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A reliable nutrient delivery system is essential for long-term cultivation of plants in space. At the Kennedy Space Center, a series of ground-based tests are being conducted to compare candidate plant nutrient delivery systems for space. To date, our major focus has concentrated on the Porous Tube Plant Nutrient Delivery System, the ASTROCULTURE™ System, and a zeoponic plant growth substrate. The merits of each system are based upon the performance of wheat supported over complete growth cycles. To varying degrees, each system supported wheat biomass production and showed distinct patterns for plant nutrient uptake and water use.

The use of Green Fluorescent Protein (GFP) as a reporter gene system is an accurate and non destructive means for generating organ, tissue and cell-specific data on gene expression in plants. While many commercial imagining systems are available for standard terrestrial laboratory imaging of GFP, none of these systems begin to meet the requirements for a flight unit that could be utilized to monitor plant gene expression in spaceflight habitats. We present here data derived from ground testing of a prototype GFP flight imaging unit, the TAGES Imaging System (TIS). The TIS software is designed to collect multiple images of the same view to facilitate the stacking of the images for enhanced detail resolution. Analyses of stacking software and tactics for improving resolution are being evaluated. The TIS is being developed as a component of the payload hardware design of the next generation of Plant Growth Facility (PGF).

The BRIC-LED (Biological Research In Canisters-Light Emitting Diode) PDFU (Petri Dish Fixation Unit) apparatus was originally developed to support the on-orbit growth and subsequent fixation of any biological material amenable to petri dish culture in space. The PDFU component has been modified to support a two-stage fluid provision option so that investigations can incorporate an initial injection of a biologically active solution followed by a subsequent fixative injection to terminate the experiment in space. Crew-operated actuator tools initiate the delivery of the liquid treatments. Aseptic protocols have been developed which permit the entire experiment to be conducted under sterile conditions.

A plant cultivation material known as the Fibrous Ion Exchange Resin Substrate (FIERS) was assessed for its ability to provide nutrients to wheat plants growing hydroponically on a porous tube nutrient delivery system. Seeds were imbibed and grown on six porous tubes; three at different wetness levels utilizing only the FIERS (as a source of nutrients) and three at comparable wetness levels but with Hoagland’s solution used as the source of nutrients. Although there were significant differences between wetness levels and methods of nutrient provision treatments, the FIERS demonstrated the capability to support plant growth through seed production.

The Porous Tube Insert Module (PTIM) is a plant growth apparatus utilizing a porous tube design. The PTIM is under development by the Bionetics Corporation and has been designed as an insert to the Plant Generic Bioprocessing Apparatus (PGBA: Developed by Bioserve Space Technologies). The Water Offset Nutrient Delivery ExpeRiment (WONDER) will perform a side by side evaluation of the PTIM's Porous Tube Nutrient Delivery System (PTNDS) and a Substrate Nutrient Delivery System (SNDS). The PGBA will serve as the environmental chamber and environmental control system for the PTIM. The PGBA will also host the WONDER sequencer software within its control computer. The PTIM integrates six porous tubes wrapped with seed mats. In the SNDS, the tubes and mats are embedded within a substrate material while in the PTNDS, they are exposed to the chamber environment. The PTIM hydraulic equipment includes porous tubes fed by computer controlled miniature pumps and valves.

The Plant Growth Facility (PGF) is under development as a Shuttle middeck apparatus to support research on higher plants in microgravity. It is designed to operate for 15 days, and will provide (1) fluorescent lighting at a minimum of 220 μmol m-2 s-1 evenly distributed (±10%) over the growth area, (2) temperature control to a set point of ±10°C of cabin ambient with a control accuracy of ±1°C, (3) humidity control ±5% for set points between 30-80% RH, and (4) carbon dioxide control ±5% over a range of 300-5000 ppm. Filters will be provided to remove ethylene and trace organics from the internal air flow.

Installation of a ‘salad machine’; in the International Space Station (ISS) will be the first step toward long-term biological regeneration of food during space missions. Salad crops have demonstrated promise for providing dietary supplements and psychosocial benefits. A cylindrical conveyer-type design (called the Phytoconveyer) under development exhibits high productivity and low energy and crew time demands. The overall dimensions are 54 × 59 × 40 cm. Power consumption is 0.25 kW and the volume of the plant growth chamber is 0.09 m3. The Phytoconveyer includes a cylindrical planting surface area comprised of six root modules. Each root module contains a porous tube wrapped in a fibrous ion-exchange resin substrate (BIONA V-3) enclosed within a black plastic cover with an open slot on the top for seed insertion. The total outer diameter of the root module is 5 cm.

The development of a spaceflight-rated Porous Tube Insert Module (PTIM) nutrient delivery tray has facilitated a series of studies evaluating various aspects of water and nutrient delivery to plants as they would be cultivated in space. We report here on our first experiment using the PTIM with a software-driven feedback moisture sensor control strategy for maintaining root zone wetness level set-points. One-day-old wheat seedlings (Tritium aestivum cv Apogee; N=15) were inserted into each of three Substrate Compartments (SCs) pre-packed with 0.25–1 mm Profile™ substrate and maintained at root zone relative water content levels of 70, 80 and 90%. The SCs contained a bottom-situated porous tube around which a capillary mat was wrapped. Three Porous Tubes were planted using similar protocols (but without the substrate) and also maintained at these three moisture level set-points. Half-strength modified Hoagland’s nutrient solution was used to supply water and nutrients.

The Magnetic Field Apparatus (MFA) is a newly developed hardware system for space flight experimentation. The main goal of the MFA is to provide a platform to conduct experiments exposing plant tissues to a high gradient magnetic field (HGMF) in a microgravity environment. The MFA is being developed as a Space Shuttle middeck facility, and once completed will be classified as generic Life Science Laboratory Equipment (LSLE) and available to all NASA-sponsored investigators. The first flight of the MFA will be on STS-107 (currently scheduled for mid-2001). It will be configured to carry dry flax (Linum usitatissimum L.) seeds into space, imbibe the seeds on-orbit, and expose the emerging roots to a high-gradient magnetic field. Time-lapse digital imagery will document root development, and the hardware will support chemical fixation at the appropriate time to preserve the specimens and terminate the experiment.

Engineers and scientists from BioServe Space Technologies and Kennedy Space Center (KSC) are developing a flight-rated payload for the evaluation of two space-based plant nutrient delivery systems (NDS's). The hardware is comprised of BioServe's Plant Generic Bioprocessing Apparatus (PGBA) and KSC's Porous Tube Insert Module (PTIM). The PGBA, a double-middeck locker, will serve as the host carrier for the PTIM and will provide computer control of temperature, relative humidity, and carbon dioxide levels. The PTIM will insert into the PGBA's growth chamber and will facilitate the side-by-side comparison of the two NDS's: 1) the porous tube NDS, consisting of six porous tubes with seeds mounted in close proximity to the tubes, and 2) a substrate-based NDS, with three compartments each containing a porous tube embedded in a particulate substrate.