How can the carbon stored in plants reach the atmosphere?

Carbon stored in plants reaches the atmosphere via cellular respiration. Cellular respiration is the set of metabolic reactions that allows plants to convert the energy from nutrients into ATP (adenosine triphosphate) and then release the waste products. The energy from the glucose molecules is broken down into ATP. Water and carbon dioxide are also required to convert the nutrients into ATP. In our case, carbon and oxygen are waste products so they are released into the atmosphere via the pores underneath the leaf of a plant or tree.