Here's why:

* Photosynthesis: Plants use CO2 from the atmosphere, along with water and sunlight, to create their own food through photosynthesis. This process produces sugars that provide energy for the plant to grow and thrive.

* Other Atmospheric Needs: While CO2 is the most critical component, plants also need some other gases from the atmosphere, like oxygen for respiration.

Let me know if you'd like to know more about photosynthesis or other plant needs!