24 hour light vs. 18/6.

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pollen205

Well-Known Member
curious2garden said:
That's not how you do a rebuttal to a quoted primary scientific article. You have to state how and back it with research demonstrating contrary findings. Until you can bring actual science you are simply wrong. Everything needs a sleep cycle.
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Really dont understand the articale.To much science for me...but thank you now I know i must go with dark

20-4 will that be ok?
 
curious2garden

curious2garden

Well-Known Mod
Staff member
pollen205 said:
Really dont understand the articale.To much science for me...but thank you now I know i must go with dark

20-4 will that be ok?
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LOL that was a poor attempt at Reductio ad Absurdum. Merriam Webster defines it as, "disproof of a proposition by showing an absurdity to which it leads when carried to its logical conclusion."

You failed because the logical conclusion of giving a plant a sleep cycle is not reducing light beyond the point the plant will survive, death does not equal sleep, nor is it the logical conclusion of sleep.
 
rkymtnman

rkymtnman

Well-Known Member
curious2garden said:
Cannabis is a C3 plant, to over simplify, they inhale in the light and exhale in the dark. So they need some time out of the light.
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1. Cannabis as a C3 can grow in 24/0 light
2. Cannabis must therefore be able to respire during lights on.
3. Photorespiration only occurs when CO2 ppm drops below 50.
4. If CO2 is ample, cannabis can photosynthesize and respire during lights on and no dark period is needed.

Thoughts?
 
curious2garden

curious2garden

Well-Known Mod
Staff member
rkymtnman said:
1. Cannabis as a C3 can grow in 24/0 light
2. Cannabis must therefore be able to respire during lights on.
3. Photorespiration only occurs when CO2 ppm drops below 50.
4. If CO2 is ample, cannabis can photosynthesize and respire during lights on and no dark period is needed.

Thoughts?
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Hi, thoughtful answer, thank you.

Essentially you hit the limit when CO2 drops below 50 ppm in the chloroplasts and enter photorespiration, rubisco begins to fix O2 instead of CO2. Theoretically all Calvin cycle plants can do this but some do it better than others. I'd love to see specific studies on cannabis.

Next problem we have is what is the CO2 in most newbie's grow rooms? Most of the kids pushing plants with 24/0 are not supplementing CO2 nor tracking it. Their plants suffer from entering photorespiration on this light schedule.

There is also the question of CO2 concentration at the chloroplast vs. concentration in the air. There is necessarily a negative gradient here, as CO2 diffuses from air through the stoma and to the chloroplasts. I do not know how steep this gradient is, and I don't know what atmospheric CO2 corresponds to the photorespiration threshold. Further what are the visible markers of photorespiration in the cannabis plant? For that we need analytical ability.

Certainly it's possible to do but unless you know exactly what you are doing and why, you cannot be sure that it's optimal or wise to do. As an analogy, humans are omnivores but we don't thrive eating only Snickers, although we can survive on them.

Nice reasoned argument, thank you; it was a pleasure talking to you,
Annie
 
rkymtnman

rkymtnman

Well-Known Member
curious2garden said:
Nice reasoned argument, thank you; it was a pleasure talking to you,
Annie
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thanks. you as well. here are 2 articles that i found:. maybe this would be some of the info needed. to be honest, most is over my head as a liberal arts major many yrs ago.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3521184/

https://www.easybiologyclass.com/difference-between-c3-and-c4-cycles-of-photosynthesis-in-plants/

so in your best guestimate, how much is the optimal dark period for cannabis? my feeling is 6 off is too much and 1 hr off is too little. you?
 
curious2garden

curious2garden

Well-Known Mod
Staff member
rkymtnman said:
thanks. you as well. here are 2 articles that i found:. maybe this would be some of the info needed. to be honest, most is over my head as a liberal arts major many yrs ago.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3521184/

https://www.easybiologyclass.com/difference-between-c3-and-c4-cycles-of-photosynthesis-in-plants/

so in your best guestimate, how much is the optimal dark period for cannabis? my feeling is 6 off is too much and 1 hr off is too little. you?
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What a pleasure to have a polite discussion on a complex topic, wherein we both don't necessarily agree. Of all the things I miss from my time in school that is the one thing I miss the most. Both boats are raised by the shared information whether agreement is reached or not :)

The NCBI was a very interesting article, the easybiologyclass was quite approachable.

I run 18/6 because I've seen no difference between that and 20/4 in my environment. Because of the chemical changes in the plant as it moves from light to dark, my guess is you need 1 hour for physiological switchover (pre and post) and then possibly 2 hours of full dark to be of benefit. But that is a wild-ass hypothesis.

It would be interesting to run some side by side grows with the same clones and lights on different timers. I'd love to see the gradient curve for room and chloroplast CO2 concentration in cannabis. I'd also love to see the growth curves of time associated with various levels of CO2 supplementation in differing photoperiods.

It's sad this kind of research can't be done by the academics who have the tools to do this right, and the help with study design.
 
rkymtnman

rkymtnman

Well-Known Member
curious2garden said:
Both boats are raised by the shared information whether agreement is reached or not :)
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the old saying: a rising tide lifts all boats. lol.

i'm a fan of 24/0 for myself. i've tried 18/6 and thought they stretched too much or greater node spacing compared to 24. i just tried 11/1 per another member here (name forgotten, sorry) and that seemed OK but it just seemed to me that the 1 hr dark, not much was accomplished ie did they really go to "sleep" in that short time frame. but 2 hrs saved on electricity so that was a plus.

curious2garden said:
It's sad this kind of research can't be done by the academics who have the tools to do this right and the help with study design.
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i actully emailed a Prof at Colo State who specialized in photosynthesis a few months ago and his reply was to consult with a professional grower. i replied that each grower i've contacted or read had their own theory as to why their light cycle was best.

maybe one day the stigma will be lifted and proper studies can be completed. until then....

nice chattin with ya! have a great afternoon.
 
curious2garden

curious2garden

Well-Known Mod
Staff member
rkymtnman said:
the old saying: a rising tide lifts all boats. lol.

i'm a fan of 24/0 for myself. i've tried 18/6 and thought they stretched too much or greater node spacing compared to 24. i just tried 11/1 per another member here (name forgotten, sorry) and that seemed OK but it just seemed to me that the 1 hr dark, not much was accomplished ie did they really go to "sleep" in that short time frame. but 2 hrs saved on electricity so that was a plus.


i actully emailed a Prof at Colo State who specialized in photosynthesis a few months ago and his reply was to consult with a professional grower. i replied that each grower i've contacted or read had their own theory as to why their light cycle was best.

maybe one day the stigma will be lifted and proper studies can be completed. until then....

nice chattin with ya! have a great afternoon.
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If you ever decide to run 20/4 I would love to hear your experience. Do you supplement CO2? If so how much?

I asked a friend of mine about this. He's a Ph.D. Biochemist who worked and did research in Plant Physiology. He growled at me that plants that evolved on this planet needed some dark since nowhere is there 24/0 LOL He also asked about ROI of biomass to light bills etc... He's a genius. He can grow cannabis in anything. Some of his tales are startling.

I can tell you why I use 18/6. I'm from medicine and I believe every living thing needs dark and sleep related to hormone levels. Further I live in the Mojave Desert just north of Los Angeles so our electricity rates are some of the highest in the nation. Therefore I don't supplement CO2 and I need to turn off my lights because my canopy regularly runs 95 to 105 for extended periods of time. So I'm in photorespiration from natural conditions.

I'm off to the commissary for groceries you have a good day too.
 
rkymtnman

rkymtnman

Well-Known Member
curious2garden said:
Do you supplement CO2? If so how much?
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my little room is not sealed but i have tried it since i had the tank from homebrewing. i didnt' really notice much difference. now i just suck in fresh outside air now when lights are on.
i just upgraded my lights to qbs so with the extra ppfd, i probably will give co2 another try next run.

but no, not 20/4. only 18/6, 11/1 and 24/0

and for your PhD buddy, here's a question: does he consider it to be 24/0 in siberia or upper scandinavia during summer time? i did some work in sweden many yrs ago and it never really got dark but not sure if it was enough light for plants to photosynthesize. hard as hell to go to sleep at night though in my hotel.

and one more point for me, i'm at high elevation 8800 ft so things just grow slower up here so more light made more sense to me.
 
buster1977

buster1977

Active Member
Brick Top said:
While some people have questioned the test results because some years later the group was caught padding some other results, tests, accurate or not I cannot swear, have shown that giving plants 72-hours of total darkness at the end of flower/just prior to harvest can increase levels/amounts of THC in some strains as much as 30%.

The THC itself is not more potent by volume but supposedly you can have a large increase in volume.

It is only my opinion, since people have questioned the research and as far as I know no one else has tried to duplicate it or disprove it, they just questions it … but considering how certain light rays and THC react together it would make sense that they should at least in most cases be some increase in overall THC.

It is the same principal as when you know you will be harvesting tomorrow when your lights turn off tonight you unplug them or flip a switch, if you have then switched, so they do not turn on again tomorrow before you begin your harvest. Or in the case of an outside grower harvesting at first light.

Either way the idea is to harvest without light rays having a chance to degrade any of the THC that was produced the night before.

Plants will only continue to perform their functions/live for a fairly short period of time once they are deprived of light but during that time they will continue their hours of darkness functions as much as they can for as long as they can. That would have to at the very least result in maximized levels of THC if not increased levels of THC, possibly as much as the tested/reports 30% increase certain strains developed. Genetics are bound to play anything from a small part to a major part in results but at least to some degree it has to happen.

Some people that swear outdoor grown pot is better will at times point to the length of the nights and the shortness of the days towards the end of flower and say look at how much more potent they became in the last weeks during the longest nights. They will say because of the extended period of time for THC production at maximum levels with the least amount of THC degrading per 24-hour period due to short days with the light rays striking the plants at lower angles the increased levels of THC late in flower was at least in part due to growing conditions and not only or even mostly plant genetics.


The same people will sometimes say the reason indoor growers try to stick with light cycles that make use of the longest period of light possible at any stage of growth is because they need to make up for the weakness of indoor lighting in comparison to the sun and think that will go a long way to make up for the difference but end up giving up quality by trying to find it. They think the natural lighting periods should be closer mimicked. I cannot say I agree with that, at least not all of it, but there is some logic to be found in parts of it.

Where I question that belief is if you are working with far less light than the sun supplies cutting the periods of light to more closely duplicate nature you are just giving your plants even less of the lower levels of light. How much of a loss might be the result? The other part is certain light rays so breakdown THC but then growing in conditions with much lower levels of those light rays, as in when growing inside rather than outside, how much less THC is degraded in an average day compared to when grown outside and is there more of a net gain found in one than the other? Will less be degraded so your overall gradual increase results in more or will along with the increased degrading process in outdoor growing will the light says stimulate the trichome heads to further increase THC, and other cannabinoid production, and there will be a larger net gain found there?

If anyone has performed definitive tests I have never read the results so it is sort of an opinion thing right now, so each person believes what they are most comfortable with.

I tend to believe that a 72-hour period of darkness just prior to harvest of an indoor crop and the longer fall nights and shorter fall days with sun lays striking plants from lower angles both cause an increase in THC production. In some strains the difference might be so slight that it would take the highest tech testing equipment to prove it and on another it might only take one hit of each test group type to make it clear.

In some cases genetics have a much greater or much lesser impact on the results of some method of growing. It just depends on what something is made up of and in what amounts as to if it will respond the same or better/more, less/worse for any growing method or trick.

There are a number of differing beliefs about various light cycles but I do not know of any that are out of the norm that have legitimate research behind them backing that the overall final results are better. People attempt various things and their observations tell them they see some positive or some negative and then they either go with it or not.

It is just what is observable and what is not and what people are unable to test but instead at best can only rely on senses to judge, which can be bent/formed by preconceptions, it is not all that uncommon for people to believe they found positive things that do not really exist and fail to find negative things that do exist.

The most standard indoors light cycle will most consistently provide the best results for the widest range of genetics and is the simplest, of course autoflower strains would add more to discuss, but in general it is the best and that is why it is the most used.

It is not that I have some problem in attempting to advance the science/art of herb growing through experimentation but I think that is best left for the pros to do and then instruct us on. They have the setups and the resources and if something turns out to be a flop they really aren’t out much but if we try something and it blows chunks, well a harvest celebration might not be much of a celebration now and then. So we can lose big.

Something I have said many times is that ever generation thinks that if it did not actually invent sex, drugs and rock & roll they at least perfected it. Something similar happens with each generation of growers. They get some Ralph Kramden super-idea and get all pumped up about it or hear of someone else’s idea or way of doing things and get all pumped up about it and they mention it in a thread and 30 people respond saying how great of an idea it is and how they will have to try it too.

I normally tend to chuckle because I can remember back to the 70’s and 80’s and 90’s when I tried those things or friends tried those things, or even older growers from the 60’s and maybe before had told me how they tried those things and in each case where there was no scientific research backing a final decision things were clear enough to say success or failure.

The successes were copied by virtually everyone but every generation of new growers will reinvent at least some of the failures and then get others whipped up on them and then they try them too …. and get the same basic poor results as in the 60’s and 70’s and 80’s and 90’s when the same things were attempted.

If a majority of skilled growers do something a certain way there is a valid reason behind it. It is because doing whatever it is in that way works the best overall.
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I could read your shit all day!... Thx man. Smart dude
 
Big Perm

Big Perm

Well-Known Member
JLH1983 said:
is it the shortened daylight or extended dark period that triggers flowering?-- ive pondered like a 14/12 or 16/12 to try for flowering... cant find any research on the subject-- or possible pros/cons?
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Does anyone else have any info on this?
 
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Big Perm

Big Perm

Well-Known Member
rkymtnman said:
i always thought it was once they get 12 hours of darkness, flowering is triggered.
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On the other hand, I have run a 13/11 cycle successfully. I'm curious now as to what triggers it. Is it the light, or is it the darkness. Probably both, but I wonder how far you can stretch it.
 
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