Do trees sleep at night?
A study was set up to answer that question, using lasers to measure the movements of two silver birches—one in Finland and the other in Austria. They were monitored from dusk to dawn on dry windless nights.
Trees do relax their branches at night, reaching their lowest position a few hours before sunrise, and then perking up again before sunrise.
Scientists say this might be a sign that the trees are sleeping.
But do they dream?
http://www.livescience.com/54864-do-trees-sleep.html