Re: How does the color of light effect gas production in plants.

Hi!

The short answer to your question is "yes"

Green light has no effect on plants because green is reflected (that's why plants look green to you and I)

The red light is absorbed and causes photosynthesis which causes oxygen to be released

Chlorophyll (the pigment which absorbs light) absorbs very little of the green and yellow-green light (500-600nm) but strongly absorbs violet, blue, orange and red wavelengths

For more information, look at the following:

http://photoscience.la.asu.edu/photosyn/education/learn.html

MIT's Photosynthesis Hypertextbook

A lot of links are here: http://uchsg14.ch.umist.ac.uk:8081/photo_web/links.htm

If you have any other questions, please feel free to e-mail me.

Sincerely,

Andreas Matern

G-15 Bradfield Hall

Department of Plant Breeding and Biometry

Cornell University

Ithaca, NY 14853

My homepage

Admin note: David Hershey adds the following:

One of the most common misconceptions about photosynthesis is that leaves reflect all the green light and do not use green light in photosynthesis. The truth is that leaves typically absorb half or more of the green wavelengths, and green light is used fairly efficiently in photosynthesis. Most leaves do reflect more green light than other colors so leaves appear green to our eyes.

The misconception about green light use in photosynthesis arises because of the chlorophyll absorption spectrum printed in many botany and biology textbooks. The chlorophyll absorption spectrum is made using a spectrophotometer and chlorophyll extracted into a test tube of an organic solvent such as acetone. The chlorophyll solution does absorb relatively little green light compared to red and blue, however, chlorophyll solution in a test tube behaves differently than chlorophyll in a leaf. In plants, chlorophyll occurs in highly structured chloroplasts, which are in complex plant cells. In a test tube, the light passes right through the chlorophyll solution so the chlorophyll has one chance to absorb a green light particle or photon. In leaves, a chlorophyll molecule in a highly structured chloroplast has many chances to absorb a green photon because the unabsorbed photon can be reflected repeatedly from chloroplast to chloroplast many times increasing its chances of being absorbed. There are also accessary pigments, the carotenoids, which can absorb green photons and pass the energy to chlorophyll.

In terms of your experiment, it may be that the green filter you used reduced the amount of light much more than the red filter. The human eye is not a good judge of the exact color makeup of the light nor the total amount of light the plant is receiving. You need an instrument called a spectroradiometer to determine the exact color composition of the light and a quantum sensor to measure the amount of photosynthetically active radiation or PAR provided.

David Hershey

Reference:

Salisbury, F.B. and Ross, C.W. 1985. Plant Physiology. Belmont, CA: Wadsworth.