Cam plants close during the night and open during the day because they are photosensitive and respond to light. To do it experimentally, try with a torch for some time.
Some Stomata close at night because of the heat, while others open at night because of the moisture. CAM plants such as cacti and pineapple open their stomata at night so that the moisture in the air...
Stomata close at night to reduce water loss. They lose water when it is open so they open in the day when CO2 is at it's best. Obviously, they only photosynthesize during the day and so at night they...