The “food factories” in plant cells are called

In most plants, the leaves are the main food factories. They capture the sun's energy with the help of chlorophyll in the leaf cells. The chlorophyll traps and packages the energy from the light of the sun in a process called photosynthesis. Leaves usually have a large surface so they can collect the most sunlight.

substitution is the answer in this case

carbon atoms, hydrogen, oxygen, and nitrogen.