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Hi, I’m scientific American podcast editor Steve Mirsky and here’s a short piece from the May 2018 issue of the magazine in the section we call “advances”, dispatches from the frontiers of science, technology and medicine. Watchful plants by Erica Tennenhouse:

Plants cannot run or hide. So they need other strategies to avoid being eaten. Some curl up their leaves. Others churn out chemicals to make themselves taste bad if they sense animals drooling on them, chewing them up or laying eggs on them, all surefire signals of an attack. New research now shows that some flora can detect an herbivorous animal well before it launches an assault, letting a plant mount a preemptive defense that even works against other pest species.

Snail slime is the lubricating mucus, the animals use as they slide along. When ecologist John Orrick of the University of Wisconsin Madison squirted snail slime into soil, nearby tomato plants appeared to notice. They increased their levels of an enzyme called lypoxygenis, which is known to detect herbivores. Orrick says none of the plants were ever actually attacked, we just gave them cues that suggest an attack was coming and that was enough to trigger big changes in their chemistry.

Initially Orrick found this defense worked against snails. In the latest study, his team measured the slimy warnings impact on another potential threat. The investigators found that hungry caterpillars which usually gorge on tomato leaves had no appetite for them after the plants were exposed to snail slime and activated their chemical resistance. This nonspecific defense may be a strategy that gets the plants more bang for their buck. By further improving their overall odds of survival says Orrick.

He reported the results with his colleagues in the journal ecologia. The finding that a snails approach can trigger a plant response that affects a different animal, intrigued Richard Carbon, a plant communications expert at the University of California, Davis. Carbon was not involved in the study, but he said it is significant that the plants are responding before being damaged and that these cues are having such far ranging effects. Carbon wonders how the tomato plants detected chemicals and snail slime that never actually touched them. Says Orrick, that’s the million-dollar question. He hopes future research will tease out the mechanisms that enable plans to perceive these relatively distant cues.

That was watchful plants by Erica Tennenhouse.