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Name: Sandy H
Status: student
Grade: N/A
Location: N/A
Country: N/A
Date: N/A

Dear Sir/Madame,
I hope that this question is relavent at this site.... but I hope that you can help me....

I was wondering, since at biology we were learning about plants diversity. And we learnt that diffent wave-lengths of light can effect the photosynthesis (and growth) of the plant. My question is, does that also apply to seed while under-going germination???

I was planning to do an investigation on this, when my teacher said she thinks that lettuce seeds might be affected.... (but I need a seed that would germinate within a week.... because of the the time allocated for the investigation...) Would wheat grass or alfalfa seeds work??? (with the different wave lengths of light...)

Seed germination relys on water [hydration] and temperature in most cases. Light has little to do with the start of plant growth until the seedling has broken the surface ofg the soil.

Steve Sample

Dear Sandy,


"The wavelength of light is critical. The seeds germinate well in white light, but also to single "colors"...particularly red light (660 nm). On the other hand, far-red light (730 nm) strongly reduces lettuce germination. "

not many plant seeds germinate within a week. Zea (corn) germinates quickly but not sure how light affects it, if at all.

Recommend that you try several different plant seeds in your experiment.

Anthony R. Brach, Ph.D.


This is an interesting question and a good one for experimentation. I personally did some work in college investigating the effect of different concentrations of non-toxic salts on germination. As expected, the salts at higher concentrations began to adversely affect seed germination.

My personal expectation on this is that one might not see much of an influence by different wavelengths of light. The reason for my expecting this is that normally seeds will germinate with only the presence of warmth and moisture (meaning generally NO light is needed). Seeds generally contain a supply of food stored compactly as starch and food production therefore early-on is not essential for germination. Depending upon the size of the seed and the planting depth, though, food production will quickly become a consideration.

The design of your experiment might include tests of germination with no light (total darkness) and then tests of more seeds of the same type with differing wavelengths of the same light duration and intensity (you cannot change more than one variable here or it will confuse your findings and make your job of explaining the data impossible). You also need to provide controlled identical background environment for each of the seeds in the experiment. By this I mean the same temperature and the same amount of moisture provided. You need to have a good number of seeds per experiments because some percentage of seed will never germinate. Note that the light you use will produce can feel the heat emanating from a light bulb. Realize that if you compare seed germination for seeds in total darkness versus seeds exposed to any type of light that those exposed to light might also experience more warmth, and any growth promotion might be partially (or fully) due to the increased temperature. If you monitor all temperatures carefully, though, you should be able to make adjustments in the various environments' temperatures to control your data.

Good luck with your investigation, and thanks for using NEWTON!

Richard R. Rupnik

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