From CO2Science: According to the nine Chinese scientists who were involved in this study, they evaluated the responses of the photosynthetic characteristics, antioxidant capacity and water use efficiency of wheat (Triticum aestivum L.) that was exposed to four different CO2 concentrations (500, 1000, 3000 and 5000 ppm) from February to May of 2014, while three volunteers were also enclosed within the vehicle (the Chinese Lunar Palace-1) for a period of 105 days, in order to oversee the experiment and perform needed tasks. And what did they thereby learn?
Paper reviewed: Dong, C., Shao, L., Wang, M., Liu, G., Liu, H., Xie, B., Li, B., Fu, Y. and Liu, H. 2016. Wheat Carbon Dioxide Responses in Space Simulations Conducted at the Chinese Lunar Palace-1. Agronomy Journal 108: 32-38.
Dong et al. report that “wheat cultivated at 1000 ppm from vegetative growth to maturity was characterized by  more appropriate relative water content,  membrane stability index,  photosynthetic rate,  chlorophyll concentration, and  antioxidant capacity,” which was (6,7) “more beneficial to growth and development in a closed artificial environment.” In addition, they note that (8,9) “there were significant effects with increased CO2 concentration on the effective quantum yield of PSII and photosynthetic electron transport of wheat plants,” and that (10) “elevated CO2 controlled the transpiration rate, which  enhanced water use efficiency.” And, last of all, they report that “during ripening,  wheat aging may be accelerated by elevated CO2, which [13,14] promotes grain growth and maturing.”
All things considered, it would thus appear that while many climate alarmists deem even the lowest of the CO2 concentrations employed in this study to be anathema to life on Earth, those inhabitants of the globe that may someday take their leave of it in a space-flight vehicle will likely find it to be essential to their ability to either return to Earth in good health or to their ability to take up semi-permanent residence on another less-prejudiced planet.