Located in the middeck was Astroculture, which had also been on board USML-1 and was flying its final 'test' mission to grow and provide nutrients for potato plants. It grew 10 small tubers to evaluate the extent to which microgravity affected starch accumulation in the plants. Starch, of course, is an important energy-storage compound, but evidence from previous missions had suggested that its accumulation
was somewhat restricted in microgravity; nevertheless, Astroculture scientists were seeing new growth in their tubers as early as 22 October.
''They look very happy and well, staying very turgid,'' said Co-Investigator Ted Tibbetts, ''which means they have not wilted, so the environment is good for them.'' Meanwhile, Astroculture's Principal Investigator, Raymond Bulla of the University of Wisconsin at Madison, pointed out leaf patterns in a photograph of the growing potato plants. ''The thing that's been exciting to us is that, in the three images that have come down at different times, the leaves are in the same position,'' he said. ''This means that the plants are healthy. If they are having problems, the leaves would have shifted.''
By 1 November, when Sacco downlinked video footage of the potatoes, their leaves were starting to wilt, although they continued to perform satisfactorily. This enabled investigators to conclude that Astroculture itself was providing the proper nutrients, light, water and humidity. When she landed on 5 November, Columbia brought back five successfully grown potatoes from the experiment. After this final test - Astroculture had previously been carried on USML-1 and two Spacehab missions, during which lighting, humidity, pH, nutrient supply and carbon dioxide and contaminant subsystems were validated - the hardware was made available commercially for sale or lease.
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