How Plants Ward Against Predator Attack: Eavesdropping

Prey animals have to be constantly on guard in order to avoid being eaten by predators. But when you're prey that can't move, this becomes far more difficult. Plants, for example, have to adapt in ways that ward off predators. Now, scientists are taking a closer look at these adaptations and have made some surprising discoveries: plants eavesdrop.

In order to deter predators, plants can boost their production of toxic or unpleasant-tasting chemicals, such as cyanide, sulfurous compounds or acids. They can also build physical defenses that can include thorns or tougher leaves. Yet these defenses come at a cost; the plants spend energy on these defenses that could be better spent in growth or reproduction.

So what causes a plant to "decide" to focus on defense or focus on growth? It turns out that they may have ways to "sense" a predator. In order to better examine plant senses, scientists examined the black mustard, a common roadside weed.

The researchers treated black mustard plants with snail mucus, the trail of slime that these herbivorous predators leave behind them while feeding. They then tested how appealing the resulting plants were to hungry snails. It turns out that the slimed plants were far less palatable to the snails than ones that were slime free.

"That shows that plants are paying attention to generalist herbivore cues and that they turn on their defenses before they even get attacked," said John Orrock, one of the researchers, in a news release.

That's not all they found, though. The scientists also noted that the plants could use the information in a time-sensitive way.

"The more recently they receive the information about impending attack, the more likely they are to use the information to defend themselves," said Orrock. "Not only do they eavesdrop, they eavesdrop in a sophisticated way."

Currently, the researchers are exploring the genetics of induced defenses. The findings could allow them to understand a bit more about how plants adapt to predators, which could aid crops.

The findings were presented at the 2013 Ecological Society of America Annual Meeting in Minneapolis.