The Secret Language of Plants – Incredible Plant Intelligence | SLICE SCIENCE

Stefano Mancuso's first trial is with a bean plant. He has grown them under various conditions, in the dark, at different lighting or humidity levels, at varied temperatures, even by modifying the magnetic field that surrounds it. He wants to find out how the bean plants always find the support stick. We did some 100 different experiments and all the times the plants were able to find the supports. So now the idea is that there is some kind of unknown way that the plants use to sense the environment. Skeptical scientists have objected, declaring that the plant is performing a simple mechanical movement and that the plant haphazardly found the nearby support stick. In reply to the critics, Stefano Mancuso placed two plants, one on each side of the stick. As he expected, both plants grew towards the support stick. Our science is a science made by animals for animals. Because we are animals we are unable normally to feel that plants are intelligent and sensitive organisms. Dare we evoke a form of plant brain? Intelligence and sensitivity is not something that is linked to a brain. The brain in itself is a stupid organ. It's just an amount of cells that we have here and every animal has. But if you look at the single cells, they are cells. There is nothing mysterious or supernatural about the cells of our brains. They are just a kind, a specific kind of cells called neurons. But you don't need neurons to make this stuff. You can have other kinds of cells having the same function. So it means transmitting signals from one cell to the other. The tremendous root network that plants possess makes a striking parallel with our highly complex brain circuits. Charles Darwin was one of the first to probe the underground life of plants. He was convinced that plants have command centers at the tip of their roots, known as the apex. Researcher at the University of Bonn in Germany, Dr. Frantisek Beluska works on apex neurobiology. All the root apices, they are coordinated in their activities and growth and they resemble some swarms, for example, insect swarms or birds. Somehow there is some communication, we still don't understand how it is going on, but they are coordinating and behave as one swarm. Frantisek Beluska's research has revealed that within the apex, plants have cells that are very similar to those found in animal muscle cells. The roots are capable of exploring the soil with extraordinary precision, and plants seem to know when to form their flowers or drop their leaves. Could there really be, as Charles Darwin once thought, a single and unique command post? So there is no central organizer and that's why these networks are not vulnerable to some stress situations. These networks can self-organize very effectively and they can survive any bad stress situation. The network resembles very closely the internet network, so one could call it a root wide web. A root wide web, root cells that function independently but in coordination with others. This is the same kind of signal we can record the animal brain. Really these networks are also used to exchange information, not just to provide water or nutrition. We have still no idea how complex the communication there is. Today, we are aware that plants have much to talk about, but we know little or nothing of it. The secret life of plants is slowly unveiled through the research of a few tenacious scientists. Canadian biologist Susan Dudley and her team have found that when the root of the impatience palida touches the root of a plant from another family, the impatience increases its water and light consumption and creates larger leaves. Okay, 20.1 square centimeters. That's a good size leaf. These plants are big. These plants actively know that they have neighbors and actively respond to the presence of neighbors. And each and every leaf, in fact, positions itself to avoid getting shaded by neighboring leaves, even within the same plant. But the impatience's reaction is totally different when its roots come across a family member. We can say that plants know who members of the same family are. And that's important information for them to know. Because members of the same family share genes. And so if you're nice to a member of the same family, if you compete less with it, or even actively share with it, then your genes are being passed on through that family member. Using such tactile root recognition, the plant can advantage its family members. This reveals that plants, in their own way, are capable of altruism. Just as amazing, plants are able to communicate between themselves other than by touch, as Dr. Stefano Mancuso demonstrates. Our Italian scientist has isolated three groups of corn plants. There is no root contact between them. He will then deprive oxygen to one of the groups. After five minutes from the start of the lack of oxygen, we had this group of plants emitting SOS signal to warn the surrounding plant that there is something that is going wrong with oxygen. In this case, we have a group of plants that are emitting a message that is, in a few words, pay attention. There is no more oxygen around. And the other group of plants are receiving this message and, according, they are able to prepare themselves to a future lack of oxygen. Here we have the plants that are without any change in the oxygen and that are not receiving any message. Here we have the plants in red that are producing a gene because they are stressed by the lack of oxygen and they are producing also a message. And the message is taken by the blue plants. They have no problem with oxygen, but they are all the same producing the gene because they are receiving the message. So definitely there is a communication between these two groups of plants. Plants can send and receive messages, but how do they do it? They are really speaking to each other. It's not a kind of language like our language. It's not based on words, but it's based on chemical molecules. Plants are able to produce many thousands of chemical molecules. Each single molecule means something. So when this group of plants are producing specific molecules and this other group of plants are detecting this molecule, this means that there is something wrong. Plants have invented alarm signals to warn their neighbors of an imminent danger. They also practice the art of chemical self-defense. This strange landscape is that of the stinging nettle, where a cocktail of molecules, fungicides and insecticides contain a well-known irritating resin. Hidden beneath their skin are numerous molecules that scientists are only beginning to recognize. On the tomato leaf, these mushroom-looking stems are topped by four cells that contain a repulsive resin that will be released when under attack by a pest. And that's not all. Plants have the amazing ability to release chemical signals that will attract the enemies of their voracious predators. This is the case of corn, when it is attacked by the Spidoptera, a small caterpillar that has a strong appetite for its leaves. These herbivorous insects do enormous damage in the cost to the American farmers, but also European farmers, millions of dollars or euros. To win any battle, it's an advantage to have allies. The Campyletus sonorensis female is the natural enemy of the Spidoptera caterpillar. But just how does this parasite wasp detect such a tiny caterpillar in a giant cornfield? What we were initially thinking is that they would respond to the feces of these caterpillars, or perhaps the body odors of the caterpillars themselves. A feces in our minds is something that is very smelly, and that would be a very reliable source of signals that these wasps could use. But then we were studying this in more detail, and we found that the plants that had been attacked by these caterpillars were much more attractive than feces or the caterpillars themselves. And that's when we started focusing on the signals that the plants produce. To his surprise, Ted Terlings found that the damaged corn leaf releases a particularly odorous molecule, a specific SOS signal that attracts the caterpillar's enemies. This indicator is like a GPS location signal for wasps, who can then target the tiny invisible caterpillar in the heart of the immense cornfield. So that was of course a very exciting moment because we started realizing the plant is doing something to get the enemies of their enemies transmit information to other organisms, like these parasitic wasps, through odors. One single caterpillar munching on a corn leaf releases the odors that attract the wasps. That's what this olfactometer reveals. But the alarm signal is not immediately released. Several hours will have passed between the first caterpillar bite and the liberation of volatile substances. The plant will then produce odors that will soon be emitted by all of its leaves. The feeding by the caterpillar is not really the same as if you would damage a leaf yourself. So you know if you damage a leaf, you can smell that there's a volatile coming off, so there's an odor coming off. But in the case of caterpillar feeding, they actually have something in their spit that the plants recognize and the plants start then producing a different odor that they produce from all the leaves, also the leaves that are not damaged, and that results in a specific signal that alerts these parasitic wasps. These odors are produced to attract the enemies of their enemies. Corn calls upon an insect to do its dirty work. This is the secret route of evolution. Plants have no way to move, no way to physically, directly defend themselves, start fighting with their enemies, and eventually this results in some sort of communication between plant and insect.