Field of Science

Plant Respiration Question

Dear Phytophactor,
My fiance and i have recently gotten into a debate about plant respiration.
She is worried about the amount of CO2 that plants may be giving off at night and prefers that we do not have them in the bedroom where we sleep.
I love plants....but i love her more.
So, the question is, what is the ratio of O2 to CO2 that plants give off? How much CO2 can a single medium size house plant give off in one night? How much CO2 is being produced if I have a bedroom full of plants? (five or six)?
I have searched the internet, and many sites agree that plants give off CO2 at night when they are in the process of respiration, but no one seems to provide any information about the exact amount of CO2 that plants actually produce.
Thank you!

The Phytophactor responds:
Dear Matthew,
You make the Phactor feel like the Car Talk guys when you send me a question like this. The basic idea is correct; plants respire and give off CO2, all the time, and at night the respiration is not off set by photosynthesis, but here's the critical thing to understand. Plants respire at a much, much lower rate than a nice warm-blooded mammal. So if your fiance is worried about oxygen depletion and CO2 buildup at night, guess who ends up in another bedroom? Alternatively you could keep your bedroom really cool at night which will slow down plant respiration even more, while at the same time providing a good reason for keeping your warm carbon dioxide producing body around. Since your plants do grow, your plants are capturing more CO2 during the day than they release via respiration all day. The two cats sleeping on my bed respire a lot more than a whole roomful of plants. So plant respiration just isn't a problem, and here the Phactor stops short of saying a silly concern although it is, but I did hear this concern once with respect to giving plants to hospital patients. Even if plants gushed carbon dioxide at night hospital rooms and your bedroom are not sealed boxes, so gases can easily diffuse to equilibrate any tiny differences that might occur. So sleep well, the plants and their respiration aren't a problem; if they were we'd have be careful about entering my greenhouse or the rainforest at night, and both of them have far greater mass of plants respiring than your bedroom. Hope this helps you sleep in restful assurance, providing you do not handle being on the winning side of this debate with a certain air of superiority and condescension (And depending upon the particular nature of your fiance, please recall the scene in the 1st Star Wars movie where the R2D2 is beating Chewbacca at a chess-like game. Let the Wookie win may be very good pre-maritaladvice.).


mr_subjunctive said...


Now if you could do something about all the people buying plants for their oxygen-producing abilities (like insufficient oxygen is a major health concern, or that a couple houseplants in the corner would do anything to fix it if it were), I'll love you forever.

(I might love you forever anyway, of course. I ain't saying. But the oxygen thing is worth a post regardless.)

Suzi Smith said...

hi came via festival of trees... ha.. remember being told at school this was why plants were taken out of hospital wards... huh, some things stuck then find they were wrong, lol (well, not wrong, but over cautious)