Effects of elevated and super-elevated carbon dioxide on salad crops for space

ABSTRACT

Space habitats typically have elevated CO₂ and NASA is considering growing leafy greens in space to supplement astronauts’ diets. Dragoon’ and ‘Outredgeous’ lettuce, ‘Amara’ mustard, ‘Extra Dwarf’ pak choi, shungiku, ‘Red Russian’ kale, ‘Toscano’ kale, and ‘Barese’ Swiss chard were grown for 4 weeks at 400, 1500, 3000, and 6000 ppm CO₂. Shoot fresh mass at 28 days was greater for one of more elevated CO₂ levels for all species/cultivars except ‘Toscano’ kale. Fresh mass varied by species/cultivar, with pak choi and ‘Dragoon’ lettuce showing the greatest yields. Super-elevated CO₂ (6000 ppm) reduced shoot mass for both lettuce cvs. compared to 3000 ppm. Elevated CO₂ increased K levels for most species/cultivars but decreased Mg for some species/cultivars. CO₂ affected Vitamin B1 and Vitamin C content but had no effect on Vitamin K. ‘Toscano’ and ‘Red Russian’ kale, and Amara mustard had the highest mineral and vitamin content.

KEYWORDS:

• Life support
• bioregenerative
• CO₂
• space
• leafy greens

Acknowledgements

We thank the many student interns who helped these and related studies at Kennedy Space Center. We also thank all the student / teacher teams in the Growing Beyond Earth® project and the Fairchild Tropical Botanic Garden staff for helping provide crop candidates for these tests.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Correction Statement

This article has been corrected with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

Funding for this research was provided by NASA Biological and Physical Sciences Program.

Notes on contributors

Raymond M. Wheeler

Raymond M. Wheeler is a plant physiologist and senior scientist at NASA’s Kennedy Space Center, where he has led the advanced life support research group. This includes controlled environment studies with crops for food and oxygen production, CO₂ removal, and wastewater processing. Over the years, Ray has studied plant responses to gravity, CO₂, light, atmospheric pressure, and hydroponic crop cultivation. Ray has been co-investigator for several spaceflight experiments, including the first test to demonstrate potato tuber development in space, and studies using the ‘Veggie’ and Advanced Plant Habitat growth chambers on the International Space Station to growth fresh vegetables for the astronauts.

LaShelle E. Spencer

LaShelle E. Spencer is a scientist with the Laboratory Support Services Contract (LASSO) at NASA’s Kennedy Space Center (KSC). She serves as Lead Horticulturist, supporting Space Crop Production research. She received her BS in Horticulture and MS in Plant and Soil Science from Tuskegee University. Prior to joining the LASSO team, she conducted extensive research on hydroponic plant growth systems for space research at Tuskegee University. Following this, she served with the Ground Research team on the Life Science Services Contract at KSC, further supporting hydroponic plant research. She later honed her skills in analytical chemistry, micro and molecular biology by participating in over a dozen bioregenerative life support themed projects, which included plants, water, and waste recycling. She has been co-investigator for several spaceflight experiments including the PH-04 chile (chili) pepper study on the International Space Station (ISS). This was the longest, most complex plant growth study to date on the ISS.

Ruqayah H. Bhuiyan

Ruqayah H. Bhuiyan is a controlled environment grower / research investigator at Corteva Agriscience R&D facility in Indianapolis, Indiana, USA. She oversees the plant quality and growth of research material in greenhouses, growth chambers, and vertical controlled environments. Ruqayah assesses the plant physiological responses to external stimuli and develops growing procedures to facilitate research. Previously, Ruqayah held a position at Vision Greens in Ontario, Canada, where she worked as the head grower for a vertical farm producing lettuce, basil, and arugula. Ruqayah completed her master’s degree in plant physiology at the University of Georgia, where she worked with Dr. Marc van Iersel on lighting systems in controlled environments.

Matthew A. Mickens

Matthew A. Mickens is a Project Scientist at NASA’s Kennedy Space Center (KSC). He received his BS and MS in Plant, Soil, and Environmental Science, and his Ph.D. in Energy and Environmental Systems with a concentration in Inorganic Chemistry from North Carolina A&T State University. Subsequently, he spent 3 years at KSC as a research fellow in the NASA Postdoctoral Program (NPP) where his primary expertise was studying plant growth and morphology responses to LED light recipes. He also spent 5 years in commercial CEA as Project Manager and Chief Science Officer for Elevate farms and oversaw the installation indoor hydroponic vertical farms and commenced their operations in Welland, Ontario, CA and Orange, NJ, USA. Upon returning to KSC, he now serves as the technical POC for advancing microgreens as a candidate space crop, heading the food safety team and task force for the future Ohalo III food production growth chamber for Mars transit vehicles, and managing KSC’s primary processing area for all plant growth chamber research.

Jess M. Bunchek

Jess M. Bunchek is a botanist (B.Sc., Purdue University), agronomist (M.Sc., The Pennsylvania State University), and current PhD candidate in space systems engineering at the University of Bremen (Germany) and the German Aerospace Center (DLR) Institute of Space Systems. While at NASA’s Kennedy Space Center, she supported space crop production on the International Space Station, primarily with the Veggie plant growth chambers. From late 2020 to early 2022, Jess overwintered in Antarctica at the German Neumayer Station III as the EDEN ISS greenhouse operator, a collaborative project between the German Aerospace Center (DLR), NASA, and the Alfred Wegener Institute for Polar and Marine Research.

Edzard van Santen

Edzard van Santen is a statistician/plant breeder and a full Professor in the University of Florida (UF) Agronomy Department since 2016, after a 29-year career as plant breeder and consulting statistician at Auburn University, USA. While at Auburn, he had an active applied breeding program in energy, forage, and turf grasses and also worked with cover crop species such as ball clover, crimson clover, and white lupin. He is currently the director of the UF/IFAS Statistical Consulting Unit, a service unit sponsored by the Senior VP for Agriculture and Natural Resource and part of the UF/IFAS research infrastructure. This Statistical Consulting Unit is charged with assisting graduate students, staff, and faculty with the design, conduct, and analysis of research studies in agronomy, animal sciences, entomology, food science, horticultural sciences, etc. He is currently also involved in the USDA funded Fostering Resilience and Ecosystem Services in Landscapes by Integrating Diverse Perennial Circular Systems (RESILIENCE CAP) grant as the lead statistician.

Gioia D. Massa

Gioia D. Massa is a plant scientist at NASA’s Kennedy Space Center working on space crop production for the International Space Station and future exploration missions. Prior to joining NASA, she worked as a postdoctoral fellow at Purdue University and Kennedy Space Center, conducting research on crops for bioregenerative life support. She has studied a range of crops for future food production in space, focusing on their horticultural and environmental requirements, including responses to light spectral quality using light emitting diodes (LEDs). She led the science team for initial testing and validation of the Veggie plant growth chamber on the International Space Station (ISS) and has conducted comparative studies with leafy greens and tomatoes on the ISS. Her other research interests include nutrition, flavor, food safety and the psychological benefits of space-grown crops. Throughout her career, Gioia has been an avid supporter of student outreach.

Matthew W. Romeyn

Matthew W. Romeyn was a plant ecologist / molecular biologist at NASA’s Kennedy Space Center (KSC). Matt was responsible for technology demonstration studies with the Veggie plant chamber on the International Space Station (ISS) and oversaw operations for KSC’s controlled environment research laboratory. His research focused on microgreens as a candidate food crop, plant microbiome studies, and he served as NASA’s lead for the PH-04 study with chile (chili) peppers grown in NASA’s Advanced Plant Habitat on the ISS. This was the longest plant experiment every conducted in space. He was passionate about the development and implementation of a crop readiness plan and on-orbit gardening handbook with the goal that in the future, crews will be able to select and independently grow plants of their choosing while in space. Tragically, Matt died in an auto accident in 2022. He will always be missed by his many colleagues and friends at KSC and the space biology community.