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The Secret Life of Plants: They Hear, Communicate and Scream

The Secret Life of Plants: They Hear, Communicate and Scream 1

We are all too chauvinistic. Considering ourselves to be the pinnacle of evolution, we distribute all living things in a hierarchy according to the degree of closeness to ourselves. Plants are so unlike us that they seem to be creatures as if not quite alive. 

The biblical Noah was not given any instructions about their rescue aboard the ark. Modern vegans do not consider it shameful to take their lives, and fighters against animal exploitation are not interested in “plant rights.” In fact, they have no nervous system, eyes and ears, they cannot hit or run away. All this makes the plants different, but not defective. They do not lead a passive existence of a “vegetable”, but they feel the world around them and react to what is happening around them. In the words of Professor Jack Schultz, “Plants are just very slow animals.”

They hear

The Secret Life of Plants became public in large part thanks to a book by Peter Tompkins, published in the early 1970s, at the height of the New Age movement. Unfortunately, it turned out to be not free from many delusions characteristic of that time and gave rise to many myths, the most famous of which was the “love” of plants for classical music and contempt for modern music.

 “Pumpkins, forced to listen to rock, deviated from the speakers and even tried to climb the slippery glass wall of the chamber,” – Tompkins described the experiments conducted by Dorothy Retallack.

We must say that Mrs. Retallack was not a scientist, but a singer (mezzo-soprano). Her experiments, reproduced by professional botanists, showed no particular plant response to music of any style. But this does not mean that they hear nothing at all. Experiments have demonstrated over and over again that plants can perceive acoustic waves and react to them – for example, the roots of young corn grow in the direction of a source of oscillations with a frequency of 200-300 Hz (approximately from a small octave salt to a pe first). Why is still unknown.

In general, it is difficult to say why plants need “hearing”, although in many cases the ability to respond to sounds can be very useful. Heidi Appel and Rex Cockcroft have shown that Tal’s rezuhovidka perfectly “hears” the vibrations created by the aphid that devours its leaves. This inconspicuous relative of cabbage easily distinguishes such sounds from ordinary noises like the wind, the grasshopper mating song, or the vibrations caused by a harmless fly on a leaf.

The Secret Life of Plants: They Hear, Communicate and Scream 2
Helen Steiner, with support from Microsoft, is working on the Florence art project, a system for communicating with houseplants. According to the concept, signals can be transmitted to the plant using light and color, and the answer can be recognized by the composition of the emitted volatiles and by the general condition of the plant. A computer algorithm “translates” these signals into words of ordinary human speech.

They scream

This sensitivity is based on the work of mechanoreceptors, which are found in the cells of all parts of plants. Unlike ears, they are not localized, but distributed throughout the body, like our tactile receptors, and therefore it was not immediately possible to understand their role. Having noticed an attack, the rezukhovidka actively reacts to it, changing the activity of many genes, preparing for the healing of injuries and releasing glucosinolates, natural insecticides. 

Perhaps, by the nature of the vibrations, plants even distinguish between insects: different types of aphids or caterpillars cause completely different responses from the genome. Other plants, when attacked, secrete sweet nectar, which attracts predatory insects such as wasps, the worst enemies of aphids. And all of them are sure to warn the neighbors: back in 1983, Jack Schultz and Ian Baldwin showed that healthy maple leaves react to the presence of damaged ones, including defense mechanisms. Their communication takes place in the “chemical language” of volatile substances.

They communicate

This courtesy is not limited to relatives, and even distant species are able to “understand” each other’s danger signals: it is easier to repulse intruders together. For example, it has been experimentally shown that tobacco develops a protective reaction when wormwood growing nearby is damaged. The plants seem to be screaming in pain, warning their neighbors, and to hear this scream, you just need to “sniff” well. However, whether this can be considered intentional communication is still unclear. 

Perhaps in this way the plant itself transmits a volatile signal from some of its parts to others, and the neighbors only read its chemical “echo”. Real communication is provided to them … “mushroom Internet”.

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The root systems of higher plants form close symbiotic associations with the mycelium of soil fungi. They constantly exchange organic matter and mineral salts. But the flow of substances is apparently not the only one moving along this network. Plants whose mycorrhiza is isolated from their neighbors develop more slowly and tolerate testing worse. 

This suggests that mycorrhiza also serves for the transmission of chemical signals – through the mediation, and possibly even “censorship” from the fungal symbionts. This system has been compared to a social network, and is often referred to simply as the Wood Wide Web.

The Secret Life of Plants: They Hear, Communicate and Scream 3
The Swiss startup Vivent offers plant lovers to purchase a ready-made device PhytlSigns. By reading weak electrical signals from the stem or leaves, it converts it into a kind of music, which, according to manufacturers, allows you to assess the state and even “mood” of the plant.

They move

All these “feelings” and “communications” help plants find water, nutrients and light, defend themselves against parasites and herbivores, and attack themselves. They allow you to rebuild metabolism, grow and reorient the position of leaves – to move. The behavior of the Venus flytrap may seem like something incredible: not only does this plant eat animals, it also hunts them. 

But the insectivorous predator is no exception among other flora. Just by speeding up the video of a week in the life of a sunflower, we will see how it turns to follow the sun and how it “falls asleep” at night, covering the leaves and flowers. In high speed shooting, the growing root tip looks exactly like a worm or caterpillar crawling towards the target.

Plants have no muscles, and movement is provided by cell growth and turgor pressure, the “density” of their filling with water. The cells act like a complexly coordinated hydraulic system. Long before video recordings and the time-lapse technique, Darwin drew attention to this, who studied the slow but obvious reactions of the growing root to the environment. 

His book ‘The Movement of Plants’ ends with the famous:

“It is hardly an exaggeration to say that the tip of the root, endowed with the ability to direct the movements of neighboring parts, acts like the brain of one of the lower animals … which perceives impressions from the senses and gives direction to various movements.”

Some scholars took Darwin’s words as another epiphany. Biologist at the University of Florence Stefano Mancuso drew attention to a special group of cells on the growing tips of the stem and roots, which is located at the border between the dividing cells of the apical meristem and the cells of the stretch zone that continue to grow but not divide. Back in the late 1990s, Mancuso discovered that the activity of this “transition zone” directs the expansion of the cells in the stretch zone, and thus the movement of the entire root. This happens due to the redistribution of auxins, which are the main plant growth hormones.

They think?

As in many other tissues, scientists notice very familiar changes in membrane polarization in the cells of the transition zone themselves. The charges inside and outside them fluctuate, like the potentials on the membranes of neurons. Of course, the performance of a real brain will never be achieved by such a tiny group: there are no more than a few hundred cells in each transition zone. But even in a small herbaceous plant, the root system can include millions of such developing tips. In sum, they already give quite an impressive number of “neurons”. The structure of this thinking network resembles a decentralized, distributed Internet network, and its complexity is quite comparable to the real brain of a mammal.

It is difficult to say how much this “brain” is capable of thinking, but Israeli botanist Alex Kaselnik and his colleagues found that in many cases, plants do behave almost like us. Scientists put common seed peas in conditions under which it could grow roots in a pot with a stable nutrient content or in a neighboring one, where it was constantly changing. 

It turned out that if there is enough food in the first pot, the peas will prefer it, but if there is too little, they will start to “take risks”, and more roots will grow in the second pot. Not all specialists were ready to accept the idea of ​​the possibility of thinking in plants. Apparently, she shocked Stefano Mancuso himself more than others: today the scientist is the founder and head of the unique “International Laboratory of Plant Neurobiology” and calls for the development of “plant-like” robots. 

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This call has its own logic. After all, if the task of such a robot is not to work on a space station, but to study the water regime or monitor the environment, then why not focus on plants that are so remarkably adapted to this? And when the time comes to start terraforming Mars, who better than plants will “tell” how to return life to the desert? .. It remains to find out what plants themselves think about space exploration. who are so admirably adapted to it? And when the time comes to start terraforming Mars, who better than plants will “tell” how to return life to the desert? .. It remains to find out what plants themselves think about space exploration. who are so admirably adapted to it? And when the time comes to start terraforming Mars, who better than plants will “tell” how to return life to the desert? .. It remains to find out what plants themselves think about space exploration.

Conclusion
 

Plants have a wonderful sense of the position of their own “body” in space. The plant, laid to one side, will orient itself and continue to grow in a new direction, perfectly distinguishing where is up and where is down. While on a rotating platform, it will grow in the direction of centrifugal force. Both are associated with the work of statocytes, cells that contain heavy statolithic spheres that settle under gravity. Their position allows the plant to “feel” the vertical right.

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