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.).
Conducting Reference Toxicity Tests
Collecting and Interpreting
Try one of these research challenges
Research Challenge #1: What
are the best conditions for lettuce seed germination and growth?
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
bioassays used in the real world?