In 2016, Zlinszky and his team released another study demonstrating that birch trees go to sleep at night (now we know that all trees – at least all the trees that have been studied so far – do sleep at night).
Trees follow circadian cycles responding primarily to light and darkness on a daily cycle. The researchers believe the dropping of birch branches before dawn is caused by a decrease in the tree’s internal water pressure while the trees rest. With no photosynthesis at night to drive the conversion of sunlight into simple sugars, trees are conserving energy by relaxing branches that would otherwise be angled towards the sun. Trees increase their transpiration during the morning, decreasing it during the afternoon and into the night. There is a change in the diameter of the trunk or stem that produces a slow pulse. During the evening and the night tree water use is declining, while at the same time, the stem begins to expand again as it refills with water.
When trees drop their branches and leaves its because they’re sleeping. They enter their own type of circadian rhythm known as circadian leaf movement, following their own internal tree clock.
Movement patterns followed an 8 to 12 cycle, a periodic movement between 2 – 6 hours and a combination of the two.
As we know, plants need water to photosynthesize glucose, the basic building block from which their more complex molecules are formed. For trees, this means drawing water from the roots to the leaves. This takes place during daylight hours.
The movement has to be connected to variations in water pressure within the plants, and this effectively means that the tree is pumping fluids continuously. Water transport is not just a steady-state flow, as was previously assumed; changing water pressure is the norm although the trees continue to pulse throughout the night as tree trunks shrink and expand.
The work is just one example of a growing body of literature indicating that trees have lives that are more similar to ours than we could have ever imagined. When we mindlessly destroy trees we are destroying a whole ecosystem and a part of ourselves in the process because we are all related through our genetic make up. A sobering thought, for some.
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