People tend to think of ozone as something in the upper atmosphere that protects the earth’s surface from UV radiation.

At the ground level, however, ozone is a pollutant that damages crops, particularly soybeans.

Lisa Ainsworth, a University of Illinois associate professor of crop sciences and USDA Agricultural Research Service plant molecular biologist, said that establishing the exposure threshold for damage is critical to understanding the current and future impact of this pollutant.

“Most of my research is on measuring the effects of ozone on soybeans, determining the mechanisms of response, and then trying to improve soybean tolerance to ozone so that we can improve soybean yields,” she said.

Ozone is highly reactive with membranes and proteins and is known to damage the human lung. It also harms plants, slowing photosynthesis and accelerating senescence. As a result, they take in and fix less carbon, reducing yield.

Ainsworth said ground level concentrations of ozone are already high enough to damage crop production.

“Ozone reacts very quickly once it enters the leaf through the stomata,” she explained. “It can form other oxygen radicals and also hydrogen peroxide. Then a series of cascading reactions causes a decrease in photosynthesis, reducing stomata conductance.”

The plant’s response to ozone mimics a hypersensitive response to a pathogen attack.

“At quite high concentrations of ozone, you can get leaf bronzing, stippling of the leaves, and necrotic spots,” Ainsworth said. “At really high concentrations, you get cell death.” The metabolic changes then feed forward to affect plant productivity.

Ainsworth’s group conducted a two year study in 2009 and 2010 at the Soybean Free Air Concentration Enrichment (SoyFACE) facility at the U of I South Farms. It was the first dose-response experiment to look at ozone and soybeans under completely open-air conditions.