C3 carbon fixation
C3 plants work with the basic type of photosynthesis. Since the stomata close during hot and dry weather in order to avoid a too high evaporation of water, which in comparison to C4 or CAM plants under these conditions a reduced photosynthetic capacity. However, they are efficient under normal temperature and light conditions.
Most plants in the middle and high latitudes are among the C3 plants. Examples of C3 crops are wheat, rye, oats or rice, for C4 plants maize, sugar cane or sorghum.
The fixation of carbon dioxide takes place in the Calvin cycle in the reaction of RuBisCO ribulose -1 ,5- bisphosphate (short RubP2 ). The resulting intermediate is highly unstable and spontaneously breaks down to two molecules of 3-phosphoglycerate ( 3- PGA short ), the first stable intermediate in the C3 plant. Since 3- PGA is made up of three carbon atoms, the name derives from it this type of plant.
In the Earth first formed the C3 plants. Your key enzyme, ribulose -1 ,5 -bisphosphate carboxylase / oxygenase ( RuBisCO ), occurred at a time when the atmosphere was rich in carbon dioxide ( CO2) and low in oxygen (O2). In this environment, assimilation did not cause any problems, since there are no losses due to photorespiration - gave - fixation of O2 instead of CO2.