that since plants and the like use carbon dioxide (like we humans do w/ oxygen), and back 200 million years or so (I'm being approximate here in time spans, so I may be off) oxygen levels (% of) was much higher than the 21% or so then (and trees / ferns / etc. covered the entire globe).

With the increase in CO2 levels today, are we (1) seeing higher or more vigorous plant growth, and also in conjunction at the same time, slowly increasing levels of oxygen due to the increase in plant growth?

I was curious if anyone has done a study in the relationship between plant growth and oxygen/co2 levels.

Thanks!