Researchers from the U.S., Switzerland and Germany have been studying these phenomena.
They first reported on the Canada goldenrod plant and its response to a known predator, the gall-inducing fly. The fly is known to feed on goldenrod leaves, causing plant damage. However, when plants were exposed to the specific scent of the fly ahead of time, they were able to build up a defense against their predators. Goldenrod that was exposed to the scent was more often passed over by flies looking to lay eggs. The “pre-warned” goldenrod also suffered less leaf damage. Somehow these plants made themselves less desirable to the flies.
In other words, these plants could identify and react to the odor of their predator. This, despite lacking what we would call a “nose” or a “brain.”
In a follow-up study, the researchers successfully isolated the specific odor that the goldenrod detects. First, they trapped 90 male flies in a small chamber and filtered airborne compounds. Then they isolated the exact chemical compound – E-conophthorin – that caused the plants to react.
The researchers used an Agilent gas chromatograph, flame ionization detector and column to analyze the emission samples.
The researchers believe the plants are able to preserve energy by triggering their defenses only when attacks are imminent. But more research needs to be done. How do the plants detect this specific odor? And how do they make themselves less attractive to their predators?
“Despite such intriguing discoveries,” the researchers write, “We currently know relatively little about the occurrence and significance of plant responses to olfactory cues in natural systems.”
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