How Do Plants Use Chemical Signalling?

Format
Video Text Images
Subjects
Kiran Gurung
Readability
7.29

How does this align with my curriculum?

How do plants use scents? Learn how some plants use chemical signals to send messages to animals or other plants.

Do you ever spritz perfume or cologne? Maybe you’ve done it to get noticed by someone special. Maybe you’ve done it simply to smell nice and feel good! 

It’s not just us humans who use scents. 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 produced by plants. For example, bees and butterflies are drawn by sweet odours. Beetles prefer spicy or fruity odours.

Left: Bees prefer plants with sweet odours. Right: Beetles prefer plants with spicy or fruity odours.
Left: Bees prefer plants with sweet odours. Right: Beetles prefer plants with spicy or fruity odours. (Source: Bee - Gideon Pisanty (Gidip) גדעון פיזנטי [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)]; Beetle - Insects Unlocked [CC BY 2.0 (https://creativecommons.org/licenses/by/2.0)])

 

Some animals use scent to attract partners. For example, queen bees release pheromones to attract drones (male bees). Musk deer release musk to attract mates. On the other hand, skunks spray to protect themselves from predators.

But guess what? Plants use scents, too!

Some plants use scents to defend themselves. For example, when cabbage white butterfly (Pieris rapae) caterpillars attack certain plants, such as cabbage and broccoli, those plants release scents. The scents produced by the plants, in turn, attract predators of the caterpillar, such as parasitic wasps.

When the caterpillar damages a leaf, the leaf produces volatiles. These volatiles attract predators, like the parasitic wasp, to the caterpillar.
When the caterpillar damages a leaf, the leaf produces volatiles. These volatiles attract predators, like the parasitic wasp, to the caterpillar (Source: © Kiran Gurung, 2018, used with permission).

Have you ever passed by a lawn being mowed and breathed in the earthy scent of freshly cut grass? That scent is actually grass sending out an alarm! Grass releases this scent in response to getting "attacked" by the lawn mower. Unfortunately for the grass, the lawn mower doesn’t have any predators that this scent can attract.

In some cases, when 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 group of VOCs consists of 6-carbon compounds called green leaf volatiles (GLVs), which is what certain plants emit when harmful insects begin feeding on them.
 

Chemical structures of some common green leaf volatiles. From left to right: cis-3-Hexenyl acetate, cis-3-Hexen-1-ol and cis-3-hexenal
Chemical structures of some common green leaf volatiles. From left to right: cis-3-Hexenyl acetate, cis-3-Hexen-1-ol and cis-3-hexenal (Source: Let’s Talk Science based on images created in molview.org ).

 

Can plants talk to each other? (2016) TED-Ed by Richard Karban (2:20)

 

 

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’s smell and appearance in order to attract male bees.

So remember, organic chemistry  is behind all of this communication. A small compound can allow plants or insects to create scents. These scents can enable them to communicate. A compound can seem sweet and inviting to one animal, while another compound can be used to make animals leave the plant alone. Plants can’t move from place to place, but they can use these organic chemicals to “talk” to other plants, and also to animals! Amazing, isn’t it?

Did you know? 

Plants do not just communicate through the air. Sometimes plants communicate with each other underground

Starting Points

Connecting and Relating

  • Are you drawn to any particular smells in nature? (e.g., flowers, soil, wet leaves, cut grass, etc.) What smells do you find pleasing? What smells do you dislike?
  • Do you ever use perfume or cologne? Why/why not?
  • Do you notice the smell of other people? Do you find any of those scents attractive? Explain.

Connecting and Relating

  • Are you drawn to any particular smells in nature? (e.g., flowers, soil, wet leaves, cut grass, etc.) What smells do you find pleasing? What smells do you dislike?
  • Do you ever use perfume or cologne? Why/why not?
  • Do you notice the smell of other people? Do you find any of those scents attractive? Explain.

Relating Science and Technology to Society and the Environment

  • Why do companies incorporate scents into products? What is the value in adding scent?
  • Many public places have become scent-free these days because some people have sensitivities and allergies to particular scents. Is it reasonable to expect people to comply with these regulations? Do you think it is possible to eliminate all scents in public spaces? Why or why not?
  • Discuss the advantages and disadvantages of using green leaf volatiles as pesticides.

Relating Science and Technology to Society and the Environment

  • Why do companies incorporate scents into products? What is the value in adding scent?
  • Many public places have become scent-free these days because some people have sensitivities and allergies to particular scents. Is it reasonable to expect people to comply with these regulations? Do you think it is possible to eliminate all scents in public spaces? Why or why not?
  • Discuss the advantages and disadvantages of using green leaf volatiles as pesticides.

Exploring Concepts

  • What are volatile organic compounds (VOCs)?
  • What is a pheromone? What types of pheromones are there and what functions can pheromones perform? (Note: This question will require additional research)
  • Conduct research to learn more about the type(s) of volatiles or pheromones that a specific plant produces. Outline the role these organic chemicals play in the survival and life cycle of the species.

Exploring Concepts

  • What are volatile organic compounds (VOCs)?
  • What is a pheromone? What types of pheromones are there and what functions can pheromones perform? (Note: This question will require additional research)
  • Conduct research to learn more about the type(s) of volatiles or pheromones that a specific plant produces. Outline the role these organic chemicals play in the survival and life cycle of the species.

Nature of Science/Nature of Technology

  • Design an investigation or survey that compares the identification of scents and preference for different scents. Conduct the investigation or survey with your classmates as subjects.

Nature of Science/Nature of Technology

  • Design an investigation or survey that compares the identification of scents and preference for different scents. Conduct the investigation or survey with your classmates as subjects.

Teaching Suggestions

  • Teachers could use this article to support teaching and learning about types of organic compounds and/or plant and animal adaptations involving the sense of smell. The article introduces the concepts of volatile organic compounds (VOCs) and how plants use scents to communicate
  • Before reading the article, students could answer and discuss the Connecting and Relating questions posed above in a whole class discussion.
  • After reading the article, students could complete a Concept Definition Web learning strategy on volatile organic compounds (VOCs) to help reinforce their understanding of this concept The ready-to-use Concept Definition Web reproducible can be found in [Google doc] and [PDF] formats.
  • As an oral speaking extension, students could also debate the value of having a no-scents policy in their school using a Pros & Cons Organizer to organize their argument. The ready-to-use Pros & Cons reproducible can be found in [Google doc] and [PDF] formats.

Teaching Suggestions

  • Teachers could use this article to support teaching and learning about types of organic compounds and/or plant and animal adaptations involving the sense of smell. The article introduces the concepts of volatile organic compounds (VOCs) and how plants use scents to communicate
  • Before reading the article, students could answer and discuss the Connecting and Relating questions posed above in a whole class discussion.
  • After reading the article, students could complete a Concept Definition Web learning strategy on volatile organic compounds (VOCs) to help reinforce their understanding of this concept The ready-to-use Concept Definition Web reproducible can be found in [Google doc] and [PDF] formats.
  • As an oral speaking extension, students could also debate the value of having a no-scents policy in their school using a Pros & Cons Organizer to organize their argument. The ready-to-use Pros & Cons reproducible can be found in [Google doc] and [PDF] formats.

Learn more

Plants can see, hear and smell - and respond (2017)

Article from the BBC about plant perception.

Ten Fascinating Facts about Aromatic Plants (2017)

Article from the UC Santa Cruz Arboretum and Botanic Garden that discusses the diversity and role of scents in plants.

References

Paré, P., & Tumlinson, J. (1999). Plant volatiles as a defense against insect herbivores. Plant Physiology, 121(2), 325-332. DOI: 10.1104/pp.121.2.325

Rosenkranz, M., & Schnitzler, J. (2016). Plant volatiles. Els, 1-9. DOI: 10.1002/9780470015902.a0000910.pub3

Scala, A., Allmann, S., Mirabella, R., Haring, M., & Schuurink, R. (2013). Green leaf volatiles: A plant’s multifunctional weapon against herbivores and pathogens. International Journal Of Molecular Sciences, 14(9), 17781-17811. DOI: 10.3390/ijms140917781