Plant leaves close at night for protection from nocturnal herbivores, insulation and to reduce water loss during the night when photosynthesis is not occurring.
The plant leaves which close at night are the shamrock plant or Oxalis plant leaves, the Prayer Plant leaves "Calathea" and the Sensitive Plant Leaves "Mimosa Pudica".
The plants leaves close up at night and then reopen in the morning.
The closing of the plants leaves is linked to defense mechanisms against nocturnal herbivory, protection from the cold and even reduced water loss.
The sensitive plant is also known as the Mimosa Pudica and is famous for it's rapid leaf folding in response to touch, but it also closes it's leaves at night and is thought to be as a defense mechanism.
Prayer plants also called Calathea plants are known for their colorful, patterned leaves which fold up like praying hands at night, which is why it's called a prayer plant.
The leaves of the prayer plant open during the day to gather up sunlight and then close at night.
Oxalis plants like the wood sorrel plant also close their leaves which is known as nyctinasty which is said to be a defense mechanism.
Even the shamrock plant closes it's leaves at night and opens back up in the day.
Then the leaves open back up as the sun starts to shine the next day.
When leaves are closed, the plant can reduce it's water loss, which is important during periods of drought or when photosynthesis is not active at night.
And closing of the leaves also helps to insulate the plant from the nighttime cold, especially in colder climates.
And some theories even suggest that the leaf folding and closing can also make the plant less appealing or less accessible to nocturnal herbivores.