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Seed Germination and Growth in Hypobaria.  

H.L. Gohil, J.R. Truett, A.J. Stimpson, R.A. Bucklin and M.J. Correll

Dept. of Agricultural & Biological Engineering, Univ. of Florida, Gainesville, FL.

   For long-term human space missions, plants will be needed for food, for air and water purification, for biofuels and for materials such as paper products.  Therefore, chambers for growing plants in the harsh conditions during spaceflight or on Mars need to be developed.  Low Pressure Growth Chambers (LPGCs) have been proposed as a possible option to grow plants in conditions where the environment has low atmospheric pressure such as on Mars (≈1 kPa).  We have constructed LPGCs that can monitor and/or control humidity, pressure, temperature, light, and gas composition.  In preliminary experiments, plants exhibited significant wilting within 15 minutes when exposed to hypobaria of 10 kPa (P_O2 = 2.1 kPa; P_CO2 =  0.0003 kPa; P_N2 = 7.9 kPa), although the plants recovered after few hours once atmospheric pressure was returned to earth-normal (101 kPa). This suggests that plants undergo stress during hypobaria.  In addition, no seeds germinated at 15 kPa (P_O2 = 3.15 kPa; P_CO2 = 0.00045 kPa; P_N2 = 11.85 kPa) for either Arabidopsis (Arabidopsis thaliana) or Tomato (Lycopersicon esculentum cv. Micro-Tom). When the atmospheric pressure was raised to 25kPa (P_O2 = 5.25 kPa; P_CO2 = 0.00075 kPa; P_N2 = 19.75 kPa), approximately half of the Arabidopsis seeds germinated while none of the tomato seeds germinated.  This poor germination may be a result of hypoxia (low oxygen) or limited water uptake and not a direct pressure effect. Studies on germination and growth of seedlings at low pressure with supplemental oxygen are currently being performed to clarify this response (support provided by UCF-UF Space Research Initiative 20040006). (Supported by NASA NNA04CK29G)