ASGSB 1999 Annual Meeting Abstracts

CARBOHYDRATE METABOLISM AND STARCH STRUCTURE IN SPACE-GROWN PLANTS. C.S. Brown^1,2, M.M. Sanwo-Lewandowski¹, O.A. Kuznetsov³, R.C. Cooper³ and K.H. Hasenstein³. ¹Dynamic Corp, Kennedy Space Center, FL; ²NSCORT in Gravitational Biology, NC State Univ., Raleigh, NC; ³Biology dept, Univ of SW Louisiana, Lafeyette, LA.

Analysis if tissue from spaceflight experiments revealed that starch concentration and the activity of the starch synthetic enzyme ADP glucose pyrophosphorylase were both lower in space-grown soybean cotyledons relative to ground controls. However the activity of the sucrose synthetic enzyme, sucrose phosphate synthase, was greater in the space-grown soybean cotyledons relative to ground controls. Other carbohydrate metabolic enzymes were unaffected. In contrast to lower starch concentration, the number of starch grains and overall starch grain volume per cell was greater as measured in EM sections. Measurements of individual starch grains indicated that they were 20-50% smaller than the ground controls. Densities of the grains were similar, but in high gradient magnetic fields the space-grown starch grains moved upward 15% faster than the ground control grains. Starch isolated from the space-grown cotyledons had a higher amylose content (20.5%) than the ground controls (14.5%). Enzymatic degradation with -amylase for 24 h resulted in a 23% degradation of the space-derived starch compared to 48% degradation of the ground control-derived starch. These results suggest altered chemical composition of starch formed in space.

(Supported by NASA grants NAG10-0142 to CSB and NAGW-4984 to the NSCORT in Gravitational Biology at NC State Univ and NAG10-0190 to KHH).

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