Circulation, definitely. Fresh air, not necessary. There is PLENTY of o2 in the air to enable respiration.
And not to get too far off topic but more of an FYI: cannabis is a C3 plant which means that it can use (through respiration) sugars throughout the day and night. C3 plants don't magically switch from fixing sugar to breaking it them apart and using them once the lights go out. Which is why you can grow under 24 hr lights on with no detrimental affects. The literature I have read stres that respiration is slightly higher during lights off, but it is pretty insignificant increase.
Soooo. Plants are absorbing AND expelling co2 and o2 all the time. The reason growers add co2 is that c3 plants can take advantage of greater than average percentages of co2 and therefore, fix sugars at a higher rate. From my understanding, the required o2 levels for respiration to occur are soo low that if it ever got to that level you would basically suffocate when you entered your room.
The down side of this...for you desert growers, is that with high heat AND low humidity, your plant will be respiring faster than it can uptake water. It will close its stomata to reduce water loss..and bam. No more co2 is absorbed for production. What the plant then does is a very wasteful process of using rubisco to creat sugars by combining o2 with Rubp instead of co2. This is half as effecting and also creates a toxic C molecule that has to be broken down. I can't remember the specifics but it makes some sort of glypholate? Acid that then has to be evbtually broken down into glycine I think it is?
At any rate, don't let your room get hot and dry! 80-85 and around 20% humidity would start creating problems.
he has been locked in that room 2 or 3 times this week (fucker is always sneaking in and then i leave and shut him in without knowing). He probably pissed in there. Fucker.
