To study the effects of the environment on development of plants, combining ideas of physics, chemistry and biology. To use the plant Raphenus sativus, the radish, as a test organism to assess water quality To design and carry out experiments to answer questions such as: how is plant development affected by the chemistry of the environment? How is it affected by light or by temperature?

To compare seedling radishes maintained on clean paper in petri dishes moistened with one of these fluids: (1) water; (2) water at low pH; (3) sea water or 2% sodium chloride; the tests to be carried out at room temperature; and under conditions of strong light and in darkness.

Procedure:

Students should work in pairs. Each pair should have 3 petri dishes, in order to test: water only, in light; water only in darkness (petri dish covered with aluminum foil); and one other test fluid that the students can choose.

For each experimental test, fold a tissue to fit into the bottom of the petri dish. Add fluid to be tested to a depth of about 1/2 centimeter, and place a set number of seeds (e.g., 20) on the tissue. Close the petri dishes; for tests to be carried out in the dark, wrap dishes in aluminum foil. Place the dishes at room temperature or in the refrigerator.

After 24 hours, pour off excess fluid from each dish. Note whether the seeds have changed in any way. Make observations and measurements on each of the following 2 to 6 days, comparing the development of the radish seedlings under different conditions. Among ways to evaluate changes in radish seeds/seedlings:

1. measure the lengths of plant parts (roots, shoots) extending from the seed coat (place, or even dry, the seedlings on millimeter paper);
2. draw pictures of the seedlings;
3. weigh seeds/seedlings, if equipment is available;
4. match colors of seedling parts with a relative or chromatic color scale. This can be constructed in the color range dark green through yellow to white, using water colors, crayons, etc.; or cutting out patches of color from magazines; or in other ways that the students may devise.