February 2, 2009

High CO2 levels can hurt soybean plants

U.S. biologists have discovered high atmospheric carbon dioxide levels negatively affect a soybean plant's defenses against leaf-eating insects.

Professor Evan DeLucia and colleagues at the University of Illinois said deforestation and the burning of fossil fuels have significantly increased carbon dioxide levels since the late 18th century.

Currently, CO2 in the atmosphere is about 380 parts per million, DeLucia, an author of the study, said, and it's predicted to reach 550 parts per million by the year 2050.

The study, led by Professor May Berenbaum, used the Soybean Free Air Concentration Enrichment facility at Illinois, which can expose the plants in a soybean field to a variety of atmospheric CO2 and ozone levels.

The researchers said they wanted to know how high CO2 levels affects the insects that feed on the plants.

They found soybeans exposed to higher levels of CO2 exhibited more signs of insect damage than those in nearby plots, attracting many more Japanese beetles, Western corn rootworms and Asian soybean aphids than soybeans in other plots.

The scientists also discovered beetles on the high CO2 soybean plants lived longer, producing more offspring, than those outside the test plot.

The research appeared in the online edition of the Proceedings of the National Academy of Science.