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Spaceflight introduces the human body to extremes not normally experienced in daily life to supplement the body's natural protections for some of the negative effects; important nutrients must be included in an astronaut's diet. Therefore the objective of this study was to evaluate chemical properties (amylose/amylopectin, dietary fiber, sugars and vitamin C) in two processed and unprocessed hydroponic sweetpotato cultivars. In both cultivars dietary fiber ranged from 0.4% to 3%. Amylose/Amylopectin ratio in both cultivars ranged from 1/99% to 14/86%. Glucose and sucrose were the dominant sugars in both cultivars. Vitamin C was reduced 35-50% when processed.

This study compared the physicochemical properties and consumer acceptance of seven nutrient film technique (NFT) and eight microporous tube membrane nutrient delivery system (MTMS) grown hydroponic carrots. NFT-grown carrots had moisture contents range from 86.3–92.1% while the MTMS-grown carrots a range of 82.0–92.0%. β-carotene contents for the NFT-carrots ranged between 2,030–9,900 μg/100 g and for the MTMS-carrots between 2,977–10,488 μg/100 g. Royal Chantenay-NFT- and Mignon-MTMS-grown were the lightest in color, whereas, Mignon-NFT, and Little Finger-MTMS were the darkest. Paramex MTMS-grown was the most acceptable cultivar to the consumers. Paramex, Kinko and Mignon have good potential to be considered for further screening.

In contribution towards the screening of eight hydroponically grown carrots, some biochemical, physical and sensory properties of the roots were evaluated. The carrots had been grown under two nutrient delivery systems, Nutrient Film Technique (NFT) and Microporous Tube Membrane nutrient delivery System (MTMS). Biochemical measures conducted included, moisture, fat and β-carotene contents, and the physical measures were texture and color. For the NFT- and MTMS-grown carrots, Nantes Touchan (91%) and Nanco Hybrid (87%), respectively, had the highest moisture contents. Fat contents for all the cultivars grown in both systems ranged from 0.1 to 0.4%. In the NFT-grown carrots, Baby Spike and Juwaroot had the highest and lowest β-carotene contents, 8777 and 248 µg/100 g, respectively. For the MTMS-grown carrots, Thumbelina had the highest β-carotene content (7840 µg/100 g). However, the lowest β-carotene value for the MTMS-grown carrots was 3059 µg/100 g.

Single leaf sweetpotato cuttings were used for rapid screening of a sample population for adaptation to hydroponics. Leaves cut at the union with the stem were planted in channels covered with white plastic. Holes were punctured through the plastic for the leaf petiole to stand in the channels. They grew in an environmental chamber at 28/22° C, 70% relative humidity and 14 hours light regime at 600 μmol m −2 s−1/10 hours dark. Five leaves per line were evaluated after 14 days. This technique differentiated the performance of genotypes and showed that there is much variability for the characters measured.

An automated nutrient replenishment system has been developed in order to provide a constant electrical conductivity (EC) value for the nutrient solution over the period of plant growth. A single nutrient film technique (NFT) system developed by the Tuskegee University NASA Center was equipped with the EC control system for growth trials with sweetpotatoes. The system is completely controlled and monitored by a PC through the use of LabView instrumentation and data acquisition software. A submersible EC probe driven by an EC controller measures the EC of the nutrient solution reservoir. EC values are passed from the controller to the PC through analog outputs. If the EC is outside a given range, the PC sends a signal to one of two solenoid valves that allow concentrated stock solution or deionized water to enter the reservoir to either raise or lower the EC respectively. For this application the set point is 1200μS cm-1, with a dead band from 1180 to 1220μS cm-1.

Several plant growth systems have been tested for crop production in microgravity and lunar/Mars environments in support of NASA's Advanced Life Support Program and long-term human space missions. These systems have incorporated such design features as the nutrient film technique (NFT), microporous plates, microporous tubes, and expandable boundary chambers and have been developed and used to support sweetpotato production at Tuskegee University. In the present research, the performance of different sweetpotato cultivars in a microporous tube system with lunar simulant medium was studied. The lunar simulant is an inert aggregate with an average particle size of about 3 mm. Buried in this solid medium is a microporous tube. Nutrient solution is circulated through the microporous tube under a slight negative pressure. This pressure is controlled to allow a slight seepage from the tube with some accumulation of water in the solid medium, but no free water.

Long-term manned space missions will require life support processes including food production. Porous plate and tube membrane systems have been identified to have potential for crop production in a microgravity environment. Of several systems tested, a stainless steel plate membrane system with a porous medium underneath has proven to be superior in terms of the uniformity of nutrient solution distribution. Several trials with sweetpotatoes, showed successful plant growth, with reduced foliage and storage root yield as compared to the nutrient film technique (NFT). These results can be attributed to reduced nutrient solution availability compared to NFT. It is expected that design improvements can increase sweetpotato yield..

A closed nutrient delivery chamber with expandable boundaries has been developed to support the growth of root crops, with potential applications in microgravity. The chamber is completely enclosed, separating the root zone from the foliage zone with a padded sealant through which the plant stem passes. The expandable boundary chamber (EBC) allows for expansion of the root zone volume, through longitudal pleats, as the plant grows. Two units have been evaluated with a trial crop of sweetpotato (Tuskegee Univ. breeding clone TU-82-155) for 120 days in a greenhouse environment. Storage root yield per plant in the EBC averaged 1.33 kg in comparison to 0.3 kg for the conventional Nutirent Film Technique (NFT) grown plants. This excellent yield warrants further design refinement and serious consideration of the system for earth use and microgravity applications.