Potatoes as a Crop for Space Life Support: Effect of CO 2 , Irradiance, and Photoperiod on Leaf Photosynthesis and Stomatal Conductance

Potatoes ( L.) have been suggested as a candidate crop for future space missions, based on their high yields of nutritious tubers and high harvest index. Three cultivars of potato, cvs. Norland, Russet Burbank, and Denali were grown in walk-in growth rooms at 400 and 800 µmol m s photosynthetic photon flux (PPF), 12-h L/12-h D and 24-h L/0 h D photoperiods, and 350 and 1,000 ppm [CO ]. Net photosynthetic rates (P ) and stomatal conductance (g ) of upper canopy leaves were measured at weekly intervals from 3 through 12 weeks after planting. Increased PPF resulted in increased P rates at both [CO ] levels and both photoperiods, but the effect was most pronounced under the 12-h photoperiod. Increased [CO ] increased P for both PPFs under the 12-h photoperiod, but decreased P under the 24-h photoperiod. Increased PPF increased g for both [CO ] levels and both photoperiods. Increased [CO ] decreased g for both PPFs for the 12-h photoperiod, but caused only a slight decrease under the 24-h photoperiod. Leaf P rates were highest with high PPF (800), elevated [CO ] (1,000), and a 12-h photoperiod, while growing the plants under continuous (24-h) light resulted in lower leaf photosynthetic rates for all combinations of PPF and [CO ]. The responses of leaf photosynthetic rates are generally consistent with prior published data on the plant biomass from these same studies (Wheeler ., Crop Sci. 1991) and suggest that giving more light with a 24-h photoperiod can increase biomass in some cases, but the leaf P and overall photosynthetic efficiency drops.