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CARBOHYDRATE DEPOSITION IN RAPHIANUS SATIVUS L. CV. CHERRY BELLE SHOOTS: PRELIMINARY GROUND STUDIES FOR THE RASTA SPACEFLIGHT EXPERIMENT. H. N. Goldsmith­¹, E. C. Stryjewski ² , G.W. Stutte² , W. McLamb ³ , D. Reed³. ¹Brown University, Providence, RI,  ² Dynamac Corporation and ³  Bionetics Corporation, Kennedy Space Center, FL.

As part of ground-based testing for the RASTA (Radish Assimilation in Spaceflight Testbed Atmosphere) experiment, amyloplast sedimentation and carbon partitioning in Raphianus Sativus L. cv. Cherry belle were characterized for future microgravity studies. Radish plants were grown on a clinostat to simulate microgravity and reduced gravity (.005g), and at 1g.  Plants were harvested at 3, 4, 5, 6, 7, and 8 days after planting (DAP) and the stems were fixed, dehydrated, and embedded in paraffin. The samples were then sectioned (12 mm) and stained with a Schiff/PAS reaction to reveal starch location. Three and 4 DAP plants were found to contain too much starch to determine sedimentation whereas these resources were depleted in 7 and 8 DAP plants. Five and 6 DAP plants contain adequate levels of starch for sedimentation studies. Analysis to determine a minimum gravity level for amyloplast sensing revealed that starch sedimented in 1g as well as reduced gravity, but were dispersed in microgravity. Therefore the gravi-sensing system in radish is sensitive to a signal 1/200 the strength of unit gravity. Although starch in the endoderm did respond to gravity, the starch in the mesophyll did not. The starch of the mesophyll tissue was found to be dispersed in all 3 treatments, indicating that these are storage tissues and not gravity sensitive. The amount of starch in the mesophyll, however, was greater in 1g than in microgravity, suggesting that less starch reserves for radish growth may be available to the plants in space.

(This work was supported in part by NASA’s Fundamental Biology Program (NCC-0034) and Spaceflight and Life Sciences Training Program.)