All prayer plants close their leaves at night and then open them during the day. They look like they are praying when their leaves are closed, hence the name prayer plants.
This special leaf movement is called nyctinasty. Prayer plant movement is related to the transition from night to day, and vice versa. When it’s dark outside, the leaves of these plants are closed.
The morning light acts as a stimulus that encourages the prayer plant’s leaves to open until darkness arrives again.
These plants move according to the circadian rhythm (just like us humans!), which means that their state changes 24 hours a day. Specialized cells responsible for these changes are called pulvini.
Scientists have not yet come to a conclusion on the reason leaves move during the day and night. The one reason that makes the most sense is related to watering needs.
It is believed that these plants open their leaves during the day so that they can catch rain and absorb moisture. The leaves close to prevent rain from sitting on them and attract fungi and bacteria.
There are some speculations related to protection from predators, but also that they close due to temperature regulations.
Who knows, maybe they close up just to be warmer during the night, or maybe they simply like to pray when there is no one around!