ASGSB 1998 Annual Meeting Abstracts

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CARBOHYDRATE DEPOSITION PATTERNS IN ETIOLATED SOYBEAN SEEDLINGS GROWN IN MICROGRAVITY.    E.C. Stryjewski¹, K.M. Johnson², H.G. Levine², W.C. Piastuch¹, J.A. Sharek², O. Martynenko³, and V. Prima³. ¹NASA Gravitational Biology Laboratory, Dynamac Corp., KSC, FL ²National Research Council, NASA/KSC ³Institute for Molecular Biology and Genetics, National Academy of Sciences, Ukraine.

Previous spaceflight experiments have shown that starch production is depressed in microgravity in a variety of plant types. To confirm these results, etiolated soybean seedlings (Glycine max cv. McCall) were imbibed and germinated in NASA’s Biological Research In Canister (BRIC) hardware several days into space shuttle mission STS-87. The seedlings grew for 6 days in the spaceflight environment. Upon recovery, selected seedlings were either fixed and processed for Schiff/PAS staining to determine starch deposition patterns, or harvested and frozen for enzymatic carbohydrate assay for total starch content per tissue type. Surprisingly, rather than supporting previous findings, starch concentrations were higher in spaceflight grown tissues than in their corresponding ground controls. Deposition patterns of the starch appear altered as well. In flight grown tissues, starch deposits are clustered around the vascular structures in the hypocotyl, whereas few such deposits are evident in the ground controls. These deposits extend through the mesophyll of the flight tissue as well, while there are no such deposits in the mesophyll of the ground control plants. One possible explanation for the difference in results between our experiment and past experiments involving soybean seedling growth in BRIC canisters, is that significant levels of ethylene have built up within the canisters during these previous studies. In our study, a new design was devised for the plant growth hardware which resulted in significantly lower ethylene levels. Perhaps it is this difference in hardware design that will allow us to observe the true reactions plants have to the space flight environment. (This work supported by NASA contract NAS10-12180, Dynamac Corp.)

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