Answer:
The separation of CO2 and the Calvin cycle and the existence of different enzymes to capture CO2.
Explanation:
The evolutionary adaptations to the calvin cycle that are seen in c4 plants are the separation of CO2 from the Calvin cycle and the existence of different enzymes to capture CO2.
C4 plants have a high affinity for CO2. They are named after the fact that oxalacetic acid has 4 carbon molecules formed after the carbon fixation process. Due to their high affinity for CO2, C4 plants have a major advantage over C3 plants: they can survive in arid environments. This is because C4 plants only reach maximum photosynthesis rates under high solar radiation intensities, causing them to set more CO2 per unit of water lost. That is, they are more economical to use water, they lose less water than C3 during fixation and photosynthesis.
C4 plants are also known as "sun plants" because they occur in areas often without shade. They also occur in arid areas with smaller amounts of water available in the soil.
In these plants, CO2 assimilation involves PEPcase carboxylation of PEP into mesophyll cells, resulting in malate or aspartate, composed of 4 carbon atoms. Malate or aspartate is transported to the sheath cells. Decarboxylation of malate or aspartate in the sheath cell releases CO2 that is reduced to carbohydrate via the Calvin Cycle. Remember that the enzyme responsible for CO2 capture in the Calvin Cycle is RuBcase. After this occurs the transport of 3C acid formed by decarboxylation of malate / aspartate to the mesophyll cell, where PEP (phosphoenolpyruvate) is regenerated.
