''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). Also ...

, 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 al ...

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 Naturalisation (or naturalization) is the ecological phenomenon through which a species, taxon, or population of exotic (as opposed to native) origin integrates into a given ecosystem, becoming capable of reproducing and growing in it, and procee ...

. It is an

aquatic plant Aquatic plants are plants that have adapted to living in aquatic environments (saltwater or freshwater). They are also referred to as hydrophytes or macrophytes to distinguish them from algae and other microphytes. A macrophyte is a plant that ...

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

stoma In botany, a stoma (from Greek ''στόμα'', "mouth", plural "stomata"), also called a stomate (plural "stomates"), is a pore found in the epidermis of leaves, stems, and other organs, that controls the rate of gas exchange. The pore is bor ...

ta. There is no root. The plant produces a minute flower fully equipped with one

stamen The stamen (plural ''stamina'' or ''stamens'') is the pollen-producing reproductive organ of a flower. Collectively the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the filame ...

and one

pistil Gynoecium (; ) is most commonly used as a collective term for the parts of a flower that produce ovules and ultimately develop into the fruit and seeds. The gynoecium is the innermost whorl of a flower; it consists of (one or more) ''pistils'' ...

. 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 In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with o ...

. This tiny plant is a nutritious food. Its green part is about 40% protein by

dry weight Vehicle weight is a measurement of wheeled motor vehicles; either an actual measured weight of the vehicle under defined conditions or a gross weight rating for its weight carrying capacity. Curb or kerb weight Curb weight (U.S. English) or kerb ...

and its turion is about 40%

starch Starch or amylum is a polymeric carbohydrate consisting of numerous glucose units joined by glycosidic bonds. This polysaccharide is produced by most green plants for energy storage. Worldwide, it is the most common carbohydrate in human diets ...

.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 am ...

s important to the human diet, relatively large amounts of

dietary mineral In the context of nutrition, a mineral is a chemical element required as an essential nutrient by organisms to perform functions necessary for life. However, the four major structural elements in the human body by weight (oxygen, hydrogen, carbon ...

s 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 to ...

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 coexist ...

. 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 C. Wells, Joh ...

Laos Laos (, ''Lāo'' )), officially the Lao People's Democratic Republic ( Lao: ສາທາລະນະລັດ ປະຊາທິປະໄຕ ປະຊາຊົນລາວ, French: République démocratique populaire lao), is a socialist ...

, 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 bo ...

, 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 an ...

''.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 Agriculture or farming is the practice of cultivating Plant, plants and livestock. Agriculture was the key development in the rise of Sedentism, sedentary human civilization, whereby farming of Domestication, domesticated species created food ...

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 Effluent is wastewater from sewers or industrial outfalls that flows directly into surface waters either untreated or after being treated at a facility. The term has slightly different meanings in certain contexts, and may contain various pollut ...

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 Carp are various species of oily freshwater fish from the family Cyprinidae, a very large group of fish native to Europe and Asia. While carp is consumed in many parts of the world, they are generally considered an invasive species in parts of ...

,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 adult m ...

References

External links

Jepson Manual Treatment

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