Could Stressed Plants Be Healthier Plants?

Most growers would never dream of intentionally stressing their crops, but researchers from the University of Maryland think a little bit of strategic neglect might do a lot of good. They’ve just received nearly $600,000 from the National Institute of Food and Agriculture (NIFA) at the U.S. Department of Agriculture to find out for sure.

Associate Professor Shirley Micallef and Professor and Chair John Erwin, both of the Department of Plant Science and Landscape Architecture, are investigating how controlled bouts of stressful growing conditions can boost beneficial plant compounds, reduce foodborne pathogen levels and extend the shelf life of kale and lettuce.

In previous studies, Micallef and her graduate student noticed that plants subjected to drought were less likely to support salmonella growth than normally watered plants. She also found that stressed plants contained higher levels of certain healthy compounds such as flavonoids and other antioxidants.

“That spurred us to try to figure out what’s going on,” Micallef said. “We want to see if there is a connection between these compounds and the levels of bacteria on the plants. We’re not only looking at foodborne pathogens like salmonella, but also spoilage bacteria, which reduce the shelf life of produce.”

The researchers will grow kale and lettuce under different kinds of environmental stress for varying periods of time. For example, they may induce drought or expose plants to short bursts of high temperature or UV light. They will monitor how these conditions impact the levels of beneficial plant compounds and bacteria that cause spoilage and foodborne illnesses.

The study will also include consumer surveys in collaboration with colleagues from the USDA Agricultural Research Service to determine how different experimental conditions impact taste and marketability.

“We are always thinking of ways to optimize growth, so it seems counterintuitive to stress plants out,” Micallef said. “But we now have a controlled environment agriculture industry with plants being grown in greenhouses where growers want to optimize water use and light levels. These conditions are easily manipulated now, and so I think it’s an opportunity for us to ask how we can regulate stress on plants for different purposes.”

Growers aren't advised to start neglecting their leafy green just yet, but the team hopes to have a set of low-tech recommendations for farmers to improve the quality of their crops at the end of the three-year study.