BRIC1-2
Title of Study
Starch Metabolism in Space-Grown Soybean Seedlings
Science Discipline
Plant biology
Investigator |
Institute |
Christopher S. Brown |
Dynamac Corporation |
|
|
Co-Investigator(s) |
Institute |
Guikema, James A. |
Kansas State University |
Research Subjects
Glycine max (soybean)
Flight seeds: 52
Ground Based Controls
24-Hour asynchronous ground control using the Orbiter Environmental Simulator
Key Flight Hardware
BRIC-60 Canister
Objectives/Hypothesis
This was the first flight of this experiment that tested the hypothesis that starch concentration in plant tissue is decreased due to the effects of the space/microgravity environment. This experiment also investigated possible mechanistic causes for the changes in starch concentration. Measurements were made of starch and soluble sugar concentrations, critical biosynthetic and degradative enzyme activities, localization of the starch grains and the plastids in which they are found, structural and ultrastructural makeup of different tissues within the plants, and detailed measurements of growth and biomass partitioning.
Approach or Method
Two canisters filled with soybeans were flown. The soybeans were harvested postflight. Measurements were made of growth, gas concentrations in the canisters, carbohydrate concentrations and related enzyme activity measurements in the cotyledons and ultrastructural analysis of cotyledon, hypocotyl, and root-tissue sections.
Results
The hypothesis that starch would be reduced in concentration in the space-grown cotyledons was supported by the results of this experiment. Starch concentration in the cotyledons was reduced by approximately 25% in the space tissue compared to the ground controls. Measurements of 11 different enzyme activities related to starch and sugar metabolism were conducted. Only ADP glucose pyrophosphorylase, a rate-limiting enzyme in starch synthesis, was affected by the space flight environment. The activity of this enzyme was lower in the space-grown cotyledons compared to the ground controls, suggesting that the lower starch concentration seen was due to a lower activity of this enzyme. Starch grain size in the cotyledons was also measured. It was found that starch grains were larger or not affected by the space flight environment. Taken together with the lower concentration of starch in the space-exposed cotyledons, this suggests that the starch grain itself may have an altered (i.e., less dense) structure in space.
Publications
Brown, C.S. et al.: Metabolism, Ultrastructure and Growth of Soybean Seedlings in Microgravity: Results from the BRIC-01 and BRIC-03 Experiments (abstract). American Society for Gravitational and Space Biology Bulletin, vol. 9(1), 1995, p. 93.
Brown, C.S. et al.: Soybean Seedling Growth, Ultrastructure, and Carbohydrate Metabolism in Microgravity. Plant Physiology, vol. 108(Suppl. 2), 1995, p. 24.
Gallegos, G.L. et al.: Effects of Microgravity and Clinoration on Stress Ethylene Production in Two Starchless Mutants of
Arabidopsis thaliana. American Society for Gravitational and Space Biology Bulletin, vol. 9(1), 1995, p. 16.
Gallegos, G.L. et al.: Effects of Microgravity and Clinoration on Stress Ethylene Production in Two Starchless Mutants of
Arabidopsis thaliana. Journal of Gravitational Physiology, vol. 2(1), 1995, pp. 153–154.
Gallegos, G.L. et al.: Effects of Stress Ehylene Inhibitors on Sweet Clover (
Melilotus alba L.) Seedling Growth in Microgravity. Journal of Gravitational Physiology, vol. 2(1), 1995, pp. 151–152.
Hilaire, E. et al.: Clinorotation Affects Soybean Seedling Morphology. Journal of Gravitational Physiology, vol. 2(1), 1995, pp. P149–P150.
Piastuch, W.C. and C.S. Brown: Protein Expression in Arabidopsis thaliana after Chronic Clinorotation. Journal of Plant Physiology, vol. 146(3), 1995, pp. 329–332.