Plants have feelings, too
Haaretz sits down with Daniel Chamovitz, the Tel Aviv botany professor whose new book examines the ways that plants do and don’t resemble human beings.
Daniel Chamovitz wants us to know that plants are sensate beings: They respond to light, to sound, to smells, to gravity. Their behavior even suggests that they have memory. But Chamovitz, a professor of biology at Tel Aviv University, isn’t a mystic or romantic about flora. He doesn’t believe that plants have consciousness, sees no evidence that they prefer Bach to Led Zeppelin (or vice versa) and insists that “there’s no plant that knows how to say ‘Feed Me, Seymour!’” as he writes in his new book, “What a Plant Knows: A Field Guide to the Senses” (Scientific American / Farrar, Straus & Giroux, 192 pages, $23).
The Pennsylvania-born Chamovitz, 49, writes, in clear and comprehensible language, about some of the amazing things discovered by science about plants in recent decades, while coming down hard at the same time on pseudoscience that attributes characteristics to them that don’t stand up to experimentation.
Chamovitz himself became hooked on the subject when his own genetics research turned up a gene sequence shared by plants and humans. Although the same genes have evolved to have completely different functions in these different life-forms, on the cellular level, they function in a similar manner, a reminder that all life is descended from the same single-celled organisms. In the book, Chamovitz proceeds through each of the sensory systems employed by plants, and explains not only how they help them adapt to their environment, but, no less interesting, how scientists devised experiments to ascertain just what plants are capable of.
Haaretz spoke with Daniel Chamovitz by phone from his office in Tel Aviv.
What were you doing growing up in Aliquippa, Pennsylvania? Is that just a fancy way of saying you grew up outside Pittsburgh?
Not at all. Half the people who lived there at the time probably never even made it to Pittsburgh, even though it’s 35 miles away. Actually, my father was born in Aliquippa. It was a mill town. The J&L Steel Corporation imported Serbians, Italians and Poles, and blacks from the South, and the Jews came to sell them clothes.
Aliquippa is really “Pennsyl-tucky,” a place where the first day of deer-hunting season was actually a school holiday. Today, there are maybe a handful of Jews left there, but when my father grew up, the town had two shuls.
Growing up there is probably the reason I made aliyah. Not because of the anti-Semitism, although there was some of that, but more because of the schizophrenia. I went to Young Judea meetings in Pittsburgh. Then, I would return to my working class life in Aliquippa. It made me realize that I either had to assimilate or become religious − or make aliyah. After high school I went to the Machon Lemadrichei Hul [leadership training program] in Israel, after which I had to spend time as a counselor back in the U.S., and so I went to Columbia University for two years. But I finished my BSc at Hebrew University.
What drew you to botany?
It was because of my time at Kibbutz Ketura, where I spent part of my time during the Machon year. When you drive a tractor, you have a lot of time to think. I was in the alfafa fields, and I noticed that when you cut it down it grows back. That’s because the part that grows is hidden underground. Wheat, though, when you cut it down, doesn’t grow back. I thought, if only we can make wheat like alfafa, we could solve world hunger.
I studied plant genetics at the Hebrew University. When I was a postdoc, I studied how plants respond to light. I cloned a group of genes that are necessary for a plant to determine if it’s in the dark or not. While at the time, these genes were only found in plants, I subsequently discovered that these genes are also part of human DNA, which was quite surprising.
Aside from the novelty of it − why does it matter that the same gene occurs in both plants and humans?
It matters first because it means that we can use plants as a model system for studying human biology. For example, almost 20 years after I first discovered these “plant” genes in humans, we now know that they are involved in a number of human diseases, including cancer. Second, and this is relevant to why I wrote “What a Plant Knows,” it made me understand the unity of biology. We tend to think of an animal world and a separate plant world. You forget that 2 billion years ago, we were the same single-celled organisms. No one was talking about that. The question I found fascinating was: How far can we take these comparisons [between humans and plants]? To understand that, we have to look at data and not at subjectivity.
What do you mean by “subjectivity”?
Subjectivity is when people “know,” for example, that their plants respond to music, regardless of what the data shows. [Chamovitz, in the book, describes how repeated laboratory experiments were unable to prove any link between music and plant growth.] During an interview I gave to NPR, one caller told me: “You are wrong about one thing: My plants know when I’m talking to them.” To me that’s sort of like a religious belief. When you’re sure you know something, rational discussion is irrelevant.
On the philosophical level, what does it mean to you to know that plants and people share a number of different senses and genetic sequences?
It helps us to see that we are part of a process of evolution. In order to survive, all organisms need to respond to clues from their environment and adjust their physiology. Being able to adapt is not what makes us human. We think that a brain and neurons are necessary for information-processing. That’s just not true. But there are plenty of organisms that exchange and process information without having neurons.
If plants smell and can feel tactile sensations, does that make them human? Does it make us less human? Of course not. Some people think it’s insulting to humans [to say we share traits with plants]. But rather than defending the human ability to see versus the plant’s ability to sense and respond to light, we should ask what characterizes us as humans. To me, what makes us human is not that we have senses, but that we care, that we think about these things. The fact that we share biology with plants can help us understand our own biology better.
What was the specific discovery you made?
So as I said, there is a group of proteins, a protein complex, that is necessary for a plant to know if it’s in the dark or the light. I discovered that animals also have the genes for this same protein complex. The question is, what do they need it for? At my lab in TAU, we’ve been using fruit flies as a model for all animals. We discovered that when they don’t have this complex, flies get leukemia (yes, flies have blood cells). Now with other scientists at TAU, we’re trying to understand specifically how this complex works. One of the things we’re discovering is that this complex (which we call COP9) is needed for cells (whether from a plant, fly or human) to respond to and fix damage to the DNA. What I find fascinating is that while, at the biochemical level, it’s the exact same COP9, the eventual application of it is different depending on the organism. Plants don’t have blood cells, so they can’t have leukemia. And animals don’t have leaves to be opened in the sunlight.
I can see how discovering things like this can be very exciting, but don’t you have to trudge through thousands of hours of tedium in order to make such a discovery?
Scientists definitely have to be versed in delayed gratification. But, we’re addicted to that “eureka” moment, that one second when you see that truth that no one else knows. It’s like a drug. Also I should add that getting to that moment isn’t all tedium. Science is a very social undertaking, and not many people realize that.
How many eureka moments have you had?
I can count them on one or two hands. Most of them were earlier in my career. As we get older, we get stuck in preconceptions. So that today, my biggest eureka moments come from my students, who still have a certain naivete. Plenty of times, they’ll come to me with an idea, and I’ll say it can’t be true − but often they’re correct.
Has your study of plant biology made you, for example, a believer in God?
Definitely not − but for me that’s an irrelevant question. But one of my closest colleagues is an ordained Orthodox rabbi and I’m sure he’d give a different answer.
People tend to believe that being human is the end-all of evolution. But we’re not. Genetically and chemically, plants are more complex than we are. They have to be, because they are rooted and unmoving. If you’re cold, you can go down to Eilat. If someone’s threatening you, you can run away. If you’re looking for a mate, you can go to a bar. A plant doesn’t have the prerogative of movement. It constantly has to adapt.
I’m not saying that the human brain isn’t amazing. I’m just saying that from a genetic point of view, plants are more complex. It doesn’t make us unique that we make decisions. Even bacteria make decisions. The only thing that makes us unique is that we reflect upon those things.
Why am I pressing on about plants so much? We have to accept that in 30 years, we’ll be 9 billion people on the planet, and we will have to feed them. We’re completely dependent on plants for clothes, medicines, food and of course oxygen.
If we don’t understand how plants sense and respond to their environments, we may not be able to ensure our own supplies of plant-grown products. I think that plant biology needs to be given equal footing with human biology. That’s why Tel Aviv University, through the Manna Center for Plant Biosciences, of which I’m director, is now developing a new academic program in food security and safety. And we take all of these issues into account.
You mention the book “The Secret Life of Plants” several times in the book, and say it did a lot of damage. How’s that?
“The Secret Life of Plants” [which was published in 1973] comes up every time I give a talk. But a huge amount of the book was based on pseudoscience that has never been reconfirmed. I’m a big believer in science, because it’s self-correcting. True findings may take a long time to be accepted, but they are eventually confirmed. Indeed, several Nobel Prizes were given for discoveries that were originally not believed or under-appreciated.