Thank you Yllaria - thats the info I was looking for. Mods you may close the thread.
I don’t know if that would affect the local CO2 concentration very much. Atmospheric CO2 concentration isn’t that big of a factor in plant growth, anyway. Their growth is more often limited by the availability of nutrients such as phosphate or organic nitrogen.
Well, it can be a factor. My mom was involved in a greenhouse project once where the greenhouse was too well-sealed (to hold in heat), and the lack of CO[sub]2[/sub] did turn out to be the limiting factor on plant growth inside. But yeah, that’s pretty rare.
Bear in mind, though, that greenhouse plants are generally coddled with fertilizer etc., so their growth is likely to have a different limiting factor than wild plants.
‘Often’ is a kind of slippery term here, since it isn’t quantitative, but this deserves a lot of qualification.
Most terrestrial plants use the C3 pathway, and these are almost always limited by carbon dioxide (as well as by the relative proportions of carbon dioxide and oxygen- the enzyme that fixes carbon is inhibited by oxygen) at very short (minutes to hours) and very long (evolutionary) time scales. If that wasn’t the case, carbon-concentrating mechanisms wouldn’t have evolved on so many different independent occasions.
At intermediate time scales (e.g. the life of the plant), C3 plants are sometimes limited by nitrogen, phosphorus, extreme low or high temperature, herbivory, light, or some other factor. However, since many ecosystems (agricultural ones especially) are fertilized this wouldn’t apply to them. Any plant that is limited by water (and that’s a lot of them) is also going to be limited by CO2, because plants effectively trade CO2 for water through their stomata. This is why most plants do show a small response to elevated [CO2], albeit often not as big as we would hope.
CO2 limitation is also not independent of these other limitations and can help ameliorate them to some extent. A plant that has more CO2 to play with can invest less nitrogen in the carboxylating enzyme and free up its nitrogen supply, or it could invest more carbon in mycorrhizal symbiosis and free up more phosphorus that way. CO2 also can ameliorate some high temperature stress, since the carboxylating enzyme becomes less efficient at high temperature.
Some systems, like corn, or like the algae that people often talk about don’t show much of a response to higher [CO2] at all, but that’s in part because corn, most cyanobacteria, etc. already have mechanisms to concentrate [CO2] within particular cells or cell compartments.