[Reading Science] Plants Also Scream When in Distress

Israeli Research Team Publishes Paper in 'Cell'
Ultrasound Emission 35 Times per Hour During Pain

Plants also emit painful screams when their branches are cut or when they are thirsty.

A research team from Tel Aviv University in Israel announced these findings on the 30th (local time) in the international bio-science journal 'Cell'.

The team planted tobacco and tomato plants inside small boxes equipped with special microphones capable of capturing ultrasonic sounds beyond the range of human hearing. The results confirmed that plants emit sounds under stress conditions. When they needed water or had recently been cut, they emitted about 35 ultrasonic sounds (20?100 kHz) per hour. In contrast, unstressed plants emitted ultrasonic sounds only about once per hour. These frequencies are inaudible to the human ear but can be heard by some animals such as bats, mice, and butterflies.

The weather has been cool in the mornings and evenings. On the afternoon of the 19th, a butterfly landed on a yellow cosmos blooming by the Anyangcheon in Yangcheon-gu, Seoul. Photo by Mun Ho-nam munonam@

How do plants produce sounds without lungs or vocal cords? Scientists are currently focusing on the xylem, the pathway that transports water and nutrients from roots to stems and leaves. The xylem consists of xylem vessels and phloem; among these, the xylem vessels contract when the plant draws water, similar to a person using a straw. During this process, bubbles form and burst, producing sounds akin to popping balloons. Especially during droughts, when plants cannot absorb water, more bubbles are generated. However, definitive research results have yet to be established.

The research team also developed a model using artificial intelligence (AI) machine learning that can distinguish, with about 70% accuracy, whether the sounds emitted by plants are due to thirst or pain from cutting. This can be applied to crop management in farms or horticultural facilities. Practicality was also confirmed. Although aided by a computer program trained to eliminate background noises such as wind, recordings made of plants grown in greenhouses rather than laboratories still captured the sounds. Furthermore, it was revealed that not only tobacco and tomato but also wheat, corn, and grapes emit sounds when thirsty.

Previously, the research team also discovered that plants can hear sounds. When the sound of bees flying was played to the beach evening primrose, it was observed to secrete sweeter nectar.