What do trees get up to at night?

You might think that a tree just sits there day and night doing very little. However, trees go through many changes between sunrise and sunset, and they even fall asleep at night!

People often think that trees and plants grow at a slow, steady rate, but they actually have a growth spurt at night and plant stems grow their fastest in the hours just before dawn. During the hours of darkness, they also have a really good drink. Absorbing water through their roots, plants pull water molecules from the ground to replace that which has evaporated from its leaves during the day. At night, trees use this time to refill all their leaves and twigs.

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The night-time drinking routine was observed for the first time during an experiment in 2016. Two trees, one in Finland and one in Austria were scanned with lasers to see if there was any change in their shape. In the 2 hours after sunset and the hour before sunrise, the trees both drooped by up to 10cm. This is caused by a drop in water pressure inside the plant cells. In fact, some trees even wrap their leaves away during the night when they are not needed, filling them again with water to open them up just before sunrise.

This raised the question as to why the tree was dropping when it was pumping water back into the plant cells. Scientists have speculated that it might be the tree resting or going to sleep! While they don’t have a central nervous system to ‘sleep’ as much, they do have a circadian rhythm, tuned in to the Earth’s 24-hour cycle, just as humans are. They even do this when they are permanently kept in light. Look after your trees with help from a Tree Surgeon Poole. A Tree Surgeon Poole like Kieran Boyland can advise on keeping your trees healthy.

Trees need a combination of photosynthesis and respiration to live. Photosynthesis is a process that uses sunlight to create a chemical reaction that makes organic materials. It grabs at the carbon dioxide to provide the ingredients for these organic materials, pumping out oxygen that it doesn’t need – but we do!

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Glucose is an important food for plants and trees, just as it is for us. They need it as a source of energy and to burn it, they require oxygen. Therefore, plants and trees breathe in a similar way to us. Respiration doesn’t require sunlight, so when a tree can’t photosynthesise, it can continue breathing or respiring during the hours of darkness.

Trees don’t require as much oxygen as we do, producing up to 4 times more than they need for respiration alone. Therefore, during the day, trees are busy making food and then eating at night. So, the next time you visit the woods at night, it’s not as quiet and peaceful as you imagine. All around, trees are relaxing, drooping, drinking, eating and finally, wrapping up for a little snooze.

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