Lemna minor, or Common Duckweed, is a tiny plant which grows in aquatic environments, including on wet mud when water levels recede. L. minor forms a dense mat up to 0.6 cm thick on still or slow-moving bodies of water and is found throughout the world in temperate and subtropical regions (Missouri Botanical Garden, n.d.; Washington State Department of Ecology, 2013). Each individual consists of a single leaf-like structure known as a thallus, or frond, which combines the functions of leaf and stem and is typically 2-5 mm long and 1.5-3.5 mm wide, and a single slender rootlet which originates near the center of the thallus and is generally less than 1 cm in length (Hilty, 2012).
Common duckweed is among the smallest of the flowering plants, and produces tiny white flowers. However, this only occurs rarely, as the primary means of reproduction is vegetative propagation.1 This vegetative propagation occurs through a budding process involving the parent frond’s two lateral pouches, with a daughter plant being produced and eventually separating from the parent (Hilty, 2012). Individual plants live for an average of four to five weeks and produce between four and twelve daughter fronds (Lemon et al. 2001). This rapid rate of reproduction allows for the formation of thick mats, with an estimated density of up to 1 x 106 plants/m2 (Cole and Voskull, 1996).
L. minor is an important food source to a variety of organisms, including species of weevils, beetles, aphids, ducks, turtles, carp, and muskrats. The rootlets of the plant are sticky when wet, which allows dispersion by various species of waterfowl to new locations, allowing it to easily colonize new areas (Hilty, 2012). L. minor can also serve as a habitat for small invertebrates; however, if it covers the entire surface of a body of water for an extended period of time, oxygen depletion can result, which is harmful for aquatic organisms (Texas A & M University, 2013).
Research has illustrated that L. minor shows promise as an efficient phytoremediation tool in the treatment of wastewater associated with an oil refinery. In a laboratory experiment conducted over the course of one month, L. minor removed upward of 72% of several different heavy metals, as well as significant amounts of nitrates, soluble solids, and oils from polluted water (Azeez and Sabbar, 2012).
Azeez, N.M, & Sabbar, A.A.(2012). Efficiency of duckweed (Lemna minor) in phytotreatment of wastewater pollutants from Basrah oil refinery. Journal of Applied Phytotechnology in Environmental Sanitation, 1(4), 163-172. Retrieved from http://www.trisanita.org/japes/apespaper2012/apes21v1n4y2012.pdf
Cole, C.T., & Voskull, M.I. (1996). Population genetic structure in duckweed (Lemna minor, Lemnaceae). Canadian Journal of Botany, 74(2), 222-230. doi: 10.1139/b96-026
Hilty, J. (2012). Common Duckweed. Retrieved from http://www.illinoiswildflowers.info/wetland/plants/cm_duckweed.htm
Lemon, G.D., Posluszny, U., Husband, B.C. (2001). Potential and realized rates of vegetative reproduction in Spirodela polyrhiza, Lemna minor, and Wolffia borealis. Aquatic Botany 70, 79-87. Retrieved from http://biology.kenyon.edu/courses/biol229/Lemon_LemnaPaper.pdf
Missouri Botanical Garden (n.d.). Lemna minor. Retrieved from http://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?kempercode=a622
Texas A & M University. (2013). Common Duckweed. Retrieved from http://aquaplant.tamu.edu/plant-identification/alphabetical-index/common-duckweed/
Washington State Department of Ecology. (2013). Free Floating Plants. Retrieved from http://www.ecy.wa.gov/programs/wq/plants/plantid2/descriptions/lemmin.html