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GLUCOSINOLATE PRODUCTION IN HYPERGRAVITY IN BRASSICA RAPA.     R.L. Darnell¹, L.H.Levine²,  P.A. Bisbee², J. Allen¹ and M.E. Musgrave¹. ¹Dept. of Plant Science, Univ. of Connecticut, Storrs, CT 06269; ²Dynamac Corp., Kennedy Space Center, FL 32899.

   Glucosinolates are an important class of secondary metabolites that play a role in flavor and nutritional aspects of several plant families, including Cruciferae. The predominant glucosinolate in Brassica rapa L. is 3-butenyl glucosinolate. Previous work found that this glucosinolate increased 75% in stems of B. rapa  grown in the microgravity conditions of the ISS compared with the ground control plants. To further investigate the role of gravity on glucosinolate accumulation, a series of experiments on the 24-ft centrifuge at Ames Research Ctr. was conducted in 2006 to determine the effects of hypergravity (2-g and 4-g). B. rapa L. cv. Astroplants (13-d old) were grown in the Plant Growth Facility following previous experimental conditions. Plants were harvested after 16 days, frozen, and lyophilized prior to analysis for glucosinolates. In general, glucosinolate concentration was the highest in stems, followed by leaves, then roots. Glucosinolate concentration was significantly lower in stems of the 2-g and 4-g plants - averaging 4.6 and 2.5 ng/g DW, respectively - compared with the stationary control plants, which averaged 7.9 ng/g DW. Similarly, there was a 2.2-fold and 7.5-fold decrease in 3-butenyl glucosinolate in roots of the 2-g  and 4-g) plants, respectively, compared with the  control (2.6 ng/g DW). There was a significant decrease in 3-butenyl glucosinolate concentration in leaves of the 4-g compared to leaves of the control plants (2.6 and 4.5 ng/g DW, respectively); however, there was no effect of 2-g on leaf glucosinolate concentration. These results add support to the hypothesis that the increase in glucosinolates observed under spaceflight conditions is due to microgravity, since hypergravity decreased glucosinolate accumulation compared to controls. Additionally, increasing gravity from 1-g, to 2-g to 4-g generally resulted in further decreases in glucosinolate accumulation. This has important implications for the nutritional quality of foods used in NASA’s life support system for long duration space missions.  Supported by NASA grant NAG10-329.