Why do plant leaves sleep?

from what i remember from a botany course I took, some plants automatically open/close their leaves to conserve water vapour from drifitng out of their stomata. similar to if you have a prolapsed anus and sat down on a chair, they are trying to limit the amount of water lost during the night

also that picture is wrong, the darker part of the leaf is always up top due to a higher concentration of chlorophyll
i could be wrong but whatever

>>9094676
addendum:
i dont believe it is really understood how this process works.

same thing with plants always growing upward and towards the sun, nobody knows how or why it works.
you can take a seed, turn it upside down in the dirt, and the plant will literally do a double take and grow upwards to pierce through the dirt and make it to the sun.
put a plant in a box with a hole at the bottom, while taping the plant to the top of the box, and it will grow downward to the slightly sunnier hole, then out into the sunlight

crazy shit man, plants are fucking scary sometimes

Plants grow when it's dark. If a plant is covered by a shadow, it'll grow till it is no longer in the shadow. (it'd have to be a semi-permanent shadow as plants grow slowly) This gives the illusion or effect of growing towards sunlight.

The reason they grow in the dark is because they aren't photosynthesizing. Photosynthesis actually takes a bit of work, and it's easier for plants to concentrate on one thing at a time. Growing or eating. This process of pulsing working/resting is call respiration and it's something all life is required to do or else it doesn't meet the standard scientific definition of life.

Also, plants can sense gravity. They know which way is up.