Reinaldo José Lopes: What stressed plants say – 03/31/2023 – Reinaldo José Lopes

Among the many priceless passages of “Good Omens: Beautiful Curses”, a comic fantasy novel written by Neil Gaiman and the late Terry Pratchett (1948-2015), there is a scene that subverts the traditional Riponga practice of talking to the little plants so that they grow strong and healthy.

It turns out that the demon Crowley, an agent of infernal forces who has been living in disguise among us since the days of Eden, hears about this custom and thinks it’s an excellent idea – as long as he can add some devilish spice to the conversation. Crowley routinely threatens the plants that decorate his flat, vowing to commit the greatest atrocities against them if they don’t grow right — and thus his pots become the most beautiful in London.

There are no demons in disguise out there traumatizing ferns (as far as we know…), but a new study indicates that plants are perfectly capable of reacting to stressful situations in an audible way — at least if you can pick up ultrasound.

Evidences about this unsuspected plant capacity have just been published in the specialized journal Cell. The data were obtained in the laboratory, with experiments involving mainly tomatoes and tobacco, but also covering several other plants, such as wheat, corn and even cacti.

The research was coordinated by Lilach Hadany, from the University of Tel Aviv, in Israel, and is yet another indication that our habit of describing plants as essentially “dumb” or “dumb” creatures compared to animals is a gross oversimplification.

Although they do not have a nervous system like us and other animals, they rely on sophisticated biochemical communication strategies, exchanging information through their root system or releasing substances into the air when their leaves are bitten by insects, for example.

Hadany and her colleagues obtained their data in the simplest way possible: They set up microphones attached to a tape recorder next to their laboratory tomato plants. Afterwards, they subjected their plants to stressful situations: they went a few days without watering them or they cut their stems.

Because they are ultrasonic, the sounds generated by stressed plants are too high for the human ear to capture them naturally. But it’s easy to “convert” them to a frequency we can hear (it’s essentially the same thing as a singer with a big bass voice singing something from the repertoire of a singer famous for her treble, say).

Once converted, the sound is like someone popping bubble wrap. The similarity perhaps makes sense because it is possible that the noise comes from the formation and “bursting” of air bubbles in the vascular system (the “veins”) of the plants, say the Israeli scientists. Interestingly, the researchers also found that quiet plants are essentially very quiet — the noises, which are emitted between 30 and 50 times an hour, only start when the plant is under stress.

The most interesting thing is open-ended questions, of course. Even if sounds are not produced as a means of communication with other organisms, it is virtually certain that some animals with ultrasonic hearing are capable of capturing them.

And that could influence their behavior in the search for food or in other aspects. And there are even possible implications for agricultural practice —in the use of irrigation, for example—, since the vegetable “crying” appears even before the dehydration of the plant becomes visible. Everything indicates that plants still have much more to tell us, if we know how to listen.

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