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Conversing with Plants

Plants can’t talk, right? New research from the University of Western Australia suggests we may be wrong!

Source: yinney/stock.xchng

Source: yinney/stock.xchng

Now I know what you’re going to say… “Plants don’t have ears”… and you would be right about that. But you don’t need ears to receive sound.

Sounds are just waves of pressure, like vibrations. So when you’re at a loud music festival and you can feel music vibrating in your chest, these are sound waves. Wavelengths occur at different frequencies, where high frequencies have shorter wavelengths and low frequencies have longer wavelengths (note image below). We hear sound because tiny hairs in our ears pick up the vibrations and our brains translate the vibrations into a sensation that we experience as sound.

Sound waves of different frequencies. Frequency is increasing from top to bottom. Source: Wikimedia commons.

Sound waves of different frequencies. Frequency is increasing from top to bottom. Source: Wikimedia commons.

The research is clear, in fact, that plants can and do respond to the presence of the pressure waves we hear as sound. One famous example of this is the way in which some plant species respond to the vibrations created by the bees that visit the flowers of these species and transfer pollen from one flower to another. Tomatoes and blueberries are among species that will only release pollen from flowers subject to vibration at those specific frequencies associated with the wing movements that generate the buzzing sound made by the bees, a phenomenon the experts have coined “buzz pollination”.

Source: Google creative commons

Source: Google creative commons

However, the issue of whether plants can respond to the presence of these vibrations is different from the issue of whether they can actually use them to communicate, and here is where the story gets really interesting. Scientists generally define ‘communication’ as a message that is intentionally sent and received, and that there is a specific and valuable purpose for this. However, it was believed that plants have actually adapted to only respond to cues (a cue being out of a plant’s control; for example in buzz pollination, where the cue is the vibration of the bees wing).

Enter Monica Gagliano, a researcher at The University of Western Australia. Monica and her colleague, Stephano Mancuso, a professor at The University of Florence, challenged established opinions on this issue with an experiment that asked the question about whether the roots of corn plants were talking.

What they found is incredible. The corn’s roots were clicking!

This ‘clicking’ was a series of regular sounds at 220Hz, which is also a sound frequency humans can hear! But do other plants listen? The answer is yes. The researchers also found that the corn root tips would lean towards the clicking (See image of corn roots below).

Source: Gagliano, Mancuso & Robert, 2012

Source: Gagliano, Mancuso & Robert, 2012

So WHY are they clicking? This question is among those yet to be answered. Yet, Gagliano’s suggests that communication through sound would be very useful, as a way to quickly send and receive information. Just as it is for humans and other animals. In fact, it is likely a vital part of a plants life.  So where does this leave us? According to Gagliano, this is just the tip of the iceberg. What we are looking at are the beginnings of a new way of thinking about plants and their interactions with their environment, including each other.

References / Some serious further reading

Gagliano, M; Renton, M; Duvdevani, N; Timmins, M & Mancuso, S (2012). Acoustic and magnitic communication in plants. Is it possible? Plant Signalling and Behaviour. 7:10, p1-3

Gagliano, M (2012). Green symphonies: a call for studies on acoustic communication in plants. Behavioural Ecology. P1-7

Gagliano, M; Mancuso, S & Robert, D (2012). Towards understand plant bioacoustics. Trends in Plant Science. 17:6, p323-325.

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