The LED light recipes that NASA scientists are developing on Earth could eventually be used by astronauts in space and growers on the ground to optimize the production of food crops.
National Aeronautics and Space Administration (NASA) has been growing plants in space for research since the early 1980s. Within the last five years, NASA has been focusing on growing plants in space primarily for food production and as an astronaut life support system.
“Initially the growth of plants in space was primarily for research to see how plants respond in a micro-gravity environment,” said Dr. Matt Mickens, who is a NASA postdoctoral fellow. “The plants being grown in space are not to replace the astronauts’ packaged diet, but to supplement their diet with fresh nutrients.
“The astronauts’ packaged diets are often low in key vitamins and minerals. This is primarily because the packaged foods have to undergo long storage periods before being consumed. Also, essential nutrients, like vitamin C, have a tendency to degrade over time. The idea is to mitigate that challenge by providing fresh food so that they can have a vibrant source of nutrients from fresh grown crops.”
The astronauts are currently growing plants on the International Space Station. There are three plant growth chambers on the space station. The first two chambers, which are identical, are the vegetable production chambers which are called Veggie.
“These two are simple chambers with red, green and blue LEDs,” Mickens said. “The LEDs and the fans are the only electrical components in those chambers. Everything else is shared with the crew. The temperature, humidity and carbon dioxide in the chamber that the plants receive are the same as what the astronauts receive in the cabin. There are also transparent barriers called bellows that unfold down from the lightcap that help to retain the humidity.”
The third growth chamber on the space station is more advanced. It is called the advanced plant habitat or APH.
“APH has complete control over the environment and it can actually support plants with a completely separate environment from the astronauts’ cabin,” Mickens said. “The chamber can control the temperature, humidity, carbon dioxide level, even how water is circulated in the system so it can be recycled. It also has more advanced lighting capabilities. In addition to the red, green and blue LEDs in the Veggie chambers, APH also has white and far red LEDs.”
Looking to upgrade lighting technology
Mickens said NASA scientists were looking for a LED fixture that had wavelength capabilities similar to the APH lightcap.
“We wanted to be able to closely simulate the APH lighting environment for ground-based studies,” he said. “This would provide us the chance to verify the science before we fly it. We decided to use the Phytofy RL LED fixture designed by OSRAM. OSRAM was already designing this fixture for researchers at Michigan State University. Chris Higgins at Hort Americas learned about the fixture and told me about it.
“The Phytofy fixture actually provided a few more options than we were looking for. The Phytofy fixture provides the red, green and blue wavelengths, but it also has two different hues of white LEDs, far red and UV wavelengths.
Mickens said NASA plans to eventually upgrade the systems in the Veggie growth chambers with new LED lighting technology, improved capability and maybe even Smart lighting technology.
“The research that we are conducting on the ground using capabilities similar to the APH, is providing us with ideas on how to upgrade the Veggie system,” he said. “Whether we want to include far red, UV or additional white light, we are doing the research now to determine if the impact of these wavelengths on plant growth is worth it.
“The plan for lunar and interplanetary exploration is to eventually scale up from both the Veggie and APH chambers, which only provide about 2 square feet of growing area. These chambers will continue to be great small scale platforms for plant growth research. However, long duration space transit missions and surface habitats are going to require significantly more growing area to provide life support for multiple crew members. Veggie and APH are only the beginning of food production in space.”
Developing lighting recipes
Most of the research that Mickens has been doing for the last three years is to identify light recipes that are optimal for the crops that are of interest to NASA. The goal is to be able to make recommendations for future experiments that NASA is looking to conduct in the APH.
“I have identified light recipes to optimize the growth of ‘Outredgeous’ red romaine lettuce, which has already been successfully grown in Veggie,” he said. “I’ve learned how to use light strategically to meet a specific purpose for the grower. If the objective is for the astronauts to optimize the overall biomass, I have a light recipe for that. Or if the objective is to keep the plants small or dwarf, but to magnify the nutrient content, I have also identified a recipe for that.
“Each crop species and variety has a sweet spot in terms of its optimal light spectrum. Finding it involves a thorough understanding of each crop’s physiological response to specific wavelengths, a little bit of trial and error and whole lot of patience.”
The research that Mickens conducted was geared primarily for the APH chamber.
“The purpose of my research was to figure out which wavelength combinations should be used for particular needs,” he said. “Crop yield is one of the most important parameters. What light recipe would produce the optimum yield in terms of fresh mass and dry mass. Also, I was looking at the effects on morphology which is the shape of the plant. I also measured nutrient content, including elemental nutrients and secondary metabolites such as carotenoids. These are anti-oxidant compounds often produced by plants as a protective mechanism to high energy wavelengths such as UV and blue light.”
Mickens said finding the right recipe for the crops is kind of a balancing act.
“With lettuce I found a way to balance the yield and the nutrients with a light recipe that was similar to sunlight,” he said. “This recipe dramatically outperformed all of the other light treatments, including red and blue LEDS, white LEDs and combinations of white and single colored LEDs.”
Based on his research Mickens can use this strategic approach to determine the optimal light recipes for any crop that NASA chooses to grow.
“Since NASA is really big on acronyms, I ended up naming my approach Strategic LED Lighting Effects on Development or SLLED,” he said. “I used this approach because I saw some subtle and significant differences between all of the light treatments. These differences allow me to fine tune combinations that can be beneficially applied and changed during certain periods of the crop cycle to achieve different goals.”
Real world applications
Mickens said he expects growers could use the light recipes he developed in vertical and indoor farms and get very similar results.
“I did my research in a basic walk-in growth chamber that could easily be used commercially as well,” he said. “Everything I did was basic and is very repeatable by commercial growers. What we are discovering here at NASA, any type of advancements in terms of plant growth whether it is lighting or any other parameter to help our mission for space exploration, would be of use for growers on Earth as well. The study results have a dual benefit.”
For more: National Aeronautics and Space Administration, Kennedy Space Center, https://www.nasa.gov/centers/kennedy/home/index.html.
This article is property of Hort Americas and was written by David Kuack, a freelance technical writer from Fort Worth, TX.