The 24/0 - 18/6 discussion

I think it's all opinion. I run 24/7 light during veg. The only pro I could say with 18/6 is probably slightly less energy costs.

To be honest, 24 hours seems fine. I've ran them with less light before and seen next to no improvement and/or difference. I say keep it at 24 IMO

Though in theory, I think the short dark period might help your plants stretch/fill out even nicer. Then again I'm not botanist and never done a true comparison.

Jeffdt1966 said:

I'm not saying not to do 24 hours ... I just think its a waste of energy with nothing more to show for it ... if it works for ya and you dont mind paying a little higher energy bill ... by all means carry on ........

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Yeah it does work. But like everyone else, something deeeep in my soul I feel like plants need the damn darkness! I guess I'll just keep on keepin' on. It really isn't much cost at this level. I got the heat under control...

Plants stomata open up at night, when it's dark. I've smoked a lot of pot since i took that plant physiology class but I remember stomata open up at night for gas exchange...Theres a fancy word for that gas exchange.

Either way, I do SOG, and veg mothers/clones under 24 hr light.
Hoping that this will make them longer to go into flower mode under 12/12 and stretch a little taller. Theres a bigger contrast from 24==>12 than from 18==12.
Maybe I should TEST this....

Yeah I know I should test too, but figured I would ask. That's the beauty of switching from 24/0 to 12/12. They start to stretch out immediately and end up a nice happy medium density.
I guess at this point, from this thread, my curiosities have shifted to root growth during dark phases...

Plants have both a dark and light cycle. Photosynthesis produces sugars and that's it. These sugars are then broken down during the dark cycle (krebs cycle) to produce everything else the plant needs - fats, esthers, proteins, cell replication, root and foliage growth, even the production of more chloroplasts so that the plant better utilized light during the light phase.

The krebs cycle takes place regardless of whether there is an actual dark period or not but at a different rate. These are figurative numbers so when you get around to looking up the real ones in a text book don't yell at me - the plant has a cap on how much it can do at one time which we will call 100%. During the light phase the plant dedicates ~70% of its energy towards photosynthesis (the production of sugar onto which plants imbed electrons for later use). The remaining 30% of its energy is used in the krebs cycle to break down these sugars to get at the stored electrons and to use them for DNA/RNA replication, cell division, protein synthesis, auxin creation...

During the night there is no light and thus the plant cannot dedicate 70% of its energy into photosynthesis and thus switches over to the krebs cycle to break down the sugars it produced during the day and actually get work done. Lets pretend the plant is a car. If you sat all day long pumping gas into it you would have a ton of gas which is great as you have a ton of potential energy - unfortunately if you never stopped pumping gas to actually drive the car the gas really does you no good. It's better to just refill the tank when it's empty and drive the car the rest of the time.

If you really want to do some science setup your own experiment with one plant under 24hrs and one under 18. I have done this several times and must say there is a huge difference in growth rates in favor of the 18hrs. If you really can't decide then run it at 21hrs and compromise

And fuck Ed Rosenthal, I've never seen a single bit of science from him or Jorge Cervantes - people need to pick up text books with actual science before they reach for a book written by pot heads (even if he is a famous one). Great if you want to memorize a recipe but terrible if you want to be able to formulate your own.

thexception said:

the best growth is to closely duplicate nature, does the sun shine anywhere on plants 24/7? No....Simple as that. There is a reason for the "downtime" & the plants do most of their growing during this time. Every living thing needs rest, plants included.

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Yes 24/7 does happen. Alaska comes to mind during the summer. And MJ is a C(3) annual which means it DOES NOT require a dark period. Only a shortened photoeriod to initiate flowering if not rudelius...

There is a thread on anotherr site about this. I am not going to post the link here but many felt the ideal schedule was 20/4. That is the same recommended schedule for autoflowers. Whatever the resoning behind that is probably the same for plants in veg. D an experiment with autoflowers, it would be quick and provide plenty of data on how the dark period effects plant growth.

I remember the krebs cycle from freshman bio hah! its the cell's metabolism basically.
I appreciate your info. I'm gonna look into it. It seems valid... if it's true ')
So you're saying that yes, cannabis does not need the dark phase like other plants, but that the darkness sort of catalyzes this sugar metabolism more rapidly?

yeah watchhowl, I did read about it being a c3 plant. That's what I'm trying to work out here.....

Look theres a new boy in town, forget 18-6 and 24-0 for veg. Here is a veg schedule that will save you a bit in electricity, will give you bigger healthier plants quicker, and in turn increase yield. This is a documented method that goes back 100 years. This is the stuff Rosenthal, Cervantes and all involved with the dutch conspiracy of silence didn't want you to know. You need to use a timer for this though, here goes, 12hrs on 5.5hrs off 1hr on 5.5 off. That is lighting cycle during veg, the increase in time for the plant to rest boosts growth and health. Then when you flip to flowering 10.5 hrs on 13.5 hrs off. And no i aint mad! This works!

When you do flip to flower, the plant starts to flower quicker too. You cant lose!

im doing my clones on a 20- to 4 cycle and im getting great daily growth under cfls

Jamblay said:

I remember the krebs cycle from freshman bio hah! its the cell's metabolism basically.
I appreciate your info. I'm gonna look into it. It seems valid... if it's true ')
So you're saying that yes, cannabis does not need the dark phase like other plants, but that the darkness sort of catalyzes this sugar metabolism more rapidly?

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Essentially. The dark period gives the plant the opportunity to kick the krebs cycle into overdrive. As you stated this is where cellular respiration occurs which powers all of the actual inner workings of the cells - this is what gets stuff done, growth, fruiting, hormones, cell division, DNA replication... People focus on photosynthesis too much, it's only one tiny process among many many others that are all just as important.

When the plant is in the dark photosynthesis isn't happening which means the plant can use the energy it produced and stored during the day to ramp up the krebs cycle which in turn ramps up all of the other metabolic functions of the plant.

Additionally evaporation rates are lower due to the change in heat from the lights which allows the plants to breathe a little easier (like someone mentioned the stoma can stay open in greater numbers and wider as the plant doesn't have to worry about excess water loss). Even if your room stays the exact same temperature during lights on and off the simple absorption of direct light changes surface area temps even if ambient are stable. This also ramps up cell metabolism.

plants never sleep. when the lights go out they don't suddenly get lazy like we do.

Well i have just told you a method that will increase your yield and save you money, no skin off my nose if anyone doesn't try it! Its not like i am getting paid for it. Go and do your homework people. There are a few sites dedicated to this method, Google 12-1

The truth is there is no one correct answer. 24/0-20/4-18/6 ect...simply because of the many, many variables involved. Strain, phenotype, type of light, enviroment, medium, nutes...everyones garden is different. Just as your doing, educate yourself as much as possible. Then put into practice what you have learned, and tune your garden. In my garden 24/0 out grows 18/6.

http://www.youtube.com/watch?v=TPBmyFsfyPc

Geozander said:

Well i have just told you a method that will increase your yield and save you money, no skin off my nose if anyone doesn't try it! Its not like i am getting paid for it. Go and do your homework people. There are a few sites dedicated to this method, Google 12-1

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The study you refer to was carried out and reported by the same folks. Nothing objective to it at all. Just the Voodoo dudes trying to keep the myths alive so they can continue to get their kick backs and advertising dollars from the nute companies....got to keep the impressionable hooked on gimmicks you know........

Yes this is the exact same topic as the last thread you posted in just with the thread name as the discussion...... and my answer is the same.

i heard something about the plant using oxygen in a dark cycle somewhere i think but i might be confused with something like roots absorbing oxygen and light pruning roots which is highly probably just pick up a highschool biology book and relearn photosynthesis real quick for a better understanding?(thats on my todo list) i hear that "the plant wont harness the light" on this site before though something along the lines of 18/6 19/5 20/4 ... etc doesnt matter cuz it wont harness anymore than 18 hours of light" i hope this helps a little i get in trouble enough for having it on 18hours instead of the 12hours on offpeak power usage i think itd be better for temperature control i was also wondering about this too as i was thinking about having my seedlings under my big light and seedlings go crazy under 600-750-1060 watts of mh light they started sprouting a bunch of leave right off the bat cuz i ran out of seed spots cuz i thought not nearly as many would germ as they did seeing as they were bag seeds so i ran out of pots and soil too i have 40plants right now before sexing waiting on my seeds order then im gonna kill some even though they r growing so well its my first indoor grow with a real light (1060watts of ushio bulbs of a phantom its so cool and silent its icy at 60% and 75% also first grow with nutrients ) i have extremely good luck though

My theory (Possibly anothers theory :/)

That indoor growers are causing epigenetic effects on their plants. This is simply a mutation of a gene caused by ones environment. With that said, it's possible that indoor growers are producing strains that thrive at 24 hours of light, because this is the main way they acquire their food, it was be reasonable that a constant supply could support a constant supply of food.

On the other hand, there could be NO epigenetic affect, and supplying 24 hours of light is damaging to the growth pattern of plants. But I am sure their is mechanisms to release proteins or signals to stop photons from being accepted. I mean there can only be many photons accepted depending on how much water is present.

Ok my 2 cents. I think the OP has checked out on this topic, but it seems to have some legs...so I'll run with it. For years 10+ I did 24/0 til flowering. Recently , (two years ago) I started using 18/6 and 20/4. I am using the same strains and same grow room, nutes and lights( same type lights some newer, I only use lights for 5000 hours or three grows). On the Indica strains I show same results...+/- 5% yield. The Sativa strains I show higher yields with the 24/0 & 20/4 cycle(+10%) than the 18/6. So overall it depends I am comfortable with the 20/4 and will use it until further notice.