Rather than worrying about sugar production, this used for water conservation.
-plants like those found in the desert
-occurs in the cytoplasm of mesophyll cells
Stomata, while lets in air, it can also let out water vapor.
So the plants want them closed during the day time. However, photosynthesis can only occur during the day.
So, they utilize night and daytime.
At night, they keep their stomata open while, letting in CO2, fixing it just like we see in the C4 pathways (PEP -> oxaloacetate -> malate). The malate is then stored.
During the day, the stomata is closed to prevent water loss. All the stored-up malate can be pumped out of the vacuole, breaking off the CO2 to perform photosynthesis, producing sugar.