why do plants grow best under green light?

Question

I've grown fast seeds plant for 2 weeks under red, green and white cellophane to produce the light color. The seeds under green light showed grest height and healthiest? why? isn't it supposed to be the worse condition for plant growth?

Answer 1

Yes, you are seemingly getting different results than you would expect. As to why, you are not giving the plants enough time to react as you would expect them to. A sprouting seed will get most of its energy from the seed for the first couple of weeks after planting. Or in the case Dicotyledon plants like beans, most of the energy from the cotyledons. As far as the plants under green light being taller this is what you would expect. Seedlings under poor light will grow taller and more spindly as time goes on. Try sprouting some of your seeds in the dark and you will see a good demonstration of this. As fat as your project goes just give it more time and you will probably see the results you expect.

Answer 2

If you insure you have equivalent intensity of light from each of the three lamps. the best growth should be under white light, second under red light, and least with green light. There may not be measurable difference in only one week. Remember that under poor light conditions the plant may actually grow elongated but weaker. Growth should be measured by the amount of biomass (dry weight) of each of the groups of plants. You should have multiple plants growing under each lighting condition to minimize random chance occurrences that may occur.

Answer 3

I don't know why.
Maybe for some reason your green light was brighter then the white and red one.
Did you measure the spectrum of your green light? Is it really pure green?
I would try to measure the spectrum and the intensity of the light in all 3 cases.
Also I would repeat the experiment more then once since the outcome could also be a coincidence.
And of course all other factors should always be the same in all tests. (temperature, humidity, amount of water given, proximity to any CO2 sources e.g. people or animals, etc. )

Answer 4

Normally, plants do better with red light mostly, but some prefer a combination of red and blue light (this will affect the stem size of your plant). There's a lot of info on the web regarding your question. You could check sources regarding led lighthing for plants, since leds provide precise wavelenghts, for example:

http://arabidopsisthaliana.com/index.htm

Answer 5

Plants usually do best under red spectrum light. You might not have a true green light. It may have other spectrum colour in it, and therefore the plants are reacting favorably.