Search

The role of cosmic ionizing radiation, including heavy ions (HZE-particles) in the induction of mutations at the molecule-, chromosome-, genome- and cell-level is discussed on the basis of different DNA organization in a pro- and eukaryotically compartmented plant system (Arabidopsis thaliana (L.) Heynh.). Data recently obtained on the biological effects of ionizing radiation make it timely to discuss comparatively the evolutionary potentials of space radiation effects in the pro- and eukaryotic genomes (plasmon, plastidom, chondriom, and nucleom) during long duration exposure on space flights.

This article highlights the first results of investigations on the general vitality and damage endpoints caused by cosmic ionizing radiation in dry, dormant plant seeds of the crucifer plant Arabidopsis thaliana (L.) Heynh. and the ascomycete Sordaria fimicola after 69 month stay in space. Wild-type and mutant gene marker lines were included in Free Flyer Biostack containers and exposed on earth and side tray of the LDEF-1 satellite. The damage in biological endpoints observed in the seeds increased in the side tray sample compared to the earth tray sample. For the ascospores we found different effects depending on the biological endpoints investigated for both expositions.

Recently, comparison of biophysical data obtained from orbital flights of short and long duration led to results which will be significant for long and/or repeated stay of man in space. Under orbital conditions biological stress is induced in dry seeds of Arabidopsis thaliana by cosmic radiation especially its high energetic, densely ionizing component, the heavy ions (HZE). For comparison of radiation impact during different space flights a biological attempt at estimating the impact of single particles with high mass and energy (HZE-particles) on seeds was developed. Subdivision into LET-groups showed a remarkable contribution of an intermediate group (LET = 35 to 100 keV/micrometer) due to medium heavy ions (Z = 6 to 10). Efficiency factors for radiation damage experimentally determined and assigned to different LET-classes were compared to radiation quality factors discussed in literature.