Affect of light on plant growth

[gwyno]

I have to get expert answers to a few questions for my first paper. Can someone please help me by answering the questions below?

Thanks,
Gwyn

1. When a plant is grown under a consistent color of light like red, green, or blue light when shown on a plant over a period of time, what would you say that would happen?
2. Since red is the closest color to the color of the sun would you say that it had the most similar affect on the plant?
3. How often should I expose the plant to light? For example: all day every day, or simulate daylight or some other frequency?
4. Will the different colors of light have a big or small effect on the plants?

[deleted-80002]

Gwyn,

These are some good questions. Visible light is a small section of the electromagnetic spectrum. Other kinds of electromagnetic radiation are things like ultraviolet light, x-rays and microwaves. The different colors of light are referred to by their wavelengths. The shortest wavelength is blue light around 450nm. Red is the longest wavelength at 700nm. Green is right in the middle.

Plants use the energy in light to make sugar (called photosynthesis). They can then use the sugar to grow. They do this using their green pigments, chlorophyll, to absorb light energy. Chlorophylls absorb red and blue light and reflect the green light (this is why plants look green).

Although the sun looks yellow it actually gives off light with wavelengths in the entire visible spectrum as well as ultraviolet (UV) and infrared light. Have you ever looked at sunlight after it has passed through a prism? You can see all the colors of the rainbow because all the wavelengths are present.

The longer a plant is exposed to light the larger it will grow. This is because there is more time for photosynthesis to occur so the plant can make more food and get larger. So you can expose your plants to light for however long you want, just make sure to make the time the same for all your different plants.

The size of the effect will depend on how long the plants are exposed to the light and if there was any contaminating light. So to optimize your experiment you will want to put the plants in a dark place where the only light source is the color you are testing. And you will want to have them exposed to that light for a long time over a period of many days or weeks.

If you want to learn some more about photosynthesis and light check out these links:

Light
http://en.wikipedia.org/wiki/Light
http://science.howstuffworks.com/light.htm

Photosynthesis
http://en.wikipedia.org/wiki/Chlorophyll
http://en.wikipedia.org/wiki/Photosynthesis
http://science.howstuffworks.com/dictio ... s-info.htm

-microkts