The music of the plants

A musical instrument for plants

The U1 device for the music of the plants is based on a variation of the Wheatstone bridge, where one or more fixed resistances and a variable one are used to measure variations of impedance (electrical resistance). In the case of the U1 what is being measured is the electrical resistance in the living tissues of plants. These variations can then be translated into a variety of different signals, including MIDI for digital musical instruments, like a synthesizer.

Fluctuations in the electrical potential of tissues can be measured in every living being. In animals and humans, these can also be related to different emotional states.

The project of the music of the plants aims at investigating, in an artistic way, the reactivity of plants to their environment and their ability to communicate and learn.

In 2007, while preparing for a performance, I found myself spending hours playing piano together with a plant. I witnessed the slow development of the process, the subtle changes in the plant’s music in response to the sound of the piano and its own sound was becoming more and more evident to me. This whole experience sparked an interest in me to understand a little more the mysterious world of plants perception and inner life.

Do plants hear?

Plants have their own senses. Some of these can be compared to all five human senses. In addition to those, plants have some 15 other senses that are unique to the vegetal world. For example, they can “sense gravity and magnetic fields and recognise and measure numerous chemical gradients in the air or in the ground”“ (1)

The idea that plants’ way of playing music changes over time when they are exposed to the sounds they are making through the U1 device may make sense from a scientific point of view. In fact, it has been suggested that plants have their own way of perceiving sound vibrations.

Several studies indicate that:

“There is a strong relationship between sound waves and plant growth. Sound waves with specific frequencies and intensities have been shown to have significant effects on a variety of biological, biochemical, and physiological activities including gene expression in plants. However, sound waves with high frequency and intensity can be harmful to the proper growth and development of plants. […] The contents of soluble sugar, protein, and the amylase activity in chrysanthemum increased significantly in response to sound waves with certain intensities (100 dB) and frequencies (1,000 Hz) which indicated that sound stimulation could enhance the metabolism of roots and the growth of Chrysanthemum (Yi, 2003b).” (2)

“The effects of music to improve crop yield and quality have been reported in tomato plants, barley and other vegetables (Hou and Mooneyham, 1999; Spillane, 1991; Xiao, 1990). Weinberger and Measures (1979) reported the effects of intensity in audible sound on the growth and development of Rideau winter wheat. The authors concluded that the vegetative growth response of winter wheat to audible sound was mainly dependent upon both frequency and intensity.” (3)

Plants seem to react to vibrations coming from insects and other plants:

“The ability of plants to increase their defenses in response to micrometer-scale vibrations lends support to recent hypotheses that plants can detect and respond to low-amplitude vibrations produced by neighboring plants (Gagliano et al. 2012a, b, Gagliano and Renton 2013). […] A vibration signaling pathway would complement the known signaling pathways that rely on phloem-borne signals, airborne volatiles, or electrical signals (Wu and Baldwin 2009; Mousavi et al. 2013).” (4)

The roots of the plants seem to be sensitive to a broader range of frequencies than the parts above the ground. They also produce a “clicking” sound, most probably as a byproduct of their growth. Putting together the facts that the roots of a plant both produces and perceives sound we unveil a whole new scenario in our understanding of the communication network that exists underground. Sounds seem to be definitely within the range of communications skills of plants.

Can we talk about “plant awareness”?

There is plenty of scientific evidence showing that plants are intelligent. But can we assume that they are “aware”, that is to say they respond to their environment in a conscious way?

From a scientific point of view, even the word ‘response’ sounds heretic when applied to plants. In 1901 the brilliant Indian scientist Sir Jagadis Chandra Bose (who in his life has produced an incredible amount of forward thinking research and inventions) was put down during the presentation of one of his works by Sir John Burdon-Sanderson, the authority on electro-physiology at that time. The point was that Bose, a physicist, had used the words “electrical responses in…” in his presentation. Burdon-Sanderson wanted him to change those words into “certain physical reactions in…” simply because the word response pertains to the domain of physiology rather than physics. For this reason, the Royal Society did not follow up on the intention of publishing Bose’s work. (5)

In 2005, more than a century later, the Society for Plant Neurobiology was founded following the First Symposium on Plant Neurobiology. This new field aims to “understand how plants perceive, recall and process experience, coordinating behavioral responses via integrated information networks that include molecular, chemical and electrical levels of signaling”. (6)

Their choice of the term ‘neurobiology’ in relation to plants was so controversial to cause a strong reaction in the official scientific world. So much that they had to change their name to Society of Plant Signaling and Behaviour.

This is exactly the shortcoming of our modern knowledge: everything is separated in different fields, each one with its terminology and each one with its dogmas. We are able to reach high peaks sometimes in one field or another, but we often miss what that means in the big picture.

As Paco Calvo, professor of philosophy of science at the university of Murcia, Spain states in his The Philosophy of Plant Neurobiology: A Manifesto:

“Plant neurobiology has taught us that plants have an internal system for organizing sets of behaviors that is functionally similar to the animal nervous system. We can, therefore, approach plant behavior and neurobiology from the point of view of ecological psychology, and analyze the plant-environment system as a whole whose behavior emerges and self-organizes at a particular scale of interaction, the one mandated by ecology. (This may be one reason why plant intelligence has been neglected for so long, but time-lapse photography has evidenced the contrary.) Consistent with this approach, plants may well perceive opportunities for behavioral interaction in the form of affordances.”

It is obvious that plants are highly intelligent beings. Having no brain, in the animal sense, they work on a modular basis, being able to lose about 90% of their bodies and still survive. They have been able to transform the surface of the Earth, making it suitable to host millions of other life forms (including us humans) through a process that, although perfectly explainable on a dry scientific level, actually is closer to magic and miracle than anything else I can think of. Plants make more than 90% of the biomass of the planet, a fact that should gain them the title of „dominating species“ on the Earth (which, in fact, they are).

They have senses that resemble those of animals. In fact, plants can ‘see’, ‘feel’, ‘smell’ and ‘taste’ and, as we have seen, it is not outrageous to think that they can ‘hear’ as well. Plants even present what in psychology is called ‘procedural memory’, the kind of memory that allows us to perform automatic actions without thinking about all the single operations involved in the process. As of yet there is no practical evidence of ‘semantic’ and ‘episodic’ memory in plants, but it is not possible to say what future research may discover.

“The list of plant competencies has been growing at a considerable pace in recent years. Plants can, not only learn and memorize, but also make decisions and solve complex problems. They can sample and integrate in real time many different biotic and abiotic parameters, such as humidity, light, gravity, temperature, nutrient patches and microorganisms in the soil, and many more, courtesy of a highly sophisticated sensorimotor system (Hodge, 2009; Trewavas, 2009; Baluška and Mancuso, 2013) that includes proprioception (Bastien et al., 2013; Dumais, 2013), with sensory information being transduced via a number of modalities. Furthermore, plants can anticipate competition for resources, growing differentially depending upon the future acquisition of minerals and water (Novoplansky, 2015). Plants also exhibit self-recognition and territoriality (Schenk et al., 1999), being able to tell apart own from alien, directing their movements towards their targets of interest (Gruntman & Novoplansky, 2004). Plants can communicate aerially (via released volatile organic compounds—VOCs—Dicke et al., 2003; Baldwin et al., 2006) with members of their own kind and with members of other species. They can even communicate bioacoustically, making and perceiving ‘clicking’ noises (Gagliano et al., 2012). Some plants can tell vibrations caused by predators apart from innocuous ones (the wind or the chirps of insects), eliciting chemical defenses selectively (Appel and Cocroft, 2014). In a sense, plants can see, smell, hear, and feel (Chamovitz, 2012).” (7)

One of the most obvious differences between the behaviour of plants and that of animals and insects is the time scale. The plant world moves at a much slower pace.

Since the invention of time-lapse cameras, we have been able to observe plant life at a more comprehensible speed for us.

This has allowed us to realise that they act pretty much like animals in their search for food. Their roots roam the under soil quickly and largely until they find nutrients, to then stop there for some time like animals do.

Inter-species communication

It is a matter of fact that plants communicate with their environment. Plants like tobacco, corn, tomato and lima beans (to name just a few) can communicate with other species as well. When attacked by an insect, they are able to summon the enemy of that insect as a reinforcement. They are able to understand when contact with another organism needs to be met with defense and counter-attack or when it represents an opportunity for symbiosis.

“A tree that is attacked by caterpillar releases airborne chemicals that will be picked up by neiboughring trees who will start producing chemicals that are toxic for the caterpillars.” (8)

The presence of neurotransmitters such as serotonin, dopamine and glutamate has been observed in plants, although their function is not yet clear. Lactose and myosin, molecules that allow animal muscle cells to move, have been found in an area close to the tip of the roots, which is considered the ‘brain’ of plants. The roots also show a high level of electrical activity.

“Charles Darwin was the first to notice that the root tip is a sophisticated sense organ capable of registering and reacting to different parameters, thus formulating what a century later would become known as the „root-brain hypothesis“. Darwin also wrote and affirmed several times that he considered plants to be the most extraordinary living things he had ever encountered” (9)

The music of the plants provides a fascinating new field of exploration and research around the topic of plant consciousness. On one hand, hearing sounds produced by a plant offers a direct feedback of the state of the plant in its environment, something that anyone who has a beloved plant can enjoy. On the other hand, it allows musicians and music lovers to deepen their ability to listen. When one engages in a musical dialogue with a plant, one enters a different level of awareness. Or should I say, “one should enter” for the dialogue to even take place.

As journalist–activist Professor Michael Pollan puts it in the foreword of Mancuso and Viola’s book “Brilliant Green: the Surprising History and Science of Plant Intelligence”:

“Most people who bother to think about plants at all tend to regard them as mute, immobile furniture of our world – useful enough, and generally attractive, but obviously second-class citizens in the republic of life on Earth. It takes a leap of imagination over the high fence of our self-regard to recognise not only our utter dependence on plants, but also the fact that they are considerably less passive than they appear, and in fact are wily protagonists in the drama of their own lives -and ours.”

Endnotes:

1- Stefano Mancuso – Brilliant Green: The Surprising History and Science of Plant Intelligence

2 – Update on the Effects of Sound Wave on Plants – Md.Emran Khan Chowdhury, Hyoun-Sub Lim and Hanhong Bae

3- Update on the Effects of Sound Wave on Plants Md. Emran Khan Chowdhury, Hyoun-Sub Lim and Hanhong Bae

4- Plants respond to leaf vibrations caused by insect herbivore chewing – H. M. Appel & R. B. Cocroft – Oecologia, August 2014, Volume 175, Issue 4, pp 1257–1266

5- Peter Tompkins & Christopher Bird – “The secret life of plants”

6- Silvia Buffagni – “The music of the plants”

7- Paco Calvo – The Philosophy of Plant Neurobiology: A Manifesto

8- Ian T. Baldwin & Jack C. Schultz – “Rapid changes in tree leaf chemistry induced by damage: evidence for communication between plants”

9- Stefano Mancuso – Brilliant Green: The Surprising History and Science of Plant Intelligence