Plants are largely constructed of carbon, almost 47 percent, and therefore have a large influence on the pattern in which carbon is cycled and stored at local, regional and global scales (Barnes et al 1998). The production of plant material not only influences the global carbon budget but represents important food, fuel, and fiber production for humanity. The carbon balance of plants is controlled by the quantity of CO2 fixed through photosynthesis and the rate of return to the atmosphere by respiration. If the amount of carbon fixed through photosynthesis is greater than the amount lost due to respiration a plant can grow.

The processes of photosynthesis and respiration occur in the leaves of all plants and control the net carbon gain of the leaves. Although these are the two processes which are controlling carbon gain they are influenced by light, temperature and the availability of water and nutrients (Barnes et al. 1998).