Science-why did the red light make the corn the greenest?

Question

I tested to see which light bulb would make corn the greenest. I used green, ulraviolet, and red light bulbs. The red light bulb made the corn the greenest. Why did the red light bulb make the corn the greenest?

Also: I need to do a research paper for my project. I looked up the history of corn and other stuff about corn. I want to look stuff up about red, green, and ultraviolet light bulbs, but I don't know what to look up! Any suggestions that I could type into Google or any websites with information i could use??

Answer 1

Chlorophyll adsorption peaks in the blue and the red. Chlorophyll reflects and does not effectively use green light (that is why plants are green, they adsorb blue and red light and reflect green, so you see green light reflected back to you). UV is not adsorbed by chlorophyll effectively for photosynthesis. Thus, your greening with red light is as would be expected since it is the only light giving a wavelength that is effectively adsorbed by chlorophyll and used for photosynthesis.

You should look up 'photosynthetically active radiation' or PAR. Alternatively, look up chlorophyll or photosynthesis or chloroplast development.

I hope this helps....

Answer 2

Plants need the full spectrum to grow well. With any limit in the spectrum they will suffer a drop in growth rate as all parts of the visible range can contribute to plant growth but if light is limited they respond best in the longer wavelengths.

The peak in the blue at 430 - 450nm is about 70% as tall (as effective) as the red wavelengths at 585 - 660 nm. In between these two peaks, at 485nm, the rate dips to less than 60% of the red peak. If you look at the graph you will see the plants growth curve plotted against the effective wavelengths.

Graph of light wavelength and plant relative growth.
http://www.clovis.co.uk/horticultural/images/graph_lwpg.jpg
http://www.clovis.co.uk/horticultural/polythene_film_facts.htm
http://www.sankey.ws/plantlumen.html
With each bulb you limited the plants to a fraction of the full spectrum the plants need. The red light was the only light offered that was in the plants most effective range.




'The chemistry of plant pigments' by Chichester may also be useful to you.