22:	Assessment of Reproductive Failure of Wheat Grown on Space Station, Mir.

Authors:	Strickland, Darren, T.(A)
Affiliations:	(A): Utah State University; Dept Plants, Soils & BioMet.
Presenter:	Strickland, Darren T., bcampbell@mendel.usu.edu

Assessment of Reproductive Failure of Wheat Grown on Space Station, Mir. D. T. Strickland1, W. F. Campbell1, B. G. Bugbee1, E. Naegle1, S. P. Klassen1, W. R. McManus2 F. B. Salisbury1, G. E. Bingham1 1Dept. PS&B, Utah State Univ., Logan, UT 84322-4820 and 2Biol. Dept. Utah State Univ., Logan, UT 84322-5305 Equipment failure thwarted attempts to grow wheat, Triticum aestivum L., from seed-to-seed in the greenhouse, Svet, onboard Mir, and in Earth-based "Mock-ups," resulting in vegetative plants with only early floral initiation being observed and plants exhibiting up to 18 leaves as opposed to the normal 6-7 in 1995. In 1996, wheat plants showed vigorous early seedling growth, produced a large biomass, ca 280 floral spikes, and ceased development at the same stage of ontogeny, anthesis, resulting in 100 % sterility. Examination of the florets via scanning electron microscopy indicated that the anthers did not dehisce and the pollen grains were small and shriveled. Laser scanning confocal microscopic examination showed that pollen grains exhibited zero, one and occasionally two, but rarely three nuclei, whereas those from Earth-grown reference plants were normally trinucleate. Atmospheric measurements taken from the Mir indicated 1-2 ppm of ethylene, while CO2 levels varied from 4,000-10,000 µmol mol-1. We have been unable to duplicate plant responses from the 1995 Mir experiment, whereas wheat plants exposed to ethylene gas in repeated experiments have mimicked wheat responses on Mir in 1996. (Supported: NASA Grant NCC 2-831 and the Utah Agric. Exp. Station).