Science Buddies: "Ask an Expert"

I am a 9th grader doing a science project on the effect of light (color) on plant growth. One of the requirements is to interview a botanist, can you help me?
I am using bean plants and plan to measure heigth above soil, would root length, weight, leaf width be of value?
I am testing primary colors with full spectrum light as control, i am planning to use artificial light in a dark garage?
should i do 12h on/ 12h off?
How many plants in each test group would be a good idea?
Does the hydroponic industry use colored/filtered light to influence growth?
If so is it for bigger growth, faster growth, or some other factor?
I really appreciate you answering my questions, I may have more later.
kristian

Hi Kristian!
I am not a botanist, but I did find some answers to your questions. These links are pretty helpful, some are actually past projects similar to yours.
http://www.selah.k12.wa.us/SOAR/SciProj2000/KatieW.html
Artificial light would be fine, you can wrap colored cellophane around a flashlight or use colored light bulbs. I wouldn't suggest doing 12 hrs timeframes, it would probably be easier to have each plant growing under a different light color. Remember to keep as many of the other variables constant (type of soil, how much water, sam environment, etc.)
http://www.usc.edu/CSSF/History/2002/Projects/J1617.pdf
http://www.colormatters.com/science_faq2.html
Hope this helped, good luck with your project!

thanks
is there an optimum wavelength of light for
plant growth
is it species specific?
is industry using it?

Hi Kristian!
Glad I could help. In answer to your other questions, here are a couple of pretty good links:
http://www.bio.net/bionet/mm/plantbio/1 ... 03008.html
http://express.colormatters.com/bulleti ... 7.162.html
http://express.colormatters.com/bulleti ... 7.162.html
Keep up the work, post back if you have any other questions...

Hi Kristian,

Here are some sites that deal with plant lighting, hopefully they will help you-these are not hard to find though and if you type in your questions to a search engine you should be able to get more results if these are not what you are looking for:
http://www.bio.net/bionet/mm/plantbio/1 ... 03008.html
http://www.bio.net/bionet/mm/plantbio/1 ... 03021.html
http://iubio.bio.indiana.edu:7131/bione ... 03030.html
http://cals.arizona.edu/pubs/garden/mg/ ... ental.html

In response to some of your earlier questions :
• You should probably test 2-3 plants for each light color. When doing experiments more is always better, because it will give you a more accurate answer.
• I am not sure if the hydroponic industry uses light, but this could probably be answered through a search engine. However, when observing your plants you should note that the plants that have grown to be bigger are simply growing faster than others. In looking at plant growth rather than development, bigger = the plant is growing faster. If you follow-up by looking at plant development, then you would want to look for bigger plants with more leaves, longer stems, etc.

Hope this helps! Please come back with any questions-good luck!

-Susan

Thanks both of you, i appreciate the help. The links both of you sent me were very helpful. I am confident the research portion of my science fair project will be much improved thanks to your help.

Ill make sure to post if i have any further questions.

-Kristian

Bringing an engineering perspective to your project, I would recommend that you determine both your light source spectrum and your filter's transmittance properties over the entire spectrum from near infrared to near ultraviolet.

If you don't have the resources to do this, then I strongly recommend that you use very low light conditions (small wattage bulbs, very small number of hours of "day", double your filter material,...).

My concern is that you can easily get identical results from all samples unless you are very close to stressing the plants with insufficient amount of light energy needed.

Given an excess of all other growing conditions, I would expect that the broad spectrum light factor would be primarily a three segment curve. A too little light region where you get sick plants, a linear region where growth rate and health is a function of increasing light, and a saturated region where the plant has already achieved its maximum growth rate and adding more light has no effect. Any actual plot would likely have some smooth transition between these regions and not be a three straight line approximation.

If enough light of the correct kind gets through all of your filters to end up in the saturated region, you won't see any difference because you will be in the saturated growth zone wrt light.