By Karen Tripepi
University of Idaho

Image13.gif (2510 bytes)ITV Series: Bill Nye the Science Guy # 143 Plants

This is an introductory lesson, intended to"kick off' a larger study of plants and plant growth. The complete unit would also include lessons in plant propagation, plant defense mechanisms and plant identification. For the culminating project students would assist in planting a garden (or tree or shrub) on the school grounds. In this lesson, students will explore the basic requirements for plant growth through a series of experimental activities. They will learn that plants use carbon dioxide, water and light to produce oxygen and glucose through the process of photosynthesis.

Learning Objectives

Students will be able to:

  • understand the relationship of plants and animals in the environment
  • name the basic requirements for plant growth
  • define the terms photosynthesis, stomata, chlorophyll and xylem
  • design an experiment to show what happens when plants are deprived of light
  • explain how oxygen and carbon dioxide move in and out of a plant
  • Large pad of newsprint paper
  • Plant Needs handouts
  • Microscopes (1 for each group of 5 students)
  • Microscope slides
  • 2 bean plants for each group of 3-4 students
  • Leaf of lettuce
  • Glass bowl
  • 2 glass jars
  • 1 or 2 fresh white carnations
  • Liquid food coloring
  • Fresh leaves of a plant with red coloration (Tradescantia works well)

Previewing Activities

If weather permits, begin this activity outdoors in an area where plants are growing. If discussion begins in the classroom, have several different kinds of plants nearby. Tell the class "This spring, we are going to be working on a project to make our school grounds a nicer place. We will be planting a garden (or tree or shrub). Have you ever planted a garden?" Invite students to share their experiences.

Ask the students to look at the plants around them. Ask them, "What do these plants need to live and grow?" List their suggestions on a large sheet of newsprint paper. Ask "What do the plants do with these things?" Record suggestions.

Introduce the video. Tell them that in this episode of Bill Nye the Science Guy, Bill describes the things that plants need to grow and the things they produce.

Focus for viewing
Give the students specific responsibilities while viewing the video segment by giving them the 'Plant Needs' hand-out. Ask students to listen carefully as Bill Nye talks about plant growth. When he mentions something that plants need to grow, or something that plants produce, they are to write it in the appropriate blank on their handout.

Viewing Activities
Begin the video with the introduction to Bill Nye the Science Guy. Pause after Bill bites into the apple. Using an overhead of the handout, ask students which blanks they have been able to fill in so far. Use their responses to fill in the blanks on the overhead.

During the next segment, ask students to listen for the name of the process by which plants use carbon dioxide, water and sunlight to manufacture oxygen and energy/ glucose. Fast forward and Begin the tape where Bill says, "Well, the car's covered with grass. Let's go!" Stop the video after Bill yells "SCIENCE!!" Ask students to share their answers to the focus questions. Have them write the word "Photosynthesis" in the blank at the top of their page.

Post-Viewing Activities

Tell students, "We are going to look more closely at the three basic needs of plants -- water, light and carbon dioxide gas.

Remind students that we have heard that plants need water to live and grow. Ask, "How does water get into the plant?" ) Ask, "How does water get from one part of the plant to another?" Listen to their suggestions.

Tell them, "We are going to look at where the water goes in this cut carnation flower". Invite a student to come and fill a jar with lukewarm water. Add food coloring until the water is darkly colored. Take the fresh carnations (older flowers will not take water up readily and will not demonstrate the movement of water very well) and cut off the bottom inch of the stem. Place the flowers immediately in the colored water. Ask the class to predict what will happen to the flower. Place the jar in a warm spot, out of direct sunlight. Observe the flowers each day and note any changes. After 2-3 days, discuss observations. Ask students, "How did the color get from the water to the petals?" Listen to their ideas. They will likely understand that the water traveled up the stem. Ask, "What does this tell us about where the water goes in a plant?"

Using a sharp razor blade, slice several thin sections from the flower stem. Place the sections on a microscope slide and allow the students to look at the sections under a microscope. Ask students to draw what they see. Tell them, "The openings that you see in the stems are thin tubes called xylem. Water moves up the stem of the plant through the xylem." Ask students to label the xylem on their drawing.


Activity 2

This activity is designed to help students see how carbon dioxide and oxygen move in and out of the plant. Begin by reviewing the process of photosynthesis. Ask students what they know about carbon dioxide and oxygen. (They are gases). Explain that there are small pores on the leaves of plants called stoma (plural: stomata). The stomata open and close to allow gases to move in and out of the plant. Draw a diagram of a stoma on the board. Have microscopes set up so that students can look at stomata on the leaves of Tradescantia. Ask students to draw what they see.
Ask students, "How can we tell that gases are moving in and out of the leaves?" Begin the video at the section called Home Experiment. Stop when the girl says, "Wait about 24 hours." Follow her directions for setting up the experiment, using the jar of water and the leaf of lettuce. Ask, "How will we be able to tell that the lettuce is giving off oxygen?" Write students' ideas on the board. After 24 hours, check lettuce leaf and observe changes. What do students notice about the leaf? Resume tape. Stop after the girl says, "Ain't that funky now?" Compare students' predictions with the results they saw on their lettuce and on the tape.
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Activity 3

Remind the students that we heard from Bill Nye that plants need light to grow. Ask, "What happens when a plant doesn't receive enough light? How much light is enough?" Have students record their ideas. Ask "How can we find out if our predictions are correct?" Discuss ideas for an experiment that will answer the question. Have students work in small groups (3-4 students per group) to design and carry out their experiments.

Experiments will probably be set up by placing some plants in total darkness and other under lights for various amounts of time each day. The exact format will be determined by each group of students, according to how they think the questions can best be answered. Note: it may take 2-3 weeks to see results.

Students will check the plants periodically, being careful to minimize the plants' exposure to light. They will record their observations. They will repeat the checks every 2-3 days until they have seen a significant change. They will also water the plants as needed.

At the end of the experiment, the class will discuss the results and compare them to their original predictions. They will do a brief write-up, describing what happened and what they now understand about the affects of light on plant growth. They will also comment on the experiment that they set up. Was it a valid experiment and did it answer their questions? Are there things they would do differently next time?

Extension Activities

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