Common Duckweed, Lemna minor, on a pond surfaceFloating on the surface of still ponds and lakes, Common Duckweed (Lemna minor) forms a verdant green carpet on the aquatic surface. The individual plants are quite small, consisting of a leaf-like thallus about 5 mm in diameter with a single root that dangles into the water. It is widespread and locally common throughout Ireland (Sterry 2004, Collins Complete Guide to Irish Wildlife p. 286). Reproduction is primarily vegetative. Duckweed is well named: as an animal feed (for ducks, as well as other fowl, fish and livestock) it provides protein of a high biological value and is highly digestible with only 5% fibre in dry matter of cultivated plants (Leng et al., 1995 Livestock Research for Rural Development 7).
Common Duckweed, Lemna minor, showing fronds and roots out of water
L. minor has an ability to respond in recognised patterns to various stresses, which has lead its use as an ISO standard for water quality (ISO 20079, 2005 Water quality—Determination of the toxic effect of water constituents and waste water to duckweed (L. minor)—duckweed growth inhibition test). Indeed, recently Appenroth et al. (2010, Chemosphere 78 pp. 216-223) has shown that L. minor is highly sensitive to nickel ions, making it a suitable tool for ecotoxilogical testing for this metal in accordance with the ISO 20079 protocol. On exposure to nickle ion concentrations of 1-100μM, fronds formed were quantitatively smaller and less green than innoculated mother fronds (above this level Appenroth et al. observed saturation in the dose–response curves but the phytotoxic responses can still be observed).
Common Duckweed, Lemna minor, showing fronds and roots out of waterL. minor has an ability to respond in recognised patterns to various stresses, which has lead its use as an ISO standard for water quality (ISO 20079, 2005 Water quality—Determination of the toxic effect of water constituents and waste water to duckweed (L. minor)—duckweed growth inhibition test). Indeed, recently Appenroth et al. (2010, Chemosphere 78 pp. 216-223) has shown that L. minor is highly sensitive to nickel ions, making it a suitable tool for ecotoxilogical testing for this metal in accordance with the ISO 20079 protocol. On exposure to nickle ion concentrations of 1-100μM, fronds formed were quantitatively smaller and less green than innoculated mother fronds (above this level Appenroth et al. observed saturation in the dose–response curves but the phytotoxic responses can still be observed).
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