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Why Do Plants Grow Up?

Lesson Plan

Why Do Plants Grow Up?

Students will be able to define phototropism and gravitropism and explain how these tropisms influence plant growth.

Understanding plant tropisms helps us appreciate how plants adapt to their surroundings, seeking out essential resources like sunlight and anchoring themselves firmly in the soil. This knowledge connects to real-world applications in agriculture and environmental science.

Audience

5th Grade Students

Time

30 minutes

Approach

Through direct instruction, visual aids, and a hands-on activity, students will explore plant growth.

Materials

Whiteboard or projector, Plant Growth Slide Deck, Small plant (e.g., bean sprout or small houseplant), Cardboard box (large enough to cover the plant), Scissors or box cutter, Water, Sunlight, Observing Tropism Activity Sheet, and Cool Down: Plant Power Exit Ticket

Prep

Teacher Preparation

15 minutes

Step 1

Warm-Up: Think About Plants

5 minutes

  1. Begin by asking students: "What do plants need to grow?" and "Which way do plants usually grow?" (Towards the sun, roots down).
  2. Introduce the idea that plants have amazing ways of knowing where to grow. Use the Plant Growth Slide Deck (Slide 1-2).

Step 2

Introduction to Tropisms

10 minutes

  1. Explain that plants respond to signals from their environment. Introduce the terms 'phototropism' and 'gravitropism'.
  2. Use the Plant Growth Slide Deck (Slides 3-6) to illustrate these concepts with clear examples and visuals.
  3. Ask students to discuss examples they might have seen in their own lives.

Step 3

Observing Tropism Activity

10 minutes

  1. Distribute the Observing Tropism Activity Sheet.
  2. Show students a plant that has been growing in a box with a hole (if prepped). Discuss what they observe and why the plant is growing towards the light.
  3. Guide students through the activity sheet, prompting them to draw and describe how plants might grow in different scenarios (e.g., if a potted plant falls on its side).
  4. Circulate to provide support and encourage discussion.

Step 4

Cool Down: Plant Power Exit Ticket

5 minutes

  1. Have students complete the Cool Down: Plant Power Exit Ticket.
  2. Collect the exit tickets to assess understanding.
  3. Briefly recap the main ideas: plants grow towards light (phototropism) and roots grow down, stems grow up (gravitropism).
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Slide Deck

Why Do Plants Grow Up?

What do plants need to grow?
Which way do plants usually grow?

Welcome students and get them thinking about plants. Ask them what they already know about how plants grow.

Plants on a Mission

Have you ever noticed how plants always seem to grow in a certain direction?
What do you think helps them decide which way to go?

Prompt students to share their observations. Guide them towards the idea that plants seem to 'know' where light and soil are.

Growing Towards the Light: Phototropism!

šŸŒ± Photo = Light
šŸŒ± Tropism = Growing towards or away from something

Phototropism: When plants grow towards a light source.

  • Think about a sunflower turning to face the sun!
  • Even houseplants will lean towards a window.

Introduce the term 'phototropism'. Emphasize 'photo' for light. Give simple examples.

Growing with Gravity: Gravitropism!

šŸŒ Grav = Gravity
šŸŒ± Tropism = Growing towards or away from something

Gravitropism: How plants grow in response to gravity.

  • Roots grow DOWN, towards gravity, to find water and nutrients.
  • Stems grow UP, away from gravity, to reach sunlight.

Introduce the term 'gravitropism'. Emphasize 'grav' for gravity. Explain why this is important for roots and shoots.

Can you trick a plant?

Imagine you put a plant in a box with only one small hole for light...

Which way do you think the plant would grow? Why?

Show an image or describe the example of a plant in a box with a hole. Ask students what they observe.

Plants: Masters of Direction!

Plants are amazing at finding what they need!

  • They use phototropism to find sunlight.
  • They use gravitropism to keep their roots in the ground and their stems reaching high.

Now, let's explore these ideas with an activity!

Summarize the two tropisms and their importance. Prepare students for the activity.

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Activity

Observing Tropism Activity

Name: ____________________________
Date: ____________________________

Part 1: Plant in a Box

Imagine a plant growing inside a cardboard box. There is only one small hole in the side of the box that lets light in.

  1. Draw what you think the plant would look like inside the box. Show how it grows towards the light.













  1. Explain why the plant grows this way. What is this type of growth called?







Part 2: Tilted Pot

Imagine a potted plant that falls over and stays on its side for a few days.

  1. Draw what you think the plant would look like after a few days. Show the roots and the stem.













  1. Explain why the roots grow down and the stem grows up, even when the pot is on its side. What is this type of growth called?







Part 3: Your Own Observations

  1. Have you ever seen a plant growing towards a window or bending to find light? Describe what you saw.












  1. Why is it important for a plant to grow towards the light and for its roots to grow down?












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Cool Down

Cool Down: Plant Power Exit Ticket

Name: ____________________________
Date: ____________________________

  1. What is phototropism? (Hint: Think about light!)



  2. What is gravitropism? (Hint: Think about gravity!)



  3. Why are these two types of plant growth important for a plant to survive?






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Answer Key

Observing Tropism Activity Answer Key

Part 1: Plant in a Box

  1. Drawing: The drawing should show the plant bending and growing towards the small hole in the box where the light is entering.

  2. Explanation: The plant grows this way because it is responding to light. This type of growth is called phototropism.

Part 2: Tilted Pot

  1. Drawing: The drawing should show the pot on its side, but the stem of the plant should be growing upwards, and the roots should be growing downwards.

  2. Explanation: The roots grow down and the stem grows up due to gravity. This type of growth is called gravitropism.

Part 3: Your Own Observations

  1. Observation: Students might describe seeing a plant on a windowsill leaning towards the window, or a plant in a garden growing taller to get more sun.

  2. Importance: It is important for a plant to grow towards the light to perform photosynthesis and make its own food. It is important for roots to grow down to anchor the plant in the soil and absorb water and nutrients.

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Answer Key

Cool Down: Plant Power Exit Ticket Answer Key

  1. What is phototropism? (Hint: Think about light!)

    • Answer: Phototropism is when a plant grows towards a light source.

  2. What is gravitropism? (Hint: Think about gravity!)

    • Answer: Gravitropism is how plants grow in response to gravity (roots grow down, stems grow up).

  3. Why are these two types of plant growth important for a plant to survive?

    • Answer: Phototropism helps plants get enough sunlight for photosynthesis (making food). Gravitropism helps roots anchor the plant and find water/nutrients in the soil, and helps stems reach up for light and air.
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