Stomata of CAM plants : -

CAM (Crassulacean acid metabolism) plants such as Bryophyllum, Opuntia and pineapple grow in dry habitats.
To reduce water loss, their stomata open at night (when it is cool and humid) and close during the day. Such stomata are called scotoactive.
At night, $CO_2$ is taken in and fixed by PEP carboxylase into malic acid, which is stored in the vacuoles.
During the day, with stomata closed, malic acid releases $CO_2$, which is used in the Calvin cycle with the energy of light.
So stomata of CAM plants open during the night and close during the day.