Quote Originally Posted by Mother
Dog,
No, I actually haven't seen any of the plants all the way through yet. :-) I guess I'll have to post a picture of mine. I couldn't locate a camera last night...

In thinking and re-thinking about plant clock time, I realize my conception of Red and Far Red effects is off...

Thinking out loud...
I don't know the link between the plant's metabolism rate and the plant's clock sense. I would guess that they are positively related, meaning when metabolism rises, the clock runs faster. Maybe they are not related, and the clock is actually governed by light quality, not quantity. In that case, the key might be to balance the metabolic rate with the plant's clock in order to optimize production (of any number of factors, depending on the balance). Maybe it's both light quality and quantity that govern clock speed.

From slowest to fastest, this is how I understand the phytochrome conversion rates of Pfr to Pr under differing "night" conditions:
1. Solid Red LED light (660 nm. Very slow, allows little to no conversion of Pfr-Pr because the red light is constantly changing Pr back into Pfr)
2. Solid Red CFL light (mostly Red, probably shorter wavelength than 660 nm, and probably at least a trace of Far Red)
3. Red Incandescent (lots of Red but even more Far Red)
4. Natural indoor darkness (no light at all, Pfr converts to Pr naturally, with temperature being the main influence)
5. Far Red LEDs (Far Red only, so Pfr->Pr conversion is very rapid. This is in position 5 and not 6 because I'm assuming the intensity of the FR LEDs is rather low)
6. Natural outdoor darkness (which has relatively high levels of Far Red light after dusk and into the night)

Indoors, under current standard conditions, we need a solid 12 hours of complete darkness for the phytochrome conversion to take place to the extent that flowering occurs. Outdoors, (in the Northern hemisphere) the Autumnal Equinox doesn't occur until Sept. 22, which means the days are longer than 12 hours for most of the flowering period outside. And that only counts the sun being above the horizon, which means there's light before and after that still. I think the reason that outdoor plants can flower like this is the high levels of Far Red in both day and night, with the ratio of Red:Far Red decreasing over time until harvest.

This makes me wonder:
1. Are the day and night clocks interrelated?
2. What controls the plant's time-sensing clock during day and night?
2a. Is it the same factor(s) for each?
3. How can there be sufficient Pfr->Pr conversion with any significant amount of Red light at night without there also being a ton more Far Red light?
4. Are metabolism rate and phytochrome conversion rate directly related?

On question 1, I think they are, but I cannot assume this is so. I'm wondering how the balance of Red and Far Red during the day will affect both the day clock and the night clock. Maybe adding lots of FR during the day can "make up" for having "too much" Red at night?

On question 2, I feel this question is too general... but it comes back to my earlier pondering of whether it's light quality, or quantity, or both. Is light timing an independent variable here, or a dependent one? My guess is dependent, upon light quality/quantity and growing stage.
On question 2a, I lean towards yes. Although blue light is clearly a trigger for daytime, I don't think it significantly contributes to the plant's clock speed.

On question 3, I feel I'm asking the wrong question here, but I'm not sure why... If my list above on phytochrome conversion rates is (reasonably) accurate, I wonder how any nighttime combination of light sources 1, 2, and 3 can ever be fast enough to keep the plant in flowering.

On question 4, I believe metabolism rate is most influenced by light quantity (more available photons = more photosynthesis) whereas phytochrome conversion is most influenced by light quality (R:FR ratio controls Pfr:Pr ratio), but I can see how they can be limiting factors for each other.

Well that's all the pondering I have for now...
Owie, owie, owie!
Pondered me to tears.
Head hurts now.
You owe me an aspirin.

Woozy
Weeze