March 5, 2014
Light Pulses Could Help Space Veggies Produce Eye-Protecting Nutrients
redOrbit Staff & Wire Reports - Your Universe Online
Astronauts could help offset exposure to eye-damaging radiation during extended spaceflights by eating leafy vegetables grown during those voyages, according to research appearing in a recent edition of the journal Acta Astronautica.
The University of Colorado Boulder researchers responsible for the study say that exposing those vegetables to a few bright pulses of light each day as they grow onboard a spacecraft could increase the amount of eye-protecting nutrients they produce, known as carotenoids.
One of those carotenoids, zeaxanthin, is particularly helped by the process, the researchers noted in a statement Tuesday. While zeaxanthin can be ingested as a supplement, evidence suggests that human bodies are better at absorbing it and other carotenoids from whole foods, such as green leafy vegetables.
NASA is currently studying ways to grow fresh produce on deep space missions as a way to keep the crew’s morale up and improve their overall nutrition. Space gardening research conducted to date has looked primarily at how to ensure that plants receive optimal light, water and fertilizer so that they can grow as large as possible in as little time as possible. However, those conditions might not be optimal for production of essential nutrients.
“There is a trade-off,” explained co-author Barbara Demmig-Adams, a professor in the Department of Ecology and Evolutionary Biology. “When we pamper plants in the field, they produce a lot of biomass but they aren't very nutritious.”
“If they have to fend for themselves – if they have to defend themselves against pathogens or if there's a little bit of physical stress in the environment – plants make defense compounds that help them survive. And those are the antioxidants that we need,” she added.
Zeaxanthin is produced when plant leaves absorb more sunlight than they can use, which typically occurs when those plants are stressed, the investigators explained. For instance, a lack of water could keep the plant from using all of its absorbed sunlight for photosynthesis, forcing it to produce the carotenoid compound to safely remove excess light and prevent it from causing damage to the plant's biochemical pathways.
Zeaxanthin plays a similar protective role in the human eye, according to Demmig-Adams, undergraduate researcher Elizabeth Lombardi, postdoctoral researcher Christopher Cohu and ecology and evolutionary biology Professor William Adams. Since the eyes collect light in much the same way as a leaf, it requires similar protection.
The study authors set out to find a way to maximize both plant growth and zeaxanthin production. Using the plant species Arabidopsis as a model, they discovered that a few pulses of bright light each day encouraged production of the carotenoid to prepare for an anticipated excess amount of sunlight. At the same time, those pulses were so short that they did not interfere with the plant’s otherwise optimal growth conditions.
“When they get poked a little bit with light that's really not a problem, they get the biomechanical machine ready, and I imagine them saying, ‘Tomorrow there may be a huge blast and we don't want to be unprepared,’” explained Demmig-Adams. “Learning more about what plants already 'know' how to do and trying to manipulate them through changing their environment rather than their genes could possibly be a really fruitful area of research.”