Plants release oxygen during the day in the presence of natural light through the process of photosynthesis. While at night, the plants uptake oxygen and release carbon dioxide, which is called respiration.
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Plants use a chemical calculator to divide their amount of stored energy by the length of the night and thereby solve the problem of how to portion out their energy reserves overnight.
Biologists from the John Innes Centre in England discovered that plants have a biological process which divides their amount of stored energy by the length of the night. This solves the problem of how to portion out energy reserves during the night so that the plant can keep growing, yet not risk burning off all its stored energy.
While the sun shines, plants perform photosynthesis. In this process, the plants convert sunlight, water and carbon dioxide into stored energy in the form of long chains of sugar, called starch. At night, the plants burn this stored starch to fuel continued growth.
āThe calculations are precise so that plants prevent starvation but also make the most efficient use of their food,ā study co- author Alison Smith said in press release. āIf the starch store is used too fast, plants will starve and stop growing during the night. If the store is used too slowly, some of it will be wasted.ā
To give the foliage a math quiz, the biologists shut off the lights early on plants that had been grown with 12-hour days and nights. Plunging the plants into darkness after only an 8-hour day forced them to adjust their normal nightly rhythm. Since the plants didnāt have time to store as much starch as usual, they had to recalculate their metabolism.
Even after this day length trickery, the plants aced their exams and ended up with just a small amount of starch left over in the morning. They had neither starved, nor stored starch that could have been used to fuel more growth.
The plants werenāt doing anything consciously. Instead, chemical reactions did the number crunching automatically. The results of the study will be published in eLife, and can currently be read via the Cornell University Library.
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As someone famous once said āThems fightenā words boy!ā
Sorry, I couldnt resist. My excuse is Im hi as fuck and taking dope and fighting kidney stones and I almost killed my plants from shear drug induced stupidity last night. So Im in kind of a strange place.
Still, I really do disagree with you on some of that. Maybe most of it. I dont know. I cant do math right now, but I wanted to be on the record that:
I am right and YOU are wrong! 
Well, mostly or maybe only partly. Iāll have to sober up some to tell for sureā¦ until then, we will have to disagree to disagree as it wereā¦
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This may make no sense, but I had another drug induced thought.
This has been a great discussion, but much of it is at least a little off the key point - like my previous post.
Is the droop an indicator that you are stressing your plant - by leaving the light ON toooo long - in a way that will decrease yield and/or quality?
OR
Does that extra lights ON time increase yield enough to offset any stress?
My new thought has to do with a recent thread about drought induced stress - which it turns out just might, maybe, possibly, dramatically increase yields.
My original thought was that stress = bad = lower yields = duh!.
BUT Ive read many times in many places that stress late in flower can actually increase resin production. Add in the drought stress information, and now Im having second thoughts.
By the way, I keep saying I hate āstoner scienceā, but I sure do enjoy it when Im helping create it and Im hi as fuck - or something like that 
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You could induce light stress in shorter photo periods with greater intensity during flowering. With cannabis and plants unfortunately there is too little research to be 100% certain what would happen.
Imagine this, if you have your lights connected to your computer to play with a timer, 18/6 and 12/12 are recommended to work with all cannabis, but species and individual plants may be able to run on different light cycles. You could try to change the length of your day and cycles to provide more light during flowering.
I like most of the research in that abstract if you give it a read. Lots was done by Russia and NASA for growing at the Arctic circle, space or other planets that wonāt be on our 24 hour light cycles. Will plants grow on other light cycles? My thoughts are they probably will adapt or could even thrive.
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Plants absorb oxygen through their roots, they can do this at any time during the photo period.
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Interesting that autos are known for it and are also grown under long photoperiods indoors. Is this phenomenon also occurring outdoors with autos?
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do not know ā¦never grew oneā¦but one of the many grow diaries i read was talking about this last week ā¦the guy was worried about his auto because it was drooping and other growers with lots of green dots said it was common in autos ā¦i just do not remember which thread it was in
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Last 2 times I grew autos they got light burned fairly easily, even on 18/6 light schedule. Iāve been able to run photoperiod plants as high as 80k lux at canopy under COBs without issues, but wonāt go much higher than 20k lux with an auto.
Iām sure environment plays a big role in how much light a plant can use, but as a general rule Iām careful now with autos.
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maybe this is why my regular plants did this in the green house ā¦sun is very strong in southern az in the summer
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Fascinating @Heritagefarms! I have a home for these brain munchies.
oleskoolās Big Red Book of Aquired knowledge.
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Interesting observations. Yr talk of lights was greek to me but i am guessing that it is a lot. Perhaps the lower angle of the sun in autoflowering regions has something to do with it? Less lumens.
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This is an interesting page to read.
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In my last grow i had grapefruit diesels in the tent with the blue dynamites. The diesels would start drooping 4 hours before lights out to the point of thinking they were sick, and the blue dynamites did nothing lol they were just always at the same level.