From Seed to Seed:
Plant Science for K-8 Educators

Activity 27: O₂h No!

Grades: K-8

Associated Lesson Topics:

• Respiration
• Stomata
• Pollution
  

National Standards:

• SCIENCE: Standard A, Standard C, Standard F
• LANGUAGE ARTS: Reading 5, 7, 10

Planting the Seed...

What do you think plants need to survive? How do you think they use oxygen? Do they "breathe" oxygen? Ask students to take a deep breath while holding a hand on their chests. What helped this movement happen? Do plants have muscles? If they don't have muscles-like humans-how do they draw their oxygen in?

Teacher Information:

In order for respiration to take place, a plant must be able to draw in oxygen and release carbon dioxide. While respiration actually occurs at the cellular level, the exchange of oxygen and carbon dioxide occurs through openings in the leaves called stomata. Stomata are also responsible for allowing carbon dioxide to enter and oxygen to exit during photosynthesis and water vapor to escape during transpiration. In this experiment, students will investigate what happens when the stomata become clogged, as frequently happens when our air becomes polluted.

Necessary Materials:

• A potted or garden plant with at least 12 leaves.
• Vaseline or clear nail polish.
  

Procedure:

• Coat the surface of the leaves with Vaseline or clear nail polish using these four treatments. Make sure your students label the leaves used in each treatment:

Treatment #1: Coat the lower epidermis (underside of the leaf) on only three leaves.
Treatment #2: Coat the upper epidermis (top side of the leaf) on only three leaves.
Treatment #3: Coat both surfaces of the leaf on three leaves.
Treatment #4: Leave at least three leaves untouched.

Emphasize the importance of repetition (in this case, using more than one leaf in each treatment) and having a control (the leaves that you don't treat) in scientific inquiry.

• Have students observe the plant daily and record changes they see in their journals.

Harvesting the Crop...

What happens to the leaves in each treatment? Students can research the answers to the following questions: What types of pollutants might coat the leaves like this in the "natural" world? What other effects do pollutants have on plants?

Alternatively, students can research the ways that plants "breathe" compared to the way that humans breathe. What effects do pollutants have on humans when they breathe them in?

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