ASGSB 1999 Annual Meeting Abstracts

FOLIAR DETECTION OF HYPOXIA IN BRASSICA RAPA PLANTS GROWN IN MICROGRAVITY. S.C. Stout¹, A. Kuang², and M.E. Musgrave¹. ¹Dept. of Plant Pathology and Crop Physiology, Louisiana State University, Baton Rouge LA. ²Dept. of Biology, University of Texas Pan-American, Edinburg TX.

Changes in water distribution in the plant growth substrate caused by microgravity may limit the availability of oxygen to the roots of space grown plants. A similar stress is encountered terrestrially by plants grown in water-saturated soils and leads to, among other symptoms, accumulation of soluble sugars and starch in the plant shoot. Because the shoot is easily harvested, carbohydrate analysis may provide a convenient measure of rootzone hypoxia. Such analyses may be complicated, however, by unusual environmental conditions such as extremely high levels of ethylene and carbon dioxide in the spaceflight atmosphere. Brassica rapa plants were grown aboard the Mir space station and in a high fidelity ground control. Whole shoots were harvested, frozen, and analyzed enzymatically for soluble carbohydrates and starch content. Leaf samples were also fixed for microscopic analysis. Space-grown plants had significantly greater concentrations of sucrose and total soluble sugars (total of hexoses and sucrose) than ground control plants. Microscopy of leaf samples showed an increase in starch deposition in space-grown plants, although enzymatic starch determination of entire shoots showed no significant differences between treatments. Preliminary work comparing waterlogging effects in ambient and elevated carbon dioxide atmospheres suggests that while elevated carbon dioxide levels may alter carbohydrate concentrations and partitioning, rootzone hypoxia may still lead to the accumulation of carbohydrates even in a high carbon dioxide background. These results indicate that waterlogging stress in the spaceflight environment can be detected by carbohydrate measurements, and that even under water management strategies similar to ground control experiments, plants grown in microgravity may be challenged by hypoxia. (Supported by NASA: NAG2-1020.)

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