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Sensitive plant or mimosa pudica plant.
Sensitive plant or mimosa pudica plant.

How Plants Talk When We’re Not Around

Some aspects of plant behavior can be studied in the same terms as animal or human behavior

One genuine surprise in recent decades has been the discovery that plants have nervous systems like animals and use some of the same compounds in communications — for example, TMAO to relieve stress and glutamate to speed transmission.

Venus flytrap at work

Biologist Peter Rogers pointed out recently that the similarities may shed a bit of light on issues around anaesthesia. Surprisingly, it is possible to anesthetize a plant. The shameplant (Mimosa pudica) and the Venus flytrap demonstrated that:

Thirty years after anesthesia debuted in the operating room, Claude Bernard, a French physiologist, demonstrated that the shameplant (Mimosa pudica), which bashfully folds into itself when touched, was unresponsive to touch after exposure to ether, a commonly used anesthetic. The plant also folds into itself at night time, but this movement was not affected by anesthesia. Bernard concluded that anesthesia does not inhibit the ability to move; rather, it inhibits the plant’s ability to sense its environment. That is to say, anesthesia blocks consciousness…

Peter Rogers, “How Venus flytraps give scientists insights on consciousness and anesthesia” at Big Think (March 27, 2022)

In 2017, anesthesia was tried on a plant again, this time the Venus flytrap:

According to [plant physiology expert Rainer] Hedrich, Venus flytraps remember when they are touched. When prey lands on the plant’s trap, it brushes against a sensory hair. The hair fires an electrical impulse and releases a wave of signal molecules throughout the trap. After two impulses, the trap closes and imprisons the animal prey. After five impulses, the plant produces digestive enzymes. Because anesthesia disrupts memory in animals, Hedrich hypothesized that anesthesia prevented the plant from remembering each stimulation.

To test this, Hedrich determined if anesthetized flytraps still release signaling molecules. They found that sensory hair still released the signal molecule when stimulated, but the signal did not spread throughout the trap. In an animal, this is similar to local pain receptors detecting pain and releasing local pain signals, but those signals never reaching the brain.

The Venus flytrap’s response to anesthesia suggests that anesthesia affects the plant at cellular and organ levels, similar to animals. And this makes it a model to study general questions related to anesthesia and even consciousness.

Peter Rogers, “How Venus flytraps give scientists insights on consciousness and anesthesia” at Big Think (March 27, 2022)

Well, “consciousness” is going a little far because we’d best be clear what we mean by that. With plants, as with, say, worms, there could be an extensive communications network without any actual consciousness in the sense of an “I” in there. The effect would be roughly similar to a “smart” building, though much more complex. That is, the communications are highly sensitive and extensive, whether or not anyone is actually “home.”

Still, the ways plants communicate are remarkable. For example, one researcher tells us that plants can use RNA to “talk to” neighbours, affecting their gene expression, It was a quite unexpected finding:

Why would a plant need to affect another plant’s gene expression? One possibility, Perata posits, is that “sharing information by exchanging RNA would allow plants experiencing a stress to warn nearby plants, not yet affected by the stress.” Competition could be another explanation, he writes; for instance, if a plant releasing miRNAs “could inhibit physiological functions in a nearby plant,” it could gain “a competitive advantage for the use of resources.” …

[Plant molecular geneticist Hailing]Jin adds that these new findings open a lot of new questions, and that there is likely much more to learn about the role of RNA in plant communication. What we currently know about it is just the “tip of the iceberg,” she concludes.

Alejandra Manjarrez, “Plants Use RNA to Talk to Neighbors” at The Scientist (October 21, 2021)

There are also extensive plant communications via fungal networks:

Simple responses to the facts of nature aid the plant in learning; for example, response to the position of the sun (heliotropism), response to recent temperature changes (vernalization), losing or gaining a response to a stimulus (habituation/dishabituation), and associating one stimulus with another (associative learning). Yes, those last two items are also studied in animal and human psychology.

What about memory? Philosopher Laura Ruggles offers an example:

During the day, the mallow uses motor tissue at the base of its stalks to turn its leaves towards the Sun, a process that’s actively controlled by changes in water pressure inside the plant (called turgor). The magnitude and direction of the sunlight is encoded in light-sensitive tissue, spread over the mallow’s geometric arrangement of leaf veins, and stored overnight. The plant also tracks information about the cycle of day and night via its internal circadian clocks, which are sensitive to environmental cues that signal dawn and dusk.

Overnight, using information from all these sources, the mallow can predict where and when the Sun will rise the next day. It might not have concepts such as ‘the Sun’ or ‘sunrise’, but it stores information about the light vector and day/night cycles that allows it to reorient its leaves before dawn so that their surfaces face the Sun as it climbs in the sky. This also allows it to re-learn a new location when plant physiologists mess with its ‘head’ by changing the direction of the light source. When the plants are shut in the dark, the anticipatory mechanism also works offline for a few days. Like other foraging strategies, this is about optimising available resources – in this case, sunlight.

Laura Ruggles, “The minds of plants” at Aeon (December 12, 2017)

Even though the plant isn’t “thinking,” it has an effective substitute for thinking in the form of cascades of chemical communications. It turns out that nature is much more densely packed with information than we have supposed.

Note: One last thing: Something else plants sometimes do is manipulate pest insects into getting themselves killed:


You may also wish to read:

Plants help each other. Are they self-aware? Can they suffer? Recent discoveries that plants can do many things that we used to think only animals could do raise some interesting questions. The elaborate communications systems in plants underline the fact that information is immaterial but they don’t imply individual consciousness.

and

How plants can count and remember with no brain. Plants like the Venus Flytrap can time things by the chemicals circulating in their systems. Although a mind is required to work with ideas, many natural systems store information by other means. Plants store information about their experiences.


Denyse O'Leary

Denyse O'Leary is a freelance journalist based in Victoria, Canada. Specializing in faith and science issues, she has published two books on the topic: Faith@Science and By Design or by Chance? She has written for publications such as The Toronto Star, The Globe & Mail, and Canadian Living. She is co-author, with neuroscientist Mario Beauregard, of The Spiritual Brain: A Neuroscientist's Case for the Existence of the Soul. She received her degree in honors English language and literature.

How Plants Talk When We’re Not Around