Light intensity vs VPD

jimihendrix1 said:

The atmosphere in nature, is about 21% Oxygen, and .04% CO2. When growing, the further one deviates from the norms of what the plants evolved with, in nature, the les optimum, the outcome.

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So... how do you deplete the atmosphere to get to the 300 ppm we had 1 century ago? Or do you go back to the time when plants first evolved and we had ~2000 ppm CO2 in the atmosphere?
How do you simulate the high CO2 atmosphere over a field at sunrise? During the night plants respirate, give off CO2 and there is little wind to disperse it.