Radiation and Life Support Systems: Effects on Plants. Focus on photosynthetic apparatus.

IIn Space, every organism is exposed to high levels of ionising radiation. The effects of ionising radiation on plants depend not only on the type of radiation, but also on doses, exposure conditions (either chronic or acute) and on the features of exposed organism including: species, cultivar, physiological and nutritional status, phase of the life cycle (phenological stage) at the moment of irradiation. Ionising radiation may induce responses on organisms at different scales: on cells, tissues, organs and whole organism. The consequences are not predictable and are due to several mechanism. Ionising radiation on plants may have: 1) indirect effects, as phenotypic expression of modifications induced at the genetic level; 2) direct damages due either to the interaction between the radiation itself with specific cellular structures (for example, the various components of cell walls) or to the production of Reactive Oxygen Species that can damage structural and functional macromolecules such as lipids, proteins and nucleic acids. In this talk were explored the radiosensitivity and the radioresistance of different plant categories.