The Importance of Dark Cycles (Calvin-Benson-Bassham cycle)

Hotwired

Hotwired

~
I try to go 24/7 for 10 to 14 days once they lose their shell. I'll keep them in a tray under four 24 watt daylight bulbs almost right on top of them. They root up nice in their rapid rooters and then they go to the 1 gal pots with a 600 ppm feed and they love it. (I use HP Promix with no food in it) They also stay VERY short.

I have grown under many light timed methods in veg. IMO, the plants do stay shorter with closer nodes under 24/7 light. Not stronger really. All methods work you just have to use what's best suited for you :alien:
 
H.A.F.

H.A.F.

a.k.a. Rusty Nails
@Artisan_tek - not trying to be obstinate, we do what we do. Here's what I noticed in the article
J.James said:
These products are then stored in the chloroplast stroma, where they are then used by the “dark cycle,” the second part of photosynthesis that absorb carbon dioxide. This dark reaction is scientifically known as the Calvin-Benson-Bassham cycle, and is independent of light energy; it completes photosynthesis by absorbing carbon dioxide to complete the synthesis of carbohydrates.
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You have people adding CO2 to tents, when maybe all they need is the darkness to use what they already have. Same with the nutes. Some of that extra stuff they need is already in the plant, they just have to process it.
 
Hotwired

Hotwired

~
Hust17 said:
Ok thank you. Interesting.

What about for clones? I was under the impression they prefer 24/0 to root?
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You know what? That's a good question. I have tried several different timing methods for these as well. I believe that they also need darkness for good root development but I'm not 100% sure. I run mine like all my veg plants 16/8
 
Hust17

Hust17

PICK YOUR OWN
I’m not very good at clones but my environment is very dry naturally so i think that plays a role, or I tell myself it does anyways haha!

I’m investing in a little turbo cloner or alike soon here for my next attempt but want to give them every shot possible.
 
H.A.F.

H.A.F.

a.k.a. Rusty Nails
Hust17 said:
I’m not very good at clones but my environment is very dry naturally so i think that plays a role, or I tell myself it does anyways haha!

I’m investing in a little turbo cloner or alike soon here for my next attempt but want to give them every shot possible.
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I would "invest" in some of those horticubes. They are very easy to use, and the clones need very high humidity - not very long light. That would fall into the "whatever you do" category. IMHO darkness is necessary. They are plants doing plant things, and in nature it gets dark.

As far as having issues, read a lot, watch videos, and look for some nugget you may have missed. I think the preparation and getting them into a medium properly makes a big difference. I saw someone just using an upside down clear plastic tote, with the plants sitting on the lid. All it needs to do is keep it humid.
 
baldmountain

baldmountain

Super Active Member
:unsure: There is too much subjective opinion in this thread. A controlled experiment would be necessary to show what light cycle is best. And it would have to involve a bunch of different strains grown under the same conditions. But not all strains like the same conditions so I'm not sure it's possible to find a single correct light cycle.

Having said all that, I don't think 24/0 is a good light cycle. My rationale, with no scientific basis, is that the plants have been evolving for quite some time with a longer light period summertime and a shorter light period fall. I would guess that the best light cycle for a strain is to look at the predominant landrace strain of the cultivar and where it came from. Then choose what a summer light cycle looks like there for veg and what a middle to late fall cycle is for flower.

18/6 for veg and 12/12 are safe. But I would encourage people to experiment too.

I worry a little that we are searching for a way to force plants to grow bigger and faster and not in a good way. Kind of like what farmers have done to chickens. They use hormones and antibiotics to force the birds to grow so fast that their legs can't support their weight. Farmers use antibiotics because the chickens are growing in an unnatural way and are constantly fighting infections. The result is meat with a weird rubbery texture that doesn't taste like much of anything. (My wife can't eat it. It makes her sick every time.)

I don't have a lot of experience growing but I think the best indoor results are going to be from an environment that is as close to what the environment of predominant landrace of the cultivar is.
 
crimsonecho

crimsonecho

Self-Proclaimed Don Quixote
Good stuff people. Really enjoyed reading it all. I kept my bonsai under 24hrs on for months and under 2/2 for months too. None seems to do them any harm with my low wattages (50w cheap leds in a 2x2). As for veg i usually go 18/6 to save electricity and in flower i went as low as 10/14 but usually it’s 11.5/12.5 or 12/12.
 
J.James

J.James

Seed Slingin' Outlaw
Breeder
Cannabis is a C3 plant.

What are C3 Plants?

About 95% of the plants on earth are C3 plants. As the name indicates, they carry out C3 photosynthetic mechanism that is Calvin cycle. C3 photosynthesis is thought to have arisen nearly 3.5 billion years ago. These plants are mostly woody and round leaf plants. In these plants, carbon fixation takes place in the mesophyll cells that are just beneath the epidermis.


Carbon dioxide enters from the atmosphere to the mesophyll cells through the stomata. Then the dark reaction starts. The first reaction is the fixing of carbon dioxide with Ribulose bisphosphate into phosphoglycerate which is a three-carbon compound. In fact, it is the first stable product of the C3 plants. Ribulose bisphosphate carboxylase (Rubisco) is the enzyme that catalyzes this carboxylation reaction in plants. Likewise, the Calvin cycle occurs cyclically while producing carbohydrates.


Difference Between C3 and C4 Plants

Figure 01: C3 Plants

Compared to C4 plants, C3 plants are inefficient regarding their photosynthetic mechanism. It is because of the occurrence of photorespiration in C3 plants. Photorespiration occurs due to the oxygenase activity of Rubisco enzyme. Oxygenation of Rubisco works in the opposite direction to carboxylation, effectively undoes photosynthesis by wasting large amounts of carbon originally fixed by the Calvin cycle at great expense, and results in loss of carbon dioxide from the cells that are fixing carbon dioxide. Likewise, interaction with oxygen and carbon dioxide occurs at the same site on Rubisco. These competing reactions normally run at a ratio of 3:1 (carbon: oxygen). Thus, it is clear that photorespiration is a light stimulated process that consumes oxygen and evolves carbon dioxide.
 
J.James

J.James

Seed Slingin' Outlaw
Breeder
Plants that solely depend to C3 pathway for carbon fixation are faced with the negative effects of photorespiration, such as the wasteful loss of CO2. Photorespiration occurs under conditions of drought, high temperatures and low nitrogen or CO2 concentrations. These conditions cause the stomata to close in an attempt to prevent excessive water loss. The closure of stomata increases O2 levels, and the enzyme rubisco reacts with O2 instead of CO2, consequently losing CO2 instead of fixing CO2.
 
gwheels

gwheels

Hobby Farmer
I have run 24-0 a lot because i ran out of timers....and 18-6 in a dedicated space. I used to swear by 24-0 but after a point they grow stressed or something.

They stay short with the inter-nodes but they do not grow as lush as plants with a darkness cycle.

And its slower growth...not at the beginning but after 2 to 3 weeks. It was worth buying the timer...the damned thing paid for itself in offtime but the plants do seem to like it a lot better.

The veg outside even responded within 1 day when i found a timer to put on that tent...24-0 to 20-4 made them flourish...even that GMO cake out there. I will only keep my clone spaces in 24-0 and then i might as well save the money and help my plants feel happy.
 
Ozjet68

Ozjet68

Insanely Active Member
J.James said:
Some growers opt to keep their cannabis plants under 24 hours of light in aims to maximize growth during the vegging stage. Most growers, however, veg their cannabis plants on an 18 light/6 hours dark light cycle. Between these two options, it is recommended that growers veg their cannabis plants on the 18/6 light cycle in order to provide a dark period, which will allow cannabis plants to complete the photosynthesis cycle.

Photosynthesis is the process by which plants convert light energy and carbon dioxide into plant food (glucose/carbohydrates) and oxygen. Cannabis plants require three resources for photosynthesis: light, carbon dioxide, and water. During the light cycle, light reactions use light to produce both ATP and NADPH (an electron carrier) in the chloroplast thylakoids. These products are then stored in the chloroplast stroma, where they are then used by the “dark cycle,” the second part of photosynthesis that absorb carbon dioxide. This dark reaction is scientifically known as the Calvin-Benson-Bassham cycle, and is independent of light energy; it completes photosynthesis by absorbing carbon dioxide to complete the synthesis of carbohydrates.

Any questions?
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I wonder then just how critical this dark period cycle is then to the whole process as I’ve done Autos on 24 hours before with solid results and numerous growers appear to run 24 hr veg with success also. Would be interesting to run simultaneous grows with both variables applied to perhaps see the difference. Surely someone’s already tried
 
I AM

I AM

Active Member
This fits in perfectly...
I was on icmag looking at Heavy Sativa grows an those guys where taking a beating running anything above 12/12 from seed. The best advice offer in many pages was...
12/12 seed to veg. 11/13 flip. 10/14 flower.

That said im not a Sativa Expert at all...
there is another thread here where we were talking about density being genetic or enviroment.

I might have been dealing with...sativa leaners. Thats why they MIGHT have kept spitting out fresh pussy hair in like week 8-9.
 
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