Objective: 

To choose an observable trait in Wisconsin Fast Plants and artificially select for it.

Materials (per group):

1 watering tray and 8 quads with watering material, label stakes, fertilizer pellets, growing medium, ties, pollinating sticks, 32 standard seeds, copper sulphate

Planting Procedure: 

  1. Soak a watering diamond and put into one section of the quad so that about half of it sticks out the bottom. Repeat for the rest of the quad.
  2. Add growing medium until the quad is ½ full, add 3 fertilizer pellets.
  3. Add growing medium until the quad is full. Tap the quad on the counter to settle the growing medium, add more to bring it back to the top.
  4. Soak the growing medium until water is dripping out the bottom.
  5. Place 1 seed, on the growing medium in the middle, in each of the 4 sections of the quad.
  6. Sprinkle dry growing medium to just cover the seeds.
  7. Use a small spray bottle to soak the top.
  8. Repeat for the other 7 quads.
  9. Fill the watering tray with tap water to the fill line.
  10. Place the watering mat in the tray to soak it.
  11. Remove the mat, snap the lid on the tray and place the mat on the lid so the narrow end extends down into the water.
  12. Place the quads on top of the mat.
  13. Place the tray in the chamber as directed.
  14. After the plants have been growing for 10 days add 10 mL of copper sulphate solution to the watering system tray

Germination:

  1. Check pots to determine germination.  Once seeds have germinated and have been growing for about 10 days make observations of seedlings in your lab book. Look for colours, size, hairs, shape of leaves and stem.
  2. Identify a characteristic that could be artificially selected for.
  3. At about day 13 the plants will be ready for pollination. The chosen plants will be pollinated to select for the chosen trait.
  4. Develop a hypothesis for the outcome of the experiment.

Pollination:

  1. Day 13 to 16: Pollination.  Swirl the pollinating stick around in the open flower of a test plant, trying to pick up the pollen from the anthers without transfer to the stigma of the same plant.  Go to an open flower on another plant and gently touch the pollen to the tip of the stigma. Go back to a different flower on the first plant.  Repeat for all flowers on the two plants.  This process will be repeated for about three days during flowering.
  2. After the last pollination, the tip of the plant above the top flower should be pinched or cut off.  Any developing buds or flowers that have not been pollinated should also be removed.
  3. After 20 more days the plants will be removed from the water and let dry for 5 days.
  4. After 5 days remove the seeds from the pods and repeat steps 1-7.
  5. Once the seeds have germinated and have grown for 10 days, make observations on the selected trait.

Analysis

Did evolution occur in the Wisconsin Fast Plants? Support your conclusion.

Experiment Notes

The two best traits to use are the number of trichomes (hairs) and the amount of purple colour. Both of these are polygenic and can be successfully selected. One generation is usually enough to show a change in frequency that is statistically significant.

Both characteristics can be analyzed statistically. The average number of trichomes per plant can be analyzed with the t-test, or, the number of plants with a specific number of trichomes can be analyzed with a chi-square test. The number of plants with a significant amount of purple colour (some use colour on stem and leaves) can be analyzed with chi-square.

Contributed by David Prescott, Head of Science Faculty, St. John's-Ravenscourt School