Utilization of potatoes for life support systems in space. IV. Effect of CO2 enrichment

Potatoes (Solanum tuberosum L.) cvs. Norland and Russet Burbank were grown in solid stands in separate controlled environment rooms at two CO2 levels, 365 micromoles mol-1 (ppm) and 1000 micromoles mol-1. Rooms were maintained under continuous fluorescent light (450 micromoles s-1 m-2 PPF), 16 C and 70% relative humidity. Norland plants were grown for 110 days and Russet Burbank plants for 126 days. CO2 assimilation rates (net photosynthetic rates) of exposed, upper canopy leaves were measured at weekly intervals beginning at 21-days-age for Norland and 28-days-age for Russet Burbank. Elevation of CO2 increased CO2 assimilation rates of Norland leaves by approximately 24%, but decreased rates of Russet Burbank leaves by approximately 12%. Assimilation rates of Norland leaves under the high CO2 decreased as plants matured so that their rates were similar to rates under the low CO2 levels after 70-days-age. Assimilation rates of Russet Burbank leaves under high CO2 remained depressed in comparison to low CO2 plants throughout the period of measurements. Yield data showed only marginal benefits from CO2 enrichment: tuber dry weight increased 2% for Norland and 12% for Russet Burbank, total plant dry weight was increased 6% for Norland and 4% for Russet Burbank. The best productivity obtained in this study (21.9 g tuber dry wt m-2 day-1 from Norland at 1000 micromoles mol-1 of CO2) indicates that the dietary energy needs of one human in space could be supplied from 34 m2 of potatoes.