Fractionation of carbon isotopes in oxygenic photosynthesis values more similar to C3 plants. In contrast to terrestrial plants, where CO diffusion in air is relatively fast and typically not limiting, diffusion of dissolved CO in water is considerably slower and can often limit carbon fixation in phytoplankton. As gaseous CO is dissolved into aqueous CO, it is fractionated by both kinetic and equilibrium effects that are temperature-dependent. Relative to plants, the dissolved CO source for phytoplankton can be enriched in C by about 8‰ from atmospheric CO. Isotope fractionation of C by phytoplankton photosynthesis is affected by the diffusion of extracellular aqueous CO into the cell, the
Photosynthesis type of photosynthesis used by living organisms. Although there are some differences between oxygenic photosynthesis in plants, algae, and cyanobacteria, the overall process is quite similar in these organisms. There are also many varieties of anoxygenic photosynthesis, used mostly by certain types of bacteria, which consume carbon dioxide but do not release oxygen. Carbon dioxide is converted into sugars in a process called carbon fixation; photosynthesis captures energy from sunlight to convert carbon dioxide into carbohydrate. Carbon fixation is an endothermic redox reaction. In general outline, photosynthesis is the opposite of cellular respiration: while photosyntesis is a process of reduction