Characterizing leafy greens growth in response to CO2, relative humidity, photon spectrum, and nitrogen concentration for space production

Date
2023
Journal Title
Journal ISSN
Volume Title
Publisher
University of Delaware
Abstract
Space crop production is imperative for space research by adequately supplementing the astronaut diet in future missions. However, the International Space Station (ISS) has unideal environmental conditions for crop growth. To produce the supplementary nutrients and minerals that space-grown crops can provide to the astronaut diet, conditions for optimal growth need to be implemented in future space crop systems. In these ground-based studies, we explored how different light qualities, relative humidity levels, and nitrogen concentrations affected the growth of leafy green species at superelevated CO2 concentrations, like those seen on the ISS (≈2800 μmol·mol−1). The first study assessed the interactions of supplemental far-red (FR) light (50 μmol·m−2·s−1) and the CO2 concentration on mustard ‘Amara’. FR light decreased seedling fresh and dry mass at superelevated CO2 concentrations but did not affect the mature counterparts. Additionally, superelevated CO2 increased mustard ‘Amara’ fresh and dry mass at both growth stages. The second study assessed the influence of increasing relative humidity (RH) levels from 40% (ambient-ISS levels) to 70% (typical setpoint for growth rooms on Earth) and substituting red and FR light for blue and green light at superelevated CO2, and the interactions these parameters had on lettuce ‘Outredgeous’ growth. Light, RH, and CO2 concentration treatments increased seedling and mature fresh and dry mass depending on the level of the other environmental parameters in tandem. The last study assessed the growth and morphology of Chinese cabbage ‘Tokyo Bekana’ and kale ‘Red Russian’ baby greens under varying FR photon flux densities (PFDs) and nitrogen (N) concentrations under superelevated CO2. Both species exhibited typical shade avoidance responses to increasing FR PFDs, although neither showed increases in edible biomass. Increasing the N concentration generally increased Chinese cabbage ‘Tokyo Bekana’ edible biomass, but not for kale ‘Red Russian’. Additionally, as the FR PFD increased, the positive effect of high N on the shoot fresh mass and total leaf area of Chinese cabbage ‘Tokyo Bekana’ diminished. Collectively, this work demonstrates that the species and cultivar are important considerations when testing growth treatments for use in space crop production. There is no general conclusion as to what environmental treatment is best for all space-grown crops to increase growth.
Description
Keywords
Space, Space crop production, Space research, International Space Station, Relative humidity, Photon flux densities, CO2 concentration
Citation