Light Cycle Length - 25 Hours/day?

[Ktboo89]

Okay guys, song was just doing some work and thinking about something that I've heard about other people doing previously... What would happen if you put your plants on a 25 hour day? (For example - 12 on 13 off.) I've seen research that humans potentially could do better if on this type of cycle... Shit, I would love to have one extra hour in my day. But how about plants?

I've heard of people using an 18 hour day for both veg and flower before.. As the plants do something like 60% of their growing in the first part of the day, then drop off drastically after that. It supposedly speeds up the cycle co you cut your flowering time by like half. This however results in decreased yield. Here's a link to an explanation, in case you're unfamiliar with the technique. http://www.invalid.com/t/18-hour-light-cycle.158852/

I'd like to also say that I'm using the traditional 12/12 light dark cycle. Not even the 11 on 13 off variation that some people use. I have no idea what would happen if you did this and don't want to fuck up an entire crop.

I can't find ANYTHING about plants being grown under lighting conditions that don't rely on the normal 24 hour earth light cycle. I thought NASA might at least have something, but alas- no. They're just recently trying to grow flowers under normal simulated earth conditions. BUT - if the lighting is artificial and relying on timers instead of the sun - why could this not be a possibility? It literally only adds three days to your growing time too... Soooo, any thoughts on this? Or is there totally a reason this has never been tried and I'm just dumb?

 

[Ktboo89]

Replace the word "invalid" with the word "rollitup" in the above link please.

 

[cannabeans]

I have never seen a 25 hr timer....

 

[Ktboo89]

I doubt they exist. It would only work with analog timers plugged into a second analog timer that shuts the first one off for an extra hour...

This is just something I thought of while pulling fan leaves. I have a buddy who does the 11/13 cycle... And I was thinking about how he loses that extra hour of light because he needs that extra hour of dark.. And how I wished it were possible to not lose that hour of light.. And then I thought - why do I have to lose that hour of light if the lighting is artificial and doesn't rely on the sun and earths 24 hour rotation? Why CAN'T they do this? Would it stress them out? Would they even notice? Would you be able to get the benefits of both 12 hours of light and 13 hours of dark at the same time?

 

[Ktboo89]

I feel like I might be on to something here.. I just can't find any information on putting plants of any kind on a 25 hour day. I found tons of studies saying that people, when taken away from outside influence tend to (after an extended period of time) drift more towards a 25 hour day.

 

[McCannabis]

I think this is brilliant!! Okay so really you could even set up your flowering time into an 18-20/12-13 light cycle! If what you're talking about is possible. She received her full light from veg, or even less, and a minimum of 12hrs of darkness! I would really be interested to see if you could teach a plant to grow on that light cycle.

 

[Oregon Grown]

I've heard of using 20hr days to get 8 weeks in under 7 weeks but with a 25hr day I don't see the extra 7hrs of light a week being worth the rotating light schedule when you can get those hrs in your next cycle. If the theory behind the 20hr day is correct that the plants fastest rate of growth is in the first 8hrs of lights on you would be prolonging your grow for less productive hours. I've never tried either so take it for what it's worth.

 

[Papa Indica]

Plants can't flower with 18 on 6 off, they'll stay in, or revert to, veg. For them to flower, the number of hours of lights on is less important than the number of hours of lights off. They need that 12 hours of darkness, (or very near to it), that is their signal that they're approaching the end of their life cycle and it's time to produce flowers before they die.
I really don't believe 12/13 is gonna give you anything more than headaches. As you said, the majority of growth is in the first 60% of the day and diminishes significantly after that so, if you're gonna go with 13 off I doubt there would be any gain by going an extra hour on the lights on side.
That's my take on it but, what the hell do I know anyway? :)

 

[MGRox]

Interesting concept and got me to do some snooping ty!
I was able to find a couple papers where total day length was varied. In both cases they were looking at aspects of internal or external coincidence in relation to flowering.

First the most specific, though note they are using a long-day plant vs short-day. However it seems the same relationships apply to short-day plants as well (sometimes inversely). Lot of goodies in this paper. They did testing with 16, 20, 14, 28 and 32 hr days.
http://www.pnas.org/content/99/20/13313.full.pdf
(NH cycle is 8 hour photoperiod regardless of daylength. Whereas T cycles were 8L:16D relationship regardless of daylength)
"Under 28-hr NH cycles (NH 28 hr), daily increases in LHY expression were advanced by 4 hr. Effects on the onset of CCR2 transcription were less obvious, but expression levels decayed earlier than under T 24 hr. Under 16-hr and 20-hr NH cycles, the rhythm of lhy::luc luminescence was delayed into the light portion of the cycle, and CCR2 expression was shifted further into the dark portion of the cycle so that high levels coincided with dawn under16-hr NH cycles."

"Flowering was accelerated under 28-hr NH cycles, although not to the same extent as under the corresponding T cycles. Delayed f lowering was observed under 20-hr NH cycles as under 20-hr T cycles, but f lowering was accelerated under 16-hr NH cycles. These results demonstrate that the photoperiodic induction of f lowering in Arabidopsis is not triggered by the absolute duration of light, because light dark cycles comprising identical photoperiods have differential effects on flowering time. The photoperiodic timer does not measure the duration of darkness either, as NH cycles that comprised shorter nights or longer nights than normal 24 hr short days (NH 16 hr and NH 28 hr) both accelerated f lowering. Lastly, floral responses do not reflect the relative durations of light or darkness within a cycle."

"Our results suggest that the photoperiodic regulation of f lowering in Arabidopsis requires an interaction of the circadian system with a light / dark cycle. According to the internal coincidence model, the effect of photoperiod may be to alter the timing of two or more circadian rhythms relative to each other, resulting in an inductive phase relationship."

"Our data suggest that photoperiod perception in plants is mediated by adjustments in the phase of circadian rhythms relative to dawn and dusk. We show that f loral responses could be accounted for by the coincidence of light with a factor with similar expression pattern as CO. Whereas CO itself seems a likely candidate, diurnal changes in the levels of the blue light photoreceptor CRYPTOCHROME 2 protein are also important for the perception of photoperiod."
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Second paper kinda covers the history; but does also cover some shorter day reference closer to the bottom (20hr).
http://genesdev.cshlp.org/content/21/19/2371.full

"Latitudinal variation in CO-dependent FT expression in trees. The peak of CO expression is later during the day–night cycle for northern aspen trees than for southern trees. Thus, when exposed to 20-h days, the CO peak already falls into the dark for the northern trees, FT is no longer activated, and growth is not supported anymore. Conversely, the CO peak for the southern trees is still in the light, FT remains active, and dormancy continues to be repressed."

Also possibly of interest is some relation of spectrum too.

"In an elegant series of experiments, George Coupland and colleagues demonstrated that far red and blue light, which are respectively perceived by phytochrome A and cryptochrome 2, regulate the stability of CO protein through inhibition of proteasome-dependent CO degradation."

"Interestingly, light of another quality, red light, which is perceived by phytochrome B, promotes, rather than inhibits, degradation of CO, and thereby delays flowering"
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IMHO, I would presume you could do a 25hr day with minimal to no negative effects. Presuming you are also staying within normal ranges for daylight (11-12) and extend night (13-14). I'll be interested to see what happens if you decide to try it out.

 

[Oregon Grown]

How do you have an 8L/16D cycle regardless of day length?

 

[G gnome]

 

[Papa Indica]

I'm sure you could run a 25 hour schedule going 12/13 with no ill effects but, I doubt there'd be enough benefit to even make it worth the trouble of getting timers set up to make it work.
But then again, as it says in my signature line, I really don't know anything.

 

[MGRox]

How do you have an 8L/16D cycle regardless of day length?

Didn't mean to confuse sorry. Saying that the 8L/16D "relationship" was the same regardless of daylength. Was just to mean that the ratio of light to dark hours was preserved. E.g. 1:2