The objective of this proposal is to determine the effects
of microgravity on the growth and development of radish (Raphanus sativus
L.). Salad-type crops that have a short planting-to-harvest cycle may be
used to supplement the primary diet of crews on short-to-medium duration
space missions. In addition to the life support applications, radish serves
as a model system for evaluating the effect of microgravity on carbohydrate
partitioning to the root.
A number of experiments were conducted during FY 2001 in order to
determine the effects of expected spaceflight conditions on growth
and development
of radish. These included evaluating effects of carbon dioxide (CO2)
concentrations for 400-to-10,000-part-per-million (ppm) CO2. These
experiments showed
that optimum concentration was near 1,500 ppm and that superoptimal
concentrations greater than 5,000 ppm resulted in a degree in plant
growth. In addition,
7 experiments were completed to determine the effects of temperature
on growth and development of 19 radish cultivars.
Leaf Epinasty
at High Ethylene Concentrations (0, 300, and 500 ppb)
Radishes were grown at temperatures ranging from 18 to 30 degrees
Celsius (°C). The cultivars were classified as intolerant (no radish formation
between 18 and 30 °C); low-temperature-tolerant (less than 22 °C),
mid-temperature-tolerant (22 to 26 °C), or high-temperature-tolerant
(greater than 26 °C). One cultivar from each classification was
then selected for experimental testing to obtain more detailed morphological,
developmental, and physiological analysis.
Experiments were performed in small, specialized growth chambers to
determine the effects of the volatile plant hormone ethylene on plant
growth. Cherry
Belle radishes were exposed to ethylene concentrations of less than
12, 25, 40, 100, 200, 300, 500, and 1,000 parts per billion (ppb).
These results
revealed a threshold response at less than 50 ppb, and significant
physiological and morphological changes are occurring with chronic
exposure to 100-ppm
ethylene. A series of experiments was initiated to develop techniques
for quantifying the production of volatile organic compounds from these
plants.
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Radishes
Growing in Oasis Foam
The Radish Assimilation
in Spacecraft Testbed Atmospheres (RASTA) experiment is an International
Space Station (ISS) spaceflight experiment scheduled to be conducted
no earlier than 2003 in a specialized plant growth chamber, the Plant
Growth Facility-Split Plenum (PGF-SP) that is being built by Bionetics
Corporation (Kennedy Space Center).
Key accomplishments:
- Completed experiments
to determine effects of superoptimal CO2 on radish development.
- Completed evaluation
of 19 cultivars for high temperature tolerance.
- Completed experiments
to determine dose response curve of radish to ethylene.
- Initiated experiments
to quantify production of volatile organic compounds from radish.
- Made presentations
at five international conferences.
- Published two
peer-reviewed manuscripts.
Key milestones:
- Initiate testing
of ersatz ISS atmosphere on radish growth.
- Determine developmental
effects of starch partitioning in radish.
- Characterize
morphological and physiological adaptations to temperature and light
stress.
- Begin evaluating
experimental protocols in prototype flight hardware.
- Submit three
peer-reviewed manuscripts for presentation.
- Present results
at international scientific conferences.
Contact: Dr. R.M. Wheeler (Raymond.Wheeler-1@ksc.nasa.gov),
YA-D3, (321) 476-4273
Participating Organization: Dynamac Corporation (G.W. Stutte and Dr. O.A. Monje)
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