Why do flowers close up at night?

Question

What benefit does a plant get from closing in the flower petals when the sun goes down?

Answer 1

Not all plant do, but for those that do this, one big advantage is that it keeps the pollen dry if the plant is in a humid environment and dew forms as the temperature cools overnight.  This makes the pollen easier to pick up by the insects (or other pollinators) that may visit the flowers early in the morning.

It can also protect the pollen from being brushed off or falling off if the flower is bumped into by accident by an animal which isn't a pollinator, so it increases the chances of the plant being able to reproduce.

Answer 2

...do all flowers do that? I mean..I knew that some did. Hmm..that's interesting.

Sorry I don't have an answer :(

Maybe to protect themselves against the cooler temperatures.