As an undergrad studying ecology and evolutionary biology, Lizzie Lombardi found herself as one of the few “plant” people on a team of University of Colorado Boulder engineering students who were tasked with a lofty mission: build a robotic system that could garden in space.
The aerospace engineering team was participating in NASA’s eXploration Habitat academic innovation challenge, known as XHab, to develop the best practices for growing fresh produce during deep space missions. The goal is both to sustain astronauts and to buoy their morale during long months of isolation.
As her teammates fretted over how to build a robotic system that could plant seeds, monitor growth, harvest the plants—and then repeat that cycle indefinitely—Lombardi began to wonder about the plants themselves. Could they grow a plant that would meet the particular nutritional needs of an astronaut taking extended jaunts in space?
At first Lombardi, unsure of how she’d go about answering the question, assumed it would remain simply something to ponder. But with the encouragement of her advisor, she sought out professors in the Department of Ecology and Evolutionary Biology who had the expertise to help her design an experiment as part of an Honors Thesis that would deliver some concrete answers.
Lombardi’s research was recently published in the journal Acta Astronautica. With the mentorship of professors Barbara Demmig-Adams and Williams Adams, both of the Department of Ecology and Evolutionary Biology, and the day-to-day coaching of postdoctoral researcher Christopher Cohu, Lombardi was able to show that using a specific technique to grow plants in space—exposing them to bright pulses of light several times a day—can increase the amount of eye-protecting nutrients the plants produce.
“At first I didn’t even consider the possibility that I was ready to do primary research for an Honors Thesis—I wasn’t sure that was in the cards for me,” Lombardi said. “It was challenging, but I loved it. I still do research and I’m increasingly sure that I will continue to pursue new frontiers in plant ecophysiology in the future.”
The spark and the know-how
When Lizzie first approached Demmig-Adams with her idea of trying to grow plants in space that would be as nutritious as possible, Demmig-Adams thought the proposition sounded a little outlandish.
“I said, ‘Lizzie, I’m a plant functional biologist; I don’t know anything about astronauts,’” she said. “At first I was going to say, ‘No. That’s not going to happen.’ But I’m glad I took a second look at it.”
The second look led to a partnership unique to universities that allow novice researchers and experienced experts in their fields to work side-by-side in the same labs. The students may provide the spark of an entirely new idea; the professors can provide the grounded-in-reality know-how.
“Faculty need to recognize the merit of a student’s off-the-wall idea and students need to listen to the experts,” Demmig-Adams said. “Lizzie was the impetus for this project, but she couldn’t do it on her own. But I never would have thought about this without her.”
More stress equals more antioxidants
The foundational knowledge that Demmig-Adams brought to the project was the fact that plants grown to optimize growth do not produce as many antioxidants as plants exposed to some stress. Because research into space gardening tends to focus on producing as much biomass as quickly as possible, Demmig-Adams knew that the plants might lose some of their nutritional value.
Lombardi and the rest of the research team decided to focus their study on an antioxidant long studied by Demmig-Adams called zeaxanthin, a carotenoid known to protect various aspects of human health, particularly eye health. Demmig-Adams had just written a review on the function of zeaxanthin in increasing the acuity of human vision and protecting against cataracts and age-related blindness. Her review also highlighted the fact that human are unable to produce zeaxanthin themselves and must consume it with their diet.
In space, astronauts are exposed to an onslaught of eye-damaging radiation, and eating foods that contain zeaxanthin could be a key strategy for protecting their eyes.
Plants produce zeaxanthin on Earth when their leaves absorb more sunlight than they can use, which often happens when the plants are stressed—perhaps by exposure to drought, or excessive heat or cold. In the 1980s, Demmig-Adams discovered that zeaxanthin safely removes the excess light to keep the sunlight from damaging the plant’s own biochemical pathways. But unstressed plants, like the ones that would be grown in space under conditions that promote maximal plant growth, would not accumulate much zeaxanthin in their leaves.
“Our eyes are a lot like a leaf—they are both about collecting light,” Demmig-Adams said. “We need the same protection to keep us safe from damage by intense light.”
A great opportunity
Demmig-Adams and Adams began to wonder if their past research in Australia might offer a solution to growing plants packed with zeaxanthin in space. In the 1990s, the pair had studied plants on the floor of a eucalypt forest in Australia. The plants were often shaded by taller trees but were occasionally hit by a shaft of intense light that pierced the canopy. Though the stream of light was usually short-lived, it was enough to cause the plants to begin producing antioxidants.
Based on those findings, the research team tested to see if the plants they were studying as a model for possible cultivation in space could be intentionally exposed to several bright pulses each day to get a similar effect. The pulses were short enough that they didn’t interfere with the otherwise optimal growing conditions, but the team found they were long enough to cause accumulation of zeaxanthin.
The research project helped Lombardi get a job in a lab on campus after graduation, and she plans to pursue an advance degree to continue on with research as a career in the future.
“I was really lucky that I had advisors who were so constructive and open-minded,” she said. “It was difficult, but I learned so much and cannot express how appreciative I am for the opportunity.”