Cry Me a River
When they're dehydrated or get parts of themselves cut off, plants, like humans, appear to make sounds akin to crying — and scientists say they've now caught it on audio.
A new study published in the journal Cell and aptly titled "Sounds emitted by plants under stress are airborne and informative," describes how plants aren't just ambiently wailing into the void, but rather make quiet, sad little popping sounds when under stress.
As Nature noted in its write-up of the new paper — which also includes the audio of these stress noises — there's still some question as to how, exactly, plants make these sorts of noises given that they have neither vocal cords nor lungs.
As scientist Lilach Hadany told Nature, the researchers' predominant theory is that the sounds come from the plants' xylems, which are "the tubes that transport water and nutrients from their roots to their stems and leaves."
"Water in the xylem is held together by surface tension, just like water sucked through a drinking straw," Nature notes. "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 record the pops, researchers at Tel Aviv University busted out flower boxes "knitted out" with microphones and found that the popping noises seemed to increase when the plants had recently been cut or hadn't been watered in a while.
Like the "singing" of mushrooms or the "screams" of trees thirsty from climate change, the sounds that the tomato and tobacco plants studied in this research emit are ultrasonic, which means humans can't detect them with just our ears alone — but other animals might be able to, the research suggests.
Led by plant scientist Itzhak Khait, these researchers noted that while there have indeed been prior studies and recordings of plants issuing stress calls, "airborne sounds emitted by stressed plants have not been investigated" — or classified — until now.
Those classifications were made in part by machine learning, which taxonomized the sounds the plants made and "succeeded in identifying the condition of the plants, including dehydration level and injury, based solely on the emitted sounds."
"It is a bit like popcorn — very short clicks," Hadany told Nature of the sped-up and pitched-down noises included in the study. "It is not singing."
More on environmental sadness: They're Dumping $30 Million of Funko Pops Directly Into a Landfill
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