# Best Co2 Temp. Why can't I get a straight answer.



## MedicalMike420 (Jan 28, 2016)

The graph is out of Ed rosenthals, the oaksterdams course book, the paragraph is from Jorge Cervantes medical growers bible.
What's the best temp for veg and also best temp for flower. Why?
Right now my temps are at 84-88.


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## since1991 (Jan 28, 2016)

Best temps for consistent co2 enriched gardens (900 - 1500 ppm at all times during lights on photoperiod) indoors under HID lamps is 82 - 86 degrees fahrenheit at plant canopy level....provided relative humidity. This is just a general guide.....it is very much cultivar dependent.


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## DemonTrich (Jan 29, 2016)

I like 85 from week 1 thru 6, wk 7 and on I drop ppm to 400 and run 77 day and 74 night.


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## personal lux (Jan 29, 2016)

MedicalMike420 said:


> View attachment 3595868 The graph is out of Ed rosenthals, the oaksterdams course book, the paragraph is from Jorge Cervantes medical growers bible.
> What's the best temp for veg and also best temp for flower. Why?
> Right now my temps are at 84-88.


82-85 degrees, 1250 ppms with a 150 deadban.


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## ShirkGoldbrick (Feb 9, 2016)

There is no true scientific knowledge currently.

The gov did a study and said something like 85F at 1200PPM CO2 with 2000umol/s. The light was some LED contraption though.

Even the newest gavitas only put out like 1500umol/s at their rated foot print. It's all a bunch of hooey anyway.

umol/s are for PAR which is photosynthetic active radiation. Basically chlorophyll doesn't absorb green because it is green. Except this is only true in vitro, in vivo it isn't true. In vivo plants will absorb green about as efficiently as it absorbs blue (MSU did a study on it), with the caveat that green doesn't reduce stretch like blue does. 

Furthermore, LED's generally suck at penetration, especially when that study was done (years and years ago way before COB).

Basically..2000umol/s with HPS is actually more than the study because of more penetration and because the green light is absorbed. The plant probably actually wants more or less for optimum water uptake efficiency, WUE, as the study was done with crappy LEDs and the whole plant couldn't have been getting anywhere near even saturation.

So you see, even science doesn't know, nothing new there though.

Ed rosenthal said something like higher growth rates at 1500ppm even up to 95F but I've heard above 85F there's THC degradation in your flower. Mind you this is PLANT temperature not air. Speaking of plant vs. air temps - no one has ever mentioned humidity so how can we know how efficient the WUE was without knowing if the vapor pressure deficit was in range for optimal growth.

In assay, try some different things out, take notes, make adjustments, find what works for you.


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## a mongo frog (Feb 9, 2016)

ShirkGoldbrick said:


> There is no true scientific knowledge currently.
> 
> The gov did a study and said something like 85F at 1200PPM CO2 with 2000umol/s. The light was some LED contraption though.
> 
> ...


Nice read!!!! Who taught you that, Puffy?


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## Resinhound (Feb 9, 2016)

Journal Physiology and Molecular Biology of Plants
Publisher Springer India
ISSN 0971-5894 (Print) 0974-0430 (Online)
Issue Volume 14, Number 4 / October, 2008
Category Research Article
DOI 10.1007/s12298-008-0027-x
Pages 299-306
Subject Collection Biomedical and Life Sciences
SpringerLink Date Thursday, February 26, 2009

Suman Chandra1 , Hemant Lata1, Ikhlas A. Khan1, 2 and Mahmoud A. Elsohly1, 3

(1) National Center for Natural Product Research, School of Pharmacy, University of Mississippi, Oxford, MS-38677, USA
(2) Department of Pharmacognosy, University of Mississippi, MS-38677 Oxford, USA
(3) Department of Pharmaceutics, School of Pharmacy, University of Mississippi, University, Oxford, MS 38677, USA

Published online: 26 February 2009

Abstract Effect of different photosynthetic photon flux densities (0, 500, 1000, 1500 and 2000 μmol m−2s−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−2s−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−2s−1 PPFD. The rate of transpiration (E) responded positively to increased PPFD and temperature up to the highest levels tested (2000 μmol m−2s−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−2s−1. In view of these results, temperature and light optima for photosynthesis was concluded to be at 25–30 °C and ∼1500 μmol m−2s−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−2s−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.


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## Resinhound (Feb 9, 2016)

ShirkGoldbrick said:


> There is no true scientific knowledge currently.
> 
> The gov did a study and said something like 85F at 1200PPM CO2 with 2000umol/s. The light was some LED contraption though.
> 
> ...


This is now big business...to assume there is no scientific data is naive.


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## drolove (Feb 9, 2016)

it has always been my understanding that you wanted mid 70s. its also my understanding that co2 allows you to run higher temps BUT....i have no idea why higher temps would be beneficial.


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## since1991 (Feb 9, 2016)

Higher temps in accordance with rh and vpd numbers......with enriched carbon dioxide air makes my growroom pop. Like super charged. Its truly amazing when all the environmental factors get dialed in with a good feed program. Turbo plants. Huge yields...the most healthy plants. Roots wanting to grow into the saucers and waste table. Just absolutely amazing.


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## ShirkGoldbrick (Feb 10, 2016)

@a mongo frog Resinhound published some of the data I was referring to.

@Resinhound that data is full of holes.

"The study reveals that this species can be efficiently cultivated in the range of 25 to 30 °C and ∼1500 μmol m−2s−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."

It was done with Red and blue LED's so 1500umol is read by a PAR meter which doesn't take into account much green light because in vitro plants can't use green light via chloroplasts. 

In vivo because the green light has such a chance to bounce around and get reflected/refracted and due to some other pigment whom I forget its name which can utilize green light and does so giving excess energy back to the plant etc. etc. the plant is able to use green light just as efficiently as blue.

This means if you're using a PAR meter 1500umol HPS > 1500umol as measured in this study.

Furthermore since it was LEDs which have poor penetration only the top of the plant was really receiving all the light. Perhaps the bottom of the plant can use light just as efficiently so 1500umol isn't enough but because the disparity in how PAR is measured between red/blue LED and HPS this may or may not be accounted for.

Finally as I said, they didn't take into account VPD.

Look at a Relative humidity/Temp VPD chart...

So for example you use and IR gun and measure leaf temperature and get 79 degrees, then 100% saturation is at 33.6. Room is 86F (30C) then you want a VPD of 10 so that's 23.6 on the chart where 23.3 is at 55% humidity and 25.4 is at 60% humidity. You want between 55-60% humidity at these temps.

</rant>
Don't tell me this is big business, my gripe is with scientific ineptitude. Horticulture in general is big business. Look at all the idiots putting bleach or CaCl2 into the water to keep it clean. This is fine if you're using JUST water to irrigate but how much do you put? Very few people actually go by ORP which I think it's 650mV will kill almost any pathogens..sweet for hydro. 

The problem is that unless you're using JUST water to irrigate and you're putting nutrients into the water almost all are going to contain some ammonium which forms with the chlorine to make chloramines which have a lower ORP and therefore aren't really cleaning anything and by the time you get the ORP high enough you've killed the plants with chlorine toxicity...TRY FINDING THAT IN A STUDY..and then ask me how I know all this happens..been there.

The science is more of a guideline but the epitome of this story is that not just marijuana but the entire horticultural industry and by extension science which is still incredibly inept and following studies/advice is great for a starting point but there's still a lot of room for improvement at best and at worst you kill all your plants.

</end>

Edit: It's Ca(ClO)2 not CaCl2, my mistake.


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## ShirkGoldbrick (Feb 10, 2016)

drolove said:


> it has always been my understanding that you wanted mid 70s. its also my understanding that co2 allows you to run higher temps BUT....i have no idea why higher temps would be beneficial.


In order for photosynthesis to occur at a faster rate the temperature must be warmer. Things speed up when they get warmer.


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## Resinhound (Feb 10, 2016)

Again to assume there isnt any scientific data proving how plants grow is absurd.You really think the goverment isn't going to make sure their investment is secure backed by good scientific data?you can sit here and claim their study was flawed all you want,however until I see a peer reviewed study with your name on it...well then you are just talking out your ass,but whatever dude.


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## drolove (Feb 10, 2016)

ShirkGoldbrick said:


> In order for photosynthesis to occur at a faster rate the temperature must be warmer. Things speed up when they get warmer.


ah i see. i guess i can fathom that. thanks


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## bdt1981 (Feb 15, 2016)

1500ppm 86-90f plenty of air movment 40humidity doez pretty good


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## NaturalFarmer (Dec 28, 2016)

83.6 degrees is the short answer but it certainly has been studied. This is for growth however, not exactly that is conducive with frosty flowering environment. Which is why I drop co2/temp in flower, or at least the last half.

*"CO2 enrichment is strongly temperature dependent. Indeed, our results suggest that for a 3°C increase in mean surface air temperature (as is generally predicted to result from the ‘greenhouse effect’ of such an increase in the CO2 content of the air), the growth enhancement factor for such a CO2 increase rises from 1.30 to 1.56. *

http://www.sciencedirect.com/science/article/pii/0167880987900235

"*The rule of thumb is that there is a doubling of the reaction rate for every 10°F rise in temperature. Plants grow faster at a higher temperature providing they have adequate levels of CO2, water, sunlight and plant nutrients."

"A higher temperature without adequate level of the necessary ingredients for growth might produce no response or even damage. Sylvan Wittwer, quoted above, states that under most circumstances the availability of CO2 is the factor which limits growth."

http://www.sjsu.edu/faculty/watkins/CO2plants.htm
*


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## rickyrozayyy (Jan 6, 2017)

Blah blah blah .. 85° blah blah blah... post progress bro!!! Good luck..


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## kirkc (May 20, 2018)

If I read the paper correctly this study was done on a single leaf. All of the scientific articles I have found use this technique for measurements. My question has been "what about buds?". What room conditions are best for the buds we want to harvest?


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## NaturalFarmer (May 20, 2018)

kirkc said:


> If I read the paper correctly this study was done on a single leaf. All of the scientific articles I have found use this technique for measurements. My question has been "what about buds?". What room conditions are best for the buds we want to harvest?


Leaves are what capture the light reactions and feed the flower.

How much photosynthesis is happening and at what stage of flower? Once senescence kicks in the last few weeks of flower, the need for higher amounts of CO2 drops and the ability for the plant to deal with the heat is reduced as well. CO2 consumption is most for stretch and swell and begins to drop a great deal once it is over(more than half).


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## nonamedman420 (May 25, 2018)

would the optimal temp vary depending on light source? like hps vs led? led growrooms need to be warmer just for optimal photosynthesis at atmospheric co2 levels, vs a hps room. this makes me think the optimal temp varies from room to room.


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## nonamedman420 (May 25, 2018)

also i read an article by nasa, talking about the effects of growing plants under elevated light levels. there came a point where, regardless of co2, temp, RH, etc... the plant needed more calcium to fuel photosynthesis than could be fed to the plant, even with foliar applications. fluence makes a high ppfd grow guide, and it has good info on co2 enrichment, and the point of diminishing returns. it's tailored to their spyderx led light, but the info should still be a good read.


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## NaturalFarmer (May 25, 2018)

Optimal temp is kind of relative and depends on how much light and CO2 but yes you will reach a saturation point once all the factors are met and the plant cannot move any faster.


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## F1_Grower (Mar 4, 2021)

since1991 said:


> Best temps for consistent co2 enriched gardens (900 - 1500 ppm at all times during lights on photoperiod) indoors under HID lamps is 82 - 86 degrees fahrenheit at plant canopy level....provided relative humidity. This is just a general guide.....it is very much cultivar dependent.


Are my temps too low for my co2 and rh levels?


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## F1_Grower (Mar 4, 2021)

F1_Grower said:


> Are my temps too low for my co2 and rh levels?


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## BurnzAU (Mar 4, 2021)

F1_Grower said:


> Are my temps too low for my co2 and rh levels?


For my liking they are. I would raise temp or lower humidity. What lights you running?


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## F1_Grower (Mar 4, 2021)

BurnzAU said:


> For my liking they are. I would raise temp or lower humidity. What lights you running?


Ok I agree, will do.

I just seen so much weird high temps and rh while ppl running co2 . I am supplying two rooms via 3/16" Y connector and one T split. Room 1 co2 levels run same due to cfm exhausting from smaller cu ft room 2 via one 6" AC and one 4" AC to larger cu ft room 1 which has just one 6" AC exhausting to room 2

Room 1 temps are 70 to 78F and RH 55% to 60% running two 1k watt hids with solistek mh bulbs and 10 150w recessed full spec/IR leds, and two vert hanging two bulb T5 florescent led veg 

Room 2 temps 72 F to 79F but i have to keep RH 65% to 70% in rm 2 which exhaust hot humid air through AC infinity to room 1 so in order for room 1 to stay 55% to 60% rh. 
I'm running 315w cmh phantoms, x2 4100k hi lux and x1 4200k Phillips bulbs.

Room 3 off of room 2 temps are 74 F to 81F RH 66 to 71%
Running
X2 leds Viparspectra 250w at 70% And x1 315cmh 4200k


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## F1_Grower (Mar 4, 2021)

nonamedman420 said:


> also i read an article by nasa, talking about the effects of growing plants under elevated light levels. there came a point where, regardless of co2, temp, RH, etc... the plant needed more calcium to fuel photosynthesis than could be fed to the plant, even with foliar applications. fluence makes a high ppfd grow guide, and it has good info on co2 enrichment, and the point of diminishing returns. it's tailored to their spyderx led light, but the info should still be a good read.


This is so 8nteresting bc in my rm 3 size 5 x 5 x 8 running same strain, same med, same nutes, ro water, very bad calimag def, while running co2, 75 to 80 F, rh 65% to 70%


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