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Aaron M. Thode
Address:
Marine Physical Laboratory Scripps Institution of Oceanography University of California, San Diego 9500 Gilman Drive La Jolla, California 92093 USA
Email:
athode@ucsd.edu
Bearing Fruit: Plant Bioacoustics is Blossoming
There is growing interest in how plants transmit, reflect, generate, and perhaps even respond to sound.
Plants comprise about 80% of the Earth’s biomass and capture over 100 billion tons of carbon per year in additional biomass. They form the foundation of the animal kingdom’s food supply; transform our atmosphere; loom over our art, agriculture, and architecture; and inspire work in many scientific disciplines, from genomics to biochemistry to ecology. Yet the role of sound in plant studies has received relatively little study from bioacousticians, remaining a topic more likely found in the realms of urban legend (playing Mozart to your plants) than in peer-reviewed literature.
Indeed, although the Acoustical Society of America (ASA) has an Animal Bioacoustics Technical Committee, nothing is formally organized with respect to plants. However, over the past decade, interest in the relationship between sound and plants has begun to, well, sprout. Over the past two decades, nearly 200 publications on the subject have appeared.
In May 2018, the ASA hosted an exploratory special session on plant bioacoustics that attempted to survey the many ways the field of acoustics intersects with fields of plants. This article germinated from that session, which explored four different topics relating acoustics to plants.
This article begins with reviewing how plants distort and transmit sounds generated by insect pests and then examines some surprising examples of how plants have evolved to reflect and enhance animal sounds, potentially opening new facets in animal-plant interaction studies. The focus then shifts to how plants can generate sounds through photosynthesis and transpiration stress, reviving long-standing interests in using non- invasive passive acoustics to diagnose and measure plant physiology.
Finally, the discussion branches into more speculative territory, as a relatively recent spate of publications suggest that plants can sense and respond to acoustic and mechani- cal stimuli, despite the fact that these organisms lack an identifiable nervous system.
Stem Seismology: How Pest Sounds Disperse in Vegetation
Bioacoustic studies of insect pests have provided the longest paper trail for bioacous- tic plant studies, with papers on the topic of detecting insect pests first appearing in 1909, with a description of the sounds of termites chewing wood (Main, 1909). A few papers per decade then dribbled through the literature during the twentieth century, but over the past 30 years, there has been a substantial jump in literature (132 articles/patents up to 2011) on detecting the presence of agricultural pests on both living and harvested plant material, which is a topic of intense agricul- tural, economic, and environmental interest. Like many acoustic subdisciplines, this advancement in interest can be directly related to the falling costs of hardware
©2019 Acoustical Society of America. All rights reserved. volume 15, issue 4 | Winter 2019 | Acoustics Today | 47 https://doi.org/10.1121/AT.2019.15.4.47