How do tobacco plants use chemical signaling as a defense strategy against predatory behavior?
In: Earth Science
Plants signal to other plants to take defensive measures, like making themselves bitter or poisonous. They do this using airborne chemicals
Tobacco plants release volatile organic compounds (VOCs) to attract hungry predators and summon defensive reinforcements. According to “The Network of Plants Volatile Organic Compounds,” a peer-reviewed article published in [Nature](https://www.nature.com/articles/s41598-017-10975-x), VOCs are chemical signals released through the air or soil. VOCs conveniently serve as a plant’s form of communication and are often used to relay a defensive strategy.
Hannah Devlin, a science editor for the Times and correspondent for [The Guardian Science](https://www.theguardian.com/science/2018/may/02/plants-talk-to-each-other-through-their-roots#:~:text=Others%2C%20take%20a%20more%20combative,chemical%20secretions%20in%20the%20soil), explains that tobacco plants identify predators through DNA indicators in the predators’ saliva. After the first few bites, the tobacco plant sends a chemical distress signal through the air. According to [National Geographic](https://www.nationalgeographic.com/science/phenomena/2010/08/27/tobacco-leaves-emit-warning-chemicals-that-summon-predators-when-mixed-with-caterpillar-spit/#close), the tobacco plant releases green leaf volatiles, a specific VOC, that attracts predators of the pest.
To provide a concrete example, a notable pest of the tobacco plant is the hornworm caterpillar. The hornworm caterpillar is commonly referred to as the tobacco hornworm, as stated in an article published by [Texas A&M](https://citybugs.tamu.edu/factsheets/landscape/chewing/ent-2008/). A paper from [The Max Planck Institute for Chemical Ecology](https://www.sciencedaily.com/releases/2011/04/110425153558.htm) states that the tobacco plant grows sweet, irresistible trichomes on its leaves, which attract hungry caterpillars. Trichomes are small deposits of hairs that grow on the tobacco plant’s outermost layer of cells that protect the plant from injury and water loss. When the caterpillars eat the tobacco plant’s trichomes, the tobacco releases odorous VOCs that summon predators of the caterpillar. Predators respond to the signal and consume the caterpillars.
The big-eyed bug is an active hunter of the hornworm caterpillar. According to a paper published by [The University of Maryland Department of Entomology](https://extension.umd.edu/sites/extension.umd.edu/files/_docs/programs/mdvegetables/Geocoris.pdf), it feeds on adult caterpillars and their eggs.
Tobacco plants are remarkably resilient, and their concealed defensive strategy is brilliant.
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