This experiment was designed to test whether the cell division changes observed in daylily (Hemerocallis cv Autumn Blaze) embryos during previous space flight experiments result directly from microgravity or indirectly through factors associated with water availability and uptake. Preliminary results from STS-29, STS-47 and STS-65 showed that genetic abnormalities occur in these plants during space flight. Because ground-based studies indicated that hydration conditions can impact the integrity of chromosomes, it is possible that the results observed on these flights were not due to direct effects on the plants, but rather to indirect effects mediated by water availability to plant cells.
BRIC 100 canisters housed 27 petri dishes of daylily cells in an agar-solidified medium for 9 days aboard the Shuttle. There was no inflight manipulation. Upon landing, 85% of the cells were chemically fixed for examination while 15% were allowed to develop for examination of postflight readaptation and recovery phenomena. Ground controls were cultured in parallel to the flight experiment.
Data from this study and previous studies indicated that embryogenic cells of daylily are an excellent model system for the study of space effects on cell division, embryological development and chromosome structure of in vitro cultured cells in space. As with previousmissions, flight materials did not grow as well as ground controls. Generally speaking, flight specimens showed various manifestations of stress. Cells with chromosome breaks, bridges, and double nuclei were found in space samples and quantified. None of these abnormalities were evident in the ground controls.
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