Re: [APD] LED lighting --a wrench in the gears....

["Jim Seidman" <js5 at seidman_net>]

Gomer Gomer writes:
"A couple things to consider. If you are looking for growth and not just
lighting a tank (which I think we all want)...then just any ol red or blue 
won't cut it. Chlorophyll A and B both have absorbtion bands that are not
easily matched with LEDs (or atleast the ones I can find). Also, you NEED 
blue for more than just growth. Blue is what the plant uses to in order to
know what direction to grow."

There are quite a variety of different wavelengths available. At just one
site, I found LEDs with wavelengths of 430, 635, and 660 nm, well within
the chlorophyll response curve. It's at http://www.ledtronics.com/

That said, there's some evidence that most submerged plants don't follow
the same response curve as terrestrial ones. This certainly makes sense
from an evolutionary point of view, as water absorbs red light and DOC
absorbs blue light, meaning that much of what the plant actually gets is in
the 500 to 600 nm range.

I am not aware of any academic research studying photosynthetic response in
submerged plants. Perhaps someone else on the list knows of work in this
area. However, there was an article in FAMA several years back where a
hobbyist measured either growth or photosynthetic rates under different
lighting. He found that cool white bulbs were near the top in performance,
implying that the light around 540 nm wasn't totally wasted.

- Jim


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