The Heat is On
You can’t visit a nursery, greenhouse, or your neighbor’s back porch without seeing them: black plastic pots. Why your new snake plant when the nursery was nice enough to supply a free one? But Department of Horticultural Science graduate student George Guenthner takes issue with that blind acceptance in defense of an unsung hero – the root system – and he’s willing to spend hours meticulously cleaning root masses and monitoring sensor systems to find a solution to a burning question: just how much heat can a root system take?
Heat stress isn’t a new concept. Previous heat stress research has focused on the above-ground portion of the plant, like leaves and buds, but has rarely addressed what’s below the surface. Strong root systems provide a foundation for plant health, but they’re also quite sensitive to their environment.
“Root cell membranes are destroyed by high temperatures.” Think of it like little holes in a water balloon. More heat means more holes, and eventually, the balloon is leaking everywhere. Heat stress also affects root respiration - a component of metabolic activity and growth. When temperatures get too high, respiration starts to break down and the roots stop ‘breathing’. And those black plastic pots can absorb impressive amounts of heat and exacerbate heat stress.
“We’ve recorded temperatures in Minnesota when it’s an 85-degree sunny day, that is close to 130 degrees Fahrenheit in a pot,” Guenthner says.
Guenthner spends most of his research time monitoring the oxygen sensors paired with his custom-built sous vide heating system. It’s one of his proudest creations and how he solved the problem of generating high, consistent heat to stress root masses. Circulating carefully heated water, he subjects roots to increasing heat levels to identify critical temperature thresholds amongst his tomato varieties.
Guenthner wants to gather more data to better understand what the critical temperature thresholds are for various plants, and use that data to inform growing decisions. In the future, he plans to explore how living biological agents like microbes and fungi could be used to mediate the negative impacts of high temperatures and help plants survive and thrive under heat stress. He hopes his work can ultimately be passed on to the consumer. “I just want to see the average person succeed with their plants, that’s what it’s all about!” And don’t fear the black plastic pot, he says. “Just remember to shade it.”
Guenther’s research is supported in part by funding from the USDA-ARS Floriculture & Nursery Research Initiative and the Grand Challenges Exploratory Research Grant. To learn more about industry-university partnerships and research in the department, visit horticulture.umn.edu/research-outreach.