Robert Heinse1, Scott Jones1, Dani Or2, T. Shane Topham3, Igor G. Podolskiy4, and Gail E. Bingham3. (1) Utah State University, Utah State University, Ag. Sci. Bldg. Room 160, Logan, UT 84322-4820, (2) EPFL Ecole Polytechnique Federale, EPFL Ecole Polytechnique Federale, GR B1 399 Station 2, Lausanne, 1015, Switzerland, (3) Space Dynamics Laboratory, Logan, UT 84322-9700, (4) Institute of Biomedical Problems, Moscow, Russia
The distribution of water controls directly or indirectly the management of water and air in coarse-textured porous plant-growth substrates. With the motivation to involve plants in future life support systems in space, the question arises whether fluid behavior in porous substrates is altered when subjected to microgravitational accelerations (~10-6-g). The Optimization of Root Zone Substrates (ORZS) experiment was designed to directly measure oxygen diffusion and water retention in prolonged (~60 days) microgravity. The system is comprised of nine dual-chamber oxygen diffusion cells controlled by an automated measurement system. Water was metered by precision peristaltic pumps to provide multi-step adjustment of water content. Matric potentials were measured using pressure transducers coupled to porous stainless steel membranes. Oxygen was measured using galvanic cells located in gas chambers at the distal ends of the porous medium compartment. Gas diffusion coefficients were determined by fitting an analytical model to temporal oxygen concentration data. The analysis and cell design is based on the work of Glauz and Rolston (1989). The 9-cell array allows three triplicate treatments. The primary scope of the presentation is to discuss the measurement hardware and conduction. We will further present matric potential and diffusion coefficients as a function of air-filled porosity data highlighting the significance of a microgravity environment on the distribution of fluids in plant growth substrates.
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