Experiment: Access to Water

Materials (for each group of 3–4 people)

1. 2 identical plants with average water needs. Good plants for this include: pansies, impatiens, petunia.
2. Sunny outdoor area or a sunny windowsill
3. Experiment Log (provided)
4. Measuring cups
5. Water
6. Optional: two small cacti/succulents in pots

Steps

Note: See section “Expanding the Activity” for additional elements you may choose to include.

1. Use the Experiment Log to write a hypothesis for the experiment and to make initial (baseline) measurements of each plant’s height, number of leaves and flowers, and their respective color. These may change during the experiment, so it is important to record these measurements accurately at this time.
2. Label the plants (one as “water” and one as “no water”)
3. Place both plants in the same area:- in a sunny location outside or on a sunny windowsill. Note: In this experiment, the amount of water is the only independent variable, so it is important to give both plants equal access to sunlight.
4. Check the plant labeled “water” every day. Provide this plant with water when the soil begins to dry out. If it rains, be sure to cover the plant labeled “no water.”
5. Repeat measurements of both plants once a week. Record results on the Experiment Log.
6. Carry out the experiment for 4-5 weeks and then discuss the results.

Discussion Questions

1. What happened to the plants that received regular water during this experiment?
2. What happened to the plants that did not receive any water?
3. Do you think plants need water to survive and grow? Why or why not?
4. How long did it take for the plants that did not receive any water to show signs of stress? What signs of stress did you notice?
5. Is it possible to revive the unwatered plant at this point by giving it water?
6. How does the unwatered cactus compare with the first plant you studied? Does it show signs of stress? What do you notice? (We will discuss adaptations to limited water resources in another lesson plan.) What features do cacti have that help them survive in an environment with limited water availability?

Expanding the Activity

1. Do more with data. Chart whole-class data throughout the experiment.
2. Explore adaptations. Include two identical desert plants (succulents) in this experiment along with the non-desert plants. Place one desert plant in the “water” conditions and one in the “no water” conditions. Compare how the plants have adapted to different water conditions in their environments.