Why Lettuce Seeds?
Of all the possible water quality bioassay organisms, lettuce seeds might be one of the last you would think of using. Lettuce doesn't live in water, so why would it even be considered? The answer is that lettuce seed bioassays have proven to be an easy and inexpensive means of testing the toxicity of some types of contaminants of concern in water and sediments, including heavy metals and some pesticides and other organic toxicants.

For high school classes, lettuce seeds provide distinct advantages over most other test organisms: they are inexpensive, easy to culture, and require no upkeep between experiments. Although any variety of lettuce might work, Lactuca sativa L. var. Buttercrunch is the standard species recommended for bioassays by the U.S. Environmental Protection Agency, the Food and Drug Administration, and the Organization for Economic Cooperation and Development.

Within any one species, individuals respond differently when exposed to any particular chemical. Between species, there are even greater differences in chemical sensitivities. You can test this idea by comparing your lettuce seed results with bioassays using another organism such as water fleas (Daphnia sp.).

Bioassay techniques

Conducting Reference Toxicity Tests (Dose/Response)
Testing Environmental Samples
Collecting and Interpreting Data

Try one of these research challenges

Research Challenge #1: What are the best conditions for lettuce seed germination and growth?
Research Challenge #2: What are the environmental impacts of road de-icing?
Research Challenge #3: Is seed germination affected by herbicide residues in soil?

More information about bioassays with lettuce seeds

Lettuce seed links

Other bioassay links

How are bioassays used in the real world?
Daphnia Bioassays
Duckweed Bioassays