Stefano Mancuso: The roots of plant intelligence

Sometimes I go browsing [through] a very old magazine. I found this observation test about the story of the ark. And the artist that drew this observation test did some errors, had some mistakes -- there are more or less 12 mistakes. Some of them are very easy. There is a funnel, an aerial part, a lamp and clockwork key on the ark. Some of them are about the animals, the number. But there is a much more fundamental mistake in the overall story of the ark that's not reported here. And this problem is: where are the plants? So now we have God that is going to submerge Earth permanently or at least for a very long period, and no one is taking care of plants. Noah needed to take two of every kind of bird, of every kind of animal, of every kind of creature that moves, but no mention about plants. Why? In another part of the same story, all the living creatures are just the living creatures that came out from the ark, so birds, livestock and wild animals. Plants are not living creatures -- this is the point. That is a point that is not coming out from the Bible, but it's something that really accompanied humanity.

Let's have a look at this nice code that is coming from a Renaissance book. Here we have the description of the order of nature. It's a nice description because it's starting from left -- you have the stones -- immediately after the stones, the plants that are just able to live. We have the animals that are able to live and to sense, and on the top of the pyramid, there is the man. This is not the common man. The "Homo studiosus" -- the studying man. This is quite comforting for people like me -- I'm a professor -- this to be over there on the top of creation. But it's something completely wrong. You know very well about professors. But it's also wrong about plants, because plants are not just able to live; they are able to sense. They are much more sophisticated in sensing than animals. Just to give you an example, every single root apex is able to detect and to monitor concurrently and continuously at least 15 different chemical and physical parameters. And they also are able to show and to exhibit such a wonderful and complex behavior that can be described just with the term of intelligence. Well, but this is something -- this underestimation of plants is something that is always with us.

Let's have a look at this short movie now. We have David Attenborough. Now David Attenborough is really a plant lover; he did some of the most beautiful movies about plant behavior. Now, when he speaks about plants, everything is correct. When he speaks about animals, [he] tends to remove the fact that plants exist. The blue whale, the biggest creature that exists on the planet -- that is wrong, completely wrong. The blue whale, it's a dwarf if compared with the real biggest creature that exists on the planet -- that is, this wonderful, magnificent Sequoiadendron giganteum. (Applause) And this is a living organism that has a mass of at least 2,000 tons. Now, the story that plants are some low-level organisms has been formalized many times ago by Aristotle, that in "De Anima" -- that is a very influential book for the Western civilization -- wrote that the plants are on the edge between living and not living. They have just a kind of very low-level soul. It's called the vegetative soul, because they lack movement, and so they don't need to sense. Let's see.

Okay, some of the movements of the plants are very well-known. This is a very fast movement. This is a Dionaea, a Venus fly trap hunting snails -- sorry for the snail. This has been something that has been refused for centuries, despite the evidence. No one can say that the plants were able to eat an animal, because it was against the order of nature. But plants are also able to show a lot of movement. Some of them are very well known, like the flowering. It's just a question to use some techniques like the time lapse. Some of them are much more sophisticated. Look at this young bean that is moving to catch the light every time. And it's really so graceful; it's like a dancing angel. They are also able to play -- they are really playing. These are young sunflowers, and what they are doing cannot be described with any other terms than playing. They are training themselves, as many young animals do, to the adult life where they will be called to track the sun all the day. They are able to respond to gravity, of course, so the shoots are growing against the vector of gravity and the roots toward the vector of gravity. But they are also able to sleep. This is one, Mimosa pudica. So during the night, they curl the leaves and reduce the movement, and during the day, you have the opening of the leaves -- there is much more movement. This is interesting because this sleeping machinery, it's perfectly conserved. It's the same in plants, in insects and in animals. And so if you need to study this sleeping problem, it's easy to study on plants, for example, than in animals and it's much more easy even ethically. It's a kind of vegetarian experimentation.

Plants are even able to communicate -- they are extraordinary communicators. They communicate with other plants. They are able to distinguish kin and non-kin. They communicate with plants of other species and they communicate with animals by producing chemical volatiles, for example, during the pollination. Now with the pollination, it's a very serious issue for plants, because they move the pollen from one flower to the other, yet they cannot move from one flower to the other. So they need a vector -- and this vector, it's normally an animal. Many insects have been used by plants as vectors for the transport of the pollination, but not just insects; even birds, reptiles, and mammals like bats rats are normally used for the transportation of the pollen. This is a serious business. We have the plants that are giving to the animals a kind of sweet substance -- very energizing -- having in change this transportation of the pollen. But some plants are manipulating animals, like in the case of orchids that promise sex and nectar and give in change nothing for the transportation of the pollen.

Now, there is a big problem behind all this behavior that we have seen. How is it possible to do this without a brain? We need to wait until 1880, when this big man, Charles Darwin, publishes a wonderful, astonishing book that starts a revolution. The title is "The Power of Movement in Plants." No one was allowed to speak about movement in plants before Charles Darwin. In his book, assisted by his son, Francis -- who was the first professor of plant physiology in the world, in Cambridge -- they took into consideration every single movement for 500 pages. And in the last paragraph of the book, it's a kind of stylistic mark, because normally Charles Darwin stored, in the last paragraph of a book, the most important message. He wrote that, "It's hardly an exaggeration to say that the tip of the radical acts like the brain of one of the lower animals." This is not a metaphor. He wrote some very interesting letters to one of his friends who was J.D. Hooker, or at that time, president of the Royal Society, so the maximum scientific authority in Britain speaking about the brain in the plants.

Now, this is a root apex growing against a slope. So you can recognize this kind of movement, the same movement that worms, snakes and every animal that are moving on the ground without legs is able to display. And it's not an easy movement because, to have this kind of movement, you need to move different regions of the root and to synchronize these different regions without having a brain. So we studied the root apex and we found that there is a specific region that is here, depicted in blue -- that is called the "transition zone." And this region, it's a very small region -- it's less than one millimeter. And in this small region you have the highest consumption of oxygen in the plants and more important, you have these kinds of signals here. The signals that you are seeing here are action potential, are the same signals that the neurons of my brain, of our brain, use to exchange information. Now we know that a root apex has just a few hundred cells that show this kind of feature, but we know how big the root apparatus of a small plant, like a plant of rye. We have almost 14 million roots. We have 11 and a half million root apex and a total length of 600 or more kilometers and a very high surface area.

Now let's imagine that each single root apex is working in network with all the others. Here were have on the left, the Internet and on the right, the root apparatus. They work in the same way. They are a network of small computing machines, working in networks. And why are they so similar? Because they evolved for the same reason: to survive predation. They work in the same way. So you can remove 90 percent of the root apparatus and the plants [continue] to work. You can remove 90 percent of the Internet and it is [continuing] to work. So, a suggestion for the people working with networks: plants are able to give you good suggestions about how to evolve networks.

And another possibility is a technological possibility. Let's imagine that we can build robots and robots that are inspired by plants. Until now, the man was inspired just by man or the animals in producing a robot. We have the animaloid -- and the normal robots inspired by animals, insectoid, so on. We have the androids that are inspired by man. But why have we not any plantoid? Well, if you want to fly, it's good that you look at birds -- to be inspired by birds. But if you want to explore soils, or if you want to colonize new territory, to best thing that you can do is to be inspired by plants that are masters in doing this. We have another possibility we are working [on] in our lab, [which] is to build hybrids. It's much more easy to build hybrids. Hybrid means it's something that's half living and half machine. It's much more easy to work with plants than with animals. They have computing power, they have electrical signals. The connection with the machine is much more easy, much more even ethically possible. And these are three possibilities that we are working on to build hybrids, driven by algae or by the leaves at the end, by the most, most powerful parts of the plants, by the roots.

Well, thank you for your attention. And before I finish, I would like to reassure that no snails were harmed in making this presentation. Thank you.

(Applause)