Hi, I'm Scientific American Podcast Editor Steve Mursky.

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 Tenning House

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 sure-fire 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 ooze as they slide along.

When ecologist John Oruk 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 lipoxygenase, which is known to detect herbivores.

Orux says none of the plants were ever actually attacked.

We just gave them cues that suggested an attack was coming and that was enough to trigger big changes in their chemistry.

Initially, Oric 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 non-specific defense may be a

...