Bioassays Using Duckweed
Duckweed it is a small aquatic plant that floats on the surface of ponds, wetlands, and nutrient-rich lakes. Worldwide, there are over 40 species of duckweed (family Lemnaceae), with 20 species found in the United States. Each plant consists of one or more fronds. The fronds look like little leaves but actually are a combination of leaf and stem, attached to a rootlet that dangles down in the water. Although duckweed is a flowering plant, it rarely flowers. Usually it reproduces through buddingnew fronds grow from buds on the parent plant. Eventually these new fronds grow their own roots and break off to become independent plants.
Duckweed is useful for conducting bioassay experiments with water samples because you can measure its growth rate by counting how many new fronds develop over a five-day period. By measuring the number of new fronds on duckweed plants growing in a test solution and comparing that to the number of new fronds in a control solution, you can test the sensitivity of duckweed to different compounds, or various concentrations of a single compound. Lemna minor is the species most commonly used for bioassays.
Duckweed bioassay method
Suggested compounds and dilutions for duckweed bioassays
Analyzing your results
More information about duckweed
Other bioassays links
How are bioassays used in the real world?
Lettuce seed bioassays
Copyright © 2009 Environmental Inquiry, Cornell
University and Penn State University