Thirty-two plants were flown in a package in the spacecraft behind and outside of the radiation shield, and identical nonflight control packages, with and without irradiation, were maintained at the launch site. All plants were observed post- flight for: 1) somatic mutation-blue or pink or colorless cells; 2) cell size-giant or dwarf conditions; 3) loss of reproductive integrity-cell death and stunting in stamen hair growth; 4) pollen grain mortality-early and late stages; 5) megaspore development; 6) normal cell divisions; and 7) chromosome aberrations. In order to facilitate computer analysis of the stamen hair, a special scoring technique was developed to "map" or record the frequency and location of mutations, morphological abnormalities, and/or losses of reproductive integrity. Microspores at various developmental stages were fixed and microscopically examined to study micronuclei frequency and the spindle mechanism in the irradiated and nonirradiated cells.

Results:

Bud blasting with flower opening was noted eight days post-recovery. Results indicate no effect of space flight factors on spontaneous levels of somatic mutation, pollen abortion, stamen hair stunting, embryo sac abortion, and chromosome aberration. An enhanced deleterious effect in flight samples attributable to weightlessness was noted, however, in the mitotic spindle mechanism in microspores, megaspores, and root tip cells. Irradiated space-flown plants showed an increased pollen abortion, pollen micronuclei, and stamen hair stunting, suggesting increased injury during the more sensitive stages of meiosis and mitosis. The Earth-irradiated group had a higher mutation rate than the flight-irradiated group. Mutation rates were equal for nonirradiated material, with the exception of the pink stamen hair cell mutation, which exhibited an antagonistic response to space flight factors. There was also an increase in flower production by the flight samples through the 26-day postflight scoring period, while no such increase was noted in the clinostat controls.