Potato Tuber Formation and Metabolism in the Spaceflight Environment 961393

Five potato (Solanum tuberosum L.) leaf cuttings were flown on STS-73 in late October, 1995 as part of the 16-day USML-2 mission. Pre-flight studies were conducted to study tuber growth, determine carbohydrate concentrations and examine the developing starch grains within the tuber. In these tests, tubers attained a fresh weight of 1.4 g tuber^-1 after 13 days. Tuber fresh mass was significantly correlated to tuber diameter. Greater than 60% of the tuber dry mass was starch and the starch grains varied in size from 2 to 40 mm in the long axis. For the flight experiment, cuttings were obtained from seven-week-old Norland potato plants, kept at 5°C for 12 hours then planted into arcillite in the ASTROCULTURE^™ flight hardware. The flight package was loaded on-board the orbiter 22 hours prior to launch. During the mission, the flight hardware maintained an environment around the cuttings of 22°C (±2°C), 81% (±7%) RH and a 12 hour photoperiod using red and blue light emitting diodes at a photosynthetic photon flux of 150 μmol m^-2 s^-1. CO₂ concentration exceeded 4000 ppm during the dark period and was controlled during the light period to approximately 400 ppm. Video downlinking of images of the plants and CO₂ exchange data during the flight demonstrated plant vitality for the first 12 days of the mission followed by senescence of the leaves. The flight package was received 4 hours after landing at the Kennedy Space Center and post-flight processing of the samples was completed within 3 hours. Four out of the five space-grown cuttings produced tubers that were similar in appearance and dimension to the ground control tubers. This is an important finding if potatoes are to be used as part of a bioregenerative life support system for long-term space exploration.