Ah, the smell of a freshly-mowed lawn. For some people, it’s a favorite summer aroma. But where exactly is it coming from?
What we are really detecting, when we experience the scent of cut grass, is a chemical called auxin. Auxin is a chemical that plants release when they are damaged. In nature, this damage is usually caused by herbivores, while in modern life, it’s caused by lawnmowers.
The primary function of auxin is to initiate a healing process. Much as a blood clot seals a wound and helps it begin to heal, auxin closes off the damaged site on a plant and begins to repair it.
Auxin may also have a communicative function. It is known that plants can detect chemicals in their environments, and detecting the auxin of a neighbor may signal a plant to begin protecting itself from an approaching herbivore, by producing more of the chemicals that make plants unpleasant to eat.
Clearly this defense mechanism is ineffective against an approaching lawnmower, but it is fascinating to think that as you mow your grass, it may be calling “Hey, watch out!” to the other side of the lawn.
Plants are aware of damage that happens to them, and, like any organism, they are motivated to do what they can to avoid it. Whether they experience this damage as what we would call pain is a question we may never be able to answer.