National Agricultural Literacy Curriculum Matrix
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3 - 5
50 minutes plus observations for 10 days
Students will investigate how light affects plant growth by observing changes in a plant’s growth and movement as light availability is altered through an experiment.
For the teacher:
- Build an example of the phototropism box according to directions
- Utility knife
For each group:
- Shoebox and/or cardboard milk cartons (have students bring these from home)
- Thick cardboard sections
- Duct tape
- Clear plastic cup (6 oz.)
- Potting soil or peat pots
- Two bean seeds
For each student:
- Tropism Twist worksheet
Essential Files (maps, charts, pictures, or documents)
phototropism: a plant’s bending and growing towards a light source
Background Agricultural Connections
Interest Approach – Engagement
- Show students a handful of sunflower seeds. Use a picture if actual sunflower seeds aren't available.
- As you show the students the sunflower seeds, ask them if they can tell you what they are. Once the sunflower seeds are identified, see if the students can tell you how sunflower seeds are produced. Use the following facts to teach your students about the production, processing, and use of sunflower seeds:
- Sunflowers produce seeds which can be eaten, pressed for oil, or used in birdseed.
- Sunflower seeds are produced mostly in North and South Dakota, Minnesota, Kansas, Colorado, Nebraska, Texas and California.1
- The type of sunflowers which are grown for seeds can grow to be 10 feet tall.
- The head of a mature sunflower is usually about 15" in diameter.
- Sunflowers are typically planted in the spring and harvested in the fall.
- Summarize the lifecycle of the sunflower using pictures to illustrate.
- Now that students have a basic knowledge about sunflowers, show them the YouTube video clip, Time Lapse: Sunflower Following the Sun. As the students watch the video, ask them to watch the leaves and the bud of the sunflower. Can they guess what the sunflower bud and leaves are following? Explain that it is the sun.
- Define the word, phototropism. Break the word down into smaller pieces, explaining that “photo” means “light” and “tropism” means “to turn.” Draw on prior knowledge and remind students that plants receive their energy from the sun. Some plants move so that the surface of their leaves receive the most sun rays.
- Tell students that in this lesson, they will design an experiment so they can observe phototropism in action.
- Distribute the Tropism Twist worksheet to each student. Ask students to write a hypothesis for the testable question, “Does light affect the direction that a seedling will grow?” in the appropriate place on their worksheet.
- Divide students into lab groups consisting of 3-4 students. Distribute shoebox, scissors, duct tape, and cardboard. Instruct students to write their names on the bottom of the shoebox.
- Show students a completed tropism testing box and guide them through the steps of creating their own boxes. Use the diagrams to guide students through the construction process.
- Carefully draw and cut out a two-inch square from the middle section of one end of the box. Students may need help from the teacher and the teacher’s utility knife. It is recommended that only the teacher be equipped with a utility knife.
- Place the lid on the front of the box. Hold the box up to the light. Look through your two-inch hole and make certain that this hole is the only source for light to get into the box. Carefully duct tape over any other cracks or crevices that may be letting light in. Do not tape the box shut.
- Using paper to create a pattern, cut two pieces the height of the inside of the shoebox and half the width. Trace the pattern on stiff cardboard and cut them out. Tape them into the box as shown.
- After tropism boxes are complete, instruct students to use the designated planting station to plant two bean seeds for their group experiment. The planting station should be supplied with newspaper, 6-ounce plastic cups, potting soil, bean seeds, water spray bottles, craft sticks, masking tape, and markers for labeling.
- Place planted seeds in a lighted area and wait for the seeds to germinate. When the seedlings are approximately two inches tall, place the watered seedlings into the shoebox as shown.
- Close the box, tape it, and place it by a sunny window so the square hole on the top can be exposed to the light.
- After five days, carefully shine a flashlight through the square hole to observe the plant growth. It is best not to disturb plants during this testing period. It can alter the final outcome.
- In another 3-5 days, check to see if the plant has grown enough to reach the top of the box. Remove the shoebox lid once the plant has reached the top of the shoebox. Have students record their observations and answer the questions on their Tropism Twist worksheet.
Concept Elaboration and Evaluation
- Sunflowers are an agricultural crop grown by farmers. Their seeds are produced for food, oil, or animal feed.
- Because plants receive their energy from the sun through photosynthesis, some plants "move" in order to face the sun and receive the most energy.
- Have students plant the bean seeds, then build the tropism boxes on another day while you are waiting for seeds to germinate.
- Using different kinds of seeds, test to see if different kinds of seedlings display phototropism more than others. Do some seedlings bend and twist the moment they germinate? Do other seedlings show no sign of phototropism? Compare and contrast growth rate and angle of growth rate between seedlings.
Plant sunflower plants in large pots or outside. Once the sunflower plants begin to flower have students observe the flowers throughout the day. Explain to students that sunflower plants display heliotropism. Heliotropism is a plant behavior where the flower of the plant will follow the sun throughout the course of the day. Plants do this to maximize the light they receive during daylight hours.
Have students plant bean seeds as described in the lesson. Place nylon netting over the cup and tie it closed so the cup’s contents cannot be displaced. Tell students that they are going to study a different kind of tropism called gravitropism, or (geotropism). Gravitropism is a plant’s movement in response to gravity. It causes roots to grow down and the shoots to grow up towards the sky. By using a clear cup, students will be able to observe the growth pattern of both the roots and shoots.
Plant bean seeds as described in the lesson. Create cone shaped covers made from different colors of cellophane. Research wavelengths and how colors are absorbed at different wavelengths. Test to see if color affects plant growth.
Suggested Companion Resources
Agricultural Literacy Outcomes
Agriculture and the Environment
- Explain how the interaction of the sun, soil, water, and weather in plant and animal growth impacts agricultural production (T1.3-5.b)
Education Content Standards
3-LS4: Biological Evolution: Unity and Diversity
3-LS4-4Make a claim about the merit of a solution to a problem caused when the environment changes and the types of plants and animals that live there may change.
Common Core Connections
Reading: Anchor Standards
CCSS.ELA-LITERACY.CCRA.R.1Read closely to determine what the text says explicitly and to make logical inferences from it; cite specific textual evidence when writing or speaking to support conclusions drawn from the text.
Writing: Anchor Standards
CCSS.ELA-LITERACY.CCRA.W.7Conduct short as well as more sustained research projects based on focused questions, demonstrating understanding of the subject under investigation.