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Does the color of light affect plant growth?

Answers:1   |   LastAnswerAt:2011.04  

Asked at 2011.04.20 23:17:47
I have a science project and need to find out if the color of light affects plant growth, and if so, what color affects it most, or what color plants grow best in. Any information is appreciated. Thank you so much!
answer Boss Nass  Answered at 2011.04.20 23:17:47
Light quality refers to the color (wavelength) of light. Sunlight supplies the complete range of wavelengths and can be broken up by a prism into bands of red, orange, yellow, green, blue, indigo, and violet.

Blue and red light, which plants absorb, have the greatest effect on plant growth. Blue light is responsible primarily for vegetative (leaf) growth. Red light, when combined with blue light, encourages flowering. Plants look green to us because they reflect, rather than absorb, green light.

Knowing which light source to use is important for manipulating plant growth. For example, fluorescent (cool white) light is high in the blue wavelength. It encourages leafy growth and is excellent for starting seedlings. Incandescent light is high in the red or orange range, but generally produces too much heat to be a valuable light source for plants. Fluorescent grow-lights attempt to imitate sunlight with a mixture of red and blue wavelengths, but they are costly and generally no better than regular fluorescent lights.
Try this experiment
My objective is to find out how different light colors affect plant growth.
- 4 boxes
- Colored Transparencies: Red, Blue, Green, Yellow, and Clear.
- 5 flower pots and plastic bowls (for drainage)
- 15 lima bean seeds
- Potting soil
- Tap water
- 5 rulers
- Scissors
- Box cutters
- Construction paper in Red, Blue, Green, Yellow, and White.
- Tape
- Cup
- Paper towel
I built three boxes with 5 different colored transparencies on top and front. I planted seeds about ½ inch
into the pots and let them grow. I recorded measurements every 2-3 days. The Plants were shown different
colored light. There were 3 different plants for each different colored light. I measured overall height and
leaf width for the tallest and best plant of each color.
The red grew the tallest, but the transparent was the healthiest. The blue died midway through the project
and the yellow was close to beating red. The green did poorly.
My hypothesis was somewhat correct because red was the tallest and green was the worst living plant. I
did not expect that the transparent plant would be the healthiest. I conclude that if you want a healthy
plant show the plants the full color spectrum, but if you want a tall plant you should only show the plant
red light.
Hence it can be said that
Yes, light color definitely affects plant growth. Natural sunlight contains the full visible spectrum, plus plenty of non-visible spectrum. When a plant is deprived of the spectrum of light on which it depends, it will suffer. The "Grow-Lights" available for plants are expensive because they have made sure to include all the important spectrum elements necessary for a healthy plant's growth.

Since Science Fair is probably coming up at your school, an interesting experiment would be taking one kind of plant, putting different specimens into different pots, and testing growth rate and health under exposure to different colors of light. This way, you can see for yourself, and wind up with a possible winning project.
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