Max PPF/PPFD with and without Co2

Smoke-A-Cola

Smoke-A-Cola

Well-Known Member
Just trying to make sure I am putting the right amount of light in my new grow space. It is my understanding that adding Co2 allows for increased light levels.

What is the max ppf/ppfd you should be running with and without Co2?

PPFD is the better figure to use right?
 
PhotonFUD

PhotonFUD

Well-Known Member
If you are running standard 400ppm atmospheric CO2 then saturation occurs ~400 to ~600 umoles. Plants can handle more, they just won't use it.

If you want them to handle more, you can add in more CO2 above the 400ppm level but you need to keep the temperatures down under 30 celcius. >1000ppfd + >30 celcius has been shown to decrease the rate of photosynthesis.

You will have variances in strains and, of course, from your specific environment but those are safe starting points. Two things to keep in mind:

1. That is ~400 to ~600 for the entire plant, not just the top with only ~50 umoles hitting plant material below. High amounts of PPFD are great for the whole plant but you only get that with the Sun.
2. Consider increasing air circulation before adding in CO2. More air circulation will help increase CO2 to the plant and reduce temps.
 
Icemud420

Icemud420

Well-Known Member
Here is the only study I have come across mentioning cannabis and PPFD.

Physiol Mol Biol Plants. 2008 Oct;14(4):299-306. doi: 10.1007/s12298-008-0027-x. Epub 2009 Feb 26.
Photosynthetic response of Cannabis sativa L. to variations in photosynthetic photon flux densities, temperature and CO2 conditions.
Chandra S1, Lata H, Khan IA, Elsohly MA.
Author information
Abstract
Effect of different photosynthetic photon flux densities (0, 500, 1000, 1500 and 2000 μmol m(-2)s(-1)), temperatures (20, 25, 30, 35 and 40 °C) and CO2 concentrations (250, 350, 450, 550, 650 and 750 μmol mol(-1)) on gas and water vapour exchange characteristics of Cannabis sativa L. were studied to determine the suitable and efficient environmental conditions for its indoor mass cultivation for pharmaceutical uses. The rate of photosynthesis (PN) and water use efficiency (WUE) of Cannabis sativa increased with photosynthetic photon flux densities (PPFD) at the lower temperatures (20-25 °C). At 30 °C, PN and WUE increased only up to 1500 μmol m(-2)s(-1) PPFD and decreased at higher light levels. The maximum rate of photosynthesis (PN max) was observed at 30 °C and under 1500 μmol m(-2)s(-1) PPFD. The rate of transpiration (E) responded positively to increased PPFD and temperature up to the highest levels tested (2000 μmol m(-2)s(-1) and 40 °C). Similar to E, leaf stomatal conductance (gs) also increased with PPFD irrespective of temperature. However, gs increased with temperature up to 30 °C only. Temperature above 30 °C had an adverse effect on gs in this species. Overall, high temperature and high PPFD showed an adverse effect on PN and WUE. A continuous decrease in intercellular CO2 concentration (Ci) and therefore, in the ratio of intercellular CO2 to ambient CO2 concentration (Ci/Ca) was observed with the increase in temperature and PPFD. However, the decrease was less pronounced at light intensities above 1500 μmol m(-2)s(-1). In view of these results, temperature and light optima for photosynthesis was concluded to be at 25-30 °C and ∼1500 μmol m(-2)s(-1) respectively. Furthermore, plants were also exposed to different concentrations of CO2 (250, 350, 450, 550, 650 and 750 μmol mol(-1)) under optimum PPFD and temperature conditions to assess their photosynthetic response. Rate of photosynthesis, WUE and Ci decreased by 50 %, 53 % and 10 % respectively, and Ci/Ca, E and gs increased by 25 %, 7 % and 3 % respectively when measurements were made at 250 μmol mol-1 as compared to ambient CO2 (350 μmol mol(-1)) level. Elevated CO2 concentration (750 μmol mol(-1)) suppressed E and gs ∼ 29% and 42% respectively, and stimulated PN, WUE and Ci by 50 %, 111 % and 115 % respectively as compared to ambient CO2 concentration. The study reveals that this species can be efficiently cultivated in the range of 25 to 30 °C and ∼1500 μmol m(-2)s(-1) PPFD. Furthermore, higher PN, WUE and nearly constant Ci/Ca ratio under elevated CO2 concentrations in C. sativa, reflects its potential for better survival, growth and productivity in drier and CO2 rich environment.
Click to expand...
 
loftygoals

loftygoals

Well-Known Member
Rahz said:
Well that's going to be controversial. My experience tells me plants will use PPFD over 600 in normal conditions.
Click to expand...
Not controversial.

This paper shows that with any canopy temp (20-40C) net photosynthesis increases upto a ppfd of 1500 umol/m2/s. That is without CO2.

Overall highest net photosynthesis occurs at 30C and 1500 umol/m2/s ppfd.
 

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Icemud420

Icemud420

Well-Known Member
I'
PhotonFUD said:
Correct, DLI is what we should be using. 18-25 mol/d is a good target.
Click to expand...

I've seen mention of up to 65 mol/d and according to purdue university studies on different plant species, most other light loving plants like sunflowers and tomatoes are recommended for a DLI between 22 and 30mol/day.



So for cannabis, bottom threshold for optimal growth and photosynthesis is a DLI of DLI of 22 would be:
24/0 schedule: 254.6 micromoles/m2/s-1
18/6 schedule: 339.5 micromoles/m2/s-1
12/12 schedule: 509.25 micromoles/m2/s-1


For Cannabis, the Top threshold for optimal growth and photosynthesis is a DLI of 65 moles per day.
***extremely important notice, only go up to these amounts if you are using supplemental CO2, do not go this high if you are not using supplemental CO2 as you will actually slow down photosynthesis and waste energy.

24/0 schedule: 752.31 micromoles/m2/s-1
18/6 schedule: 1003.08 micromoles/m2/s-1
12/12 schedule: 1504.6 micromoles/m2/s-1


The generally accepted guidelines for artificial light PPFD in flowering are this:
in a 12/12

PPFD of at least 510 micromoles/m2/s-1 for the low end of optimal intensity
PPFD of at least 800-1100 micromoles/m2/s-1 for perfect optimal lighting without additional CO2.
PPFD of at least 800-1500 micromoles/m2/s-1 for perfect optimal lighting WITH additional CO2.
 
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CobKits

CobKits

Well-Known Member
Icemud420 said:
I'


For Cannabis, the Top threshold for optimal growth and photosynthesis is a DLI of 65 moles per day.
***extremely important notice, only go up to these amounts if you are using supplemental CO2, do not go this high if you are not using supplemental CO2 as you will actually slow down photosynthesis and waste energy.

24/0 schedule: 752.31 micromoles/m2/s-1
18/6 schedule: 1128.465 micromoles/m2/s-1
12/12 schedule: 1504.6 micromoles/m2/s-1

.
Click to expand...
so if somebody was using far red and running 13.5-14 hours a day it would be best to stay below a max of 1300 ppfd? (still a shitload of light)
 
Icemud420

Icemud420

Well-Known Member
CobKits said:
so if somebody was using far red and running 13.5-14 hours a day it would be best to stay below a max of 1300 ppfd? (still a shitload of light)
Click to expand...
Great question, but I don't know to be honest.. I mean based of DLI of 65, then yes, according to the math at 14 hours, would be a MAX PPFD of 1152.48 umol/m2/s-1.

If you go for the bare minimum accepted DLI of other sun loving plants at 22 mol/d, then the MAX (min) PPFD would be 390.07 umol/m2/s-1 at a 14 hour day.

So based on those 2 numbers its quite a range.

Using the forumula: DLI = PPFD x hours of daylight x 0.0036
 
Icemud420

Icemud420

Well-Known Member
CobKits said:
so if somebody was using far red and running 13.5-14 hours a day it would be best to stay below a max of 1300 ppfd? (still a shitload of light)
Click to expand...
I just realized I calculated the 18/6 figures above incorrectly, so I edited the post so they correctly reflect the PPFD's at 18/6. At 12/12 and 24/0 they were correct in the original post
 
MeGaKiLlErMaN

MeGaKiLlErMaN

Well-Known Member
Easy answer, It will always help... but its not really needed till youre pushing way more light than we currently do... The drop off on this chart is where you need CO2. Supplementation will never hurt... but its not always as cost effective as people think. Even shorter answer... after 1500PPFD at 86F... good luck hitting that lol




Temp graph2.jpg
 
MeGaKiLlErMaN

MeGaKiLlErMaN

Well-Known Member
Rahz said:
Well that's going to be controversial. My experience tells me plants will use PPFD over 600 in normal conditions.
Click to expand...
Icemud420 said:
I'



I've seen mention of up to 65 mol/d and according to purdue university studies on different plant species, most other light loving plants like sunflowers and tomatoes are recommended for a DLI between 22 and 30mol/day.



So for cannabis, bottom threshold for optimal growth and photosynthesis is a DLI of DLI of 22 would be:
24/0 schedule: 254.6 micromoles/m2/s-1
18/6 schedule: 339.5 micromoles/m2/s-1
12/12 schedule: 509.25 micromoles/m2/s-1


For Cannabis, the Top threshold for optimal growth and photosynthesis is a DLI of 65 moles per day.
***extremely important notice, only go up to these amounts if you are using supplemental CO2, do not go this high if you are not using supplemental CO2 as you will actually slow down photosynthesis and waste energy.

24/0 schedule: 752.31 micromoles/m2/s-1
18/6 schedule: 1003.08 micromoles/m2/s-1
12/12 schedule: 1504.6 micromoles/m2/s-1


The generally accepted guidelines for artificial light PPFD in flowering are this:
in a 12/12

PPFD of at least 510 micromoles/m2/s-1 for the low end of optimal intensity
PPFD of at least 800-1100 micromoles/m2/s-1 for perfect optimal lighting without additional CO2.
PPFD of at least 800-1500 micromoles/m2/s-1 for perfect optimal lighting WITH additional CO2.
Click to expand...

@Greengenes707
This may have been where @PhotonFUD was getting the 400uMols from... Maybe not... but thats pretty close... Either way... Im still throwing 1200PPFD down in veg lol.
 
PhotonFUD

PhotonFUD

Well-Known Member
O
loftygoals said:
Not controversial.

This paper shows that with any canopy temp (20-40C) net photosynthesis increases upto a ppfd of 1500 umol/m2/s. That is without CO2.

Overall highest net photosynthesis occurs at 30C and 1500 umol/m2/s ppfd.
Click to expand...
Ok I think this would be a great lesson for people to learn some things.

A number of you have referenced the Chandra study, which is a very excellent paper, as the basis for the >1000ppfd being beneficial claims. I will first point out that when referencing a document you should read it in its entirety and understand it beforehand. It is very key to know how it may, or in this case may not, support your position.

Kudos to the first person who identifies what element makes this study somewhat invalid for this purpose. Hint: it is in the Material and Methods section.
 
loftygoals

loftygoals

Well-Known Member
PhotonFUD said:
O


Ok I think this would be a great lesson for people to learn some things.

A number of you have referenced the Chandra study, which is a very excellent paper, as the basis for the >1000ppfd being beneficial claims. I will first point out that when referencing a document you should read it in its entirety and understand it beforehand. It is very key to know how it may, or in this case may not, support your position.

Kudos to the first person who identifies what element makes this study somewhat invalid for this purpose. Hint: it is in the Material and Methods section.
Click to expand...
What is this? Guessing games?

Tell us *what you think* makes this invalid and we can decide for ourselves.

Giving out a cryptic challenge and acting like you are the cannabis professor in some weedy undergrad class is a load of shite. You may well have spotted something pertinent who knows? Not us!

I can think of several issues with the paper but as far as I'm aware there is no better data out there so I'll take what I can get.
 
MeGaKiLlErMaN

MeGaKiLlErMaN

Well-Known Member
loftygoals said:
What is this? Guessing games?

Tell us *what you think* makes this invalid and we can decide for ourselves.

Giving out a cryptic challenge and acting like you are the cannabis professor in some weedy undergrad class is a load of shite. You may well have spotted something pertinent who knows? Not us!

I can think of several issues with the paper but as far as I'm aware there is no better data out there so I'll take what I can get.
Click to expand...
Can I graduate with a degree in weed? If so where in Colorado is this school?? lol
 
PhotonFUD

PhotonFUD

Well-Known Member
It is sitting right there and wouldn't be cryptic for a horticulturalist. And well, you can get a degree in horticulture and that would qualify you as a professional.

Not trying to be adversarial, this is a good exercise to learn from. Put all you know about light for plants together and give it a shot. Have some fun with it, every wins when someone learns something.

Hint #2: Hmmm, why isn't there any references to Emerson?
 
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