Crassulacean Acid Metabolism is a carbon fixation pathway present in some plants.It is also known as CAM photosynthesis.
These plants fix carbon dioxide duringthe night, storing it as the four- carbon acid malate. The fixation process now occurs in mesophyll cells(found in leaves) so that they will be more exposed to air and in order to take in more carbon dioxide. The malate which is the product of the fixation process, is pumped deeper in(the leaf) so that it won't be exposed to air and to oxygen. This is to avoid photorespiration and the wasteful process,, since RuBisCo is used in the Calvin cycle.