New Study Sheds Light on Plants Nighttime Defense
By Jim Core
March 28, 2001
Agricultural Research Service
scientists and cooperators have gained new insights into how plants defend
themselves against insect attacks at night, according to findings published in
the March 29 issue of Nature.
James H. Tumlinson, III, and other researchers at the ARS
Center for Medical, Agricultural and
Veterinary Entomology, Gainesville, Fla., originally discovered that when
beet armyworm caterpillars chew on plants, the plants produce chemical aromas
that lure a wasp--a natural enemy of the caterpillars--to attack the crop
pests. They subsequently isolated, identified and artificially produced a
chemical found in the saliva of the caterpillars that prompts corn seedlings to
produce the wasp-attracting chemical aromas.
They soon recognized that different caterpillar species elicit plants to
produce specific chemical aromas that appeal to natural enemies of the very
same caterpillar species. In effect, scientists have discovered that a
caterpillar triggers its own doom mechanism.
More recent findings by ARS entomologists Consuelo M. De Moraes and
Tumlinson, along with Mark C. Mescher of the University of Georgia, shed light on the role of
chemical cues in a host plants nighttime defenses.
Little attention has been given to nighttime volatile response by plants and
its effects on the behavior of nocturnal herbivores, according to De Moraes,
perhaps because it has been assumed that herbivore-induced chemicals occur
mainly during the day.
However, the authors found that tobacco plants (used only as a laboratory
tool) release herbivore-induced plant chemicals during both day and night and
that several volatile compounds are released predominantly at night. These
chemicals were found to be highly repellant to female moths searching for sites
to deposit their eggs. If the moths sense a chemical aroma, it indicates the
crop is already larvae infested, and they find another, safer location for
their offspring to develop.
ARS scientists will conduct further studies that could help plant breeders
develop new crop varieties with enhanced defense systems.
ARS is the chief scientific research agency of the
U.S. Department of Agriculture.
Scientific contact: Consuelo M. De Moraes, ARS Center for Medical,
Agricultural and Veterinary Entomology, Gainesville, Fla., phone (352)
374-5712, fax, (352) 374-5707,