Objectives:The plant used in the experiment was a special clone of Tradescantia that was heterozygous for flower color and hence useful for easy detection of somatic mutations. These plants are characterized by twelve large somatic chromosomes that are well suited for detailed cytologic analysis. This experiment was to determine the effect of weightlessness and other spacecraft environmental conditions on spontaneous and radiation-induced somatic mutation rates and on selected cytologic changes.
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Approach:
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.
Marimuthu, K.M. et al.: The Cytological Effects of Spaceflight Factors, Vibration, Clinostat, and Radiation on the Root Tip Cells of Tradescantia. Radiation Research, vol. 42, 1970, pp. 105-119.
Marimuthu, K.M. et al.: The Effects of Spaceflight Factors and Gamma Radiation on Flower Production and Microspore Division and Development in Tradescantia. Radiation Botany, vol. 10, 1970, pp. 249-259.
Schairer, L.A. et al.: Radiobiological Studies of Plants Orbited in Biosatellite II. Life Sciences and Space Research: Proceedings of the 12th Plenary Meeting of COSPAR, Prague, Czechoslovakia, May 11-14, 1969, North Holland Publishing, 1970, pp. 19-24.
Sparrow, A.H. et al.: Genetic and Cytological Studies of Tradescantia Irradiated During Orbital Flight. Bioscience, Vol. 18 (No. 6):582-590, 1968.
Sparrow, A.H. et al.: Genetic and Cytological Studies of Tradescantia Irradiated During Orbital Flight. Japanese Journal of Genetics, vol. 43, 1968, pp. 470-471.
Sparrow, A.H. et al.: Radiobiologic Studies of Tradescantia Plants Orbited in Biosatellite II. Experiments of Biosatellite II, NASA SP-204, 1971, pp. 99-122.
Sparrow, A.H. et al.: Radiobiological Studies of Tradescantia Plants Orbited in Biosatellite II. BIOSPEX: Biological Space Experiments, NASA TM-58217, 1979, p. 152.
Sparrow, A.H. et al.: Radiobiological Studies of Tradescantia Plants Orbited in Biosatellite II. Radiation Research, vol. 35, 1968, p. 502.
Sparrow, A.H. et al.: Tradescantia Experiment in Biosatellite II. Proceedings of the Symposium on Radiation Biology and Space: International Congress of Radiation Research, Evian, France, 1970.
Cytogenesis
Damage, Chromosome, tradescantia (flowering plant), Microscopy, markers
Damage, Developmental abnormalities, tradescantia (flowering plant), Microscopy
Damage, Developmental abnormalities, wheat, plant, Microscopy
Humidity, ambient
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Mutation rate: dicotyledon
Mutation rate: somatic
Mutation rate: stamen
Radiation, dose, Provided, for study of synergism with weightlessness
Survival rate, Flowering plant (Tradescantia), Observation
Temperature
Temperature, Capsule, Biosatellite II, Recorder