Fractionation of carbon isotopes in oxygenic photosynthesis Calvin cycle during the day, when stomata are closed to prevent water loss, and the light reactions can drive the necessary ATP and NADPH production. This pathway differs from C4 photosynthesis because CAM plants separate carbon by storing fixed CO in vesicles at night, then transporting it for use during the day. Thus, CAM plants temporally concentrate CO to improve Rubsico efficiency, whereas C4 plants spatially concentrate CO in bundle sheath cells. The distribution of plants which use CAM photosynthesis includes epiphytes (e.g., orchids, bromeliads) and xerophytes (e.g., succulents, cacti). In Crassulacean acid metabolism, isotopic fractionation combines the effects of
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