Title: |
The Light Eaters |
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Author: |
Zoë Schlanger |
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Category: |
Non-fiction |
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Rating: |
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Date Reviewed: |
July 12, 2025 |
In 1973, a book called The Secret Life of Plants was published and became a giant success. The Secret Life Plants described how plants had consciousness; they could communicate with humans, how they could sense and react to human emotions - it was a complete fraud. The fallout of this book meant for the next couple of decades all research into plant senses and abilities was consider pseudo-science and botanists avoided any investigations into plant consciousness. Decades after The Secret Life of Plants, David Rhoades-Davey, a professor at the University of Washington, made a startling discovery. Trees could communicate with each other! Rhoades-Davey learned that when one tree was attacked by leaf-eating caterpillars, it emited chemical compounds to warn the nearby trees of the assault. The nearby trees then pumped toxins into their leaves, so that when the hungry caterpillars arrived, they were unable to chew on the leaves. The findings of Rhoades-Davey were scorned, and he had a hard time publishing his research, but we now know he was right - plants do communicate with each other. In fact, plants are capable of manufacturing and dispersing a host of finely tuned chemicals, such as a scent that will call a specific species of wasp that preys on a particular caterpillar. Botanists now are learning all sorts of astonishing abilities of plants. Can they hear? We don't know how, but the roots of pea plants always drive toward the sound of running water. Some plants use their flowers as a sort-of dish to listen for the humming frequency of bee wings - when the bees approach, nectar is released to the flower. In living beings, electrical signals are transmitted between cells using calcium molecules. There is a jellyfish that has a gene that creates a green bio-flourescence whenever its calcium is electrically stimulated.
This gene can be implanted into any plant or animal and still have the visible green flourescence (the book notes you could even implant the gene in a human and it would work, but it would not be ethical to do so). Researchers inserted the gene into
plants and then stressed the plants by pinching a leaf. A green wave of electrical stimulus can clearly be seen moving through the entire plant - the plant "feels" it is under attack. The mystery is where does this electrical impulse go - plants
have no central nervous system, no brain to react to the electrical signals. Yet the plant is clearly sensing the attack and will respond. More research is required.
Another chapter describes how sunflowers can recognize their kin that are growing nearby. A sunflower will deliberately tilt its stem and move its leaves so as to not shade the leaves of a related nearby sunflower.
But how does the sunflower recognize the presence of the adjacent relative? Can it somehow see the the other plant? We know sunflowers are photosensitive because they turn to follow the sun. Indeed, plants remember where the sun rises, and so at
dawn will turn their leaves to face the direction of the previous sunrise. Below ground, the roots of sunflowers will share a patch of high nutrient soil if they recognize their kin, but otherwise they will attempt to monopolize the patch all to themselves if they detect the roots of a different
species. No one knows how sunflowers can do these things. Are they sensing microbes from the other plants? Soil is densely packed with microbes. Are roots directed by a central plant intelligence, or are they "independent thinkers", like each arm of
an octopus is now thought to possess its own sub-brain that cooperates with main brain but also acts independently.
The most amazing section of the book describes a vine called a boquila in South America that is expert at mimicking nearby plants. If the boquila vine grows near plant A, then it's own leaves will be shaped to closely resemble the plant A leaves.
Further along the vine, its leaves will be re-shaped to match the appearance of a different species of plant. How does the vine do this? Even if placed near a non-native species, such a plant from New Zealand, the boquila vine can mimic its leaves.
Can the vine "see" the other plant leaves? Experiments are ongoing to see if the vine can mimic the leaves of a plastic plant - if it can, then clearly it is getting visual cues and not microbial ones, because an artificial plant doesn't have a microbe community.
There is a whole lot of intriguing information about plants in The Light Eaters. Highly recommended. |
