the seedling hydration procedure. The initial command did not take place and without video
downlinks, the entire experiment would not have been completed. An additional issue arose in
seed germination. The seeds were stored from 6 to 8 months prior to hydration and resulted in
only 58% germination in the first run with progressive deterioration in the following 2 runs. The
last major issue to arise was found in the transfer of the frozen materials from the shuttle to
NASA cooler bags. Because the samples were allowed time to “warm up” during transfer, the
RNA from the STS-116 samples degraded. This issue was mediated by implementing a “3-
minute rule” in the following runs (Kiss 2009).
Although several issues did arise during the first part of Tropi, invaluable information was
gained from this experiment. A novel positive phototrophic response to red light was observed
in hypocotyls of seedlings that developed in microgravity. It is hypothesized that A. thaliana
exhibits red-light phototropism in microgravity, while on Earth, it is suppressed by normal
gravity. A greater phototrophic response was also observed in blue-light-based trials. A more
prominent curvature was detected when shoots were briefly exposed to red light followed by
blue light (Millar 2010).
European Modular Cultivation System (EMCS) Tropi experiment unique equipment (EUE) shown stimulating
Arabidopsis seedlings with blue light (left). EMCS Tropi EUE shown stimulating Arabidopsis seedlings with red
light (right). Ames Research Center, Moffett Field, California image.