The smell of fresh-cut grass is an attack warning

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We love the smell of fresh-cut grass. But in reality what we are smelling is a warning signal being released by plants under attack.

The pheromones emitted by freshly-mown grass are known as GLVs – short for green leaf volatiles. Scientists believe that GLVs smell good because they remind us of food. Vegetables release GLVs when they are chopped, and fruit releases GLVs as they mature. In other words, we are genetically programmed to react positively to the smell. 

GLVs are a group of volatile organic compounds based on six carbon atoms. Almost all green plants are able to release them, and they typically do so in great quantities when they are attacked or damaged. So the volatiles are actually ‘cries of horror’ from the cut grass which are received by other plants and animals.

A study of corn demonstrated that the plants release GLVs when predators chewed on them. The GLVs made other corn plants produce substances which make them less tasty, preparing for an attack.

Another study showed that a specific predatory beetle, the seven-spot ladybird, reacted to GLVs from soy plants when they were attacked by aphids. The soy plants’ smell summoned the predatory beetle species that eliminate aphids most efficiently.

Scientists have also proved that plants use GLVs to protect themselves against fungi and frost damage.
But not yet against lawn mowers.

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