Fractionation of carbon isotopes in oxygenic photosynthesis the bundle sheath cells. Different forms of CCM in phytoplankton include the active uptake of bicarbonate and CO through the cell membrane, the active transport of inorganic carbon from the cellular membrane to the chloroplasts, and active, unidirectional conversion of CO to bicarbonate. The parameters affecting C fractionation in phytoplankton contribute to "δ"C values between -18 to -25‰. Fractionation of carbon isotopes in oxygenic photosynthesis Photosynthesis converts carbon dioxide to carbohydrates via several metabolic pathways that provide energy to an organism and preferentially react with certain stable isotopes of carbon. The selective enrichment of one stable isotope over another creates
Fractionation of carbon isotopes in oxygenic photosynthesis elevated O concentrations would increase the efficiency of photorespiration. Atmospheric CO on Earth decreased abruptly at a point between 32-25 million years ago. This gave a selective advantage to the evolution of the C4 pathway, which can limit photorespiration rate despite the reduced ambient CO. Today, C4 plants represent roughly 5% of plant biomass on Earth, but about 23% of terrestrial carbon fixation. Types of plants which use C4 photosynthesis include grasses and economically important crops, such as maize, sugar cane, millet, and sorghum. Isotopic fractionation is differs between C4 carbon fixation and C3, due to the spatial separation in