Notice how trees droop their branches in the evening. After a long day of photosynthesis, trees want to relax their branches at night so they droop them down. This might be similar to the stretching a human does before going to sleep.
How do Trees go to Sleep?
Scientists, using laser measurements, have also discovered that during dawn, or close to sunrise, the branches of trees drop even lower than before.
Why do Trees get Tired?
Some believe that the drooping of branches is due to loss of internal water pressure which causes the leaves and branches to lose their rigidity. Sunlight is needed by trees to create sugar from carbon dioxide and since this happens only during the day, at night the trees seem to relax or you can say ‘sleep’.
During the day the leaves and branches are facing upwards, towards the sunlight. The trees seem to sway and are happy. During the night, the trees have also lost their energy and are ready to sleep.