Trees Have a Heart

By Sara Wright
​Reprinted from Abiquiu News 3/20

​Scientist Diana Beresford Kroeger proved that the biochemistry of humans and that of plants and trees are the same – ie the hormones (including serotonin) that regulate human and plant life are identical. What this means practically is that trees possess all the elements they need to develop a mind and consciousness. If mind and awareness are possibilities/probabilities then my next question isn’t absurd: Do trees have a heartbeat?
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According to studies done in Hungary and Denmark (Zlinszky/Molnar/Barfod) in 2017 trees do in fact have a special type of pulse within them which resembles that of a heartbeat.

To find this hidden heartbeat, these researchers used advanced monitoring techniques known as terrestrial laser scanning to survey the movement of twenty two different types of trees to see how the shape of their canopies changed.

The measurements were taken in greenhouses at night to rule out sun and wind as factors in the trees’ movements.

In several of the trees, branches moved up and down by about a centimeter or so every couple of hours.

After studying the nocturnal tree activity, the researchers came up with a theory about what the movement means. They believe the motion is an indication that trees are pumping water up from their roots. It is, in essence, a type of ‘heartbeat.’ These results shocked everyone. At night, while the trees were resting slow and steady pulses pumped and distributed water throughout the tree body just as a human heart pumps blood. It has been assumed that trees distribute water via osmosis (a process that defies gravity and never made sense to me) but this and other new finding suggests otherwise.

Scientists have discovered the trunks and branches of trees are actually contracting and expanding to ‘pump’ water through the trees, similar to the way our hearts pump blood through our bodies. They suggest that the trunk gently squeezes the water, pushing it upwards through the xylem, a system of tissue in the trunk whose main job is to transport water and nutrients from roots to shoots and leaves.

But what "organ" generates the pulse?

Recently forest science researchers have found that the pulse is mostly generated by diameter fluctuations in the bark only. This was somewhat surprising, as traditionally it was thought that bark is totally decoupled from the transpiration stream of the tree. To better understand this mysterious situation, we need to have a closer look at bark.

Bark can be divided into a dead (outside) and living (inside) section. The living section contains a transport system called phloem. The phloem relocates sugars – produced during photosynthesis in the leaves – to tissues, which require sugars for energy. The direction of transport then leads to a downward directed stream of sugar-rich sap in bark towards the roots. The phloem uses water as transport medium for these sugars, and under certain conditions it appears that this water can be drawn out of the phloem into the transpiration stream of the stem. Plant biologists were able to show that these conditions are most likely to occur during the rapid increase of transpiration in the morning hours. During this time, the tension in the capillaries that transport the water upwards in rapidly increases.

Just like a rubber band, too much tension would cause the water column inside the capillaries to burst; this is one horrible way that trees can die during drought.

To prevent this snapping, water from phloem is drawn into the capillaries, and the loss of water from the phloem causes the stem to shrink. Once the tension in the capillaries declines as a consequence of decreasing transpiration, the formerly lost water will be replaced back into the phloem, and so the stem expands again.

 The exact pathway of this water transfer takes place within the phloem that acts like a sponge that gets saturated and squeezed continuously.

 The only difference between our pulse and a tree’s is a tree’s is much slower, ‘beating’ once every two hours or so, and instead of regulating blood pressure, the heartbeat of a tree regulates water pressure. Trees have regular periodic changes in shape that are synchronized across the whole plant.

It seems obvious to me that the ‘heart’ of a tree extends through its entire trunk just under the bark, the place where the pulse of a tree beats continuously.
 
Part 2   Trees Sleep?
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.