ITHACA, N.Y. -- When some insects zero in on a flower for nectar, their ultraviolet vision is guided by a bull's-eye "painted" on the plant by chemical compounds. Now, chemical ecologists at Cornell University have discovered a second job for these compounds: warding off herbivores.
Even before a flower bud -- such as the creeping St. John's wort -- opens for business, the same chemicals, called DIPs (for dearomatized isoprenylated phloroglucinols), are both coloring the flower in patterns unrecognizable to the human eye and protecting the plant's reproductive apparatus by killing or deterring caterpillars, the scientists report in the upcoming Proceedings of the National Academy of Sciences (Vol. 98, No. 24).
"Now that we know where to look, anti-feedant chemicals like the DIPs undoubtedly will be found in other plant species, and they offer clues to more natural insect control agents," says Thomas Eisner, Cornell's Schurman Professor of Chemical Ecology and one of six authors of the report. An anti-feedant chemical discourages herbivorous insects and can harm those that don't get the message.
One place DIPs are found is in hops, the female flowers of the commercial hop, which give beer its bitter flavor and also protect against pathogenic microorganisms, Eisner says. "If your beer is safe and enjoyable to drink, you ought to thank a flower."
Also participating in the Cornell study, which was supported by
grants from the National Institutes of Health, were Jerrold Meinwald,
the Goldwin Smith Professor of Chemistry; Athula Attygalle, director
of the Mass Spectrometry Facility in the Department of Chemistry and
Chemical Biology; Mathew Gronquist, graduate student in that
department; Alexander Bezzerides, graduate student in the Department
of Neurobiology and Behavior; and Maria Eisner, senior research
associate in that department, who is Thomas Eisner
Contact: Roger Segelken
Cornell University News Service