CAM daytime photosynthesis. Illustration of the daytime mechanism for crassulacean acid metabolism (CAM) photosynthesis, used by some plants to obtain energy from sunlight. CAM plants close their gas-exchange pores (stomata) in the day. The 4-carbon compound malate, produced and stored in the mesophyll cell's vacuole (yellow) at night, is transferred in the day to the chloroplast (green). The Calvin-Benson cycle and ATP (adenosine triphosphate) energy cycles are used to produce sugars and regenerate PEP (phosphoenolpyruvate). For the night-time reaction, see image C023/8821. For this artwork without labels, see C023/8824.