Climate change could help bugs, hurt plants
Higher carbon dioxide levels associated with man-made emissions – generally thought to play into climate change and global warming – appear to make plants, soybeans anyway, more susceptible to insect damage by impairing their chemical defensive systems.
Plants exposed to high carbon dioxide levels in a University of Illinois study lost their ability to produce jasmonic acid, a hormone which starts, when insects attack, a chain of chemical reactions in plant leaves leading to the production of a compound called a protease inhibitor, say UI professors May Berenbaum and Evan DeLucia.
Soybeans use protease inhibitor to protect themselves against damaging pests, Japanese and Western corn root worm beetles in the UI study, published online today by the Proceedings of the National Academy of Sciences. Insects that ingest the protease inhibitor, a type of protein called an enzyme, are unable to digest the leaves properly, eat less and die sooner.
Absent the compound, adult insects feast, live longer and produce more offspring – and do more damage. Berenbaum, who heads the UI Entomology Department, DeLucia, head of the Plant Biology Department, and colleagues want to study whether the effect occurs in other plants, where defensive methods may differ.
Still, Berenbaum said the results raise a new concern in the complex web of impacts from climate change. One school of thought has plants benefitting from more carbon dioxide by accelerating photosynthesis and boosting plant growth.
"That's the multimillion-dollar question," Berenbaum said when asked if the enhanced photosynthesis might offset damage like that identified in the UI study, as well as increased damage from caterpillars and other insect larvae, aphids and other pests likely to thrive with warming.
"I think (their study) undermines the assumption that everything is going to be rosy," she said.