If you grew up in the suburbs, you recognize it immediately: the sweet, sharp smell of someone mowing a lawn or ballfield. As it wafts into your nostrils, it somehow manages to smell exactly like the color green. But what are we really smelling when we inhale that fresh-cut grass scent? And why do we like it so much?
Chemically speaking, that classic lawn smell is an airborne mix of carbon-based compounds called green leaf volatiles, or GLVs. Plants often release these molecules when damaged by insects, infections or mechanical forces — like a lawn mower.
Plants manufacture slightly different forms of GLVs depending on what's happening to them, said Ian Baldwin, a plant ecologist and founding director of the Max Planck Institute for Chemical Ecology in Jena, Germany. In a 2010 study published in the journal Science, he and colleague Silke Allmann, of the University of Amsterdam, found that tobacco leaves punctured and rubbed with insect saliva released a different bouquet of volatile compounds than leaves that had been poked and brushed with water.
植物生态学家、德国耶拿马克斯普朗克化学生态学研究所创始所长Ian Baldwin说，植物制造的GLVs会根据它们所遭遇的不同入侵而略有不同。在2010年发表于《科学》杂志上的一项研究中，他和阿姆斯特丹大学同事Silke Allmann发现，被昆虫侵食和唾液摩擦的烟叶释放出的挥发物，与被水冲刷过后所释放的挥发物不同。
GLVs are small enough to take to the air and float into our nostrils. In some cases, they can be detected more than a mile from the plant where they originated. Other species, such as insects that eat plants and the predators that eat those insects, are extremely sensitive to different GLV aromas. For instance, Baldwin and Allmann discovered that predatory Geocoris bugs are attracted to the GLVs released by plants chewed on by a pest called the tobacco hornworm. In other words, the specific smell of the besieged plants indicates to the predators that a snack is nearby.