''Wolffia arrhiza'' is a species of flowering plant known by the common names spotless watermeal and rootless duckweed, belonging to the

Araceae The Araceae are a family of monocotyledonous flowering plants in which flowers are borne on a type of inflorescence called a spadix. The spadix is usually accompanied by, and sometimes partially enclosed in, a spathe (or leaf-like bract). A ...

, a family rich in water-loving species, such as ''

Arum ''Arum'' is a genus of flowering plants in the family Araceae, native to Europe, northern Africa, and western and central Asia, with the highest species diversity in the Mediterranean region. Frequently called arum lilies, they are not closely ...

'' and '' Pistia''. It is the smallest

vascular plant Vascular plants (), also called tracheophytes () or collectively Tracheophyta (), form a large group of land plants ( accepted known species) that have lignified tissues (the xylem) for conducting water and minerals throughout the plant. They ...

on Earth.Pietryczuk, A., et al. (2009)
The effect of sodium amidotrizoate on the growth and metabolism of ''Wolffia arrhiza'' (L.) Wimm.
''Polish Journal of Environmental Studies'' 18:5 885-91.Pan, S. and S. S. C. Chen. (1979)
The morphology of ''Wolffia arrhiza'': A scanning electron microscopic study.
''Bot Bull Academia Sinica'' 20 89-95.Czerpak, R., et al. (2004)
Biochemical activity of auxins in dependence of their structures in ''Wolffia arrhiza'' (L.) Wimm.
''Acta Societatis Botanicorum Poloniae'' 73:4 269-75. It is native to Europe, Africa, and parts of Asia, and it is present in other parts of the world as a naturalized species. It is an aquatic plant which grows in quiet water bodies such as ponds. The green part of the plant, the frond, is a sphere measuring about 1 mm wide, but with a flat top that floats at the water's surface. It has a few parallel rows of stomata. There is no root. The plant produces a minute flower fully equipped with one stamen and one pistil. It often multiplies by

vegetative reproduction Vegetative reproduction (also known as vegetative propagation, vegetative multiplication or cloning) is any form of asexual reproduction occurring in plants in which a new plant grows from a fragment or cutting of the parent plant or spec ...

, however, with the rounded part budding off into a new individual. In cooler conditions the plant becomes dormant and sinks to the bed of the water body to overwinter as a turion.Al Khateeb, N
Duckweed use for sewage treatment and fodder production in Palestine.
Water & Environmental Development Organization, Palestine. The plant is a

mixotroph A mixotroph is an organism that can use a mix of different sources of energy and carbon, instead of having a single trophic mode on the continuum from complete autotrophy at one end to heterotrophy at the other. It is estimated that mixotrophs comp ...

which can produce its own energy by

photosynthesis Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored i ...

or absorb it from the environment in the form of dissolved

carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon mak ...

. This tiny plant is a nutritious food. Its green part is about 40% protein by dry weight and its turion is about 40% starch.Fujita, M., et al. (1999). Nutrient removal and starch production through cultivation of ''Wolffia arrhiza''. ''Journal of Bioscience and Bioengineering'' 87:2 194-8.Czerpak, R. and I. K. Szamrej. (2003)
The effect of β-estradiol and corticosteroids on chlorophylls and carotenoids content in ''Wolffia arrhiza'' (L.) Wimm. (Lemnaceae) growing in municipal Bialystok tap water.
''Polish Journal of Environmental Studies'' 12:6 677-84. It contains many

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha a ...

s important to the human diet, relatively large amounts of dietary minerals and trace elements such as

calcium Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar t ...

magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...

, and

zinc Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...

, and

vitamin B B vitamins are a class of water-soluble vitamins that play important roles in cell metabolism and synthesis of red blood cells. Though these vitamins share similar names (B1, B2, B3, etc.), they are chemically distinct compounds that often coex ...

. It has long been used as a cheap food source in

Myanmar Myanmar, ; UK pronunciations: US pronunciations incl. . Note: Wikipedia's IPA conventions require indicating /r/ even in British English although only some British English speakers pronounce r at the end of syllables. As John Wells explai ...

, Laos, and

Thailand Thailand ( ), historically known as Siam () and officially the Kingdom of Thailand, is a country in Southeast Asia, located at the centre of the Indochinese Peninsula, spanning , with a population of almost 70 million. The country is b ...

, where it is known as ''khai-nam'' ("eggs of the water"). 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 ''In vitro'' (meaning in glass, or ''in the glass'') studies are performed with microorganisms, cells, or biological molecules outside their normal biological context. Colloquially called " test-tube experiments", these studies in biology ...

''.National Academy of Sciences
Making aquatic weeds useful: Some perspectives for developing countries.
1976. Page 149. It is also useful as a form of agricultural and municipal water treatment.Körner, S., et al. (2003)
The capacity of duckweed to treat wastewater.
''Journal of Environmental Quality'' 32:5 1583-90. It is placed in effluent from black tiger shrimp

farms A farm (also called an agricultural holding) is an area of land that is devoted primarily to agricultural processes with the primary objective of producing food and other crops; it is the basic facility in food production. The name is used fo ...

to absorb and metabolize pollutants.Suppadit, T., et al. (2008)
Treatment of effluent from shrimp farms using watermeal (''Wolffia arrhiza'').
''ScienceAsia'' 134 163-8. The plants grow quickly and take up large amounts of

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

and

phosphorus Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ear ...

from the water. The plants that grow in the wastewater can then be used as feed for animals, such as carp,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.

Nile tilapia The Nile tilapia (''Oreochromis niloticus'') is a species of tilapia, a cichlid fish native to the northern half of Africa and the Levante area, including Israel, and Lebanon. Numerous introduced populations exist outside its natural range. It i ...

,Chareontesprasit, N. and W. Jiwayam. (2001).
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. and

chicken The chicken (''Gallus gallus domesticus'') is a domesticated junglefowl species, with attributes of wild species such as the grey and the Ceylon junglefowl that are originally from Southeastern Asia. Rooster or cock is a term for an adu ...

References

External links

Jepson Manual Treatment

USDA Plants Profile
{{Taxonbar, from=Q159100 Lemnoideae Freshwater plants Phytoremediation plants