Succulents are known to keep their stomata closed during the day check transpiration. How do they meet their photosynthetic requirements?

 

 
Succulent plants grow in dry and xeric conditions So, they have to shut down the stomata during day time, to prevent water loss through transpiration. So and the gaseous exchange does not take place.
Thus plants have developed the mechanism to fix CO2 during night in the form of malic acid  which is a 4 carbon compound and store CO2, release it during day, inside the photosynthetic cells.