Butterflies and moths are welcome visitors to many plant species. Plants attract insect pollinators with the colors, forms, nectars and scents of their flowers to ensure fertilization and reproduction. However, female moths are also threatening to the plant: Once attracted by the flower's scent, they lay their eggs on the green leaves, and shortly voracious young caterpillars hatch. Scientists from the Max Planck Institute for Chemical Ecology have now discovered how tobacco plants successfully solve this dilemma. The researchers found that herbivory changed the opening time of the flower buds from dusk to dawn. In addition the emission of flower scents was dramatically reduced. This change in flower timing was elicited by specific molecules in the oral secretions of the larvae, and required the jasmonate signaling cascade, which is known to elicit a host of other defense responses in plants. Instead of night-active moths, these morning-opening flowers attract day-active hummingbirds which are also able to transfer pollen - without threatening the plant's life.
Outbreak of tomato hornworms
During field experiments performed by PhD students of the Department of Molecular Ecology headed by Prof. Ian T. Baldwin in the Great Basin Desert of Utah (USA) in summer 2007, a massive outbreak of tomato hornworms (Manduca quinquemaculata) occurred. Almost every tobacco plant of the native species Nicotiana attenuata on the field site was attacked by these herbivores which prefer plants of the nightshade family. Danny Kessler intensively studied the infested plants and noticed that these plants had many flowers that opened after sunrise although tobacco is typically a night-flowering plant and usually opens its flower buds after sunset. This finding resulted in experiments conducted in the following two years that showed that the flowering time postponed by 12 hours was directly related to herbivory.
|Contact: Ian T. Baldwin|
Max Planck Institute for Chemical Ecology