The phenomenon of release of energy by oxidation of various organic molecules, for cellular use is referred to as respiration. The compounds that are oxidised during this process are referred to as respiratory substrates. During the process of respiration, oxygen is utilised, and carbon dioxide, water and energy are released as byproducts. The energy released is utilised by the organisms for a number of purposes.
Respiration in plants mainly occurs in the green leaves of the plants. The leaves on its upper and lower surface contains opening referred to as stomata through which the exchange of gases takes place.