Plants under attack signal reinforcements with perfume
An international research team has looked at how field mustard (Brassica rapa) reacted when attacked by insect pests, including caterpillars, aphids and even a slug.
The researchers found that the plants used different odours to attract the natural enemies of that particular insect.
Most surprisingly, different odour bouquets were used in response to exotic as opposed to native herbivores.
They found that the reactions to exotic and native herbivore species were not defined by a single volatile substance, but by the ratio of different volatiles.
The problem with exotic herbivores is that they may induce similar odours as native herbivores, thereby confusing native enemies that may not be able to handle the new hosts.
This was not the case in the study of van Dam and her colleagues: exotic herbivores, even if they had a similar way of feeding as their native counterparts, induced significantly different odour profiles.
Van Dam sees the results as “spectacular proof” of how specifically plants respond to their environment.
“The plants may not have a nervous system, eyes, ears, or mouths, but they are capable of determining who is attacking them.
“Based on this, they can transmit reliable information to specialised parasitic wasps that can learn the odours to find their preferred host.
“What I find truly amazing is that they’re even capable of distinguishing between a native and an exotic herbivore.”