Biology · Plant Science
Study how light colour affects plant growth
Grow seedlings under red, blue, green and white light and compare height and leaf colour.
- DifficultyEasy
- Estimated time2–4 weeks
- Budget₹250–₹500
- ClassClass 7–10
- TeamSolo or up to 3
- You needHousehold materials
Prerequisites: None beyond your class work
Original · by TechnifyedExperimentScience Fair ProjectBeginner friendlyLow costWell documented
Overview
Grow seedlings under red, blue, green and white light and compare height and leaf colour.
Why build this?
It tests a question with a clear prediction from the chemistry of chlorophyll.
What you will learn
- Which colours chlorophyll absorbs
- How to measure growth over weeks
- How to control water and soil
Skills you will use
Materials and tools
- 16 seedlings of the same age
- Four boxes
- Coloured cellophane or LED bulbs
- Ruler
- Water
Tools and software
Step-by-step roadmap
Start
You will finish with: growth curves and an explanation of why green light gives the weakest growth.
- 1
Prerequisites
Nothing special to know first. Then collect the 5 items in the materials list.
- 2
Learn
- Which colours chlorophyll absorbs
- How to measure growth over weeks
- How to control water and soil
- 3
Plan
Write your question, your hypothesis and the one thing you will change. Draw the table you will fill in before you start.
- 4
Build
- Cover a window in each box with a different colour filter.
- Put four seedlings in each box with equal water.
- Measure height and count leaves twice a week for four weeks.
- Photograph the plants each week.
- Plot average height against time for each colour.
- 5
Test
Repeat every reading at least three times and check the result against what the science predicts.
- 6
Document
Record every reading with its unit, photograph the setup and draw a graph of the result. Report structure
- 7
Present
Explain the question, the method and the graph in two minutes; keep the setup ready to demonstrate. Presentation structure · Viva questions
- 8
Publish
Share the report and photos with your class, a science fair or your school magazine.
Expected outcome
Growth curves and an explanation of why green light gives the weakest growth.
Other versions of this project
Beginner version
Compare white light and green light only.
Advanced version
Measure leaf chlorophyll by extracting with alcohol and comparing colour depth.
Make this project better
- BasicCompare white light and green light only.
- This projectStudy how light colour affects plant growth
- AdvancedMeasure leaf chlorophyll by extracting with alcohol and comparing colour depth.
Science fair mode
Text marked "You write this" is a prompt for your own work; everything else is specific to this project.
- Problem
- You write thisWrite your question as: How does [what you change] affect [what you measure]?
- Hypothesis
- If plants receive only green light, then they will grow least because chlorophyll reflects green.
- Variables
- Independent: colour of light. Dependent: plant height and leaf number. Controlled: water, soil, seedling type, light hours
Materials and procedure are in Materials and the Roadmap.
Observation table
You write thisDraw a table with one column for what you change, one for each repeat reading and one for the average.
- Graph
- You write thisPlot what you changed along the bottom and what you measured up the side; use a bar chart for categories and a line graph for numbers.
- Results
- You write thisState what the graph shows in one or two sentences, with numbers.
- Conclusion
- You write thisSay whether the result supports your hypothesis and why you think so.
Display board
- Title and your name
- Question
- Hypothesis
- Materials
- Procedure (with photos)
- Data table and graph
- Conclusion
- What you would do next
Questions judges ask
- Why do plants look green?
- Which colours drive photosynthesis most?
- What did you keep the same?
- What would you change if you did this again?
- What was your biggest source of error, and how did you reduce it?
- Where is this idea used in real life?
Working as a team
Solo or up to 3. Suggested roles:
Report and presentation
Report structure
- Title and question
- Background: the science behind it
- Hypothesis
- Materials
- Method (steps, with a diagram or photo)
- Observations (table)
- Results (graph and calculation)
- Sources of error
- Conclusion
- What you would do next
- References
Presentation structure
- The question
- Why it matters
- The idea behind it
- Setup (photo)
- Method in three steps
- Results (one clear graph)
- What the result means
- Errors and limits
- Conclusion and next step
Viva questions
Try answering before you open each one.
Why do plants look green?
Chlorophyll reflects green light and absorbs red and blue.
Which colours drive photosynthesis most?
Red and blue.
What did you keep the same?
Water, soil, seedling type and hours of light.
Resources
Source and attribution
Original
Written by Technifyed. Free to use for your own school or college project; write the report in your own words. Added 1 Oct 2026.
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