Wolffia arrhiza, commonly known as rootless duckweed[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.] Native to Europe, Africa, and parts of Asia, it has also become naturalised in various other regions around the globe.
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 mm wide. It has a flat top that allows it to float on the water’s surface. It has a few parallel rows of
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[ There is no root. The plant produces a tiny flower, complete with one stamen and one gynoecium. Many morphologists consider these to be an inflorescence of one tiny male flower 0.33 mm in height, with a single female flower 0.3 mm diameter; the smallest inflorescence to be reported.][Al Khateeb, N. Water & Environmental Development Organization, Palestine.] As a mixotroph, it can produce its own energy by photosynthesis or absorb it from the environment in the form of dissolved carbon.[
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Taxonomy
Wolffia arrhiza was first described in 1771 by Carl Linnaeus as Lemna arrhiza in 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 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 important to the human diet, relatively large amounts of and trace elements such as calcium, magnesium, and zinc, and vitamin B.[ 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").][Bhanthumnavin, K. and M. G. McGarry. (1971). Wolffia arrhiza as a possible source of inexpensive protein. Nature (letter) 232:495.] 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.[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 sewage.[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 Penaeus monodon aquaculture 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 and phosphorus from the water.[ The plants that grow in the wastewater can then be used as Compound 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,[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 .[
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