Gas exchange rates of potato stands for bioregenerative life support

Abstract Plants can provide a means for removing carbon dioxide (CO 2 ) while generating oxygen (O 2 ) and clean water for life support systems in space. To study this, 20 m 2 stands of potato ( Solanum tuberosum L.) plants were grown in a large (113 m 3  vol.), atmospherically closed chamber. Photosynthetic uptake of CO 2 by the stands was detected about 10 DAP (days after planting), after which photosynthetic rates rose rapidly as stand ground cover and total light interception increased. Photosynthetic rates peaked ca. 50 DAP near 45 μmol CO 2  m −2  s −1 under 865 μmol m −2  s −1 PPF (average photosynthetic photon flux), and near 35 μmol CO 2  m −2  s −1 under 655 μmol m −2  s −1 PPF. Short term changes in PPF caused a linear response in stand photosynthetic rates up to 1100 μmol m −2  s −1 PPF, with a light compensation point of 185 μmol m −2  s −1 PPF. Comparisons of stand photosynthetic rates at different CO 2 concentrations showed a classic C 3 response, with saturation occurring near 1200 μmol mol −1 CO 2 and compensation near 100 μmol mol −1 CO 2 . In one study, the photoperiod was changed from 12 h light/12 h dark to continuous light at 58 DAP. This caused a decrease in net photosynthetic rates within 48 h and eventual damage (scorching) of upper canopy leaves, suggesting the abrupt change stressed the plants and/or caused feedback effects on photosynthesis. Dark period (night) respiration rates increased during early growth as standing biomass increased and peaked near 9 μmol CO 2  m −2  s −1 ca. 50 DAP, after which rates declined gradually with age. Stand transpiration showed a rapid rise with canopy ground cover and peaked ca. 50 DAP near 8.9 L m −2  d −1 under 860 μmol m −2  s −1 PPF and near 6.3 L m −2  d −1 under 650 μmol m −2  s −1 PPF. Based on the best photosynthetic rates from these studies, approximately 25 m 2 of potato plants under continuous cultivation would be required to support the CO 2 removal and O 2 requirements for one person.