Does The Color of Light Affect Plant Growth?

This experiment attempts to discover whether the color of the greenhouse material impacts the growth of the seedlings inside.

Research Questions:

• What colors of light do plants need in order to gather energy from sunlight?
• Why are greenhouses green?
• What is full spectrum light?
• Which colors of filters block ultraviolet light?
• How to plants convert sunlight into energy?
• How do plants use chlorophyll?

Plants are commonly grown in greenhouses, which provide extra warmth and humidity by forming a barrier between young plants and the outside environment. This allows plants to thrive when outdoor conditions would be too harsh for them.  Though greenhouses are classically built out of clear glass or plastic, there are some built from semi-porous netting. The term greenhouse does not just apply to structures that are green, though many greenhouses are covered in green, semi-transparent plastic. Plants require sunlight to grow, which they transform into usable energy in their chlorophyll. This experiment attempts to discover whether the chlorophyll in plants can transform light into energy when certain colors of light are missing from the spectrum.

Materials:

• 50 1 foot long pieces of 1x1 wood
• A hammer
• Nails
• Green cellophane
• Blue cellophane
• Clear cellophane
• Yellow cellophane
• Red cellophane
• scissors
• glue or tape
• Potting soil
• Planting containers (smaller than 1’ by 1’)
• Water
• Marigold seeds

Most of these materials will be easy to find at a hardware store. An adult can help saw the wood into 1 foot long pieces for you to use or the hardware store can do it for you. If your local hardware store doesn’t carry colored cellophane, you can try looking at an arts and crafts store.

Experimental Procedure:

1. After gathering all the necessary materials, you will need to construct your miniature greenhouses. Start by separating the foot-long pieces of 1”x1” boards into groups of 10. You will need 10 pieces to construct each greenhouse.
2. Use two nails to attach the wood together at each corner.
3. Once you have built five greenhouse frames, you are ready to add the greenhouse covers. Cut out pieces of colored cellophane large enough to cover the sides of the greenhouse frames.
4. Attach the colored cellophane to the frames using tape or glue, making sure that each greenhouse is covered in a different color. Do not cover the bottom of the frames.
5. One greenhouse will need to be covered in clear cellophane. This will be your control.
6. Fill the potting trays with soil.
7. Plant the seeds according to the package instructions.
8. Water the seedlings daily and record results on a growth chart such as the ones below. Monitor the experiment for at least two weeks.

Terms/Concepts: Chlorophyll; Full spectrum; Natural light;  Light filter; Germinate; Greenhouse design

References: