We learn through observation, memory, and awareness of the world around us. Do plants do the same?
The tunnel is pitch black, leading vertically upwards. There is no sign of the proverbial light at the end, though the pea plant, inching its way upward, hopes against hope that it is up there somewhere. Whether there is or not, it has no choice but to keep moving.
And then, suddenly, it does have a choice. The tunnel splits into two, one going upwards to the left and the other to the right. Which path is the right one? Without any guidance, the best solution is to pick a path at random. But wait! Here comes a gentle breeze from a fan at the end of the tunnel. The pea plant tries that path…and there is no light at the end.
The next day, the same thing happens. A dark tunnel, a mysterious fork, and a blowing wind. The pea plant picks randomly, moving towards the wind again…only to be stranded in darkness. Next time, it tries the path without the fan, and—oh! Sweet, nutritious, energy-giving blue light. But the next day, the random choice takes it towards the fan…
After several days of this, the pea plant learns to avoid the fan. It always takes the non-windy tunnel, and always finds the light.
And then, the behaviour changes: the fan starts appearing on the same side as the light. The pea-plant figures out and adapts to that too. At least, that’s what happened during Dr. Monica Gagliano’s experiment with the common pea, Pisum sativum.
Was the plant actually observing and learning things?
We’ve all heard of the dogs of Ivan Pavlov. Every day, the famous psychiatrist rang a bell before feeding his two hounds, and, over time, they began associating the ring of the bell with being fed. If the bell rang, they would immediately start salivating.
This was Pavlov’s demonstration of “classical conditioning”, an important theory in psychology. Keep experiencing a stimulus (such as the bell ringing) along with an event (being fed), and you start associating the former with the latter. Any being, living or otherwise, that shows evidence of classical conditioning can learn, grow, and change accordingly. You can see why this is useful if you imagine, say, a roaring stimulus being associated with the event of a lion about to pounce on you.
Numerous studies on conditioning have been made—on dogs, on pigeons, and, of course, on humans. But what about our oft unnoticed companions, the plants? Our humble rices, wheats, dals and vegetables? Such a thing seems unimaginable, but all new discoveries require a leap of faith.
Dr. Monica Gagliano took this leap with a running start.
Gagliano’s experiment was quite similar to Pavlov’s, but with peas.
Imagine a plant in a pot, with a small PVC pipe over it. The pipe is split into two tunnels, known as a Y-maze. It can grow to either tunnel undisturbed, but it can’t grow up, unless it wants to meet the plastic. And then, at the end, we have the fan and the light. The fan blows like the ring of a bell and then the blue food appears. If these plants are capable of being conditioned, they’d eventually figure things out and always choose the correct path to get to the light.
That, somewhat astonishingly, is exactly what happened. About 60% of the plants adapted to the fan’s signalling, and ended up always choosing the right path to the light.
In the underbrush, lying next to roads, and sometimes flowering in distinctive pink tufts, this creeping pea-and-legume family member, the Mimosa pudica, is a familiar sight in the countryside. What makes it special? Touch one of its leaves, and the plant will instantly recoil, folding its leaves into sharp thorns.
Mimosa, or “touch-me-not” as the plants are commonly called, are only the most familiar in the category of “plants that move”. Other plant movements are more stunning.
Venus flytraps, for instance, know how to count. Their jaws are lined with trigger hairs, that sense movement. When the trigger hair is touched, a nerve signal jolts through the plant to close its trap. But snapping the trap is an energetically expensive affair. To avoid failed attempts, the Venus flytrap closes its jaws only after something moves and touches at least three different trigger hairs. This prevents it from closing at the breeze or a small bit of leaf.
Beyond such cases of mistaken identity, plants and animals do not differentiate between each other, for much the same reason humans tend not to care too much about plants. What is an animal to a hoofed goat, except inedible? What is a plant to another plant, other than a competitor? Why differentiate between organisms unless there is something important, like if they affect your fitness, or even if they affect your food.
In the nitrogen-poor soil of Borneo, you will find very odd plants, much like large basins with the lid propped open. The lids of these “pitcher plants” secrete nectar, alluring tiny rodent mammals called shrews, which lean over the basin to reach their sweet. While they’re there, why not take the opportunity to finish one’s morning business? Plop goes the poop into the waiting pitcher, floating in a stew of digestive juices until the nitrogen is absorbed by the plant.
Plant, animal, or even poop - what does it matter if it is not useful?
If other creatures don’t differentiate between each other too much, humans certainly do. Veganism may be a relatively recent trend, as things go, but the concept of not killing animals, or avoiding harm to other creatures, is an ancient one. (So, of course, is cannibalism).
The Jain practice of ahimsa or non-violence prohibits killing larger animals. In its stricter forms, it also disallows the consumption of potatoes and other root vegetables, for fear of harming the tiny creatures that live on them under the ground. Similarly, honey is banned because it causes violence to bees, and alcohol is a no-no as lots of microorganisms will be killed in the fermenting process. In fact, the reason Jain monks cover their mouths is to prevent insects and other tiny creatures from being accidentally killed by their breathing.
Other cultures take things a bit more subtly. It may be okay to eat meat that is already served, as long as you don’t go killing creatures yourself. Or you avoid eating animals, but fish don’t count. Modern vegetarianism makes use of science, which tells us what exactly is a plant and what isn’t, so people only have to figure out at what point they consider an egg to have become a chicken.
The principle is simple: Be aware of where your stuff is coming from; take what you need, and not too much.
Vegans too avoid animal products like milk and honey, which don’t kill animals directly but still cause them harm. Of course, there is a limit to what humans can do: as philosopher and writer Rhys Southan pointed out in an essay, if giant aliens landed and started treating humans as vegans treat animals, nothing would stop them clearing out cities to make space for themselves to live, or plundering human food to survive. They make keep a few humans at home and cuddle them as pets, but, even with all the non-violence and non-predation, they’d still be a catastrophe for humanity.
Brush your finger against a touch-me-not plant, and it will instantly recoil—but after a discreet interval, it will reopen its leaves. After all, it does neet to catch the sunlight while it can.
Touch the plant a second time now, and it will again recoil for a while before unfurling. Repeat the process, and the plant will eventually stop opening up altogether. It gets the point: something nasty is around, and it’s not going to go away for a while.
Anyone who’s seen the Mimosa has probably made this observation, but Dr. Gagliano decided to prove it scientifically. To do that, she built an adorable, miniature roller coaster. She then exposed the baby plants to her “death drop”. Over and over, the plants dropped in their little pots by a height of half a foot.
Eventually, after being dropped ten, twenty, thirty times…the delicate leaves of the touch-me-nots stopped folding in on themselves. They stayed out, and proud, after they learned that the stimulus (plant rollercoaster) did not lead to a certain event (being assaulted by a herbivore with gnashing molars).
The most fascinating part? The plants remembered.
After a month of remaining undisturbed, when they were dropped from the rollercoaster again, their leaves stayed out fearlessly.
Dr. Gagliano’s experiments stunned plant scientists across the world. If the plants were learning, did that make them aware of their surroundings? Did it mean these plants have brains? Did it mean these plants, which scientists have subjected to a variety of tests over centuries, can hear, think and feel? Are they…conscious?
That last question depends on what exactly you mean by “consciousness”.
Plants and animals have been found in incredible symbiosis, as have their distant cousins, the fungi. Fungi form massive networks linking roots of trees across forests, uniting them almost as one large organism. They are hardly separable from each other; equally close is the connection between the network and the tree.
But if they are conscious, how conscious would they be? Are they aware of each other's differences, or similarities? Are they aware that they are different organisms, or do they imagine they are one?
Some studies say plants are, in fact conscious, albeit through a different definition: some define consciousness more in terms of reacting to obstacles in the plant's path. One such experiment was conducted by researchers from Spain and Canada who grew twenty French bean plants in a cylindrical booth. They attached a pole on one end and nothing on the other, and found out that it was easier to predict how the plants with poles would grow.
This led them to conclude that plants did have some form of “consciousness”, as it was almost like they could sense the obstacle and grow accordingly.
Conscious plants would cause tremendous problems in the ethical realm. Agriculture would become tremendously unethical, for one. Humans have chosen and bred plant varieties for centuries, teaching them to flower and fruit together. Then, we cut them down in a mass harvest, long stalks of corn screaming silently underneath a tractor.
Perhaps this would not trouble us too much—after all, we need to eat, and we still do factory farm. But what about genetically modified crops, or even plant hybridisation? Is it ethical to change the fundamental code of an organism, then raise it ourselves? What about grafting: if we took two halves of a conscious organism, and then melded it together—would it create a new third? Or would it create two halves, constantly in war, constantly unhappy?
Then there’s the question of deforestation. Centuries old oaks and timber and rainforest, like ancient wise men and women of a tribe, cut down to make someone’s tremendously boring physics assignment, or even an environmental science assignment. But perhaps this should not trouble us too much—after all, we need to write.
What about house plants? We can’t possibly be domesticating wild animals, turning our tables and balconies into dim zoos, trapping plants in pots and forcing them to grow up and sideways and flower when we want. Maybe this would change. Maybe our cement jungles would grow even drabber, as we’d reluctantly let go of plants. Or perhaps, we’d grow them even more, like a captive breeding program, protecting varieties which would otherwise perish.
After Dr. Gagliano, other researchers have attempted to replicate her experiments. So far, nobody has been able to get the same results, putting her findings somewhat in doubt. There’s a possibility that those Mimosa and peas may not have been learning; they might have just happened to appear so due to chance.
This is not the first time people are thinking of plant consciousness though; neither will it be the last. There have always been communities who perceived ecosystems and plants as alive and conscious as part of their culture.
Tribal communities in Rajasthan, India, have been documented to use 36 different plants in a variety of rituals, such as marriages, praying to different Gods, and in worship. Plants of the Eremophila genus have been used by Aboriginal communities across Australia. Interestingly, this particular genus most commonly seems to be burned. The smoke produced from the burning is used for various purposes, including the sterilisation of surgical tools. In today’s world, it partly boils down to terminology.
If plants can learn and are conscious, and sense the same things we do, what does this mean for humanity?
We humans are so far removed from the production process, we often don’t realise the consequences of our consumption—which is why we end up overusing resources and overexploiting the environment, in the way other animals tend not to do. The animal rights and veganism movements have certainly made people more aware of the food they eat and the animals they affect. If people see that plants have feelings too, will that awareness spread further?
Even if we do need a scientific paper to convince us of things that certain communities have believed for centuries, then maybe—just maybe—that will make everyone better protectors than we have been.
Maybe—just maybe—Mimosa and pea plants will help us work for a better world. And then, in time, we will learn to touch them not.
The Editors' Bookshelf
Welcome to The Editors' Bookshelf where you get weekly book recommendations straight from our editors! This week, we have Rhea suggesting Kindred by Octavia E. Butler. When you purchase a book through our Bookshop.org link, we earn a small commission.
I just want to start of by saying wow.
I’ll be honest - I didn’t have the highest expectations when I picked up this book. I read it on a recommendation from a friend and in hindsight, I am so glad I did. In fact, I would have finished it in one sitting, if not for my undesirable but important academic commitments. But I digress.
Kindred follows the story of a young black author named Adana, or Dana as everyone calls her. Newly married and settling into a a new house with her (white) husband Kevin, her life is finally coming together. That is, until she is teleported into 18th century America, where slavery is prevalent, and interracial marriages are unheard of.
Turns out, her life is linked closely to that of her ancestor, Rufus Weylin, and she is summoned to him every time he is close to death. But in a time as dangerous as that one, well, who is to say if she can make it back alive?
Well written and intriguing, this book is definitely one for the ages.
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