Duckweed

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Duckweed
Duckweeds.jpg
Close-up of two different duckweeds : Spirodela polyrrhiza (larger) and Wolffia globosa, which are less than 2 mm long.
Scientific classification e
Kingdom: Plantae
Clade: Angiosperms
Clade: Monocots
Order: Alismatales
Family: Araceae
Subfamily: Lemnoideae
Single plants of duckweed (Lemna gibba) in a side view and from below show how simple these plants are.

Duckweed, water lens, or bayroot, are freshwater aquatic plants. They float in still or slow-moving fresh water and wetlands. There are five genera, with a total of 33 to 38 species.[1][2]

These plants are very simple: They lack an obvious stem or leaves. Most of each plant is a small organized "thallus" or "frond" structure only a few cells thick. Often it has air pockets and floats on or under the water surface. Some have no root and some have one or more simple rootlets.[3]

Reproduction is usually by asexual budding. Occasionally, three tiny flowers are produced for sexual reproduction. These flowers have two stamens and a pistil. From this occasional reproduction is produced a seed in an air bag that floats. The flower of the duckweed genus Wolffia is the smallest known, just 0.3 mm long.[4]

Duckweed ecology[change | change source]

Getting nutrients is a factor for aquatic plants.[5] Duckweeds tend to be found in fertile, even eutrophic conditions. They can be spread by waterfowl and small mammals on their feet and bodies,[6] and by moving water. In water with constant currents or overflow, the plants are carried down the water channels and do not grow so thickly. In some places, weather causes the plants to multiply greatly when water-flow is low. Then they are carried away as rainy periods follow.

Duckweed is an important high-protein food source for waterfowl. It contains more protein than soybeans.[7] The tiny plants provide cover for many small aquatic species. Pondwater species such as bullfrogs and fish such as bluegills use the plants as shelter.

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.[8]

Duckweed may be used for wastewater treatment to capture toxins and for odor control. If a mat of duckweed is maintained for the removal of the toxins, it also prevents the development of algae and controls the breeding of mosquitoes.[9]

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 similarly sized water body with a clear surface.

Research and applications[change | change source]

In July 2008, the U.S. Department of Energy (DOE) Joint Genome Institute announced that the Community Sequencing Program funded sequencing of the genome of the giant duckweed, Spirodela polyrhiza. This was a priority project for DOE in 2009. The research was intended to facilitate new biomass and bioenergy programs.[10][11]

Duckweed is a good candidate as a biofuel because it grows rapidly, produces five to six times as much starch as corn per unit of area, and does not contribute to global warming.[12][13][14][15] Unlike fossil fuels, duckweed removes carbon dioxide from the atmosphere instead of adding it.[16]

Duckweed filters out contaminants (bacteria, nitrogen, phosphates) from natural bodies of water, wetlands, and wastewater.[17][18][19]

Related pages[change | change source]

References[change | change source]

  1. Wenqin Wang, Randall A. Kerstetter, Todd P. Michael: Evolution of Genome Size in Duckweeds (Lemnaceae). In: Journal of Botany, Volume 2011, 9 Seiten, doi:10.1155/2011/570319.
  2. Heng Li, Elias Landolt: Lemnaceae. – textgleich online wie gedrucktes Werk, In: Template:BibISBN.
  3. Sculthorpe, Cyril Duncan (1985). The biology of aquatic vascular plants. Koeltz Scientific Books. ISBN 978-3-87429-257-3.
  4. Landolt, Elias (1986). Biosystematic investigations in the family of duckweeds (Lemnaceae) Vol. 2: The family of Lemnaceae: a monographic study. – Morphology, karyology, ecology, geographic distribution, nomenclature, descriptions. Zürich: Eidgenössische Technische Hochschule Zürich.
  5. Keddy, Paul A. (2010). "Fertility". Wetland Ecology: Principles and Conservation (2nd ed.). Cambridge University Press. p. 79. ISBN 978-0-521-73967-2. Retrieved 7 May 2012.
  6. Hutchinson, G. Evelyn (1975). A Treatise on Limnology: Vol. 3: Limnological Botany. New York: John Wiley & Sons.
  7. Landesman, Louis. "Dr. Wastewater's Duckweed Application Page". Archived from the original on 27 October 2009. Retrieved 31 January 2012.
  8. "Duckweed Wastewater Treatment and Reuse for Fodder (West Bank)". Idrc.ca. Archived from the original on 8 June 2011. Retrieved 13 November 2011.
  9. Iqbal, Sascha (March 1999). "Duckweed Aquaculture: potentials, possibilities andl limitations for combined wastewater treatment and animal feed production in developing countries". SANDEC Report 6 (99). http://www.eawag.ch/forschung/sandec/publikationen/wra/dl/duckweed.pdf. Retrieved 31 January 2012. 
  10. "Duckweed genome sequencing has global implications. E! Science News". Esciencenews.com. 8 July 2008. Retrieved 13 November 2011.
  11. Wang, W. et al. The Spirodela polyrhiza genome reveals insights into its neotenous reduction fast growth and aquatic lifestyle. Nat. Commun. 5:3311 doi: 10.1038/ncomms4311 (2014).
  12. Michael, Todd P. "Genome sequencing of the duckweed Spirodela polyrhiza: a biofuels, bioremediation and carbon cycling crop" (PDF). Archived from the original (PDF) on 3 October 2011. Retrieved 7 May 2012.
  13. "Researchers Find Fuel in Odd Places". Ncsu.edu. Retrieved 13 November 2011.
  14. Sims, Bryan. "Duckweed Quacks Volumes of Potential". Biomassmagazine.com. Retrieved 13 November 2011.
  15. "Duckweed a possible solution to energy needs, researchers say". Pressofatlanticcity.com. 3 May 2010. Retrieved 13 November 2011.
  16. "Carbon Neutral Energy". Americanenergyindependence.com. Retrieved 13 November 2011.
  17. "Duckweed Genome Sequencing Has Global Implications. Pond scum can undo pollution, fight global warming and alleviate world hunger". News.rutgers.edu. 8 July 2008. Retrieved 13 November 2011.
  18. John W. Cross. "Practical Duckweed: Application Areas and Sponsors". Mobot.org. Retrieved 13 November 2011.
  19. Knibb, Wayne (July 2001 – June 2004). "Bioremediation of aquaculture waste and degraded waterways using finfish". Queensland Government Department of Primary Industries & Fisheries Tools. Archived from the original on 20 October 2007. Retrieved 6 February 2012.

Other websites[change | change source]