A bioassay uses a living organism--usually a plant or a
bacteria--as a test agent for the presence or concentration of a chemical
compound or a disease. The idea is to choose a test agent that is very
sensitive to the condition you are testing.
Have you ever read about how miners took canaries down
into mines to act as early warnings of gas leaks? Because canaries are more
sensitive to gas than people, the birds reacted to very small amounts of gas
and gave miners a chance to escape. You could say canaries were a bioassay for
Different plants are often used as bioassays because they
respond in a predictable way and are often very sensitive to the condition that
is being tested. A standard toxic dose--the level at which no seeds of the
bioassay plant sprout or all the plants die--is established as a reference
point. Then samples are tested and compared to the reference standard.
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