Quality characteristics of the radish grown under reduced atmospheric pressure

This study addresses whether reduced atmospheric pressure (hypobaria) affects the quality traits of radish grown under such environments. Radish (Raphanus sativus L. cv. Cherry Bomb Hybrid II) plants were grown hydroponically in specially designed hypobaric plant growth chambers at three atmospheric pressures; 33, 66, and 96 kPa (control). Oxygen and carbon dioxide partial pressures were maintained constant at 21 and 0.12 kPa, respectively. Plants were harvested at 21 days after planting, with aerial shoots and swollen hypocotyls (edible portion of the radish referred to as the “root” hereafter) separated immediately upon removal from the chambers. Samples were subsequently evaluated for their sensory characteristics (color, taste, overall appearance, and texture), taste-determining factors (glucosinolate and soluble carbohydrate content and myrosinase activity), proximate nutrients (protein, dietary fiber, and carbohydrate) and potential health benefit attributes (antioxidant capacity). In roots of control plants, concentrations of glucosinolate, total soluble sugar, and nitrate, as well as myrosinase activity and total antioxidant capacity (measured as ORAC_FL), were 2.9, 20, 5.1, 9.4, and 1.9 times greater than the amount in leaves, respectively. There was no significant difference in total antioxidant capacity, sensory characteristics, carbohydrate composition, or proximate nutrient content among the three pressure treatments. However, glucosinolate content in the root and nitrate concentration in the leaf declined as the atmospheric pressure decreased, suggesting perturbation to some nitrogen-related metabolism.     

Germination and elongation of flax in microgravity.

This experiment was conducted as part of a risk mitigation payload aboard the Space Shuttle Atlantis on STS-101. The objectives were to test a newly developed water delivery system, and to determine the optimal combination of water volume and substrate for the imbibition and germination of flax (Linum usitatissimum) seeds in space. Two different combinations of germination paper were tested for their ability to absorb, distribute, and retain water in microgravity. A single layer of thick germination paper was compared with one layer of thin germination paper under a layer of thick paper. Paper strips were cut to fit snugly into seed cassettes, and seeds were glued to them with the micropyle ends pointing outward. Water was delivered in small increments that traveled through the paper via capillary action. Three water delivery volumes were tested, with the largest (480 microliters) outperforming the 400 microliters and 320 microliters volumes for percent germination (90.6%) and root growth (mean=4.1 mm) during the 34-hour spaceflight experiment. The ground control experiment yielded similar results, but with lower rates of germination (84.4%) and shorter root lengths (mean=2.8 mm). It is not clear if the roots emerged more quickly in microgravity and/or grew faster than the ground controls. The single layer of thick germination paper generally exhibited better overall growth than the two layered option. Significant seed position effects were observed in both the flight and ground control experiments. Overall, the design of the water delivery system, seed cassettes and the germination paper strip concept was validated as an effective method for promoting seed germination and root growth under microgravity conditions.     

Antioxidant capacity reduced in scallions grown under elevated CO2 independent of assayed light intensity

Long-duration manned space missions mandate the development of a sustainable life support system and effective countermeasures against damaging space radiation. To mitigate the risk of inevitable exposure to space radiation, cultivation of fresh fruits and vegetables rich in antioxidants is an attractive alternative to pharmacological agents. However it has yet to be established whether antioxidant properties of crops can be preserved or enhanced in a space environment where environmental conditions differ from that which plants have acclimated to on earth. Scallion (Allium fistulosum) rich in antioxidant vitamins C and A, and flavonoids was used as a model plant to study the impact of a range of CO₂ concentrations and light intensities that are likely encountered in a space habitat on food quality traits. Scallions were hydroponically grown in controlled environmental chambers under a combination of 3 CO₂ concentrations of 400, 1200 and 4000 μmol mol⁻¹ and 3 light intensity levels of 150, 300, 450 μmol m⁻² s⁻¹. Total antioxidant activity (TAA) of scallion extracts was determined using a radical cation scavenging assay. Both elevated CO₂ and increasing light intensity enhanced biomass accumulation, but effects on TAA (based on dry weight) differed. TAA was reduced for plants grown under elevated CO₂, but remained unchanged with increases in light intensity. Elevated CO₂ stimulated greater biomass production than antioxidants, while an increase in photosynthetic photo flux promoted the synthesis of antioxidant compounds at a rate similar to that of biomass. Consequently light is a more effective stimulus than CO₂ for antioxidant production.     

Biodegradation pathway of an anionic surfactant (Igepon TC-42) during recycling waste water through plant hydroponics for advanced life support during long-duration space missions.

The degradation of an anionic surfactant (Igepon TC-42) was investigated as part of an integrated study of direct recycling of human hygiene water through hydroponic plant growth systems. Several chemical approaches were developed to characterize the degradation of Igepon and to measure the accumulation of intermediates such as fatty acids and methyl taurine. Igepon was rapidly degraded as indicated by the reduction of methylene blue active substances (MBAS) and component fatty acids. The Igepon degradation rate continued to increase over a period of several weeks following repeated daily exposure to 18 micrograms/l Igepon. The accumulation of free fatty acids and methyl taurine was also observed during decomposition of Igepon. The concentration of methyl taurine was below detection limit (0.2 nmol/ml) during the slow phase of Igepon degradation, and increased to 1-2 nmol/ml during the phase of rapid degradation. These findings support a degradation pathway involving initial hydrolysis of amide to release fatty acids and methyl taurine, and subsequent degradation of these intermediates.     

Growth protocols for etiolated soybeans germinated within BRIC-60 canisters under spaceflight conditions.

As part of the GENEX (Gene Expression) spaceflight experiment, protocols were developed to optimize the inflight germination and subsequent growth of 192 soybean (Glycine max cv McCall) seeds during STS-87. We describe a method which provided uniform growth and development of etiolated seedlings while eliminating root and shoot restrictions for short-term (4-7 day) experiments. Final seedling growth morphologies and the gaseous CO2 and ethylene levels present both on the last day in space and at the time of recovery within the spaceflight and ground control BRIC-60 canisters are presented.     

Chromosomes and plant cell division in space: environmental conditions and experimental details.

Details of the plant cultivation system developed for the CHROMEX experiment flown aboard the Shuttle Discovery (March, 1989) in NASA's Plant Growth Unit (PGU) are presented. The physical regime as measured during Spaceflight, both within the orbiter cabin environment and within the PGU itself, is discussed. These data function as a guide to what may be representative of the environmental regime in which Space-based plant cultivation systems will be operating, at least for the near-term. Attention is also given to practical considerations involved in conducting a plant experiment in Space. Of particular importance are the differences expected to occur in moisture distribution patterns within substrates used to cultivate plants in Space vs on Earth.     

Orbit selection and its impact on radiation warning architecture for a human mission to Mars

With the recent announcement of the discovery of the possibility of life on Mars, there is renewed interest in Mars missions, perhaps eventually in human missions. Astronauts on such missions are at risk to occasional periods of enhanced high energy particle flux from the sun known as Solar Particle Events. These events can pose a substantial risk to the health of the astronauts and to the on-board electronics. Effective forecast and warning of these events could provide time to take steps to minimize the risk (retreating to a safe haven, shutting down sensitive equipment, etc.) Providing that forecast capability, will require additional monitoring capability. The extent of this architecture is sensitive to the orbit selected for the transfer to and from Mars. This paper looks at the major classes of Mars missions (Conjunction and Opposition) and sub-categories of these classes and draws conclusions on the number of monitoring satellites needed for each, with a goal to reducing total system cost through optimum orbit selection.     

The "gaseous" environment in sealed BRIC-100VC canisters flown on 'Mir' with embryogenic daylily cell cultures.

As part of the "Cellular Mechanisms of Spaceflight-Specific Stress to Plants" experiment, nine BRIC (Biological Research in Canisters) 100VC canisters, each containing four 100 mm dia polycarbonate petri dishes with embryogenic daylily (Hemerocallis sp.) cultures, were launched on 12 Jan 97 (STS-81), transferred to 'Mir' and returned on 24 May 97 (STS-84). Pre-flight, flight and ground control data for temperature, relative humidity, CO2 and ethylene in the BRIC canisters are presented.     

Results from the RXTE All-Sky Monitor

Selected results from the Rossi X-ray Timing Explorer All-Sky Monitor are presented to illustrate the phenomenology of the light curves. The sensitivity to periodic intensity variations is indicated by the folded light curve of AM Her. The gray line between transient and persistent sources is emphasized. Light curves of a range of systems comprising black holes or neutron stars and low and high mass companion stars show that the behavior of these systems is often, but not always, characteristic.