It is normal for stressed plants to show altered phenotypes, including changes in color, smell, and shape. What is not normal is that plants also “cry.”
But now, scientists say they have unearthed a sound that they say is a cry from plants produced when in stress, dehydrated or cut.
And the airborne sounds can be recorded from a distance and classified, according to researcher Lilach Hadany from Tel-Aviv University in Israel.
“We recorded ultrasonic sounds emitted by tomato and tobacco plants inside an acoustic chamber, and in a greenhouse, while monitoring the plant’s physiological parameters. We developed machine learning models that succeeded in identifying the condition of the plants, including dehydration level and injury, based solely on the emitted sounds,” said the finding published in journal Cell.
Interestingly, the informative sounds may also be detectable by other organisms. thus the reasrrch opens avenues for understanding plants and their interactions with the environment and may have significant impact on agriculture.
The theory is that plants make noises centers on their xylem, the tubes that transport water and nutrients from their roots to their stems and leaves. Water in the the xylem is held together by surface tension, just like water sucked through a drinking straw. When an air bubble forms or breaks in the xylem, it might make a little popping noise; bubble formation is more likely during drought stress.
To investigate plants’ airborne sound emissions, scientists constructed a reliable recording system, where each plant is recorded simultaneously by two microphones. First, they recorded plants within an acoustic box and developed machine learning algorithms to classify the recorded sounds.
Then they tested the system in a greenhouse, while monitoring physiological parameters of the recorded plants.
But the exact mechanism on how plants produce sound need further study because plants do not have vocal cords or lungs.