Effect of reduced atmospheric pressure on growth and quality of two lettuce cultivars. (August 2022)

• Record Type: Journal Article
• Authors: Stutte, Gary W.; Yorio, N.C.; Edney, S.L.; Richards, J.T.; Hummerick, M.P.; Stasiak, M.; Dixon, M.; Wheeler, R.M.
• Is Part Of: Life sciences in space research. Volume 34(2022)
• Page Start: 37
• Page End: 44
• Publication Date: 2022-08
• Subjects: Lactuca sativa L. -- Bioprotectant -- Anthocyanin -- Antioxidant -- ORAC -- Hypobaria; Space biology -- Periodicals; 571.0919
• DOI: 10.1016/j.lssr.2022.06.001
• Languages: English
• ISSNs: 2214-5524

Abstract

Highlights: Two lettuce cultivars were grown at three atmospheric pressures, 33 kPa, 67 kPa, and 97 kPa, that are relevant to long duration space missions. Plant growth was reduced in red and green leafed lettuce cultivars grown 33 kPa. Anthocyanin concentration of the red-leafed cultivar Outredgeous increased as atmospheric pressure decreased. Abstract: Future space missions will likely include plants to provide fresh foods and bioregenerative life support capabilities. Current spacecraft such as the International Space Station (ISS) operate at 1 atm (101 kPa) pressure, but future missions will likely use reduced pressures to minimize gas leakage and facilitate rapid egress (space walks). Plants for these missions must be able to tolerate and grow reliably at these reduced pressures. We grew two lettuce cultivars, 'Flandria' a green bibb-type and 'Outredgeous, ' a red, loose-leaf type, under three pressures: 96 kPa (ambient control), 67 kPa (2/3 atm), and 33 kPa (1/3 atm) for 21 days in rockwool using recirculating nutrient film technique hydroponics. Each treatment was repeated three times using a different hypobaric chamber each time. A daily light integral of 17.2 Moles Photosynthetically Active Radiation per day was provided with metal halide lamps set to deliver 300 µmol m −2 s −1 photosynthetic photon flux (PPF) for a 16 h photoperiod at 22 °C. Oxygen was maintained at 21 kPa (equal to 21% at 1 atm) and CO2 at 0.12 kPa (equal to 1200 ppm at 1 atm). Leaf area for 'Outredgeous' was reduced 20% and 38% at 67 kPa and 33 kPa respectively; shoot fresh mass was reduced 22% and 41% at 67 kPa and 33 kPa respectively when compared to control plants at 96 kPa. These trends were not statistically significant at P ≥ 0.05. Leaf area for 'Flandria' showed no difference between 96 and 67 kPa but was reduced 31% at 33 kPa; shoot fresh mass was reduced 6% and 27% at 66 kPa and 33 kPa respectively compared to 96 kPa. There were 10% and 25% increases in anthocyanin concentration at 66 kPa and 33 kPa compared to 96 kPa, potentially increasing the bioprotective capacity of the plant. Previous studies with other cultivars of lettuce showed slight change in growth across this range of pressures, suggesting responses may vary among genotypes, hypobaric exposure treatments, and / or environmental conditions. Collectively, the findings suggest further testing is needed to understand the effects of atmospheric pressure on plant growth.