NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Evidence of root zone hypoxia in Brassica rapa L. grown in microgravityA series of experiments was conducted aboard the U.S. space shuttle and the Mir space station to evaluate microgravity-induced root zone hypoxia in rapid-cycling Brassica (Brassica rapa L.), using both root and foliar indicators of low-oxygen stress to the root zone. Root systems from two groups of plants 15 and 30 d after planting, grown in a phenolic foam nutrient delivery system on the shuttle (STS-87), were harvested and fixed for microscopy or frozen for enzyme assays immediately postflight or following a ground-based control. Activities of fermentative enzymes were measured as indicators of root zone hypoxia and metabolism. Following 16 d of microgravity, ADH (alcohol dehydrogenase) activity was increased in the spaceflight roots 47% and 475% in the 15-d-old and 30-d-old plants, respectively, relative to the ground control. Cytochemical localization showed ADH activity in only the root tips of the space-grown plants. Shoots from plants that were grown from seed in flight in a particulate medium on the Mir station were harvested at 13 d after planting and quick-frozen and stored in flight in a gaseous nitrogen freezer or chemically fixed in flight for subsequent microscopy. When compared to material from a high-fidelity ground control, concentrations of shoot sucrose and total soluble carbohydrate were significantly greater in the spaceflight treatment according to enzymatic carbohydrate analysis. Stereological analysis of micrographs of sections from leaf and cotyledon tissue fixed in flight and compared with ground controls indicated no changes in the volume of protoplast, cell wall, and intercellular space in parenchyma cells. Within the protoplasm, the volume occupied by starch was threefold higher in the spaceflight than in the ground control, with a concomitant decrease in vacuolar volume in the spaceflight treatment. Both induction of fermentative enzyme activity in roots and accumulation of carbohydrates in foliage have been repeatedly shown to occur in response to root zone oxygen deprivation. These results indicate that root zone hypoxia is a persistent challenge in spaceflight plant growth experiments and may be caused by microgravity-induced changes in fluid and gas distribution.
Document ID
20040088615
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Stout, S. C.
(Louisiana State University Baton Rouge, LA 70803, United States)
Porterfield, D. M.
Briarty, L. G.
Kuang, A.
Musgrave, M. E.
Date Acquired
August 21, 2013
Publication Date
March 1, 2001
Publication Information
Publication: International journal of plant sciences
Volume: 162
Issue: 2
ISSN: 1058-5893
Subject Category
Life Sciences (General)
Funding Number(s)
CONTRACT_GRANT: NAG2-1020
CONTRACT_GRANT: NAG1-00139
CONTRACT_GRANT: NAG2-1375
Distribution Limits
Public
Copyright
Other
Keywords
long duration
STS-87 Shuttle Project
Non-NASA Center
STS Shuttle Project
Mir Project
NASA Discipline Plant Biology
Flight Experiment
manned
NASA Experiment Number 9600004
NASA Experiment Number 9401653
short duration

Available Downloads

There are no available downloads for this record.
No Preview Available