Role of Metabolic Gases in Reproductive Failure Under Spaceflight Conditions: Ground Based Studies With Arabidopsis

Results obtained during the shuttle mid-deck locker experiment CHROMEX-03 suggested that failure of reproductive development of plants during spaceflight was related to a limitation in availability of metabolic gases to developing tissues due to the lack of convective air movement in microgravity. The purpose of this ground-based experiment was to determine the effect of different O₂ and CO₂ concentrations on plant reproductive development and growth. Fourteen day old Arabidopsis thaliana (L.) Heynh plants were grown as for the spaceflight experiment and exposed for six days to either air or one of six different air/nitrogen dilutions. Growth and reproductive responses to treatments of less than 50 mL·L^-1 O₂, 100 μL·L^-1 CO₂ were significantly different (P=0.05) from each other and all other treatments, while responses to treatments with greater than 140 mL·L^-1 O₂, 300 μL·L^-1 CO₂ were not significantly different from the air treatment. The results support our initial interpretation of the causes of reproductive failure in Arabidopsis during spaceflight and may be useful in designing future plant habitats.