Supplemental Co2 is sometimes used in grow rooms. Plants use Carbon Dioxide (Co2) and emit Oxygen (O2) as part of the natural cycle of photosynthesis which the plant performs in order to make simple sugars as a source of food.
Nitrous Oxide (N20) is a completely different gas and is not used in the process of photosynthesis and therefore is not beneficial to add. This is also not to be confused with Nitrogen gas (N2) which makes up about 80% of the air we breathe.

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