Wisconsin Fast Plants® and Product Testing

Students can work in groups of five, with each student in a group being responsible for testing a different concentration of a substance.

One 45-minute class period is needed for students to set up their experiments. Ten minutes is needed each day to count and record germinated seeds.

Purchase products for testing or have students bring them from home. Pre-approve any products for suitability and safety. Suitable products are liquids or soluble materials. Avoid testing pesticides and herbicides. Also avoid strong chemical cleaners such as those designed for cleaning ovens, removing grease from concrete, or unclogging drains. Some products may be flammable or poisonous if swallowed. Carefully read any warning labels. Vinegar is interesting to test, but leaves a persistent odor on any labware it contacts. Products that might be tested include sodas, shampoos, hand cleaners, bubble baths, dish and laundry detergents, and isopropanol (rubbing alcohol). Some interesting variations are to test regular vs. diet sodas and regular vs. antibacterial detergents.

Many consumer products are very viscous when undiluted. It may take 15 minutes or more for these products to be absorbed into filter paper. For these products, have the groups prepare the full strength plate, Plate 2, before preparing the dilutions.

Preparing Test Dilutions

Set up a workstation for each group of 5 students with the following materials:

• test tube rack with 5 test tubes and 5 stoppers
• 5 dropping pipets (fewer pipets can be used if students carefully rinse them between uses)
• test substance
• beaker or cup with water
• empty beaker

Preparing Germination Plates

This can be done in conjunction with preparing the test dilutions or during a subsequent lab period.

Set up a workstation for each group of 5 students with the following materials:

• test tube rack with dilutions
• 5 dropping pipets
• 5 filter paper circles
• 5 petri dishes
• plastic bag
• beaker or cup with water
• empty beaker

Have the students place the plastic bags with completed plates under fluorescent lights. For best germination, the lights should be about 15 to 20 cm above the plates. If you will be examining phenotypes of these seedlings for genetics, lower the lights to 5 to 8 cm above the plates. Fast Plants seeds normally germinate in 2 days. Some products may inhibit but not totally prevent germination. To allow for this, students should collect germination data on 3 or more consecutive days.

Have students look at the ingredients lists on product labels. What chemicals are listed? Students can research these chemicals on the Internet to learn more about what they are and what they do. Often, it becomes apparent why a chemical is included in a product. Students can use this information in forming a hypothesis and interpreting their results.

Optional: After germination, seedlings can be planted and grown to maturity to observe the complete Fast Plants life cycle and to check for possible detrimental effects on growth and development. Other seeds can be tested to see if they react differently to the same test substances. Radish seeds (159000) work especially well. Students can graph their data as histograms.

To incorporate more math and standardize data, students can convert their raw data into percent germination.