Plants Are People Too
(dedicated to our beautiful yard)
I’ve always been fascinated by the plant kingdom, because I’m a science guy, so I’m interested in everything. Let’s not forget that without the oxygen plants supply we couldn’t live, and they also remove CO2 from the atmosphere. For the past few years I’ve been taking care of the fairly large yard here, and I really enjoy it. Pruning, pinching off dead flowers, weeding, I feel I’ve become attuned to the various needs and seasonal rhythms of the shrubbery and trees here. I’m a treehugger anyway, so I feel like I’m on a friendly basis with these guys. Are they grateful for my attentions, or are they even aware of me? Can they in any way be sentient, and what does that mean? I think these are questions worth exploring. First, though, I want to show you how like us plants really are.
Much of my investigation came from two books: What a Plant Knows, by Daniel Chamovitz (2012), and The Secret Life of Plants, by Peter Tompkins & Christopher Bird (1973), a classic work which Chamovitz to some extent rebuffs (I highly recommend both). Like us, plants can be said to have five senses: they can see, feel, smell, taste, and hear, but in slightly different ways. How do plants see? They don’t have eyes, but they do have about a dozen photoreceptors (humans have four). Remember, to a plant, light is both food and time. As with all life, we’re governed by circadian rhythms regulated by the amount of light. And yes, plants being transported long distances can get jet lag too. The tips of the plant are its “eyes,” where the photoreceptors are, but the response to changes in light occurs in the stem, which begins to imply something akin to a nervous system.
They feel heat and cold, or when they’re touched (some don’t care for it while others seem to respond, though more research is needed). A plant knows that a particular vibration in its leaves is that of a munching caterpillar, and manufactures a chemical to make the leaves less tasty. They’ve learned that over millions of generations of genetic memory. The peas and green beans in my garden are constantly feeling around for something to climb onto, and I do my best to keep up with them because it’s to the advantage of both of us (please don’t tell them that I plan to cook and eat them).
Plants smell, taste, and even communicate by means of the wonderful world of chemistry. They create aromas to attract either pollinators or humans so they can proliferate. I think the best idea plants ever had was the flower. Angiosperms, the flowering plants, first appeared about 130 million years ago, and we’re all very grateful. Plants also make salicylic acid as a defense hormone to boost their immune systems. [Note: it’s found in concentration within the bark of the red willow, and the Indians used it as a pain killer. Later, it was synthesized into acetylsalicylic acid, better known as aspirin.] When a plant is attacked by insects or some disease, it emits chemical signals which other plants pick up, like an alert, and respond by chemically girding their loins. The Cuscuta pentagona is a parasitic vine that smells plants it prefers, especially tomatoes. Fruits and vegetables produce ethylene gas during the ripening process, which triggers ripening in its buddies. They’re so sensitive to it they can detect it in ratios as small as 1 in 100 million. It also acts as a regulator of the aging process of leaves that we enjoy as autumn foliage.
Plants can apparently remember, and more than just genetically. The Venus’ fly-trap has thick black hairs on its inner surface. When a fly or something else touches one, nothing happens. But if a second hair is touched within twenty seconds, an electrical circuit is completed and the trap slams shut. It’s easy to call that an automatic response, something instinctual, so let’s look at some experiments from the 20th Century. In 1966 Cleve Backster, who was a prominent authority on the lie detector (polygraph), hooked up a houseplant to the device. He dipped a leaf in hot coffee, with little or no reaction. He thought about burning the leaf with a match, and the moment he was thinking about it, the needle went wild. Two years later he instructed a student to come into the lab each day and torture a geranium, burn it, pull its leaves off, etc. Another student came in each day to nurture or water it. Within a few days, when the torturer approached the plant, the needle reacted so violently it was as if the plant was afraid, or at least anxious. Are we talking about an emotional response? In 1970 at the Timiryazev Academy of Agricultural Sciences in the Soviet Union, a barley sprout had its roots dipped in hot water, and the same reaction was described by one scientist as like a silent scream. So do plants feel pain? Again, we’re talking about something that acts as a nervous system.
Do plants hear? Many people have experimented with different kinds of music, and claim that over time the plant leans towards or away from it, showing discrimination in musical taste, I suppose. They may also be reacting to vibrations from the speakers. A study at the University of Berne, in Switzerland, indicated that in times of drought, pine and oak emit ultrasonic vibrations. Is that a groan of some kind, or another autonomic response? While plants may not have ears, they certainly are aware of different frequencies of sound, as we saw with the caterpillar earlier. They have a sense of balance, too. If one falls or is knocked over, it will bend to grow upwards, just as roots will move back downwards.
Until I began this piece I didn’t know that Charles Darwin devoted much of his later life to a meticulous study of plant behavior. He couldn’t seem to escape the idea that they might be sentient life forms. He thought that what might act as a nervous system was the electrical potential traveling from cell to cell, and he has been proven correct. One of the last things he wrote was about the properties of a plant’s radicle — that part of the plant’s embryo that develops into the root — which “acts like the brain of one of the lower animals.” In the book mentioned above, Chamovitz writes that plants have neuroreceptors, “which function in cell-to-cell signaling in a way similar to our neurons to each other.”
As I kept digging around, I ran across another intriguing way that we and the plants are alike. Hemoglobin, the iron protein that carries oxygen to the rest of the body, is eerily similar to chlorophyll, which plants for photosynthesis of light. Both molecules contain the same proportion of carbon, oxygen, hydrogen, and nitrogen, but in hemoglobin they’re structured around iron (giving blood its red color), and in chlorophyll they’re structured around magnesium. I thought that was fascinating.
The question remains, are plants sentient beings? And what does that mean, anyway? We’re still not sure how to define consciousness, having our own example as our own example, so perhaps anthropocentric bias is inevitable. Animals are conscious, but we don’t know if they’re self-aware. Plants are aware of the visual environment, aromas, chemical signals, and temperature. One of the markers to define higher intelligence is an awareness of the passage of time, and plants are certainly aware of that; they depend on it. If plants are conscious beings, that consciousness might be so different as to be unfathomable, a problem we may face upon contact by an alien race. How to communicate? Well, I can only offer my own experience. We have a monster rhododendron in the front yard, probably a dozen feet high and as wide. After the flowers die each year, they must be pinched off so the plant will put out more blossoms the next year. I pulled 1406 off this guy. It was also severely tangled inside with a thicket of old branches wrapped around each other. This wasn’t like any pruning I was used to, and that section of my Rodale’s didn’t cover it, either. I went in and underneath with the loppers, looked around, and quieted myself. I silently thought, show me where to cut. You can say what you want, but it was a pretty good job, and I doubt I could have done it by myself.
Here in the Northwest, the Coast Salish called them the plant people. That echoes ancient indigenous societies in their view that everything was alive, and therefore deserving of respect. The echo was given new expression by the late master of mythology, Joseph Campbell, as the difference in addressing the natural world as ‘it’ or ‘Thou.’ People have claimed telepathic communication with plants, and I’m not inclined to doubt them. Who knows? Their being many millions of years older than us would have given them ample time to develop an advanced consciousness, unless that wasn’t what they needed to survive and evolve. Maybe instead, after they invented flowers to attract pollinators, they discovered they could use us to improve them, as Michael Pollan hints in The Botany of Desire (book & documentary). For all we know they could be far advanced, and think about us with pity: “Look at those miserable wretches, flying around everywhere all the time. They don’t even have roots to sink into the ground! It’s, like, beyond pathetic.”