Results of cytogenetic studies of seeds after their extended orbital flight aboard the Salyut orbital scientific station.

Air-dry seeds of Lactuca sativa (lettuce) with a different level of spontaneous mitagenesis were used in these experiments. A part of the seeds was given pre-flight gamma radiation in doses of 1 and 10 krads. Comparison of the results for the in-flight experiments, laboratory and "transport" control showed an increase of cells with chromosome aberrations and an increase of radiobiological effect in irradiated seeds flown aboard the Salyut scientific station. A comparative analysis was made of the cytogenetic changes in seeds after their exposure to different periods of weightlessness during the Cosmos 368, Zond 8 and Salyut missions. The effect of weightlessness of different duration on the development of cytogenetic changes in irradiated and unirradiated seeds is discussed.