Developmental and Physiological Processes Influencing Seed Production in Microgravity

Plant biology

Arabidopsis thaliana (mouse-ear cress)
Flight plants: 12

48-Hour asynchronous ground control using the Orbiter Environmental Simulator

Plant Growth Unit

This experiment hypothesized that a plant may become limited in gas exchange due to the lack of convective air movement in microgravity. Since plants depend on convective air movement to aid the uptake of metabolically important gases, the lack of convection may affect these processes. One process that is sensitive to oxygen levels is seed production; therefore, this study focused on the changes in seed production, which may indicate reduced oxygen transport to the plants.

Two Plant Growth Chambers (PGCs) were utilized in the Plant Growth Unit positions 3 and 4. Each chamber held six plantlets that were 14 days old at planting. The foam/agar plug nutrient system was utilized. A Warburg solution was added to the chamber to maintain CO₂ levels. Planting occurred 1 day before launch. Measurements of pollen viability and root growth were made postflight, and material was fixed for subsequent microscopy.

The plants produced numerous flowers, which had a good appearance except for those in the latest developmental stages. Pollen viability was approximately 50% as assessed by fluorescein diacetate staining immediately after landing. Light microscope examination of the pollen showed a range of morphologies, from normal to collapsed, corresponding to the viability staining results. This amount of viable pollen should have been able to fertilize the flowers and initiate embryo development. However, no evidence of this was found, suggesting a pollen transfer problem. No differences between flight and ground material were observed in leaf or bract structure at the light microscope level.

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