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Increased atmospheric carbon dioxide has been found to reduce plant water use, and consequently, the uptake of nitrogen, so particularly benefiting crop yields in arid regions. [10] The carbohydrate content of crops is increased from photosynthesis, but protein content is reduced due to lower nitrogen uptake.
Jean Senebier (25 May 1742 [1] – 22 July 1809 [2] [3]) was a Genevan Calvinist pastor and naturalist.He was chief librarian of the Republic of Geneva. A pioneer in the field of photosynthesis research, he provided extensive evidence that plants consume carbon dioxide and produced oxygen.
Through photosynthesis, plants use CO 2 from the atmosphere, water from the ground, and energy from the sun to create sugars used for growth and fuel. [22] While using these sugars as fuel releases carbon back into the atmosphere (photorespiration), growth stores carbon in the physical structures of the plant (i.e. leaves, wood, or non-woody stems). [23]
Carbon on Earth naturally occurs in two stable isotopes, with 98.9% in the form of 12 C and 1.1% in 13 C. [1] [8] The ratio between these isotopes varies in biological organisms due to metabolic processes that selectively use one carbon isotope over the other, or "fractionate" carbon through kinetic or thermodynamic effects. [1]
Biochemical CCMs concentrate carbon dioxide in one temporal or spatial region, through metabolite exchange. C 4 and CAM photosynthesis both use the enzyme Phosphoenolpyruvate carboxylase (PEPC) to add CO 2 to a 4-carbon sugar. PEPC is faster than RuBisCO, and more selective for CO 2.
The free energy created is then used, via a chain of nearby electron acceptors, for a transfer of hydrogen atoms (as protons and electrons) from H 2 O or hydrogen sulfide towards carbon dioxide, eventually producing glucose. These electron transfer steps ultimately result in the conversion of the energy of photons to chemical energy.
In natural ecosystems, the greatest utilization of carbon is through the uptake of carbon in photosynthesis and the second greatest utilization of carbon is through the release of carbon in cellular respiration. [5] minute changes to these two fluxes can have a larger effect on the carbon dioxide in the atmosphere. [6]
Of the increased amounts of carbon dioxide that are introduced to the atmosphere each year, approximately 80% are from the combustion of fossil fuels and cement production. The other ~20% originate from land use change and deforestation. [18] Because gaseous carbon dioxide does not react quickly with other chemicals, the main processes that ...