Crassulacean acid metabolism, also known as CAM photosynthesis, is a Carbon Fixation pathway present in some plants. These plants fix carbon dioxide (CO2) during the night, storing it as the four-carbon acid malate. The CO2 is released during the day, where it is concentrated around the enzyme RuBisCO, increasing the efficiency of photosynthesis. The CAM pathway allows stomata to remain shut during the day, reducing evapotranspiration ; therefore, it is especially common in plants adapted to arid conditions.
The CAM cycle is shown below... Notice how all the reactions occur in the same cell but at different times of the day .
The fixation step occurs at night with the guard cells open to receive carbon dioxide during the cool night. This process is driven by use of starch to make the PEP required for PEPcarboxylase activity. The malic acid is transported to the vacuole and accumulates there at night. There is a strong pH change in the vacuole at night! During the night
During the day The malic acid is transported back to the cytosol for the decarboxylation reaction. This floods the Calvin cycle with carbon dioxide while the guard cells are closed. The energy of course comes from the light reactions and accumulated starch is used the next night for another round of carbon fixation.
These adaptations enable the plant to thrive in conditions of :
High daytime temperatures
Low soil moisture
“ This is because they close off their pores to conserve water and work on producing energy by using the C3 process and the C4 compound they created during the night. So they can survive when the drought season come. But plant that undergo this pathway have slower growing rate“