Drowning in conflicting plant graphs - help! (LED)

[headshake]

I'm no director of research - far from it... but my limited understanding tells me that plants do not use the entire light spectrum. In fact, it uses quite limited amounts of white, yellow, orange and green. So an HPS that pumps out tons of "white" light (not to mention heat) is wildly inefficient. It is successful due to the high photon flux rate across the spectrum.

white, or visible light is composed of red, orange, yellow, blue, green indigo and violet light (or wavelengths). the part of the electromagnetic spectrum that we see is from about 390nm-750nm. plants use all the wavelengths except for green, which they reflect, hence why plants look green to us.

I've seen these lights LEDs with dimmers and I've wondered why you would use them. OK, with young seedlings you don't need to raise the light if you can dim it. And I guess you could tweek them to better mimic sprning / summer / fall lighting but really, the major factor is time phase (12/12 vs. 18/4) so once your seedlings are into veg wouldn't you just crank the LEDs all the way up and leave them there to maximize output / penetration?

the reason i suggested dimmers was because you would have independent control of all the wavelengths at your fingertips. you would be able to tweak the ratios of every wavelength (that are currently available).

i, also, by no means am an expert. just an avid reader with more questions.

i applaud all of you for pushing the envelope.


-shake

headshake Reviewed by headshake on 05-07-2010. Drowning in conflicting plant graphs - help! (LED) Still trying to design my LED light through clear understanding and not just mimicking. There is one photosynthetic response curve that shows yellow light has more effect than blue light and that green, while lower, is almost as useful. Other articles say green light may stunt plant growth and that yellow is not much more useful (despite the huge success of HPS). Then there is the photosynthesis action spectrum showing that violet/purple light (400nm) has the highest absorption peak Rating: 5