It seems like there is some dispute over which wavelengths are ideal for photosynthesis in chlorophyll a and b. All the numbers i've seen are similar, but I was wondering if anyone has come across a study that is particular to cannabis, specifically... or would it not differ plant to plant as the pigments are the same..

Anyways, the reason I ask is because I plan to use LEDs, and want to grab the ideal wavelengths.. I was thinking one blue and one red per each pigment (chlor. a nd b), so four wavelengths total. This is what most data I've seen leads me to believe will work best...

anyways, thanks for any help.. here's the rough data i've come across:

chlorophyll a: 430-440 and 660-680
chlorophyll b: 490 and 650

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I guess I could also experiment with a handful of wavelength candidates by seeing which ones produce the "blackest" leaves while under their light only... because those particular wavelengths are being absorbed the most... right?

feel free to dispute that.. please

also, should i be concerned with antennae pigments as well, specifically carotenoids??

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leaf coloration is more indicative of nutrient uptake as opposed to light spectrum. my anecdotal personal experience being the variance of other properties under different lights (mh, ps, cfl etc) such as internodal spacing and bushiness, stem strength and bud density. My personal questioning is specifically in relation to budding, as ive had small lightweight resinous buds off mh only and dense thick slightly less potent buds off of hps and also larfy lightweight, but very resinous and crystal covered off of cfl. Ive had people tell me there is no reason to use hps during veg and mh during flower, yet i wonder about high altitude sativas yielding the best chron in cali outdoors, and know that the light is neither blue or red-yellow, and can only surmise the spectrum is much more intense across the board. Thus the wavelengths of the led you choose is about the bud you will see final product, not the blackest leaves after short growth. good luck

i was talking about observing the leaves while the LEDs were on, and seeing as how i wouldnt be using green LEDS, there wouldnt be any green light to reflect, so they would appear black, provided all of the light from the LEDS was ABSORBED instead of REFLECTED.. but after some thought, i think im just going to go hps... thanks tho

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these are the materials that have helped me gain some understanding of this question....

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Ride hard, Ride long....git put away Wet each and every time....no holdin' Back.....enjoy the journey ...... cuz that's ALL there is! Walk on and walk tall folks!

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Hey Alpha boo-boo!
Your numbers for nm/wavelengths look just about right! The problem I have is that every graph I look at looks a little bit different, so the target numbers tend to "slide" up or down a little bit.
That really shouldn't be a problem, according to the way one real LED expert (a rocket scientist type guy) explained it to me. "Each LED is centered on a specific wavelength, but it will also emit a few nano-meters on either side (in decreasing amounts). Also; the plant itself is able to accept light, at nearly optimal wavelengths, with just a slight, proportional, loss in photosynthesis". In other words, if your off by a couple of nano-meters - it's no big deal. I, too, have seen slightly different numbers by different experts - all claiming to be "exact". I think if you're fairly close, that's good enough!

You also asked about the "other" pigments like carotinoids (which depend on different wavelengths than chlorophyl-A& B). I talked with one LED expert who swore, up and down, that "all you need are the four wavelengths that produce chorophyl-A&B". I don't claim to be an LED expert myself, but I have done a fair amount of research on LED grow lights; especially pertaining to cannibis. And let's face it - something is missing in the "Flowering Dept." with LED's. I know that the plant can synthesize some amount of these other pigments, to make up for less than ideal light conditions, but if all other wavelengths (besides the primary four) are totaly missing - that's just asking too much of the poor plant! Like I said, I'm not an expert, so this is just my opinnion - cannibis needs more wavelengths of light than just four to produce various pigments and horemones that are essential for strong flowering. That's my $.02 worth!

thanks man, that helps. thanks to tahoe too.... only thing is, why do you have a pic of my girlfriend for your avatar?? not cool man...p.s. are you on the shroomery??

anways.. have you heard of the emerson effect? it has to do with far-red light and i guess it states that chlorophyll production with red and far-red light together will produce moreso than the sum of its parts (ie red or far-red)... kind of interesting..

also, the flowering is jacked with LEDs from what I've seen, but I think they would be an ideal light for a clone/seedling/veg. room, right? anyways, thanks for the help.. somebody with ambition and brains should get to the bottom of this..

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Jackie Treehorn... treats objects... like women... man..

yes I am/was/rarely these days/maybe more again soon?..... and she told me she was done with you? guess I owe ya one?! sorry 'bout that.....hahahahaha....

no I am not familiar with that....I like look it up....thanks....

there are some really neat ones (LEDs) from an Australian co. only found them the other day and will continue to look into that....

however, I am a strong proponent of balanced lighting using a combination of MH/HPS?and other yet to be confirmed.... walk on man!

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Ride hard, Ride long....git put away Wet each and every time....no holdin' Back.....enjoy the journey ...... cuz that's ALL there is! Walk on and walk tall folks!

"A House Full of Gratitude Has No Place for Fear To Hide"

Yeah, I've heard of the Emerson Effect! It's been quite a while since I've looked at it, because I really didn't understand how, or why, it works that much. I'll take another look at it. But like you said; the proper combination of wavelengths yields a much better growing result than one would normally expect. I'll have to refresh my feable memory and get back to you on that one - (LOL)!

Far red light (at about 710nm, as I recall) also causes another very useful phenomonum (spelling!). At lights off time; if the last wavelength of light that cannibis (or presumably, any other "short day" plant) receives is far red @ 710nm - the plant "goes to sleep" a lot faster - something on the order of 1 1/2 - 2+ hours faster! That allows the "sleep hormone" to accumulate faster; so that the plant "thinks" it's been dark for longer than it really has. I have read claims of people flowering with this method at 14 hours light - 10 hours dark. The benefit is pretty obvious - two hours of extra light per day equals a better yield with the same flowering period! I have never actually tried this, but perhaps someone else has tried it; or at least heard of it. If it sounds interesting, I could explain it in a little more detail!