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An Evaluation of Nutrient provision strategies for spaceflight applications.  J.U. Okere¹, G.K. Tynes², R.G. Stoesz³ and H.G. Levine². ¹Dept of Biology, University of Miami, FL. ²Gravitational Biology Laboratory, Dynamac Corp., Kennedy Space Center. ³Valencia Comm. College, Kissimmee, FL. 

     The Water Offset Nutrient Delivery Experiment (WONDER) will evaluate the growth of plants within both a Porous Tube Nutrient Delivery System and a Substrate-based Nutrient Delivery System (SNDS) under three separate wetness level set-points.  The base-lined SNDS utilizes Turface™ (a clay-based substrate) and slow dissolving fertilizer pellets (Osmocote™) which supply nutrients for plant growth upon the addition of water.  This has proven to be effective, however, the standard Osmocote formulation does not contain all of the trace elements required for plant growth.  It was hypothesized that the Turface functioned as a source of the necessary trace elements.  This study was therefore designed to: (1) evaluate the nutritional contribution of the Turface substrate, and (2) evaluate the nutritional efficiency of a new Osmocote Plus formulation which includes a trace element component (in place of some of its macronutrients) in its manufacture.  Five experimental treatments, each containing 24 wheat (Triticum aestivum cv Yecora rojo) seeds, were evaluated for their ability to support plant growth under conditions similar to those envisioned for WONDER (23^o C, 75% RH, 1,000 ppm CO₂, 185 mmoles m^-2 s^-1). Water samples were taken from each experimental compartment on days 0, 6, 12 and 19.  After 21 days of growth, all plant tissues were harvested and subjected to tissue analyses.  The Osmocote treatment exhibited faster growth than the Osmocote Plus (trace element) formulation.  The Turface-Only treatment had sufficient nutrients to support early wheat growth, but failed to provide sufficient nutrients for long-term growth.  The Turface with Hoaglands treatment exhibited faster plant growth than the glass beads with Hoaglands treatment.  Leaching of compounds from the glass beads (which had been assumed to be inert) was apparent.  This research was supported by the Spaceflight Life Sciences Training Program (SLSTP) and NASA (NAS610-12180).