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Re: Lighting Myths

Nice comprehensive posting on the subject of lights Karen!

I can only add one more comment that hasn't been repeated recently and
that is that when we talk about the red and blue colors that plants are
able to use more efficiently for photosynthesis, these are actually
spectral bands. Not all red light is the same to plants. The peak spills
over a little into orange and the blue peak spills a little into violet.

Here is some information from an old Plant Science text book which gives
a reference from "After Curtis and Clark, introduction to Plant
Physiology. 1950" which measures CO2 absorption to measure the rate of
photosynthesis. The actual spectral absorption bands of chlorophyl are
narrower. The blue peak is from 0.4 microns wavelength to 0.5 microns
(max 300 units of CO2 absorption) The "green" valley in the middle was
about 200 units (only a 30% drop in efficiency from blue to green and
yellow light. The second peak is from .60 microns to about .70 microns
with a maximum of 350 units. The red peak is not quite twice as
efficient as the yellow green valley. The two peaks are 0.655 (orange -
red) and 0.440 (blue - violet).

Somebody actually posted a chart with similar data balues onto the APD
as ASCII art so if you're really curious you might dig it up there. A
better method would be to do an hour or so of searching with the Web
search engines and find a nice color high res image of the graph.
Somebody else also made some spectral images using a diffraction slit
and camera and posted the results on his web page. Was it Hoa?

Steve Pushak                              Vancouver, BC, CANADA 

Visit "Steve's Aquatic Page"      http://home.infinet.net/teban/
 for LOTS of pics, tips and links for aquatic gardening!!!