Why plants bend toward light is the mystery you will investigate in today’s science warm-up. You will examine an observation, develop a possible explanation, and support your thinking with evidence.
Observe the Phenomenon
A plant is placed on a table near a window. When it is first placed there, its stem grows straight upward.
After several days, something changes. The plant’s stem gradually bends toward the window, and its leaves begin facing the sunlight.
Why Do Plants Bend Toward Light?
Think about what the plant needs, what it receives from sunlight, and how changing its direction might help it survive.
Your science question: Why does the plant’s stem change its direction of growth?
You do not need to know the official scientific explanation yet. Use what you already know about plants to develop the best explanation you can.
Scientists do not always begin an investigation with the correct answer. They begin with observations, develop possible explanations, collect evidence, and revise their thinking.
Your Five-Sentence Response
Write a response containing at least five complete sentences.
Your response must include:
- A clear claim explaining why the stem bends toward the window
- A description of what the plant receives from sunlight
- An explanation of how bending might help the plant survive
- At least one observation from the phenomenon as evidence
- Scientific reasoning connecting your evidence to your claim
You may begin with this sentence:
I think the plant’s stem bends toward the window because…
Questions to Help You Think
Consider these questions before writing:
- What do plants need sunlight for?
- How might facing the window help the leaves?
- Is the plant moving all at once, or is it changing as it grows?
- Which observation supports your explanation?
- What might happen if someone turned the plant away from the window?
Use these questions to guide your thinking, but combine your ideas into one clear five-sentence response.
Post Your Response in the Comments
Post your response in the comment section below.
Before submitting it, make sure you:
- Wrote at least five complete sentences
- Answered the science question directly
- Included evidence from the observation
- Explained why your evidence supports your claim
- Checked your spelling and punctuation
- Used only your first name and class period
- Did not include personal information
Respond to a Classmate
After posting your explanation, read at least one classmate’s response. Reply to that student with a respectful and science-focused comment.
You may use one of these sentence starters:
- I agree with your explanation because…
- My explanation was similar because…
- One difference between our explanations is…
- Your response made me wonder…
- One observation that supports your idea is…
You may disagree with an idea, but your response must remain respectful. Discuss the scientific explanation, not the person who wrote it.
Take the Extra Challenge
If you finish early, answer one of these questions at the end of your comment:
- What might happen if the plant were turned away from the window?
- Would the plant bend toward an artificial light?
- How could we test whether light caused the change?
- Would the roots respond to light in the same way as the stem?
- What evidence should we collect during an investigation?
Understanding why plants bend toward light begins with careful observation. Make your best claim, support it with evidence, and be prepared to revise your explanation when you receive new information.
When you’re finished, check out the rest of our blog for more tips, ideas, and activities to help you learn and grow. Be sure to follow our classroom Instagram page for behind-the-scenes moments, project highlights, and fun updates. Let’s work together to make learning fun, exciting, and something you look forward to every day!
