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GAUGING THE INTERNAL GAS CONTENT OF BRASSICA RAPA  SILIQUES GROWN IN SPACE.  K.L. Wilsen, J. Blasiak and M.E. Musgrave. Biology Department, University of Massachusetts, Amherst, MA 01003.

Experiments conducted previously on the Mir space station revealed that although Brassica siliques formed normally in the microgravity environment, both the ripening process and seed quality were affected. Because the internal atmosphere of gases in the silique is of great importance for normal seed development, we are developing a protocol to determine the internal gas content of Brassica siliques grown on board the space station. The goal is to establish the combined effects of microgravity, the man-made cabin atmosphere and lack of convection on the relative concentrations of gases inside a maturing silique. Compared to ambient atmosphere (21% O₂, 325 ppm CO₂, <5 ppb ethylene), the atmosphere around developing seeds inside the silique is reduced in O₂ (7-12%) and highly elevated in CO₂ (6000-8000 ppm) and ethylene (3-12 ppm).

Further, we will devise a method for sampling and preserving siliques in such a manner that gas profiles of the preserved material, determined by means of gas chromatography, are representative of gases present at the time of sampling. Eventually, this technology will be used to gauge the internal gas concentrations of siliques grown and harvested on ISS. Post-flight analyses of gases must reflect real time gas compositions of plants growing on board. Ultimately, this information will be used to understand the factors inhibiting healthy plant reproduction in space. 

(Supported by NASA: NAG2-1375.)