ASGSB 1998 Annual Meeting Abstracts

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PHOTOSYNTHESIS IN SPACE: GROUND-BASED EVALUATION OF ENVIRONMENTAL FACTORS AFFECTING WHEAT DEVELOPMENT IN CLOSED ENVIRONMENTS.   G.W. Stutte, G.D.Goins, D.K. Chapman. Dynamac Corporation, Kennedy Space Center, FL

Ground-based studies to develop protocols for direct determination of photosynthesis of wheat in microgravity are being conducted in preparation for a space flight experiment selected during NASA NRA 96-OLMSA-01A. This space flight experiment will be conducted in the Biomass Production System (BPS), a double middeck-sized plant growth chamber being developed by Orbital Technologies Corporation (Madison, WI).

A series of tests to determine the effect of rooting media conditions on shoot growth, photosynthesis, and transpiration of wheat cv. USU Super Dwarf have been conducted at Kennedy Space Center using rooting modules designed for the BPS . Arcillite particle sizes of 1-2 mm appear sufficient to maintain adequate media water potential to support plant growth for 20 days at a water tension of -0.1 kPa, but not at -0.5 kPa. Transpiration rates have averaged 2.6 L m^-2 day^-1 over a 20 day experiment, with a maximum rate of 4.4 L m^-2 day^-1 at full canopy coverage. Maximum photosynthetic rates were 7 µmol m^-2 s^-1 at 310 µmol m^-2 s^-1 PAR at 15 DAP. Photosynthetic rates declined slightly as plants increased in height after day 15. This is likely due to decreased light interception by the wheat canopy due to mutual shading in the plant growth chambers.

(Supported by NASA: NCC-027)

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