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Plants vs. Predators

Marcel Dicke Marcel.Dicke at medew.ento.wau.nl
Thu May 18 07:39:01 EST 1995


In article <3p2qn4$328 at ixnews4.ix.netcom.com>, aregula at ix.netcom.com (Aregula ) says:
>
>I am trying to find out what ways do plants protect themselves against
>predators(insects, animals).  I know of different natural poisons they
>use, but there do not seem to be many ways they can defend themselves
>against pests.  Does anyone know of any natural defense mechanisms
>plants of general variety use?
>
>Any comments would be appreciated.
>Thank you.


Plants can have two basic types of defense:
1. The best-known type is DIRECT defense that affects the herbivore 
directly. This comprises e.g. the use of toxins, digestibility reducers,
hairs, spikes etc. etc.
2. The second type has been studied since the 1980s and is becoming very 
well documented. It is INDIRECT defense, where the plant affects the
effectiveness of carnivorous enemies of plant attacking organisms.
INDIRECT defense can comprise shelters that are used by carnivores
(e.g. the horns of the bullhorn acacia are used as nesting sites by ants
that defend the plant). A more spectacular aspect is that plants RESPOND
to being damaged by herbivorous mites or insects by starting to produce
volatile chemicals that lure the carnivorous enemies of the herbivores.
The plant can disseminate very specific blends of volatiles, e.g.
plants can emit different blends when damaged by different species of
herbivores.
Moreover, the plant sends out the SOS-signals from infested leaves as well
as from uninfested leaves (systemic response).
As also mentioned by Maarten van Helden, there is now evidence that also
uninfested neighbouring plants become attractive to carnivores after being
exposed to the SOS-signals from their infested neighbour.

For more information:
Dicke, M. 1994. Local and systemic production of volatile herbivore-induced
     plant terpenoids: their role in plant-carnivore mutualism. J. Plant
     Physiol. 143: 465-472.
Mattiacci et al. 1995. beta-glucosidase: elicitor of herbivore-induced 
     plant odors that attract host searching parasitic wasps. Proc. Natl.
     Acad. Sci. USA 92: 2036-2040.
Bruin et al. 1995. Do plants tap SOS-signals from their infested 
     neighbours? Trends in Ecology and Evolution 10: 167-170.


Marcel Dicke



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