What Kind of Light will Produce the Greatest Plant Growth, Regular Light or a Fluorescent Bulb?

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Author: Dr. Muriel Gerhard

Grade Level: 7th - 8th; Type: Biology


To determine what kind of light will produce the greatest plant growth, regular light or fluorescent light?

Research Questions:

  • What is photosynthesis?
  • What are the requirements for plant growth?
  • What is electromagnetic energy?
  • What is the visible spectrum?
  • How is fluorescent light different from Incandescent light?
  • Is heat a factor in plant growth?
  • Which type of light bulb produces a greater amount of heat, fluorescent or incandescent?
  • What are grow lights?


  • a package of radish seeds
  • potting soil
  • planting pots
  • water,
  • a watering can
  • metric ruler
  • a pen
  • labels
  • tape
  • a fluorescent light
  • an incandescent lamp

Experimental Procedure:

  1. Gather all the materials you will need for this project. These include a package of radish seeds,potting soil, planting pots, water, a watering can, a fluorescent light, a metric ruler, tape, a pen,labels, an incandescent lamp and a camera if you wish to take pictures.
  2. Copy the charts provided on the next page so that you can readily record your observations of plant growth and summarize your findings. Reproduce 10 copies of the Daily Chart and one of the Summary Chart.
  3. Fill your planting pots with equal amounts of potting soil. Follow the directions on the package of radish seeds. To insure that you have a sufficient number of specimens, set up at least 4 pots to be exposed to fluorescent and 4 pots to be exposed to incandescent lighting after the seeds germinate.
  4. Water the seeds daily. Radish seeds germinate rapidly and are therefore a good choice.
  5. At this time you may wish to start taking photos.
  6. When the seedlings are about a half inch high, label each set of 4 with a specific designation such as #1IN for 1 incandescent, #2 IN, 3IN etc and #1FL for fluorescent and #2 FL etc.
  7. Place one set of 4 under a fluorescent lamp and the second set of 4 under a lamp with an incandescent bulb. Place both sets of plants in a section of the room that has a minimal exposure to sunlight. Adjust the plants so that they are placed in equal distances from the light sources. Water them each day for the next 10 days. Make your observations, record the growth of the plants using your metric ruler. Note the number of leaves and record the average number for each group.
  8. Review your finding. What are your conclusions? Write your report. Include your bibliography. Based on what you have found, how would you explain what has happened? Given what you know now, are there any changes you would make in this experiment if you were to do it again? What would they be?

                                                              Chart of Daily Observations

Plant Height of Plants Number of Leaves Other


                                                                 Summary Chart 

Kind of Light Average Plant Height Average # of Leaves Other Observations
Plants exposed to Incandescent Light      
Plants exposed to Fluorescent Light      


Terms/Concepts: Photosynthesis, fruiting, blooming, the visible spectrum, fluorescence, electromagnetic energy, wave length, hormones, grow lights.


Morholt,E.,Brandwein, P.,Joseph,A. ASourcebook for the Biological Sciences, Harcourt, Brace and World, 1986

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