Carbon dioxide is essential for plants to live and grow. Plants are autotrophs, meaning they can generate their own energy to live and grow by using the simple substances around them. People, on the other hand, are heterotrophs; we need to consume external sources of energy (food), like meat and vegetables.
The simple substance plants use to generate energy: Carbon Dioxide.
During the photosynthesis process, plants use light energy to break apart the molecular bonds of the CO2 compound, shake it up with some H2O, and wahla! They’ve created hydrocarbons (CH-) and oxygen (O2).
The hydrocarbons (aka sugars, carbohydrates) are used as the source of energy for metabolic processes, such as photosynthesis and evapotranspiration, and are the building blocks for cell growth and development. Oxygen is the waste byproduct of photosynthesis, and our symbiotic relationship with plants is rooted.
When the environmental conditions are right – plentiful water, balance of nutrients, good weather, and lots of sunshine – plants will maximize stomatal opening in their leaves and gulp up as much CO2 as possible. The more CO2 under these optimal conditions, the more they’ll consume and photosynthesize, and the faster they will grow. This plant response is what drives many indoor farmers and greenhouse growers to enrich their plant environments with CO2.
Read more at Dr. Greenhouse