Here's how it works:

* Photosynthesis: Plants use a process called photosynthesis to make their food (glucose).

* CO2 Absorption: They absorb carbon dioxide gas from the atmosphere through tiny openings on their leaves called stomata.

* Conversion: The absorbed carbon dioxide combines with water in the presence of sunlight and chlorophyll (green pigment) to produce glucose and oxygen.

So, while carbon dioxide exists in various forms, it's the gaseous form that plants directly utilize for photosynthesis.