What is the least amount of dark hours to keep 99% of plants in flower?

[ShroomDr]

Shroom dr would you agree that there is going to be a significant difference between having your room lights on (so that you can see the plants) and having the actual grow lights in the tent - re influencing the length of the dark period.

and given that your initial question is 'what is the least amount of dark hours to keep 99% of plants in flower' i would still maintain that it is 12hours. given that many tropical sativas actually require more than 12 hours darkness to flower.

interesting topic though. i would like to see you see how far you could push some strains and what influence it had on the overall flowering time.

VG

As i see it, my plants always get 11h 59m of very intense light, then, about 1/2 the time they get up to 2 hours of what would classify as 'darker than dusk' (and then 10 hours of uninterrupted darkness [which is darker than any night around this city]).

The room i have the tents in is only lit by two 23w CFL's on the ceiling fan. I also cram the plants inside the tent, only the few by the door actually get any direct light (the inside corners of the tent are very shaded).

Im not positive of the nature of your question, obviously i think there is significant difference between the direct lighting of the 1000w vs. the indirect 46w of CFL's. But I feel i would be overstepping the boundary if i were to classify this 'lights off tent open' period as an addition to the 'dark period'. I guess it could be, its certainly something i havent tested. It would be interested in the results (12/2/10 vs. 14/10), but it wouldnt help me at all (i need the time to do maintenance).

I guess technically without nailing down the effect of 'lights off, tent open', one shouldnt claim 10 hours is enough, however i base my assumption of the effect on the fact that i wouldnt leave the tent closed for 5 hours, open to do 2 hours of maintenance, and then keep it closed for 5 more hours. I assume this would fuck shit up.

Perhaps i should have added the caveat of indoor hybrids, excluding tropical sativas and autoflowers, as that is my real focus. Outdoors, given the equinoxes, perihelion, and aphelion, it is basically impossible to 'cause and effect' the lighting, there are too many changing variables.

 

[imadoofus]

theory is the concept of science. it is the very basis of all knowledge- the yearning for truth.

to everyone asking for facts, no such thing exist in natural science. science too, is adaptive and constantly evolving. we can only offer validations through repeated examples, even then, not definitive.

mr shroom makes a valid point regarding minimum hours needed for flowering, as it was his inadvertant experience that lead him to question the necessity of 12/12.

he relates experience, generalized by adding variables in the pretense of different strains and light cycles.

as a community, i regress the contempt of the majority to be utterly content with what we ''think'' we know for certain. application is fine in the form of accepted validations, but even these must be expanded on. for, if we applied with what we'ved learned currently to what we didnt know previously, there would be some seriously red faces.

with a little trial and error, something insignificant in the grand scheme of things, whom wouldnt rejoice in the ability to add 10%-30% more weight onto their final product by merely switching from 12/12 to, say, 14/10.

i would happily delve into experimenting with this ''concept'', alas, already preoccupied with other grows. should no one else be able to accomodate experimenting with light cycles at the moment, debating and discussing it are exactly whats needed.

run and tell that, homeboi ; )

 

[spurr]

imadufs wrote:

theory is the concept of science. it is the very basis of all knowledge- the yearning for truth.

to everyone asking for facts, no such thing exist in natural science. science too, is adaptive and constantly evolving. we can only offer validations through repeated examples, even then, not definitive.

There are two types of "theory": (1) a laypersons definition of theory, which is more akin to hypothesis; and (2) "scientific theory", which is a scientific consensus of a proven explanation/result (via. scientific method) of a phenomenon.

Scientific theory is as close to stating a fact to explain/describe a phenomenon/result as science comes. Ex. instead of saying X is a fact if Y takes place, we would say scientific theory proves X will happen if Y takes place. And the reason is what you stated, scientific explanations/descriptions of phenomenon/results are not written in stone, thus they can't be fact (but they are definitive unless proven otherwise at a later date).

However, in science there is much use of facts. Ex. it's a fact the banana was yellow when the scientists tested the hypothesis that yellow bananas are less ripe than brown bananas. Thus, the proven (and accepted by consensus) scientific theory is that yellow bananas are less ripe then brown bananas based upon the fact that the bananas were yellow (and brown) when tested.

---------------------------

In terms of the thread topic, it's the critical night hours that are needed to limit the buildup Pfr (far-red phytochrome) that is important to flowering, i.e. "photoperiodism". In terms of flowering, cannabis is called a short-day plant, even though it, and others, are really long-night plants. When Pfr buildup is limited due to longer nights, thus less far-red light over the whole day (in the range of ~720-740 nm), short-day plants are triggered to flower.

Cannabis, and other short-day plants, will flower with nights as short as 9-10 hours, OTOH, critical day hours for cannabis to grow is 6 hours. Equatorial races of cannabis will also flower with ~10 hours of night, but it takes a longer to trigger flowering. Microbeman posted a few great studies elsewhere about the phenomenon of flowering of equatorial plants separately from the issue of photoperiodism (I will post them here later; along with other studies).


Here is a good paper on this topic, and other topics to due with plant photobiology:

"Many hands make light work"
Paul F. Devlin, John M. Christie and Matthew J. Terr
J. Exp. Bot. (2007) 58 (12): 3071-3077.

• (full text HTML) http://jxb.oxfordjournals.org/content/58/12/3071.full
• (full text PDF) http://jxb.oxfordjournals.org/content/58/12/3071.full.pdf+html

(excerpts)

...

Finally, timing of flowering in many species is governed by light. In this case, duration of light is the important factor. Lengthening days (or more strictly shortening nights) signal the approach of spring while shortening days (lengthening nights) signal the approach of winter. This regulation of flowering by light is mediated through interaction with an internal 24 h timekeeper known as the circadian clock to ensure that the flowering process is receptive to light during the evening. When plants receive a light input at this time it either triggers flowering in long-day plants or inhibits flowering in short-day plants (Yanovsky and Kay, 2003). Flowering, though, can also be triggered under prolonged unfavourable light conditions such as heavy shading by neighbouring plants (Franklin and Whitelam, 2005). This ‘last resort’ ensures survival into the next generation, producing seed as quickly as possible.

...

Another photomorphogenic response that is extremely important in agriculture is the regulation of flowering time. The latitudinal range of many crops is limited by the daylength during the growing season. For example, crops adapted to short days encountered at the equator are often unable to flower in more polar regions where daylength is much longer during the summer. In this issue, Izawa (2007) discusses what is known about the control of flowering time in rice and contrasts this to the situation in Arabidopsis. He goes on to propose a possible explanation for the adaptation of rice from its natural habitat in the tropics to the more northern latitudes where it is currently grown (Fig. 2). This explanation is based on the antagonistic action during long days of the evolutionary conserved Hd1 pathway and the unique Ehd1 pathway. An understanding of different mechanisms regulating flowering time may be important in adapting a wide range of crop species to different latitudes in response to long-term trends in environmental change.

 

[Lunar]

critical dark period

critical dark period

is what you are referring to ed rosenthal state that him and mel frank agreed that all marijuana plants would flower under a 12/12 regime to find the dark period for what you are running you go from vegging 24 or 18/6 then you go to 14/10 and adjust the dark period gradually longer until you see your ladies start to flower i find most of my indicas flower somewhere in the 10.5 hour dark range again this is very strain specific and if you are running multiple varieties it is probably best to stick to something that works for all of them

 

[Thomkal Vwalaa]

Maybe so, but it lacks the very thing this sub-forum was made for: scientific proof and references. Opinion based upon conjecture and anecdotal evidence and hearsay and hypothesis is fine, but IMO it has little place in this sub-forum.

I have been collecting references I have on this topic, and I will try to post some info and studies in the next few days. I hope others will do the same...

will you please just get over yourself. great thread otherwise. I've been interested in light cycle manipulations for years.

and we should leave mel and ed out of this. they operate on many false ideas. ed takes grow tips from me now

 

[spurr]

Lunar wrote:

is what you are referring to ed rosenthal state that him and mel frank agreed that all marijuana plants would flower under a 12/12 regime to find the dark period for what you are running you go from vegging 24 or 18/6 then you go to 14/10 and adjust the dark period gradually longer until you see your ladies start to flower i find most of my indicas flower somewhere in the 10.5 hour dark range again this is very strain specific and if you are running multiple varieties it is probably best to stick to something that works for all of the

Critical night length isn't usually variety specific (using the word strain is a misnomer unless one means an individual plant/clone from a variety or race), but, critical night length is race (i.e. ecotype) specific.

For example, most varieties of cannabis (those intentionally crossbred by humans, hybrids like Sunk #1, NL#5, Blueberry, SSH, etc.) will (most generally) flower with the same critical night length of ~10 hours. OTOH, different races of cannabis (those not intentionally crossbred by humans, like pure Thai and Afghan races) will flower with different critical night lengths.

To be safe, using 12 hours of darkness is a sure bet, but it's also longer than needed for nearly all races (ecotypes) and varieties (hybrids or crosses) of cannabis.

 

[spurr]

Wow this is an interesting thread!

Maybe so, but it lacks the very thing this sub-forum was made for: scientific proof and references. Opinion based upon conjecture and anecdotal evidence and hearsay and hypothesis is fine, but IMO it has little place in this sub-forum.

I have been collecting references I have on this topic, and I will try to post some info and studies in the next few days. I hope others will do the same...

will you please just get over yourself. great thread otherwise. I've been interested in light cycle manipulations for years.

and we should leave mel and ed out of this. they operate on many false ideas. ed takes grow tips from me now

The whole point of this sub-forum is to get away from opinion and claims based upon conjecture and anecdotal evidence and hearsay and hypothesis...

 

[Thomkal Vwalaa]

The whole point of this sub-forum is to get away from opinion and claims based upon conjecture and anecdotal evidence and hearsay and hypothesis...

and actual research on Cannabis is limited, so let's not limit our discussion to published (or not) work from paid (or student) researchers.

In DJ Shorts book he addresses light cycles and fine tuning them to meet your plant's preference. He suggests that Blueberry's preferred light cycle is not 12/12 but gives no real details... how rude!

 

[VerdantGreen]

Critical night length isn't variety specific (using the word strain is a monomer unless one means individual plants within a variety or race), but, critical night length is race (i.e. ecotype) specific.

For example, all varieties of cannabis (those intentionally crossbred by humans, hybrids and/or crosses, like Sunk #1, NL#5, Blueberry, SSH, etc.) will (most generally) flower with the same critical night length of ~10 hours. OTOH, different races of cannabis (those not intentionally crossbred by humans, like pure Thai and Afghan races) will flower with different critical night lengths.

To be safe, using 12 hours of darkness is a sure bet, but it's also longer than needed for nearly all races (ecotypes) and varieties (hybrids or crosses) of cannabis.

hi spurr, if what you say is true, how can it be that certain hybrid varieties of cannabis (eg geurilla gold) will start to flower in early july (about 8 hrs dark) at my lattitude whereas blueberry will start to flower in early september ( about 11 hours darkness) ?

 

[spurr]

and actual research on Cannabis is limited, so let's not limit our discussion to published (or not) work from paid (or student) researchers.

Cannabis isn't special, that is why we use other C3 plants, and esp. "model organisms" in lue to data specific to cannabis.

 

[spurr]

hi spurr, if what you say is true, how can it be that certain hybrid varieties of cannabis (eg geurilla gold) will start to flower in early july (about 8 hrs dark) at my lattitude whereas blueberry will start to flower in early september ( about 11 hours darkness) ?

What are the parents of guerrilla gold?

In terms of blueberry, DJ short used very small breeding populations (IIRC 1 male). Thus it could be that he used a mutant (genotype) strain (aka cultivar) that had longer then normal critical night length that became a fixed trait in his blueberry variety.

Some varieties are crosses and not hybrids, if they are crosses (i.e. similar/related parents, like similar races, say Afghan x Hindu-Kush) then they can act more like true races in terms of unique critical night lengths.

 

[VerdantGreen]

hey spurr Geurilla Gold parents are mighty mite (well known for being early flowering), kona gold and afghan i think. the early flowering trait seems to be quite dominant and anything crossed with it starts and finishes earlier. early flowering varieties are very valuable for those of us with less than ideal climates. so yeah it was bred in canada for the very purpose of being early.
blueberry as you say is very inbred, and the cut that i have tends to grow pretty much normally for a couple of weeks after flipping to 12/12 (indoors) and then stretch for another couple of weeks before topping out.

one related question that i wanted to ask is, if you say that tropical sats will flower under 12/12 but just take longer to start, could i take my original hazes (which have been flowering under 10/14 to try and get them to flower before outgrowing my cab) and put them back to 12/12 whne they were well into flower? - they are about 7-8 weeks in now and flowering pretty convincingly.

 

[imadoofus]

theory, whether laymans or inductive, is assumption. scientific theory and scientific law are relative AND independent of each other.

copied-

''Stephen Hawking in A Brief History of Time states, "A theory is a good theory if it satisfies two requirements: It must accurately describe a large class of observations on the basis of a model that contains only a few arbitrary elements, and it must make definite predictions about the results of future observations." He goes on to state, "Any physical theory is always provisional, in the sense that it is only a hypothesis; you can never prove it. No matter how many times the results of experiments agree with some theory, you can never be sure that the next time the result will not contradict the theory. On the other hand, you can disprove a theory by finding even a single observation that disagrees with the predictions of the theory." The "unprovable but falsifiable" nature of theories is a necessary consequence of using inductive logic.''

your scientific banana example precurses into metaphysics, then, the application of a recordable observation, quantum physics. double slit experiment comes to mind, its implications as of yet, unfathomable.



einstein wrote ''math is the universal language''.

which, when one contemplates what math defines, isnt true in its entirety. math is merely a perception of gravity.

simplicity defines everything.

relating to the thread topic, thank you for the info, fascinating read. someone mentioned as for cannabis, we are as of yet just starting to unravel its mysteries. as for me, im enternally gratious to hold a thread of insatiable curiousity.

 

[imadoofus]

does anyone know the name of the flowering hormone that is necessary for flowering to occur? ive tried to look it up, but there is only mention of pfr.

i, for one, am greatly intrigued by what dr shroom as presented. even though there is plenty of ''theories'' and conjecture, looking for prime examples to expand on.

no matter the level of elightenment i achieve during my brief visit on this plane, i, ultimately, am every human trait personified when it comes to marijuana-

i desire the most reward for the minimum effort.

 

[spurr]

theory, whether laymans or inductive, is assumption. scientific theory and scientific law are relative AND independent of each other.

No one stated scientific theory and scientific law were the same thing. Scientific law seeks to explain things on a grand scale, ex. law of relativity, as a rule.

copied-

''Stephen Hawking in A Brief History of Time states, "A theory is a good theory if it satisfies two requirements: It must accurately describe a large class of observations on the basis of a model that contains only a few arbitrary elements, and it must make definite predictions about the results of future observations." He goes on to state, "Any physical theory is always provisional, in the sense that it is only a hypothesis; you can never prove it. No matter how many times the results of experiments agree with some theory, you can never be sure that the next time the result will not contradict the theory. On the other hand, you can disprove a theory by finding even a single observation that disagrees with the predictions of the theory." The "unprovable but falsifiable" nature of theories is a necessary consequence of using inductive logic.''

Nothing in that contradicts what I wrote, maybe re-read what I wrote again. "Scientific theory" is not called "scientific fact" because it can be disproved, and fact, by definition, can not be disproved.

Also, note how you claimed scientific theory is "not definitive", yet I claimed it is "definitive unless proven otherwise at a later date", just like Mr. Hawking claimed scientific theory is "definite". So, once again, Mr. Hawking and myself are in agreement.

your scientific banana example precurses into metaphysics, then, the application of a recordable observation, quantum physics. double slit experiment comes to mind, its implications as of yet, unfathomable.

Did you hit the pipe too much today!?! My example of the banana was to show, that in science, we use facts all the time during experimentation. Using facts during experimentation and calling "scientific theory", "scientific fact" are two different things.

einstein wrote ''math is the universal language''.

which, when one contemplates what math defines, isnt true in its entirety. math is merely a perception of gravity.

simplicity defines everything.

Put down the bond man!

someone mentioned as for cannabis, we are as of yet just starting to unravel its mysteries. as for me, im enternally gratious to hold a thread of insatiable curiousity.

Finally, we agree!

 

[spurr]

does anyone know the name of the flowering hormone that is necessary for flowering to occur? ive tried to look it up, but there is only mention of pfr.

Yes, I wrote about it on the last page: Pfr = far-red phytochrome; and Pr = red phytochrome.

EDIT:
more specially, the phytochrome that controls flowing (i.e. Pfr) is known as "phytocrhome B", aka "phyB". Also, a reduction to critical level of Pfr is what is required for flowing to occur, not a increase in Pfr.

ref:

"The Contrasting Effects of Phytochromes A and B on Flowering"
A Companion to Plant Physiology, Fifth Edition
by Lincoln Taiz and Eduardo Zeiger
2010, Chap. 25. Topic 25.11
http://5e.plantphys.net/article.php?ch=t&id=250
​

i, for one, am greatly intrigued by what dr shroom as presented. even though there is plenty of ''theories'' and conjecture, looking for prime examples to expand on.

Putting the word theories in quotes, next to conjecture is disingenuous. Unless by using the term theories you mean a laypersons definition of the word, which is pretty much the same as writing hypothesis.

 

[spurr]

hey spurr

Geurilla Gold parents are mighty mite (well known for being early flowering), kona gold and afghan i think. the early flowering trait seems to be quite dominant and anything crossed with it starts and finishes earlier.

Ah, that makes sense.

blueberry as you say is very inbred, and the cut that i have tends to grow pretty much normally for a couple of weeks after flipping to 12/12 (indoors) and then stretch for another couple of weeks before topping out.

Good to know, I have never grown blueberry.

one related question that i wanted to ask is, if you say that tropical sats will flower under 12/12 but just take longer to start, could i take my original hazes (which have been flowering under 10/14 to try and get them to flower before outgrowing my cab) and put them back to 12/12 whne they were well into flower? - they are about 7-8 weeks in now and flowering pretty convincingly.

Yup, that should work fine. But, you may want to try 11/13 and gauge the reaction in case your cutlivar does better with longer nights. But it should work fine using 12/12.

 

[spurr]

Good refs to read from:


"The Control of Flowering"
A Companion to Plant Physiology, Fifth Edition
by Lincoln Taiz and Eduardo Zeiger
2010, Chap. 25
http://5e.plantphys.net/categories.php?t=t

1. "Characteristics of the Phase-Shifting Response in Circadian Rhythms"
http://5e.plantphys.net/article.php?ch=t&id=243


2. "Support for the Role of Blue-Light Regulation of Circadian Rhythms"
http://5e.plantphys.net/article.php?ch=t&id=245


3. "Genes That Control Flowering Time"
http://5e.plantphys.net/article.php?ch=t&id=244


4. "The Self-Propagating Nature of the Floral Stimulus"
http://5e.plantphys.net/article.php?ch=t&id=468

• ^^^ that is a really neat topic I would love to try with cannabis!

5. "A Gene That Regulates the Floral Stimulus in Maize"
http://5e.plantphys.net/article.php?ch=t&id=251


6. "The Contrasting Effects of Phytochromes A and B on Flowering"
http://5e.plantphys.net/article.php?ch=t&id=250​

Other refs from the same book:

1. "Diversity of Phytochrome Chromophores"
http://5e.plantphys.net/article.php?ch=e&id=362​

Great refs from NASA symposium on photosynthesis, etc.:

"International Lighting in Controlled Environments Workshop"
T.W.Tibbitts (editor) 1994 NASA-CP-95-3309
http://www.controlledenvironments.org/Light1994Conf/Contents.htm

1. "PHYTOCHROME-MEDIATED RESPONSES IMPLICATIONS FOR CONTROLLED ENVIRONMENT RESEARCH FACILITIES"
Harry Smith
http://www.controlledenvironments.org/Light1994Conf/2_1_Smith/Smith text.htm


2. "PHYTOCHROME, PLANT GROWTH AND FLOWERING"
R.W. King and D.J. Bagnall
http://www.controlledenvironments.org/Light1994Conf/2_4_King/King text.htm​

 

[imadoofus]

no, really, i like your banana ; )



''The "unprovable but falsifiable" nature of theories is a necessary consequence of using inductive logic.''

maybe i should pass the bong, my man mr hawking is stating theory is just that- theory. whether scientific, philosophical, pyschological, metaphysical... all proposed assumption. nothing is truly definitive, even you have to acknowledge that.

interesting you presumed i was attempting to invalidate anything you wrote prior, which from my perspective, is flattering. considering your obvious education, such jejune behavior doesnt become us, now does it? at least, i would expect refrain from bellicose attitudes in this topic.

all theory is the very foundation of science. my example of scientific theory and scientific law, though lacking the elegance of your ''assumed'' yellow banana, demonstrates that regardless of the application, all relative to the scientific process. even scientific law was born from validation of a theory, even though inductive theory cannot become a scientific law.

science is observation. and, even that is subjective. its been validated our observation of reality alters it- if anyone reading is curious about this, google ''double slit experiment''.

as to putting the bong down, i could merely ''observe'' gravity and drop it. for, in its essence, gravity is god. something so simple as a force holding all the matter, elements, atoms, particles together, yet, for all our technology and intelligence, we can only offer ''scientific theory'' to explain it. which, if you could ''validate'' to anyone, theres a nobel peace prize with your name etched on it.

''Putting the word theories in quotes, next to conjecture is disingenuous. Unless by using the term theories you mean a laypersons definition of the word, which is pretty much the same as writing hypothesis.''


please dont attempt to correct my grammar, its as impeccable as it is articulate. theory is synonymous with hypothesis, thats the point.

imadoofus, not spurrned ; )

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[spurr]

This is getting pretty far from the thread topic, so I will not respond again about this topic:

theory is synonymous with hypothesis, thats the point.

Not it is not, only a laypersons definition of theory is synonymous with hypothesis, that is what you are misunderstanding. Otherwise, why does science have two words that mean the same thing?

That is what I was trying to be funny and joking with you about when I said put down the bong; that and you were going even-further-off-topic 'waxing lyrical' as my good buddy Mr.F likes to say. I wasn't trying to be rude, just poking fun.

As I wrote, there are two types of theory: (1) a laypersons, that is synonymous with hypothesis; and (2) scientific, that is not synonymous with hypothesis.

It works like this (overly-simplified):

1. form a hypothesis
2. test hypothesis with scientific method
3. if hypothesis is true use result to form a scientific theory (i.e. result of experiment stating what/why/how/etc)
4. propose scientific theory in a peer-reviewed journal article by describing experiment (for example)
5. allow wider range of peers to review and consider and verify said scientific theory by reading journal article and doing their own experiment for validation or invalidation
6. be happy if scientific theory becomes accepted as consensus on the topic