, or absent entirely. They were suspected of being related to the Araceae as long ago as 1876, but until the advent of [[molecular phylogeny]] it was difficult to test this hypothesis. Starting in 1995 studies began to confirm their placement in the Araceae and since then, most systematists consider them to be part of that family.<ref name="cabrera"/>


Their position within their family has been slightly less clear, but several twenty-first century studies place them in the position shown below.<ref name="cabrera">{{citation | journal = American Journal of Botany | year = 2008 | volume = 95 | pages = 1153–1165 | doi = 10.3732/ajb.0800073 | title = Phylogenetic relationships of aroids and dickweeds (Araceae) inferred from coding and noncoding plastid DNA | author = Lidia I. Cabrera, Gerardo A. Salazar, Mark W. Chase, Simon J. Mayo, Josef Bogner and Patricia Dávila }}</ref> They are not closely related to ''[[Pistia]]'', however, which also is an aquatic plant in the family Araceae.<ref name="cabrera"/>
Their position within their family has been slightly less clear, but several twenty-first century studies place them in the position shown below.<ref name="cabrera">{{citation | journal = American Journal of Botany | year = 2008 | volume = 95 | pages = 1153–1165 | doi = 10.3732/ajb.0800073 | title = Phylogenetic relationships of aroids and duckweeds (Araceae) inferred from coding and noncoding plastid DNA | author = Lidia I. Cabrera, Gerardo A. Salazar, Mark W. Chase, Simon J. Mayo, Josef Bogner and Patricia Dávila }}</ref> They are not closely related to ''[[Pistia]]'', however, which also is an aquatic plant in the family Araceae.<ref name="cabrera"/>


{{clade
{{clade
Line 47: Line 47:
}}
}}
|2={{clade
|2={{clade
|1='''Lemnoideae''' (dickweeds)
|1='''Lemnoideae''' (duckweeds)
|2=''most of the family Araceae''
|2=''most of the family Araceae''
}}
}}
}}
}}


The genera of dickweeds are: ''[[Spirodela]]'', ''[[Landoltia punctata|Landoltia]]'', ''[[Lemna]]'', ''[[Wolffiella]]'', and ''[[Wolffia]]''.
The genera of duckweeds are: ''[[Spirodela]]'', ''[[Landoltia punctata|Landoltia]]'', ''[[Lemna]]'', ''[[Wolffiella]]'', and ''[[Wolffia]]''.


==Research==
==Research==
In July 2008 the U.S. Department of Energy (DOE) Joint Genome Institute announced that the Community Sequencing Program would fund the sequencing the genome of the giant dickweed, ''Spirodela polyrhiza''. This was a priority project for DOE in 2009. The research is intended to facilitate new biomass and bio-energy programs.<ref>[http://esciencenews.com/articles/2008/07/08/dickweed.genome.sequencing.has.global.implications dickweed genome sequencing has global implications. E! Science News.]</ref>
In July 2008 the U.S. Department of Energy (DOE) Joint Genome Institute announced that the Community Sequencing Program would fund the sequencing the genome of the giant duckweed, ''Spirodela polyrhiza''. This was a priority project for DOE in 2009. The research is intended to facilitate new biomass and bio-energy programs.<ref>[http://esciencenews.com/articles/2008/07/08/duckweed.genome.sequencing.has.global.implications Duckweed genome sequencing has global implications. E! Science News.]</ref>


dickweed is being studied by researchers around the world as a possible source of clean energy. In the United States, in addition to being the subject of study by the DOE, both [[Rutgers|Rutgers University]] and [[North Carolina State University]] have ongoing projects to determine if dickweed might be a source of cost-effective, clean, [[renewable energy]].<ref>[http://lemna.rutgers.edu/JGICSP.html Genome sequencing of the dickweed Spirodela polyrhiza: a biofuels, bioremediation and carbon cycling crop]</ref><ref>[http://www.ncsu.edu/research/results/vol8n2/09.html Researchers Find Fuel in Odd Places]</ref> dickweed is a good candidate as a biofuel because as a [[biomass]] it grows rapidly, has 5 to 6 times as much starch as corn, and does not contribute to global warming.<ref>[http://sebs.rutgers.edu/spotlight/dickweed.asp Pond Scum As Superhero? A world of power lies in dickweed, a plant the size of a pinhead, according to Rutgers scientists]</ref><ref>[http://www.biomassmagazine.com/article.jsp?article_id=2714&q=&page=all dickweed Quacks Volumes of Potential]</ref><ref>[http://www.pressofatlanticcity.com/news/press/cumberland/article_4ae59e12-56f1-11df-a5d8-001cc4c002e0.html dickweed a possible solution to energy needs, researchers say]</ref><ref>[http://www.the-scientist.com/article/display/56076/ In the muck]</ref> dickweed is considered a carbon neutral energy source, because unlike most fuels, it actually ''removes'' carbon dioxide from the atmosphere.<ref>[http://www.americanenergyindependence.com/carbonneutral.aspx Carbon Neutral Energy]</ref>
Duckweed is being studied by researchers around the world as a possible source of clean energy. In the United States, in addition to being the subject of study by the DOE, both [[Rutgers|Rutgers University]] and [[North Carolina State University]] have ongoing projects to determine if duckweed might be a source of cost-effective, clean, [[renewable energy]].<ref>[http://lemna.rutgers.edu/JGICSP.html Genome sequencing of the duckweed Spirodela polyrhiza: a biofuels, bioremediation and carbon cycling crop]</ref><ref>[http://www.ncsu.edu/research/results/vol8n2/09.html Researchers Find Fuel in Odd Places]</ref> Duckweed is a good candidate as a biofuel because as a [[biomass]] it grows rapidly, has 5 to 6 times as much starch as corn, and does not contribute to global warming.<ref>[http://sebs.rutgers.edu/spotlight/duckweed.asp Pond Scum As Superhero? A world of power lies in duckweed, a plant the size of a pinhead, according to Rutgers scientists]</ref><ref>[http://www.biomassmagazine.com/article.jsp?article_id=2714&q=&page=all Duckweed Quacks Volumes of Potential]</ref><ref>[http://www.pressofatlanticcity.com/news/press/cumberland/article_4ae59e12-56f1-11df-a5d8-001cc4c002e0.html Duckweed a possible solution to energy needs, researchers say]</ref><ref>[http://www.the-scientist.com/article/display/56076/ In the muck]</ref> Duckweed is considered a carbon neutral energy source, because unlike most fuels, it actually ''removes'' carbon dioxide from the atmosphere.<ref>[http://www.americanenergyindependence.com/carbonneutral.aspx Carbon Neutral Energy]</ref>


dickweed also functions as a bioremediator by effectively filtering contaminants such as bacteria, nitrogen, phosphates, and other nutrients from naturally occurring bodies of water, constructed wetlands and waste water.<ref>[http://news.rutgers.edu/medrel/news-releases/2008/07/dickweed-genome-sequ-20080707 dickweed Genome Sequencing Has Global Implications. Pond scum can undo pollution, fight global warming and alleviate world hunger]</ref><ref>[http://www.mobot.org/jwcross/dickweed/practical_dickweed.htm Practical dickweed: Application Areas and Sponsors]</ref><ref>[http://www2.dpi.qld.gov.au/far/9212.html Queensland Government Research project Bioremediation of aquaculture waste and degraded waterways using finfish]</ref> One study in Australia surrounding aquaculture suggests that although dickweed is initially effective as a nutrient filter, over time some nutrient build-up returns.<ref>[http://aciar.gov.au/project/FIS/2004/065 Culture of promising indigenous fish species and bioremediation for barramundi aquaculture in northern Australia and Papua New Guinea]</ref>
Duckweed also functions as a bioremediator by effectively filtering contaminants such as bacteria, nitrogen, phosphates, and other nutrients from naturally occurring bodies of water, constructed wetlands and waste water.<ref>[http://news.rutgers.edu/medrel/news-releases/2008/07/duckweed-genome-sequ-20080707 Duckweed Genome Sequencing Has Global Implications. Pond scum can undo pollution, fight global warming and alleviate world hunger]</ref><ref>[http://www.mobot.org/jwcross/duckweed/practical_duckweed.htm Practical Duckweed: Application Areas and Sponsors]</ref><ref>[http://www2.dpi.qld.gov.au/far/9212.html Queensland Government Research project Bioremediation of aquaculture waste and degraded waterways using finfish]</ref> One study in Australia surrounding aquaculture suggests that although duckweed is initially effective as a nutrient filter, over time some nutrient build-up returns.<ref>[http://aciar.gov.au/project/FIS/2004/065 Culture of promising indigenous fish species and bioremediation for barramundi aquaculture in northern Australia and Papua New Guinea]</ref>


<gallery>
<gallery>
Image:LentejasDeAgua.jpg|Common dickweed in [[Galicia (Spain)|Galicia]], Spain
Image:LentejasDeAgua.jpg|Common duckweed in [[Galicia (Spain)|Galicia]], Spain
Image:Lemna minor1.jpg|''Lemna minor''
Image:Lemna minor1.jpg|''Lemna minor''
Image:Lemna trisulca0.jpg|''Lemna trisulca''
Image:Lemna trisulca0.jpg|''Lemna trisulca''
Line 71: Line 71:
<gallery>
<gallery>
File:Spirodela polyrrhiza marais poitevin.jpg|''Spirodela polyrhiza''
File:Spirodela polyrrhiza marais poitevin.jpg|''Spirodela polyrhiza''
File:Canaux du marais à Maillezais.jpg|Canal green with dickweed
File:Canaux du marais à Maillezais.jpg|Canal green with duckweed
File:Curve of dickweed covered water edged with several bald cypress trees.JPG|dickweed-covered water edged with several [[bald cypress]] trees
File:Curve of duckweed covered water edged with several bald cypress trees.JPG|Duckweed-covered water edged with several [[bald cypress]] trees
</gallery>
</gallery>


Line 86: Line 86:


==External links==
==External links==
* [http://www.mobot.org/jwcross/dickweed/ The Charms of dickweed] by John W. Cross.
* [http://www.mobot.org/jwcross/duckweed/ The Charms of Duckweed] by John W. Cross.
* [http://waynesword.palomar.edu/1wayindx.htm Wayne Armstrong's treatment of the Lemnaceae] and allies
* [http://waynesword.palomar.edu/1wayindx.htm Wayne Armstrong's treatment of the Lemnaceae] and allies
* [http://delta-intkey.com/angio/www/lemnacea.htm Lemnaceae] in Watson, L. and M.J. Dallwitz (1992 onwards). ''[http://delta-intkey.com/angio/ The families of flowering plants]: descriptions, illustrations, identification, information retrieval.'' Version: 3 May 2006. http://delta-intkey.com
* [http://delta-intkey.com/angio/www/lemnacea.htm Lemnaceae] in Watson, L. and M.J. Dallwitz (1992 onwards). ''[http://delta-intkey.com/angio/ The families of flowering plants]: descriptions, illustrations, identification, information retrieval.'' Version: 3 May 2006. http://delta-intkey.com
* [http://lemna.rutgers.edu The dickweed Genome Project]
* [http://lemna.rutgers.edu The Duckweed Genome Project]


{{Bioenergy}}
{{Bioenergy}}

Revision as of 09:29, 20 September 2010

Lemnoideae
Close up of two different duckweeds: Spirodela polyrrhiza and Wolffia globosa. The latter are less than 2 mm long.
Scientific classification
Kingdom:
Plantae
(unranked):
Angiosperms
(unranked):
Monocots
Order:
Alismatales
Family:
Araceae
Subfamily:
Lemnoideae
Genus

Duckweeds, or water lentils, are aquatic plants which float on or just beneath the surface of still or slow-moving fresh water bodies. They arose from within the arum or aroid family, (Araceae),[1] and therefore, often are classified as the subfamily Lemnoideae within the Araceae. Classifications created prior to the approximate end of the twentieth century tend to classify them as a separate family, Lemnaceae.

These plants are very simple, lacking an obvious stem or leaves. They consist of a small 'thalloid' or plate-like structure that floats on or just under the water surface, with or without simple rootlets. The plants are highly reduced from their earlier relatives in Araceae.

Reproduction is mostly by asexual budding, but occasionally three tiny 'flowers' consisting of two stamens and a pistil are produced and sexual reproduction occurs. Some view this 'flower' as a pseudanthium, or reduced inflorescence, with three flowers that are distinctly either female or male and which are derived from the spadix in Araceae. The flower of Wolffia is the smallest known flower in the world, measuring merely 0.3 mm long.[2] The fruit produced through this occasional sexual reproduction is a utricle, and a seed is produced in a sac containing air that facilitates flotation.

Duckweed in various environments around the world

Duckweed is an important high-protein food source for waterfowl and also is eaten by humans in some parts of Southeast Asia (as khai-nam). Sometimes it is cited as an overlooked source for application as a food for a hungry world that produces more protein than soybeans.[1] [2]

Some duckweeds are introduced into freshwater aquariums and ponds where they may spread rapidly. This introduction may be deliberate or unintended and once established in a large pond, may be difficult to eradicate. Occurring naturally by being carried on the feathers, shells, and coats of native species, the plant is introduced readily by birds, turtles, reptiles, and aquatic mammals visiting multiple ponds, rivers, and lakes. In water bodies with constant currents or overflow, the plants are carried down the water channels and do not proliferate greatly. In some locations a cyclical pattern driven by weather patterns exists in which the plants proliferate greatly during low water flow periods, yet are carried away as rainy periods ensue.

The tiny plants provide cover for fry of many aquatic species. The plants are used as shelter by pond water species such as bullfrogs and bluegills. They also provide shade and, although frequently confused with them, can reduce certain light-generated growths of photoautotrophic algae.

The plants can provide nitrate removal, if cropped, and the duckweeds are important in the process of bioremediation because they grow rapidly, absorbing excess mineral nutrients, particularly nitrogen and phosphates. For these reasons they are touted as water purifiers of untapped value.[3]

The Swiss Department of Water and Sanitation in Developing Countries, SANDEC, associated with the Swiss Federal Institute for Environmental Science and Technology, asserts that as well as the food and agricultural values, duckweed also may be used for waste water treatment to capture toxins and for odor control, and, that if a mat of duckweed is maintained during harvesting for removal of the toxins captured thereby, it prevents the development of algae and controls the breeding of mosquitoes. [3] The same publication provides an extensive list of references for many duckweed-related topics.

These plants also may play a role in conservation of water because a cover of duckweed will reduce evaporation of water when compared to the rate of a similar size water body with a clear surface.

Taxonomy

The duckweeds long have been a taxonomic mystery, and usually have been considered to be their own family, Lemnaceae. They primarily reproduce asexually. Flowers, if present at all, are small. Roots are either very much reduced, or absent entirely. They were suspected of being related to the Araceae as long ago as 1876, but until the advent of molecular phylogeny it was difficult to test this hypothesis. Starting in 1995 studies began to confirm their placement in the Araceae and since then, most systematists consider them to be part of that family.[4]

Their position within their family has been slightly less clear, but several twenty-first century studies place them in the position shown below.[4] They are not closely related to Pistia, however, which also is an aquatic plant in the family Araceae.[4]

Gymnostachydoideae

Orontioideae (skunk cabbages and golden club)

Lemnoideae (duckweeds)

most of the family Araceae

The genera of duckweeds are: Spirodela, Landoltia, Lemna, Wolffiella, and Wolffia.

Research

In July 2008 the U.S. Department of Energy (DOE) Joint Genome Institute announced that the Community Sequencing Program would fund the sequencing the genome of the giant duckweed, Spirodela polyrhiza. This was a priority project for DOE in 2009. The research is intended to facilitate new biomass and bio-energy programs.[5]

Duckweed is being studied by researchers around the world as a possible source of clean energy. In the United States, in addition to being the subject of study by the DOE, both Rutgers University and North Carolina State University have ongoing projects to determine if duckweed might be a source of cost-effective, clean, renewable energy.[6][7] Duckweed is a good candidate as a biofuel because as a biomass it grows rapidly, has 5 to 6 times as much starch as corn, and does not contribute to global warming.[8][9][10][11] Duckweed is considered a carbon neutral energy source, because unlike most fuels, it actually removes carbon dioxide from the atmosphere.[12]

Duckweed also functions as a bioremediator by effectively filtering contaminants such as bacteria, nitrogen, phosphates, and other nutrients from naturally occurring bodies of water, constructed wetlands and waste water.[13][14][15] One study in Australia surrounding aquaculture suggests that although duckweed is initially effective as a nutrient filter, over time some nutrient build-up returns.[16]

  • Common duckweed in Galicia, Spain
    Common duckweed in Galicia, Spain
  • Lemna minor
    Lemna minor
  • Lemna trisulca
    Lemna trisulca
  • Lemna gibba.
    Lemna gibba.

Turning the canals of the Poitevin Marsh (Marais Poitevin, France) into the "Green Venice":

  • Spirodela polyrhiza
    Spirodela polyrhiza
  • Canal green with duckweed
    Canal green with duckweed
  • Duckweed-covered water edged with several bald cypress trees
    Duckweed-covered water edged with several bald cypress trees

See also

Wikimedia Commons has media related to Lemnaceae.

References

  1. ^ Sheh-May Tam, Peter C. Boyce, Tim M. Upson, Denis Barabé, Anne Bruneau, Felix Forest and John S. Parker (2004), "Intergeneric and infrafamilial phylogeny of subfamily Monsteroideae (Araceae) revealed by chloroplast <011>trnL-F sequences", American Journal of Botany, 91: 490–498, doi:10.3732/ajb.91.3.490{{citation}}: CS1 maint: multiple names: authors list (link)
  2. ^ Landolt, E. (1986) Biosystematic investigations in the family of duckweeds (Lemnaceae). Vol. 2. The family of Lemnaceae - A monographic study. Part 1 of the monograph: Morphology; karyology; ecology; geographic distribution; systematic position; nomenclature; descriptions. Veröff. Geobot. Inst., Stiftung Rübel, ETH, Zurich.
  3. ^ Duckweed Wastewater Treatment and Reuse for Fodder (West Bank)
  4. ^ a b c Lidia I. Cabrera, Gerardo A. Salazar, Mark W. Chase, Simon J. Mayo, Josef Bogner and Patricia Dávila (2008), "Phylogenetic relationships of aroids and duckweeds (Araceae) inferred from coding and noncoding plastid DNA", American Journal of Botany, 95: 1153–1165, doi:10.3732/ajb.0800073{{citation}}: CS1 maint: multiple names: authors list (link)
  5. ^ Duckweed genome sequencing has global implications. E! Science News.
  6. ^ Genome sequencing of the duckweed Spirodela polyrhiza: a biofuels, bioremediation and carbon cycling crop
  7. ^ Researchers Find Fuel in Odd Places
  8. ^ Pond Scum As Superhero? A world of power lies in duckweed, a plant the size of a pinhead, according to Rutgers scientists
  9. ^ Duckweed Quacks Volumes of Potential
  10. ^ Duckweed a possible solution to energy needs, researchers say
  11. ^ In the muck
  12. ^ Carbon Neutral Energy
  13. ^ Duckweed Genome Sequencing Has Global Implications. Pond scum can undo pollution, fight global warming and alleviate world hunger
  14. ^ Practical Duckweed: Application Areas and Sponsors
  15. ^ Queensland Government Research project Bioremediation of aquaculture waste and degraded waterways using finfish
  16. ^ Culture of promising indigenous fish species and bioremediation for barramundi aquaculture in northern Australia and Papua New Guinea
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