Quote Originally Posted by farredeyed
Do I have the whole concept wrong? It seems this whole thing is taking advantage of being able to control light frequencies indoors and using red and far red to bounce the phytochrome back and forth unnaturally to feed constantly and speed up growth, while keeping blue seperately controlled.
You're close, but manipulating the speed at which phytochrome conversion takes place is not the point, it's the method. The point is to increase the total amount of photosynthesis, which in turn drives more plant growth. Since flowering requires no less than 12 hours of "darkness", we cannot simply leave the day lights on longer to get more photosynthesis. Instead, we add light to the night period that will not trigger the plant's daytime sensors (i.e. no light below 500 nm) but will still run the plant's photosynthetic engines.

The link between the plants flowering and darkness is due to phytochrome.
"Phytochrome exists in two photoreversible forms: Pr (Amax = 666 nm) and Pfr (Amax = 730 nm). Absorption of red light by Pr converts the molecule to Pfr, the biologically active form; subsequent irradiation with far-red light changes phytochrome back to the inactive Pr form."
from:
http://www.plantcell.org/cgi/reprint/1/8/765.pdf

It seems that it's phytochome's inactivation is what leads to flowering: When phytochrome is not being activated by Red light, it naturally "deactivates" to Pfr, and after a certain amount of this happening, flowering occurs. I'm not yet sure why. Sal has mentioned mRNA a few times, but I'm not sure of the link between that and phytochrome deactivation.

It's convenient to think about the whole phytochrome process in terms of a plant's "internal clock". At the plant's "total darkness clock rate" it takes 12 hours to make the plant flower. When we add light for photosynthesis, we alter that clock rate. There's a range light that we can add to cause photosynthesis during the night period (500-700nm) and there's a range that also slows the rate of Pfr conversion to Pr (i.e. slows the plant's clock, the range is guessed at in a bit), so we have to find a balance between the amount of photosynthetic activity, and a fast enough conversion of Pfr to Pr (fast enough clock rate) that will still induce flowering.

Quote Originally Posted by farredeyed
I do not, at all,understand how introducing yellow, orange or green would make sense. If the plants photosynthesis of light is much lower rates at those frequencies, why not just use that electricity to add more red or blue?
I believe the plant's level of photosynthesis rises within that range until it peaks at around 660-ish (this is the regular chlorophyll a/b curve). The idea here is to find the color that is the best trade-off between higher photosynthesis and lower Pr->Pfr conversion. That's probably in the orange range, as Sal uses in his example below. You can have some level of the photosynthsis at night that you're looking for, while slowing down the phytochrome conversion significantly less than you would have with red light, since ~660 is the peak sensitivity for Pr and ~730 for Pfr. The total sensitivity range for Pfr is ~720-745, so if we can assume a similarly wide range for Pr (which may or may not be a sound assumption), it would be ~650-675. Less Pr->Pfr conversion means you need less Far Red to counterbalance it to maintain rate that is equivalent to the plant's "total darkness clock rate". Wanting less Far Red is only because Far Red is the hardest color of light to efficiently get into your grow room...

Quote Originally Posted by salmayo
We're interested in Yellow, Orange or Green since Red is comparatively slower without Far Red and Far Red is expensive in most terms. (One question to consider is, how much Far Red can you DO WITHOUT, to save money on equipment and electricity?) What would you do If you got the same yield from a Watt of Orange as from a Watt of Red PLUS half a Watt of Far Red, and the cost of 1 Watt Orange was less in terms of initial equipment investment and electric bill? I'd not pay for the extreme cost of Far Red LEDs, unless the cost of the Orange LED frequencies were more extreme for a particular application.
I don't know if that's more than you were looking for... :stoned: but that's the process as I understand it. I also make no guarantees for it's accuracy, but I do my best.

Sal, thanks again for the info, and you take care of yourself.