Plant Communication Initiated By Herbivore Interaction

Alterations in phenotype limit the possibility of continued herbivory.

http://www.ice.mpg.de/dbs-staff/hopa/alwe3983/web/main_en.htm

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Predators of herbivores are drawn to the plant; they remove the herbivores.

Parasitoids are drawn to the plant; they attack the herbivores and keep them from eating as much- this increases the number of seeds produced

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Herbivores can be lured to the plant instead of herbivore predators.

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Jasmonic Acid◦ A hormone necessary to stimulate indirect defense

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Extrafloral nectar (EFN)◦Beckons ants◦Beckons carnivorous arthropods

For example, parasitic wasps

Chemicals that are important in sending information◦ Within a species◦ Interspecies

Origin of the word is “semion”, meaning a “signal or mark” One example:

◦ Undamaged wheat seedlings lure aphids◦ Wheat seedlings that are being attacked by a significant number of aphids dispense odors that

keep aphids away

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Diagram by Pare and Tumlinson from the journal Plant Physiology, October 1999, Volume 121, page 326

Insect herbiv

Insects secrete compounds from their mouths when eating such as volicitin. This causes the plant to diffuse volatiles that then attack predators of herbivores, such as parasitic wasps.

Volatiles have structural semblances They are distinct from volatiles diffused by

◦ Undamaged plants◦ Plants not being eaten by herbivores

This implies stimulation of biosynthetic pathways ◦ That are related◦ That are found in a variety of plant types◦ That are perceptible by a wide range of insect

parasitoids and predators

Factors affecting amount or condition◦ Degree of injury◦ Behavior of insects when attacking plant

Factors affecting blend of a volatile compound◦ Type of insect◦ Juvenile or adult insect stage

Other compound classes◦ Aldehydes◦ Short chain alcohols

Secreted in minutes after tissue injury Stimulates extrafloral nectar (EFN) release

in non-injured parts of injured plants Stimulates other local plants Can cause a “defensive response” alone Can be necessary to stimulate a “defensive

response Gaseous nature of volatiles speeds

communication in the damaged plant itself◦ More rapid movement than an internal

communication system

Environmental conditions that cause a plant to produce more HI-VOCs◦ “water stress” (in lima bean plants)

Environmental conditions that cause a plant to produce fewer HI-VOCs◦ Low light intensity (in corn, cotton and lima

beans)◦ Shorter days (in corn, cotton and lima beans)◦ Significant amounts of fertilizers (in celery plants)

Scientists have speculated about why plants would waste metabolic energy to do this.

It is thought this is actually more like eavesdropping on a plant that is “warning” non-damaged parts of itself.

1. Heil, Martin and Silva Bueno, Juan Carlos. (2007). “Herbivore-Induced Volatiles as Rapid Signals in Systemic Plant Responses”. Plant Signal Behav. 2007 May–Jun; 2(3): 191–193. Retrieved from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2634055/

2. Wayra G Navia-Giné, Wayra et al. (2009). “Insect-induced gene expression at the core of volatile terpene release in Medicago truncatula”. Plant Signal Behav. 2009 July; 4(7): 639–641. Retrieved from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2710562/

3. Dicke, Marcel and vanLoon, Joop. (2003). “Multitrophic effects of herbivore-induced plant volatiles in an evolutionary context”. Plant Signaling and Behavior. Retrieved from: www.landesbioscience.com/journals/psb/article/8971

4. Pare, P.W. and Tumlinson, J.H. (1999) “Plant Volatiles as a Defense against Insect Herbivores”. Plant Physiol. 1999 October; 121(2): 325–332. Retrieved from:http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1539229/?tool=pubmed