Plants and Light Sources - Do Plants Grow Better with Sunlight or Artificial Light?
The Plants and Light Sources Experiment compares how plants grow under natural sunlight versus artificial light. This fundamental plant biology experiment helps students understand photosynthesis, light requirements, and indoor growing techniques.
Perfect for exploring plant biology, photosynthesis, and light spectrum science, this controlled experiment provides clear observable results about how different light sources affect plant health and growth.
🔬 Research Question
Do plants grow better with sunlight or artificial light?
This experiment tests whether plants can grow as well under artificial lighting as they do under natural sunlight, and which light source produces healthier, stronger plants.
🧠 Background Research
Plants use photosynthesis to convert light energy into chemical energy (food). The process requires light, carbon dioxide, and water to produce glucose and oxygen.
Light and photosynthesis fundamentals:
- Chlorophyll - Green pigment that captures light energy
- Light spectrum - Plants use primarily red and blue wavelengths
- Light intensity - Brighter light generally means more photosynthesis
- Duration - Most plants need 12-16 hours of light daily
- Quality - Full spectrum light contains all wavelengths plants need
Natural sunlight vs. artificial light:
- Sunlight - Full spectrum, variable intensity, free but weather-dependent
- Artificial light - Controlled spectrum and intensity, consistent but uses energy
- Indoor growing - Allows year-round cultivation regardless of season
- Spectrum differences - Some artificial lights lack certain wavelengths
Understanding light requirements helps explain how indoor gardening and greenhouse growing work.
💭 Hypothesis
Prediction: Plants will grow better under natural sunlight because sunlight provides the full spectrum of light that plants evolved to use, while most artificial lights may lack certain wavelengths or adequate intensity.
Expected outcome: The sunlight plant should show better growth, greener color, and stronger stems compared to the artificial light plant, though both should survive if given adequate light duration.
🛠️ Materials Needed
Living Materials:
- 2 identical plants (same species, size, and health)
- 2 similar-sized pots with saucers
- Potting soil (if repotting needed)
Lighting Equipment:
- Desk lamp or grow light
- Timer outlet (optional but recommended)
- Area with good natural sunlight
Measurement Tools:
- Ruler for measuring plant height
- Plant labels or tags
- Camera (optional, for documentation)
- Data recording sheet
- Watering container
Optional Advanced Tools:
- Light meter (measures light intensity)
- Different types of artificial lights to test
⚗️ Experimental Procedure
- Plant preparation: Select 2 identical plants of the same species, size, and health condition. Label one "Sample A - Sunlight" and the other "Sample B - Artificial Light."
- Initial measurements: Record starting height, number of leaves, stem thickness, and overall health condition of both plants. Take photos if possible.
- Sunlight setup: Place Sample A on a windowsill or location where it receives direct sunlight for most of the day (ideally 8+ hours).
- Artificial light setup: Place Sample B under the lamp in a room away from natural light. Position the lamp 12-18 inches above the plant.
- Light timing: Turn the artificial light on at dusk and off at dawn to match the sunlight plant's light duration. Use a timer if available for consistency.
- Daily care: Water both plants equally when soil feels dry. Ensure both receive the same amount of water and care.
- Daily observations: Record daily measurements of height, leaf count, color, and general health for both plants.
- Duration: Continue the experiment for 2-3 weeks, making daily observations and measurements.
- Final analysis: Compare final measurements with starting data and determine which light source produced better growth.
📊 Expected Results & Analysis
Typical experimental outcomes:
| Measurement | Sample A (Sunlight) | Sample B (Artificial Light) | Difference |
|---|---|---|---|
| Height Growth | 2.5 inches | 1.8 inches | Sunlight +0.7 inches |
| New Leaves | 6 new leaves | 4 new leaves | Sunlight +2 leaves |
| Leaf Color | Deep green | Light green/pale | Sunlight healthier color |
| Stem Strength | Strong, thick | Thin, may lean | Sunlight stronger |
| Overall Health | Excellent | Good but weaker | Sunlight superior |
Analysis: Results typically show sunlight producing superior plant growth. Natural sunlight provides full spectrum light with optimal intensity and quality. Artificial light plants often grow more slowly, have paler leaves, and weaker stems, though they can still survive and grow.
Why sunlight usually wins: Full spectrum light, natural intensity changes throughout the day, and evolutionary adaptation to solar radiation give sunlight-grown plants advantages.
⚠️ Safety Information
- Electrical safety when using lamps and timers
- Keep water away from electrical outlets and cords
- Use stable surfaces for plants to prevent falls
- Position lamps securely to avoid tipping
- Check that artificial lights don't overheat plants
- Adult supervision recommended for electrical setup
- Handle plants gently during measurements
🌱 Photosynthesis and Light Science
Understanding the plant biology behind the results:
How Photosynthesis Works:
- Chlorophyll captures light energy
- Light energy splits water molecules
- Carbon dioxide combines with hydrogen
- Glucose (plant food) and oxygen are produced
Light Spectrum Importance:
- Red light (660-700nm) - Flowering and fruiting
- Blue light (400-500nm) - Leaf growth and photosynthesis
- Green light (500-600nm) - Less used, reflected back
- Full spectrum provides complete plant nutrition
🔬 Project Extensions & Variations
Advanced Investigations:
- Test different types of artificial lights (LED, fluorescent, incandescent)
- Vary the distance between light and plant
- Test different light durations (8, 12, 16 hours)
- Compare different plant species
- Measure light intensity with a light meter
Science Fair Enhancements:
- Create daily growth charts and graphs
- Take time-lapse photography
- Research indoor farming and hydroponics
- Study seasonal changes in sunlight
- Investigate grow light technology
Frequently Asked Questions
Why do plants usually grow better in sunlight than artificial light?
Natural sunlight provides the full spectrum of light that plants evolved to use, including the optimal balance of red, blue, and other wavelengths. Most artificial lights lack certain wavelengths or don't provide the same intensity as sunlight.
What type of artificial light works best for plants?
Full-spectrum LED grow lights work best because they provide the red and blue wavelengths plants need most. Fluorescent lights work moderately well, while incandescent bulbs are generally too hot and don't provide the right spectrum.
How many hours of light do plants need each day?
Most plants need 12-16 hours of light daily for optimal growth. Some plants require specific day/night cycles, but for this experiment, matching the natural sunlight duration (about 12 hours) works well.
Can plants survive completely on artificial light?
Yes! With the right type of artificial lighting, plants can grow entirely indoors. This is how hydroponics and indoor farming work. The key is using lights that provide the correct spectrum and intensity.
Why might my artificial light plant look pale or weak?
Pale, weak growth usually indicates insufficient light intensity or poor light spectrum. The plant may be getting some light but not enough quality light for robust photosynthesis and healthy development.
How far should I place the artificial light from my plant?
Generally 12-18 inches for most desk lamps or grow lights. Too close can burn the plant, too far reduces light intensity. LED lights can be closer than fluorescent or incandescent lights since they produce less heat.
What if both my plants grow the same amount?
Sometimes artificial lights work very well! Document your results - if both plants grew equally, that's valuable data showing that your artificial light setup was effective. Consider what type of light you used and why it worked.
Can I use this experiment to start an indoor garden?
Absolutely! This experiment teaches the basics of indoor growing. If your artificial light setup works well, you can expand it to grow herbs, vegetables, or other plants indoors year-round.