Above: That freshly-mowed grass smell is an example of plant communication
Image © Pgiam, iStockPhoto.com
Do you ever spritz some perfume or cologne? Maybe you’ve done it to get noticed by your crush, or simply to feel good.
It’s not just us humans who use scents for different things. Did you know that there are lots of fascinating ways that animals and plants use scent to interact with each other?
Did you know? Insects are attracted to specific types of odours of plants. For example, bees and butterflies are drawn by sweet odours, while beetles prefer spicy or fruity odours.
Some animals use scent to attract partners. For example, queen bees release pheromones to attract drones (males).
But guess what: plants use scents, too!
Some plants use scents to defend themselves. For example, when Pieris rapae caterpillars attack certain plants, those plants release scents. These, in turn, attract predators of the caterpillar.
Above: Volatiles of damaged leaf attract predators, like the wasp, to prey on the caterpillar.
Image © Kiran Gurung, 2018
Have you ever passed by a lawn being mowed and breathed in the earthy scent of freshly cut grass? That scent is actually grass crying for help! It releases this scent in response to getting "attacked" by the mowers. Unfortunately for the grass, the lawn mower doesn’t have any predators that this scent can attract.
When these plants are attacked, they release scents in the form of organic compounds called volatiles. Volatile organic compounds (VOCs) are substances that start off as a liquid or solid, but easily become gaseous. One type of VOC are 6-carbon compounds called green leaf volatiles (GLVs), which is what certain plants emit when harmful insects begin feeding on them.
Above: Chemical structures of green leaf volatiles.
Image © Kiran Gurung
Did you know? Many plants emit volatiles to trick animals into helping them pollinate! For example, the flower of the bee orchid (Ophrys apifera) mimics a female bee in smell and appearance in order to attract bees.
Chemistry is behind all this. When you think that a small compound can allow plants or insects to create scents, and that these scents can do some powerful things, chemistry is actually fascinating! One compound can seem sweet and inviting to an animal, while another compound can be used to protect the plant. Plants can’t move from place to place, but they can use these power-packed chemicals to “talk” to other plants, and also to animals!
Plants can see, hear and smell - and respond (2017)
The formation and function of plant volatiles (2002)
Pichersky & J. Gershenzon, Current Opinion in Plant Biology 5
Plant Volatiles as a Defense against Insect Herbivores (1999)
P.W. Paré & J.H. Tumlinson, Plant Physiology 121
Hirshon, American Association for the Advancement of Science