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SPACEFLIGHT EFFECTS ON CELL STRUCTURE AND CHLOROPHYLL CONTENT OF WHEAT.  G.W. Stutte, O. Monje. C. G. Simone and S. M. Anderson.  Dynamac Corp., Mail Code DYN-3, Kennedy Space Center, FL.

   Successful growth and development of plants in microgravity depends on the photosynthetic apparatus of tissues to be performing properly.  The objective of this experiment was to determine the effects of microgravity on cell structure, chloroplast development and chlorophyll content of Triticum aesativum L. cv. USU Apogee that had been grown in microgravity. Leaves of developing wheat that had developed entirely in microgravity were sampled at the completions of a series of seven 21-day-day experiments conducted in the Biomass Production Chamber (BPS) during Increment IV of the International Space Station.  Leaves were also sampled from 14 and 24-day-old plants that were returned alive to Earth.   Plants grown under identical light, temperature, relative humidity, photoperiod, and CO₂ conditions in a second BPS chamber were sampled as ground controls. Leaf tissue was either fixed in 3% gluteraldehyde for post-flight ultrastructural analysis or frozen at –26^oC in the ARTIC freezer for biochemical analysis.  There was little difference in the development of cells of wheat under microgravity conditions.  Chloroplasts of microgravity grown plants were more ovoid than those developed at 1g on Earth, and the thylakoid membranes had a trend to greater packing density.  There were no statistically significant differences in either chlorophyll content or leaf starch content between the flight and ground control plants. These results suggest that wheat adapts to microgravity-associated changes in chloroplast structure. 

(This research was supported by grant from NASA OBPR Fundamental Biology Programs (NCC10-0027))