The Electric Tree 🌳

In another report on Chelsea, I read about an exhibit that was in the marquee. It caught my eye because it rather chimed with my interest in the subject of plant consciousness about which I wrote (rather excessively) in a previous newsletter.

On the Enmeshed Positive Pathways floral exhibit by Dmitris Koutroumpas and Gaia Eros Florals, Devon based composer Alex Duncan was capturing the aspect of plant consciousness that those in the field class as electrophysiology. Mr Duncan was transmitting electrical activity from fungi into a synthesiser to produce what he described as ‘otherworldly’ and ‘warbling’ sounds using a device to turn the electrical activity running through fungi into a synthesiser, which then chose the notes to play from a computer. He described the sounds they created as otherworldly, high-pitched and warbling.

Mr Duncan apparently found it exciting from a composer’s point of view, to be getting notes from nature. He said that

mushrooms tended to provide a structured sound, leaving the listener with notes that gently modulated between a couple of different frequencies. Foxgloves created “wild” sounds, and trees oscillated between low and, when distressed, very high notes. He found that in forests, if trucks passed by and created vibrations in the ground, the trees produced “stressed”, more erratic sounds.

As I’ve said, all of this was interesting to me more from the plant consciousness angle and, coincidentally, it also meshed rather well with a talk by Richard Feynman that I’d just listened to on YouTube. Feynman was one of the most brilliant and most talked about physicists in the USA. He worked on the Manhattan Project in the early 1940s, won a Nobel Prize in 1965 and spent the rest of his career as Professor of Theoretical Physics at Caltech. He died in 1988. In addition to books and papers, he left behind a series of astonishingly lucid talks which are wonderfully easy for the layman to understand.

The talk I listened to was about trees. Let’s start with a question: what is a tree? Most people have an answer to that - poetic, biological, horticultural or merely observational. But listen to Richard Feynman on trees and at the end of a whole load of electrophysiology you will be able to answer differently.

He begins by likening a tree to a tube which takes water in at the bottom and sucks it up to the very top. The biggest redwood trees are c 116 metres high ie over 350 feet. Yet, he reminds us, the strongest suction pump in the world can only raise a column of water to ten metres before the column starts to break up. This is because a pump doesn’t pull water up in the literal sense, it reduces pressure at the top and with this system there’s a hard limit. You cannot go below a vacuum (zero pressure) so once you reach that ie the pump is working as hard as it can, the water column can’t stay continuous but breaks into vapour bubbles.

So even an ideal pump can’t lift water higher than 10 metres this way. Capillary action added in might get you another 3 metres, tops. This is all regardless of the diameter of the tube. Galileo and his pupils knew this scientifically and laymen discovered it by finding out that it was not possible to pump water out of coal mines.

Yet, a mature oak tree on a warm windy day will move 400 litres or 80 gallons of water from the earth, against gravity, to its topmost leaf. They accomplish this via what is called the cohesion-tension mechanism. Water molecules ‘stick’ to each other (cohesion) and evaporation at the leaves (transpiration to biologists and botanists) creates a negative pressure which pulls the column upward under tension like a stretched thread.

This system amazed Feynman because, in engineering terms, a long column of liquid under tension should snap (cavitate). Yet trees maintain it reliably - effectively running continuous water columns under negative pressure over heights far beyond that achievable by pumps. A tree is solving a fluid mechanics problem that human engineering struggles with by exploiting the properties of molecules and using distributed, passive processes.

But that is really only the beginning of the story. For further ‘miracles’, we have to look at the fact that it isn’t really water that the tree is moving. It is a solution of sodium, phosphate, potassium etc which actually makes it an electrolyte solution and that is what is being pulled up and through the xylem (which together with the phloem forms the ‘vascular or circulatory system’ of the tree) by molecular attraction from the top. Moreover, the composition of the electrolyte solution (ie the sap) moves throughout the system, responding to the tree’s needs and consequently creating changes in voltage.

An insect bites a leaf and within less than a second an electrical signal leaves the wound site - not a chemical diffusing through tissue but an electrical signal ie a wave of voltage change similar to what happens in our nerves but marginally slower, though the overall the picture is the same. In my aforementioned ‘Down the Rabbit Hole’ piece about plant consciousness, I mentioned that neuroscientists become very upset at the concept of a tree having anything approaching a nervous system.

So, at the time of the stimulus ie the insect bite, electrical communication sends information across the organism and uneaten leaves start producing unpalatable chemicals. Moreover, this type of communication is also proceeding below ground so the forest floor is effectively an electrical mess of wires telling the tree next door what is going on.

This is the physics of biology. A biologist/horticulturalist wouldn’t write about it in these terms - he would discuss it all in biological terms, like ‘The Wood Wide Web’ - mycorrhizal (fungal) networks and root exudates etc. Feynman comments, significantly, that we tend to divide the world quite arbitrarily into different domains. In his domain, physics, a tree presents as a big electrical machine - a giant electrical circuit that grows itself, powers itself, fixes itself, reproduces itself, recycles itself and, conveniently for us, just happens to sequester carbon as a side effect. There’s no engineer on earth who could approach developing something like that and yet trees managed it a few hundred million years ago without any fuss at all.

As he concluded, rather lyrically I thought, we have been looking at the most elegant electrical systems that have ever been produced and calling them scenery.