View source for Wolffia arrhiza

{{Short description|Species of flowering plant in the family Araceae}}
{{speciesbox
| image     = Wolffia arrhiza kz02.jpg
| image2    = WolffiaArrhiza2.jpg
|status=LC
|status_system=IUCN3.1
|status_ref=<ref>{{cite IUCN|title=''Wolffia arrhiza''|last=Lansdown|first=R.V.|year=2019|access-date=30 April 2023|page=e.T164241A120209232|doi=10.2305/IUCN.UK.2019-2.RLTS.T164241A120209232.en}}</ref>
| genus     = Wolffia
| species   = arrhiza
| authority = ([[Carl Linnaeus|L.]]) [[Horkel]] ex [[Wimm.]]
| synonyms = {{Specieslist
| Bruniera vivipara | Franch. 
| Horkelia arrhiza | (L.) Druce 	
| Lemna arrhiza | L.
| Lemna microscopica | Schur
| Lenticula arrhiza | (L.) Lam.
| Wolffia delilii | Miq. 
| Wolffia michelii | Schleid.
}}
}}

'''''Wolffia arrhiza''''', commonly known as '''spotless watermeal''' or '''rootless duckweed''', is a species of flowering plant in the [[Araceae]] family, which includes other water-loving plants such as ''[[Arum]]'' and ''[[Pistia]]''. It is the smallest [[vascular plant]] on Earth.<ref name=piet>Pietryczuk, A., et al. (2009). [http://www.pjoes.com/index.php?s=abs_id&id=2009180515 The effect of sodium amidotrizoate on the growth and metabolism of ''Wolffia arrhiza'' (L.) Wimm.] ''Polish Journal of Environmental Studies'' 18:5 885-91.</ref><ref name=pan>Pan, S. and S. S. C. Chen. (1979). [http://ejournal.sinica.edu.tw/bbas/content/1979/2/bot202-01.PDF The morphology of ''Wolffia arrhiza'': A scanning electron microscopic study.] ''Bot Bull Academia Sinica'' 20 89-95.</ref><ref name=czer>Czerpak, R., et al. (2004). [http://www.botany.pl/pubs-pdf/Acta%20Societatis%20Botanicorum/2004/4_269275.pdf Biochemical activity of auxins in dependence of their structures in ''Wolffia arrhiza'' (L.) Wimm.] {{Webarchive|url=https://web.archive.org/web/20110911021110/http://www.botany.pl/pubs-pdf/Acta%20Societatis%20Botanicorum/2004/4_269275.pdf |date=2011-09-11 }} ''Acta Societatis Botanicorum Poloniae'' 73:4 269-75.</ref> Native to Europe, Africa, and parts of Asia, it has also [[introduced species|naturalized]] in various other regions around the globe.<ref>{{GRIN | accessdate = 2 January 2018}}</ref><ref>{{cite web|url=http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=200027354|title=Wolffia arrhiza in Flora of North America @ efloras.org|work=efloras.org}}</ref>

== Description ==
''Wolffia arrhiza'' is an [[aquatic plant]] which grows in quiet water bodies such as ponds. The plant’s green part, known as the frond, is a spherical structure about 1&nbsp;mm wide. It has a flat top that allows it to float on the water’s surface. It has a few parallel rows of [[stoma]]ta.<ref name=pan/> There is no root. The plant produces a tiny flower, complete with one [[stamen]] and one [[gynoecium|pistil]]. It often multiplies by [[vegetative reproduction]], with the rounded part budding off into a new individual.<ref name=pan/><ref>{{Cite web |url=http://www.mobot.org/jwcross/duckweed/Russe/wolfia-e.htm |title=MoBot: ''Wolffia arrhiza'' |access-date=2010-12-05 |archive-date=2017-07-26 |archive-url=https://web.archive.org/web/20170726133232/http://www.mobot.org/jwcross/duckweed/Russe/wolfia-e.htm |url-status=dead }}</ref> In cooler conditions, the plant becomes dormant and sinks to the bottom of the water body to overwinter as a [[Turion (botany)|turion]].<ref name=nak>Al Khateeb, N. [http://www.ipcri.org/watconf/papers/nader.pdf Duckweed use for sewage treatment and fodder production in Palestine.] {{Webarchive|url=https://web.archive.org/web/20100215173417/http://www.ipcri.org/watconf/papers/nader.pdf |date=2010-02-15 }} Water & Environmental Development Organization, Palestine.</ref> As a [[mixotroph]], it can produce its own energy by [[photosynthesis]] or absorb it from the environment in the form of dissolved [[carbon]].<ref name=czer/>

== Taxonomy ==
''Wolffia arrhiza'' was first described in 1771 by [[Carl Linnaeus|L.]] as ''Lemna arrhiza'' to the genus ''[[Lemna]]'' known for several duckweed species. It was transferred to the current genus ''[[Wolffia]]'' in the 19th century based on works of [[Johann Horkel]] and the third edition of the ''Flora von Schlesien preußischen und österreichischen Antheils'' by [[Christian Friedrich Heinrich Wimmer]] in 1857.

== Human uses ==
This tiny plant is a nutritious food. Its green part is about 40% protein by [[dry matter|dry weight]] and its turion is about 40% [[starch]].<ref name=fujita>Fujita, M., et al. (1999). Nutrient removal and starch production through cultivation of ''Wolffia arrhiza''. ''Journal of Bioscience and Bioengineering'' 87:2 194-8.</ref><ref name=czer2>Czerpak, R. and I. K. Szamrej. (2003). [http://www.pjoes.com/pdf/12.6/677-684.pdf The effect of β-estradiol and corticosteroids on chlorophylls and carotenoids content in ''Wolffia arrhiza'' (L.) Wimm. (Lemnaceae) growing in municipal Bialystok tap water.] {{Webarchive|url=https://web.archive.org/web/20170808174811/http://pjoes.com/pdf/12.6/677-684.pdf |date=2017-08-08 }} ''Polish Journal of Environmental Studies'' 12:6 677-84.</ref> It contains many [[amino acid]]s important to the human diet, relatively large amounts of [[dietary mineral]]s and trace elements such as [[calcium]], [[magnesium]], and [[zinc]], and [[vitamin B12|vitamin B{{ssub|12}}]].<ref name=czer2/> It has long been used as a cheap food source in [[Myanmar]], [[Laos]], and [[Thailand]], where it is known as ''khai-nam'' ("eggs of the water").<ref>Bhanthumnavin, K. and M. G. McGarry. (1971). [http://www.nature.com/nature/journal/v232/n5311/abs/232495a0.html ''Wolffia arrhiza'' as a possible source of inexpensive protein.] ''Nature'' (letter) 232:495.</ref>  The plant is prolific in its reproduction, growing in floating mats that can be harvested every 3 to 4 days; it has been shown to double its population in less than four days ''[[in vitro]]''.<ref>National Academy of Sciences. [https://books.google.com/books?id=n2krAAAAYAAJ&dq=wolffia+arrhiza+protein&pg=PA149 Making aquatic weeds useful: Some perspectives for developing countries.] 1976. Page 149.</ref>

It is also useful as a form of [[Agricultural wastewater treatment|agricultural]] and [[sewage|municipal water treatment]].<ref name=korner>Körner, S., et al. (2003). [https://www.soils.org/publications/jeq/articles/32/5/1583 The capacity of duckweed to treat wastewater.] ''Journal of Environmental Quality'' 32:5 1583-90.</ref> It is placed in [[effluent]] from [[Penaeus monodon|black tiger shrimp]] [[aquaculture|farms]] to absorb and metabolize pollutants.<ref name=supp>Suppadit, T., et al. (2008). [http://www.scienceasia.org/2008.34.n2/scias34_163.pdf Treatment of effluent from shrimp farms using watermeal (''Wolffia arrhiza'').] {{Webarchive|url=https://web.archive.org/web/20201214121202/http://www.scienceasia.org/2008.34.n2/scias34_163.pdf |date=2020-12-14 }} ''ScienceAsia'' 134 163-8.</ref> The plants grow quickly and take up large amounts of [[nitrogen]] and [[phosphorus]] from the water.<ref name=fujita/> The plants that grow in the wastewater can then be used as [[Compound feed|feed]] for animals, such as [[carp]],<ref name=naskar>Naskar, K., et al. (1986). Yield of ''Wolffia arrhiza'' (L.) Horkel ex Wimmer from cement cisterns with different sewage concentrations, and its efficacy as a carp feed. ''Aquaculture'' 51:3-4 211-16.</ref> [[Oreochromis niloticus|Nile tilapia]],<ref name=chare>Chareontesprasit, N. and W. Jiwayam. (2001). ##[http://docsdrive.com/pdfs/ansinet/pjbs/2001/618-620.pdf An evaluation of ''Wolffia'' meal (''Wolffia arrhiza'') in replacing soybean meal in some formulated rations of Nile tilapia.] ''Pakistan Journal of Biological Sciences'' 4:5 618-20.</ref> and [[chicken]]s.<ref name=nak/>

== References ==
{{Reflist|2}}

== External links ==
{{Commons category|Wolffia arrhiza}}

* [http://ucjeps.berkeley.edu/cgi-bin/get_JM_treatment.pl?8328,8340,8341 Jepson Manual Treatment]
* [http://plants.usda.gov/java/profile?symbol=WOAR2 USDA Plants Profile]

{{Taxonbar|from=Q159100}}

[[Category:Lemnoideae]]
[[Category:Freshwater plants]]
[[Category:Phytoremediation plants]]
[[Category:Plants described in 1771]]
[[Category:Flora of Lebanon]]