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A bioassay determines the impact of a certain substance on living organisms. You can use a bioassay to examine substances, such as "compost tea" from a Decomposition Column, to determine if they influence plant growth.

You can also test household substances such as sugar and coffee. At what concentration are your seeds most affected?


  • four black film cans with lids
  • water twenty drops or about 2 mm of a solution to test
  • eight to ten seeds of a small, fast-germinating plant, such as turnips, Chinese cabbage, or Fast Plants
  • eye dropper or thin soda straw four paper towel wicks 1 cm x 4 cm
1. Label four film cans 1.0, 0.1, 0.01, and CONTROL.

2. Add ten drops plain water to can labeled CONTROL. Add 10 drops of the test solution to film can labeled 1.0.

3. Add nine drops of water EACH to film cans labeled 0.1, and 0.01. Add one drop of full strength substance from 1.0 film can to can labeled 0.1. Mix. Take one drop of 0.1 strength solution and add to can labeled 0.01. Mix well after each addition.
4. Insert one wick strip and two seeds into each can as described in germination chamber. Cover with cap.

Observe germination over the next 12 hours to 5 days. Graph how the varying concentrations of your test substance affect a specific response, such as germination rate. What other organisms can you use for a bioassay? What other substances can you test?

National Science Foundation   Bottle Biology, an instructional materials development program, was funded by a grant from the National Science Foundation administered by the University of Wisconsin-Madison.   Wisconsin Fast Plants