It is not often that you read a book that changes the way you view life. The Light Eaters is such a book. Author Zoe Schlanger grew weary of reporting on climate change, so she searched for a positive story. She found it in plants. She describes how she began her journey, saying, "Plants seemed like the right place to lay my weary, apocalyptic attention. Surely, they would refresh me. But I soon learned they would do more than that. Plants have, over the course of years of obsession, transformed my understanding of what life means and what its possibilities are. Now, as I gaze around, I see more than a soothing wash of green. I see a masterclass in living to one's fullest, weirdest, most resourceful potential."
"Their way of life is so astonishing, I will soon learn, that no one yet really knows the limits of what a plant can do. In fact, it seems that no one quite knows what a plant really is."
The Light Eaters gets us a little closer to understanding them. The author highlights how new technology and creative botanical minds are generating plant epiphanies. Researchers suggest that plants have agency, intelligence, and, possibly, consciousness. The field of botany is rocked by controversy. The mysterious and inspiring nature of plants can no longer be denied. Get ready for a wild ride!
Consider Boquila trifoliata, or the chameleon vine. It grows in Chile, where it climbs up other plants. As it twines its way up a host plant, its leaves change to match the leaves of the host. This sort of mimicry in plants has never been observed before. And it gets crazier! These chameleon vines can climb up and mimic up to four different species of trees simultaneously. No one knows how they do it, but there are competing theories. Some researchers think plants can see and use vision to mimic other plants. Others believe some form of microbial information transfer is at play. Ongoing studies are trying to elucidate the mechanism behind this unbelievable ability.
The author responds to this phenomenon by saying, "Either way, it seems time to dim the lights on the idea of plants as individual entities with neat borders. Where a plant starts and stops is not clearly understood. It may not even be a useful question. Ignoring the many ways plants and their collaborators interact – and, ultimately, constitute the plant itself – leaves us with a very partial view of reality. Plants are composites of interpenetrating forms of life that resist an either-or classification. Perhaps much like us. The completely self-contained individual is a myth that needs to be replaced with a more flexible description. Each of us is a sort of loose committee."
Imagine fern sex, the author suggests. "First of all, they reproduce using spores, not seeds. But here's the kicker: they have swimming sperm. Before they grow into the leaf we all know, they have a completely separate life as a gametophyte fern, a tiny lobe plant just one cell thick – not remotely recognizable as the fern it will later become. You'd miss them on the forest floor. … The sperm alone isn't the most amazing thing about fern reproduction. In 2018, at the beginning of my infatuation, research was emerging to suggest that ferns compete with other ferns for resources by emitting a hormone that causes the sperm of neighboring fern species to slow down. Slower sperm means less of that species survives, so the sabotaging fern can have more of whatever is scarce, be it water, sunlight, or soil."
The fact that plants have agency, and influence over their neighbors and the environment, stirs controversy among botanists. Scientific journals are full of debates about the extent to which plants have nervous systems, intelligence, and consciousness. Part of the challenge is that plants have abilities that far exceed our own in some ways. This should induce humility in us, but being humble is hard.
One of the concerns of critics of plant intelligence is how it will be portrayed in popular culture. If the media simplifies the story too much, the research may seem like a waste of money, and funding can dry up for decades. We have a strong tendency to overlay human narratives on other organisms. Can we trust the public to imagine different intelligences? This would require a mind-expanding leap. Fortunately, the exploits of plants leap off the page in The Light Eaters.
Her story about goldenrods gave me so much to think about. “Researchers have recently found that goldenrods that live in peaceful areas without much threat from predators will issue chemical alarm calls that are incredibly specific – decipherable only to their close kin – on the rare occasion they are attacked. However, goldenrods in more hostile territory signal to their neighbors using chemical phrases easily understood by all the goldenrods in the area, not just their biological kin. Instead of using coded whisper networks, these goldenrods broadcast the threat over loudspeakers. It is the first time research has confirmed that these chemical communications benefit the plant receiving them and the sender."
This new understanding of plant communication prompted Rick Karban, a plant researcher in California, to ask, "If animals have solved their problem in a particular way, it's not unreasonable, I think, to ask, ‘Huh, I wonder if plants have done something analogous.’" Rick studied sagebrush and discovered that the plants he studied have dialects.
“They use specific, coded language to alert their kin to signs of danger and broad generic warnings to communicate more significant threats to all the plants around them. Plants know their neighbors' identity and their enemies' shifting status. They communicate through complex, multi-layered chemical signals that are alive with meaning.”
This prompted Rick to see if plants have personalities. It turns out that sagebrush and other plants have unique individualistic responses to their environment. Rick found that some sagebrush plants send strong distress signals at the slightest threat. The plant community around these types of plants learns not to react to their signals. On the opposite end of the spectrum are the plants that only signal distress when something serious happens. The plant community responds much more strongly to those plants. So clearly, plants can recognize the plant that cried wolf versus the plant that issued a serious warning.
Zoe Schlanger asks: How do they do it? "That is quite literally the essence of the entire question of plant intelligence: How does something without a brain coordinate a response to any stimuli at all? How does information about the world get integrated, triaged by importance, and translated into action that benefits the plant? How can the plant sense its world at all without a centralized place to parse all that information?"
Researchers at the University of Wisconsin have shed some light on this issue by inserting jellyfish genes responsible for producing green fluorescence proteins into plant cells. The offspring of these plants were able to glow green.
These modified plants were growing in a lab where researchers studied how plants respond to their environment. The author visited this lab to see the results of their experiments firsthand. As part of her visit, she took a pair of tweezers and squeezed the leaf of a plant. "The plant lights up like a Christmas tree, the veins blazing like a neon sign. The green luminance moves from the wound site outward, across the rest of the plant, in a bioluminescent ripple. I am watching this plant experience a cascade of feeling. A wave of sensation. As the light travels along the vein system, the image reminds me of something. It looked unmistakably like the branching pattern of human nerves… Within two minutes distant parts of the plant have received the signal."
You can see the bioluminescent ripple in this video.
This is a striking example of how convergent evolution can produce similar ways of being in different organisms. While there is much debate around this, it is clear that plants have a version of a nervous system.
This begs the question of how they coordinate information processing. Researchers are hesitant to discuss this, but a growing number of them are considering the possibility that the entire plant functions as a brain—a distributed network akin to the multiple brains in octopuses.
![This emerald green sea slug is lit up by chloroplasts, which look like tiny stars throughotu its body. It appears to be glowing green along the center of its body. This emerald green sea slug is lit up by chloroplasts, which look like tiny stars throughotu its body. It appears to be glowing green along the center of its body.](https://substackcdn.com/image/fetch/w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F0643bf78-6e70-438f-bc39-1cf3457e422b_1200x1165.jpeg)
Speaking of sea creatures and mind-bending ideas, consider the boundary-spanning Emerald Green Sea Slug. This remarkable creature… "lives in watery places all along the Atlantic coast of the United States and spends its early life a brownish color with a few red dots. It has one goal in those early moments: to locate the hair-like strands of the green algae Vaucheria litorea. When it finds them, it punctures the algae's wall and begins to slurp out its cells as though through a straw, leaving the clear tube of empty algae behind. The algal cells are bright green, owing to the chlorophyll-filled chloroplasts inside them, which are responsible for photosynthesis.
Under a microscope the whole exchange looks uncannily like the slug is drinking bubble tea, one bright green boba entering its mouth at a time. The slug digests the cells but keeps the chloroplasts within them intact, spreading them out through its branched gut. Now, the slug itself has turned from brown to brilliant green. After a few algal bubble teas, the slug never needs to eat again. It begins to photosynthesize. It gets all the energy it needs from the sun, having somehow also acquired the genetic ability to turn the chloroplasts, eating light, exactly like a plant. How this is possible is still unknown. Remarkably, the now-emerald-green slug is shaped exactly like a leaf, except for its snail-like head. Its body is flat, broad, heart-shaped, and pointed at its tail end like a leaf tip. A web of leaflike veins branch across the surface. The slug orients its body in the same way a leaf does, angling its flat surface to maximize the sunlight that falls upon it.
The green sea slug blurs the boundary between animal and plant, but it also offers a striking example of how easily the boundary between organisms and the environment can be traversed. The slug’s essence is acquired through its interaction with its environment."
Nature is an entangled, shape-shifting mirage of organisms. The plants are not who we thought they were, and we are not who we think we are. We are a loose coalition of microbes. We are mutualism in action.
People often do not fit neatly into predefined categories. Many of the scientists featured in this book have unusual backgrounds. Several are introverted and more interested in plants and animals than people. Their interest in and dedication to plants over the decades led to these groundbreaking discoveries. By putting forward unconventional ideas, they risked the ridicule of their colleagues and, in some cases, their careers.
As we learn more about plants, we are also learning more about people. Boundaries blur everywhere you look. Our minds are expanding. We are opening up space for new ways of thinking and new ways of being. Gender used to be bounded by XX and XY, but now we have learned it’s more complicated than we realized. Our labels for neurodiversity are expanding into new territory. We keep trying to place people into categories, but our minds constantly circumvent the system and find a way to express who we are at our core.
Plants and people are weird. We are all weird beyond comprehension, and that is okay. It is the way nature works. We should treasure the inherent nature we were born with and allow our full selves to manifest throughout our lives. We should all reconnect with a childlike state of wonder where anything is possible.
Once I spoke the language of the flowers,
Once I understood each word the caterpillar said,
Once I smiled in secret at the gossip of the starlings,
And shared a conversation with the housefly
in my bed.
Once I heard and answered all the questions
of the crickets,
And joined the crying of each falling dying
flake of snow,
Once I spoke the language of the flowers…
How did it go?
How did it go?
Forgotten Language by Shel Silverstein
Great article!! Just what I needed as I recover from last night’s debate! The world of plants is awesome and beautiful. And the poem was a perfect match.
This was wonderfully mind expanding! As I walk through my garden today, I will look at the plants growing there with new eyes!