Arabidopsis seed production limited by CO2 in simulated space experiments

Arabidopsis thaliana (L.) Henyh. plants were successfully grown many times in simulated space experiments from seed to seed in our laboratory. Attempts were unsuccessful when closed cultures were used. Only when gas exchange was permitted between culture atmosphere and ambient or when atmospheric volume was large did Arabidopsis produce seeds. Some factor(s) in the atmosphere limited seed production. CO2 was examined because of its nutrient status and is amenable to analysis. Plants were grown axenically in closed test tubes modified for gas sampling. CO2 levels decreased in the first week. Unexpectedly in the following weeks, CO2 increased to about 10 times ambient. Studies are needed to identify the reason for this increase. Sealing cultures to isolate plants from crew environment may affect seed production and compromise a life support system. Appropriate cultural conditions and methods must be determined and incorporated to support and enhance biological space experiments and systems.