crassulacean acid metabolism (CAM) plants minimizes loss through separation in time. The stomata of CAM plant is opened at the night and carbon dioxide is trapped in and then closed in the morning to minimize water Loss.
The carbondioxide that is trapped in is ferried via phosphoenol pyruvate (PEP) and then broken down by PEP carboxylase to form oxaloacetate from there it is further broken down to malate or malic acid and other organic acid. It is therefore stored in the vacoule as malic acid until when it is needed in the day where it will be broken down into pyruvate and Carbondioxide.
Loss is minimize by through the closure of stomata during the day this is to prevent excessive transpiration when the weather is hot and stomata is opened.
CAM plants live in extremely dry and hot environments. These species have adapted to take CO₂ in arid and semiarid areas by opening stomas during the night, when the temperature decreases and humidity increases, to avoid excessive water loss and dehydration. During the day, temperature increases, so these plants close stomas in order not to lose water. Hence CAM plants have very little requirements of water during CO₂ fixation.
So the strategy of these plants is to separate temporarily two processes. Both of them occur in the mesophil of the leaves, but not simultaneously.
During the night, it occurs the Hach and Slack cycle, taking CO₂ with open stomas. Then CO₂ is fixated in malic acid that will be stored in vacuoles of the photosynthetic cells.
And during the day, the Calvin cycle takes place, with closed stomas to avoid transpiration.
The malic acid is synthesized in big amounts during the night, and it decarboxylates during the day releasing CO₂ that will be used in the Calvin cycle to produce carbohydrates.
