[noreason]

Hi growers,hope someone take a minute to help me understand.

I know plants use oxygen to do respiration.Less in the day and more at night,so for my first try with CO2 I keep sealed the room in the day and then,when the light are just went off I let fresh air enter for a while and seal the room again to keep the right temperature and RH.

A small amount of fresh air enter in the room when I go to check the plants daily,but it's pretty consumed by my own respiration.

I wonder how many times and when,you guys let fresh air enter the growroom.

Ps:I read a couple of times,amounts of CO2 over 1000 ppm can cause rubisco inactivity...what do you think about?

Have a nice weekend folks

[Marshall]

if the temp, rh and co2 are controlled, which in a sealed room it should be, there is no reason for fresh air. I never provide fresh air except for what comes in when I enter or leave the room.


there may be an argument for venting at night to provide oxygen but have not heard much debate or need for that

[noreason]

thanks Marshall,any other imput?

[Cannabean]

I do the same as Marshall, no fresh air during the day, only co2 supplementation and temp controlled via window ac. I think ideal co2 ppm is around 1500.

[KRD]

Fresh air should be the co2 your putting in there with gas or a burner. As long as its working you should be fine no need to let outside air in that would defeat the purpose.

[spurr]

Hey,

I am the source in the cannabis world (AFAIK) who pointed out the problem with high Co2 over ~1,200 ppm is the inhibition of "rubisco activase", that in turn greatly lowers the conversion of "inactive rubisco" into "active rubscio". Rubisco activase is needed to convert inactive rubisco into active rubisco. If you have read about that issue it comes from what I have posted in the past, I can post references if you're interested.

It's the active rubisco that allows for highest rate of photosynthesis, for plants to photosynthesize they need active rubisco. Also, a few studies I have read found Co2 saturation for cananbis is ~1,000 ppm. Using 700-1,000 ppm Co2 is ideal. AFAIK, there is zero scientific proof or evidence that using 1,500 ppm is beneficial; and there is more then a little proof and evidence showing 1,500 ppm is too much.

Using 1,500 ppm of Co2 is yet another false claim based on conjecture by so-called cannabis gurus like Jorge Cervantes, Greg Green, Mel Frank, et al.

An evolutionary reason why over ~1,000 ppm co2 is too much, is when C3 terrestrial plants where first evolving the ambient Co2 was ~500-700 ppm, maxing out around ~800-1,000 ppm. Thus, plants evolved to use ~7,00-1,000 ppm.

FWIW, the other environmental factor that reduces rubisco activase, and thus lowers conversion of inactive rubisco into active rubisco, is temps over ~89'F.

When using a sealed room with high Co2 an issue to be considered is ethylene. It is produced by the plant and affects maturation, senescence and abscission of leafs and flowers. Ethylene buildup also hinders auxin transport if ethylene is built up too high. Ethylene buildup can also reduce flower size. It's a good idea to vent the room at least once a day, esp. in latter stages of flowering to remove buildup of ethylene.

There should be plenty of O2 in a sealed room for light independent reactions such as respiration, mostly because a sealed room isn't really sealed 100%. If you let fresh air in at night, that would be good for two reasons: (1) to vent ethylene and (2) to help drop RH (and thus increase VPD).


Here are a couple of ethylene refs, I can post rubisco and cannabis Co2 refs if you'd like to read more:

1. "Ethylene In The Greenhouse": The authors explain how to detect ethylene, how to take action against it and how to stop problems before they happen.
By W. Roland Leatherwood and Neil S. Mattson
April 2010
https://www.greenhousegrower.com/magazine/?storyid=3153





2. "Ethylene, Plant Senescence and Abscission"
Stanley P. Burg
Plant Physiol. 1968 September; 43(9 Pt B): 1503–1511.
https://www.ncbi.nlm.nih.gov/pmc/arti...00512-0034.pdf

[B. Friendly]

you'd be surprised how air has a way of providing what you need,
it's the ultimate vacuum, if something is missing, then it's replaced from the greater enviro through transfusnion or something...

If you are worried about using co2 don't be, it's well worth every penny cuz you'll shoot up 25% in yeild by adding co2

never found an enviro that did not appreciate enhanced co2

just look at the equation for Photosynthesis:
A general equation for photosynthesis is:

6 CO2(gas) + 12 H2O(liquid) + photons → C6H12O6(aqueous) + 6 O2(gas) + 6 H2O(liquid)
carbon dioxide + water + light energy → glucose + oxygen + water

add co2 and you get more Photosynthesis...!!!

I rest my case bro

[spurr]

B.Friendly,

Was that post to me? If so, I didn't, nor did anyone else in this thread, claim adding Co2 isn't helpful. However, adding more than ~1,100-1,200 ppm of Co2 can/does inhibit rate of photosynthesis due to inhibition of "rubisco activase". That in turn inhibits the conversion of inactive rubisco into active rubisco; and it's active rubisco that is needed for photosynthesis. Over the day the amount of active rubisco is depleted, i.e. converted into inactive rubisco during the process of photosynthesis, thus, if rubisco activase isn't kept at sufficient levels, active rubisco can't be kept at sufficient levels. That means rate of photosynthesis (Pn), net rate of photosynthesis (total Pn over a whole day), and thus Co2 fixation, is inhibited.

Ideally Co2 at 700-1,000 ppm is the best goal, cannabis reaches Co2 saturation around 1,000 ppm. The goal when growing plants is to provide the highest Pn and highest net rate of photosynthesis (Pnnet).

[junior_grower]

I ahve to say spurr is on point after the 1000ppm subject was brought up I hit the books and hes spot on.

[spurr]

Thanks for fact checking me, I really do appreciate it Too few people think critically after reading claims online, or from so-called cananbis gurus who pen books. I really like what I have read of your posts so far, may I ask what you are going to school for (degree wise)?