Monday, August 30, 2010
Ian Baldwin, of the Max Planck Institute for Chemical Ecology in Jena, Germany, and colleagues have discovered a multi-step protective mechanism of tobacco plants against Manduca sexta caterpillars. In response to a chemical in the caterpillars’ larvae, the plants release an odorous substance into air to attract another species of insects, called “big-eyed bugs” (Geocoris). These carnivores come to the scene and attack the caterpillars. The response is triggered within 24 hours, which is a relatively short period of time. The discovery occurred as a result of field studies in a nature preserve in southwestern Utah.
The phenomenon starts with the recognition of the caterpillars by the plant. As a PhD student in the Department of Molecular Ecology Silke Allmann explained, “The plant cannot see its attacker, but plants can sense the digestive substances that attacking larvae have in their oral secretions when these substances come into contact with the leaves.” To test that, the scientists coated some of caterpillars’ eggs on two groups of tobacco plants and glued them. On one of the groups, the glue was mixed with caterpillars’ split. The latter got more attention of the attackers, getting 25% of eggs destroyed against 8% for the other group.
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