CO2 levels impact plant defenses

CHAMPAIGN, Ill., March 26 (UPI) -- U.S. biologists have determined a plant's defenses against leaf-eating insects decrease as levels of atmospheric carbon dioxide increase.

University of Illinois researchers found soybeans grown at elevated CO2 levels attract many more adult Japanese beetles than do plants grown in lower CO2 levels.

"Currently, CO2 in the atmosphere is about 380 parts per million," said Professor Evan DeLucia, an author of the research. "At the beginning of the Industrial Revolution it was 280 parts per million, and it had been there for at least 600,000 years -- probably several million years before that."

The study led by entomology Professor May Berenbaum used a facility that can expose plants in a soybean field to a variety of atmospheric CO2 and ozone levels without isolating the plants from other environmental influences, such as rainfall, sunlight and insects.

The scientists found not only did insects eat more leaves, as expected, but also soybeans grown at elevated CO2 levels attracted many more adult Japanese beetles, western corn rootworms and Asian soybean aphids than did soybeans in lower CO2 environments.

The research is detailed in the Proceedings of the National Academy of Sciences.