The Plant Scream: Is it true?

Yes, some plants do scream when they are stressed. Like any other living thing, plants want to remain alive. Research shows that when plants are cut, they emit ultrasonic sound waves that can be interpreted as a scream. It is undetectable to the human ear. Humans process pain because of their nervous system. Plants lack a proper nervous system, therefore we cannot say the plant's "scream" is due to pain perception. It is rather, a form of communication for survival.

According to a study on tobacco and tomato plants by Tel-Aviv University, plants scream when they are stressed by drought, insects, and also when cut. Organisms that could detect these sounds up to several meters away, responded to protect

themselves. Ultrasound sound produced by plants is detected by high frequency microphones (which are similar to what are used to study bats). Scientists have used these microphones on tomatoes and tobacco plants, in conditions where they are cut or dry, or if they are normally taken care of.

Science is sometimes stranger than fiction: the Harry Potter series had introduced us to the imaginary plant- Mandrake, which screams when uprooted.

They observed that the stressed tomato and tobacco plants emitted waves of high frequencies (65 decibels), when an adult human ear can only hear up to 20 Kilohertz. To investigate plants' ability to emit airborne sound waves, they constructed a reliable recording system in which each plant was recorded simultaneously with two microphones within an acoustically isolated anechoic box.

Plant sound emissions could offer a novel way of monitoring a crop's water state - a question of crucial importance in agriculture. A possible mechanism that could be generating the sounds is cavitation - the process whereby air bubbles form and explode in the xylem. Cavitation explosions have been shown to produce vibrations. Since the sound waves emitted carry information about the state of the plant, it can actually be a very important in communication, and therefore has been favored by natural selection. For example, if plants emit sounds in response to a caterpillar attack, predators such as bats could use these sounds to detect attacked plants and prey on the caterpillars, thus assisting the plants. It can be speculated that plants could potentially hear their drought-stressed or injured neighbors, and react accordingly. Such investigations in the plant bioacoustics field and particularly the ability of plants to emit and react to sounds under different conditions and environments, may reveal a new pathway of signaling, parallel to VOCs between plants and their environment.