What the tomato said
Even tomatoes will talk from severe stress… Scientists from Tel Aviv and Boston have proven that plants are able to respond to stress from drought or cutting the trunk quite loudly. .. «voice» up to 70 dB, if you translate their voices, sounding in the ultrasonic range, to audible. We asked our biologists to explain this effect.
So far, talking plants have only been found in science fiction.
People tend to spiritualize plants. Well, you must admit, each of us at least once talked with his favorite flower on the windowsill, urging him to bloom faster, for example. Unfortunately, there is no reliable information that they hear us, but the fact that they feel pain and react to it with their ultrasonic voice is now our reality. The idea of the plant kingdom, which was previously considered silent, has been changed by a group of scientists from Israel and the United States, whose article was recently published in a fairly authoritative scientific journal.
We could already judge that a plant is under stress, but only by a change in its appearance. Now, it turns out, we can not bring matters to the point that our favorite flower will wither, but hear his “call for help” much earlier? Scientists conducted an experiment by bringing special microphones to the plants, which picked up changes in the ultrasonic range of waves. After the “voices” of the stressed tomato and tobacco were converted to the normal, audible range, the scientists heard characteristic pops. Their frequency and loudness varied depending on the type of plant, on the causes of stress and depending on where it all happened.
An employee of the Federal Research Center «Fundamental Foundations of Biotechnology» of the Russian Academy of Sciences, Candidate of Biological Sciences Alexander Zhgun, helped us figure out how the experiment was carried out:
“At the first stage of the test, Israeli scientists placed plants in a sealed box, isolated from all sounds, put two microphones inside, with the help of which they recorded only those sounds that came from the plant,” Alexander Alexandrovich explains. — Two types of influence were used: the plants were either deprived of watering, or the trunk was cut off. If the whole plant almost did not make any sounds in the ultrasonic range, at a frequency of 20 to 150 kHz, then after the cut it could give out 35–50 claps.
— The water in the vessels of plants is under pressure and saturated with small air bubbles. When the system dries up or collapses as a result of mechanical damage, these bubbles burst, cavitation occurs, which eventually manifests itself as pops. This is reflected in the weak vibration, which was first detected at the ultrasonic level. It turned out that different plants cavitate differently, this can serve as a new diagnostic criterion. It is especially important that some rodents and insects are potentially able to pick up such vibrations, which can be an additional communication factor.
— Each plant has deep fibers — xylemmas responsible for the upward flow of water and dissolved salts from the roots to the leaves, and phloems responsible for the downward flow of organic substances to the roots and other non-photosynthetic organs from the leaves.
— Right. And for this experiment, the researchers recorded the background noise of the greenhouse for several days using the same microphones, so that they could then cancel it out from the noise emitted by the plants. Even a pot of earth was recorded separately in order to exclude possible processes in it that produce sounds elusive to the human ear.
There were no sounds from him. So, having decided on the backgrounds, the scientists set up recording equipment near 23 tomato bushes and began to record them around the clock, never watering them. Interestingly, starting from the 4th day and up to the 6th, their “voices” appeared more and more often, but then the number of claps began to fall. What this may be connected with remains to be studied.
— In the greenhouse, plants that were not watered had fewer sounds than in the acoustic chamber. If in isolation they made several dozen sounds per hour, then in the greenhouse the same number was recorded per day.
— Only if we take the emitted ultrasounds under stress as the main criterion. However, the relationship between their number and the actual state of the plant still needs to be clarified.
— Now no one doubts that plants are alive, but the fact that they can emit ultrasounds is really something new. The Israelis used a sensitive technique that can detect faint sounds in the ultrasonic range. Presumably, in the future, these sounds can be used to establish a system for monitoring the condition of plants in a greenhouse for more timely watering. We put microphones near the plants — when they start clicking like during a drought, we start the automatic watering system, if pests attacked them and they started clicking differently, then we need to come with a chemical and spray from pests.
By the way , sounds can also affect the plants themselves, but this is a completely different noise range, such sounds are clearly audible to us. It was noticed that when irradiated with sounds of a certain intensity, in particular, the growth rate of plants changed. In particular, strong noise pollution with its vibration led to inhibition of growth.
There is also such a thing as the resonance of sounds, which triggers the pollinating insect. When a bee approaches the plant, the anthers (the part of the stamen containing pollen. — Auth.), sensing its approach, enter into resonance and trigger increased maturation of pollen, the release of nectar. Someone will call it «communication», and someone — simple physics.