Respiration

Figure 7.7: Like other organisms, plants respirate to break down food, using oxygen and producing carbon dioxide. The interaction between photosynthesis, respiration, and other plant biofunctions is illustrated above.
Image from URL: http://jrscience.wcp.muohio.edu/climate_projects_05
Once the plant has its food made, it still has to break that food down into useful components. As with other organisms, such as people or fish, this process, called respiration, uses oxygen and produces carbon dioxide. In plants respiration mainly takes place at night when there is no photosynthesis occurring.