Wolffia arrhiza
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Monocots
Order: Alismatales
Family: Araceae
Genus: Wolffia
Species:
W. arrhiza
Binomial name
Wolffia arrhiza
(L.) Horkel ex Wimm.

Wolffia arrhiza is a species of flowering plant known by the common names spotless watermeal and rootless duckweed, belonging to the Araceae, a family rich in water-loving species, such as Arum and Pistia. It is the smallest vascular plant on Earth.[2][3][4] It is native to Europe, Africa, and parts of Asia, and it is present in other parts of the world as a naturalized species.[5][6]

Description

Wolffia arrhiza 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.[3] There is no root. The plant produces a minute flower fully equipped with one stamen and one pistil. It often multiplies by vegetative reproduction, however, with the rounded part budding off into a new individual.[3][7] In cooler conditions the plant becomes dormant and sinks to the bed of the water body to overwinter as a turion.[8] The plant is a mixotroph which can produce its own energy by photosynthesis or absorb it from the environment in the form of dissolved carbon.[4]

Human uses

This tiny plant is a nutritious food. Its green part is about 40% protein by dry weight and its turion is about 40% starch.[9][10] It contains many amino acids important to the human diet, relatively large amounts of dietary minerals and trace elements such as calcium, magnesium, and zinc, and vitamin B12.[10] 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").[11] 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.[12]

It is also useful as a form of agricultural and municipal water treatment.[13] It is placed in effluent from black tiger shrimp farms to absorb and metabolize pollutants.[14] The plants grow quickly and take up large amounts of nitrogen and phosphorus from the water.[9] The plants that grow in the wastewater can then be used as feed for animals, such as carp,[15] Nile tilapia,[16] and chickens.[8]

References

  1. Lansdown, R.V. (2019). "Wolffia arrhiza". IUCN Red List of Threatened Species. 2019: e.T164241A120209232. doi:10.2305/IUCN.UK.2019-2.RLTS.T164241A120209232.en. Retrieved 30 April 2023.
  2. 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.
  3. 1 2 3 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.
  4. 1 2 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.
  5. "Wolffia arrhiza". Germplasm Resources Information Network. Agricultural Research Service, United States Department of Agriculture. Retrieved 2 January 2018.
  6. "Wolffia arrhiza in Flora of North America @ efloras.org". efloras.org.
  7. MoBot: Wolffia arrhiza
  8. 1 2 Al Khateeb, N. Duckweed use for sewage treatment and fodder production in Palestine. Water & Environmental Development Organization, Palestine.
  9. 1 2 Fujita, M., et al. (1999). Nutrient removal and starch production through cultivation of Wolffia arrhiza. Journal of Bioscience and Bioengineering 87:2 194-8.
  10. 1 2 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.
  11. Bhanthumnavin, K. and M. G. McGarry. (1971). Wolffia arrhiza as a possible source of inexpensive protein. Nature (letter) 232:495.
  12. National Academy of Sciences. Making aquatic weeds useful: Some perspectives for developing countries. 1976. Page 149.
  13. Körner, S., et al. (2003). The capacity of duckweed to treat wastewater. Journal of Environmental Quality 32:5 1583-90.
  14. Suppadit, T., et al. (2008). Treatment of effluent from shrimp farms using watermeal (Wolffia arrhiza). ScienceAsia 134 163-8.
  15. 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.
  16. 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.
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