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seed PRODUCTION IN HYPERGRAVITY in BRASSICA AND ARABIDOPSIS. M.E. Musgrave¹, A. Kuang², J. Allen¹, R. Darnell¹, R. Wagers-Hughes² and J. Blasiak¹. ¹Department of Plant Science, University of Connecticut, Storrs, CT 06269, ²Biology Department, University of Texas Pan American, Edinburg, TX  78541.

   To investigate potential effects of hypergravity on seed development, we conducted a series of experiments on the 8-ft and 24-ft centrifuges at Ames Research Center during summer 2006.  Brassica rapa L. cv. Astroplants and Arabidopsis thaliana L. var. Columbia were grown in the Plant Growth Facility (PGF) and Plant Growth Unit (PGU) respectively, according to the experiment conditions on STS-87 (B-STIC) and STS-68 (CHROMEX-5).  Brassica siliques in tissue culture were also grown in chambers 1-3 of the PGF in a new experiment (B-POD), designed to give information about late stages of seed development not covered in the B-STIC experiment timecourse.  During a 16-d timecourse beginning 11-d after pollination, these siliques were destructively sampled to determine the composition of their internal atmosphere and the biochemical composition of the developing seeds. Our results show that pollen formed in hypergravity had normal viability in both species. Arabidopsis flowers are self-pollinating, and seed development proceeded normally at hypergravity in this species, with full-sized siliques present at the end of the 11-d hypergravity treatment.  Brassica rapa flowers were manually pollinated during daily stops of the centrifuge, resulting in siliques ranging in age from 8-15 days after pollination at the end of the 16-d experiment. Ultimately the full data set from these new experiments at 2-g and 4-g will be compared with our existing data on seed development in microgravity and at 1-g to understand how aspects of seed development vary across a gravity continuum. We have hypothesized that the changes in seed development occurring in microgravity may be caused by lack of convective air movement within the developing seed pod. Because buoyancy-driven convection is gravity dependent, we expect to enhance internal gas mixing by subjecting plants to hypergravity treatments.  This is the first report of seed production in hypergravity.  Supported by NASA grant NAG-10-329.