What Makes Fresh Cut Grass Smell?

You know that grassy smell right after you mow the lawn? It’s kinda fresh, or maybe reminds you of spring and warm weather. Grass doesn’t normally smell like that, though. So what’s the deal when it gets cut? Well, when their leaves are injured, grass and other leafy plants make organic compounds for protection. Some of these chemicals called Green Leaf Volatiles, or GLVs, evaporate into the air and produce that signature scent, and we think these GLVs are important signals that attract the predators of grass munching insects. When a leafy plant is damaged, it makes lots of chemicals to protect itself; Some of these chemicals are signaling molecules inside the plant. Jasmonic acid and salicylic acid, for example, help the plant synthesize compounds that make it less appetizing or defend against fungal and bacterial infections. Other signaling molecules like traumatic acid tell the plant to make more cells to close up the wound. Green Leaf Volatiles act a little differently, though. They’re volatile organic compounds, which means they easily become gases and are released into the air. Basically acting as a call for help. See before lawnmowers existed leafy plants were hurt by insects like caterpillars eating them. The wounded plant releases a bunch of GLVs which include chemicals like aldehydes, alcohols, and esters. Some of these chemicals are the culprits behind that fresh grassy smell. But more importantly for the grass, these chemicals act as a dinner signal to other insects like parasitic wasps, which come lay their eggs in the caterpillars and eventually kill them. To figure out how important these smelly chemicals are to plants, a researcher from Texas A&M University was studying a mutant strain of corn that couldn’t make GLVs. And corn is botanically a grass. Over time this mutant corn had more insect damage than its GLV producing counterparts in in a lab setting and in the field. Predatory insects just don’t show up as often to eat their herbivorous pray without a chemical signal to tip them off. So next time you smell that fresh cut grass remember that is just adding insect to injury Thanks for asking and thanks especially to all of our patrons on Patreon who keep these answers coming. If you’d like to submit questions to be answered or get some videos a few days early, go to patreon.com/SciShow and don’t forget to go to youtube.com/SciShow and subscribe. …almost anything to give their little bundle of joy a competitive advantage which has led to the strange explosion of the myth that playing classical music for babies…

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