Containers in which growing tradescantia plants are being flown in a Brookhaven National Laboratory experiment on board the first biosatellite. The roots of these young plants are sealed in tubes filled with nutrient solution, located at each end of the container. The flower buds are arranged in a single tier for uniform exposure to the gamma radiation from a small radioactive source on board the satellite. The primary purpose of the experiment is to determine whether ionizing radiation combined with weightlessness will produce a different frequency of mutations in plant cells than radiation alone. A control sample of Tradescantia on board the biosatellite will be exposed to the same effects of weightlessness, but will be in a special compartment shielded from the radioactive source.