Adv. Space Res. Vol.14,No. 11,pp. (11)171-(11)176,1994 Pergamon 1994 COSPAR Printed in Great Britain. 0273-1177/94 $7.00 + 0.00 PROXIMATE NUTRITIONAL COMPOSITION OF CELSS CROPS GROWN AT DIFFERENT CO 2 PARTIAL PRESSURES R. M. Wheeler, C. L. Mackowiak, J. C. Sager, W. M. Knott and W. L. Berry Controlled Ecological Life Support Systems Breadboard Project, Biological Research and 1.fie Support Office, and The Bionetics Corporation, Kennedy Space Center, FL 32899, U.S.A. (National Aeronautics and Space Administration (Mail Code MD-RES)) ABSTRACT Two CELSS candidate crops, soybean (Gtycine max) and potato (Solarium tuberosum), were grown hydroponi- cally in controlled environments maintained at carbon dioxide (CO2) partial pressures ranging from 0.05 to 1.00 kPa (500 to 10,000 ppm at 101 kPa atmospheric pressure). Plants were harvested at maturity (90 days for soybean and 105 days for potato) and all tissues analyzed for proximate nutritional composition (i.e. protein, fat, carbohydrate, crude fiber, and ash content). Soybean seed ash and crude fiber were higher and carbohydate was lower than values reported for field-grown seed. Potato tubers showed little difference from field-grown tubers. With the exception of increased crude fiber of soybean seed with increased CO 2, no trends were ap- parent with regard to CO 2 effects on proximate composition of soybean seed and potato tubers. Crude fiber of soybean stems and leaves increased with increased CO2, as did soybean leaf protein (total nitrogen). Potato leaf and stem (combined) protein levels also increased with increased CO2, while leaf and stem carbohydrates decreased. Values for leaf and stem protein and ash were higher than values generally reported for field-grown plants for both species. Results suggest that CO 2 partial pressure should have little influence on proximate composition of potato tubers or soybean seed, but that high ash and protein levels might be expected from leaves and stems of crops grown in controlled environments of a CELSS. INTRODUCTION Much of our current knowledge of agricultural plant productivity and nutritional value is based on information from "field studies". However if plants are to be used for human life support in space (i.e. a Controlled Ecologi- cal Life Support System or CELSS), growing conditions will differ from those typically encountered in the field /6/: For example, CELSS crop production environments will require accurate control of temperature and humidity to sustain optimal growth and productivity; fighting and photoperiod control likely will be provided (at least in part) with electric lamp systems; cultural systems likely will utilize some type of redrculatlng hydroponic culture to conserve nutrient and water; and atmospheric composition and possibly total atmospheric pressure will differ from terrestrial field environments. In addition, fluctuations normally found under field conditions will not be present in the controlled environment of a CELSS. In recent years, numerous CELSS studies have been conducted to examine the effects of various controlled en- vironment factors on plant growth and development, but few of these studies analyzed the plant materials for nutritional value/7/; thus there is only limited information on the nutrition value of CELSS crops. As part the Breadboard Project at Kennedy Space Center, FL, USA, we have conducted controlled environment studies with several CELSS candidate crops/5/, and in particular have been interested in the effects of carbon dioxide (CO2) on plant growth development. We report here on the nutritional value of soybean and potato plants grown to maturity in controlled environments over a range of CO 2 partial pressures to simulate conditions that might be expected in a CELSS. MATERIALS AND METHODS Plant materials used for the studies were soybean (Gtycine max (L.) Merr.) cvs. McCall and Pixie and potato (Solanurn tuberosum L.) cvs. Nodand and Denali. All plants were grown in controlled environment grt,,vth chambers using fluorescent (Vita-Lite) lighting maintained near 300/~mol m "2 s -1 photosynthetic photon flux (PPF) with a 12-h photoperiod. Temperatures were maintained at 26"C (day) / 20°C (night) for soybean and 20°C (day) / 16"C (night) for potato. Plants were grown hydroponically using a recirculating nutrient film tech- nique with a modified, 1/2 strength Hoagland solution with nitrate as the sole source of nitrogen ]4/. Carbon dioxide (CO2) was added to the chamber atmosphere to provide approximately 0.05, 0.10, 0.20, and 0.50 kPa partial pressure (500, 1,000, 2,000, and 5,000 ppm) for soybean studies and 0.05, 0.10, 0.50, and 1.00 kPa for 01)171