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 the net photosynthetic rates ranged from 10 to 13 μmol CO·m·s, with the conclusion that all terrestrial plants having the same photosynthetic capacities that were light saturated at less than 50% of sunlight. Later in 1958-1963 at Cornell University, field grown maize was reported to have much greater leaf photosynthetic rates of 40 μmol CO·m·s and was not saturated at near full sunlight. This higher rate in maize was almost double those observed in other species such as wheat and soybean, indicating that large differences in photosynthesis exist among higher plants. At the University of Arizona, detailed gas exchange research