Modelling low-level effects

Elucidating the interaction between anti-oxidants and radiation-induced damage to cells to build a model of the causes of low-level radiation effects

Nicol Caplin

Significantly less is known about the effects of low-dose chronic exposure to ionising radiation (IR) on plants than the effects of acute high doses. The importance of this lack of understanding is exemplified by the few studies of chronic low-dose effects that focused on genetics and epigenetics, which have potentially profound implications for environmental radioprotection. Renewed interest in nuclear power production and management of legacy and future radioactive waste has led to debates about the “no effects” exposure threshold and consequences for non-human biota. The current threshold for radiation dose having “no detrimental effect to populations” for terrestrial plants is 10 mGy d-1 (IAEA, 1992) and this is now being challenged by researchers. In a long-term experiment that examines morphology and physiology of plants exposed to IR, five generations of Arabidopsis thaliana have been exposed under controlled conditions to soil activities (90 kBq kg-1) comparable to those found in parts of the Chernobyl Exclusion Zone (CEZ) (30 uGy h-1). It is believed that no previous experiments have been carried out in which morphological and physiological parameters have been examined for LDIR in Arabidopsis over five generations. A novel experimental protocol has also been developed for the purpose of analysing root system development in situ. Enzyme activity and metabolite levels were measured as an indicator of antioxidant production in plants under IR stress. E. sativa seeds flown on the International Space Station for a prolonged stay of six months and sent back to Earth provided data on cosmic radiation as a source of radiation stress to plants.