β-Radiation Stress Responses on Growth and Antioxidative Defense System in Plants: A Study with Strontium-90 in Lemna minor

In the following study, dose dependent effects on growth and oxidative stress induced by -radiation were examined to gain better insights in the mode of action of -radiation induced stress in plant species. Radiostrontium (Sr-90) was used to test for -radiation induced responses in the freshwater macrophyte Lemna minor. The accumulation pattern of Sr-90 was examined for L. minor root and fronds separately over a seven-day time period and was subsequently used in a dynamic dosimetric model to calculate -radiation dose rates. Exposing L. minor plants for seven days to a Sr-90 activity concentration of 25 up to 25,000 kBqL(-1) resulted in a dose rate between 0.084 +/- 0.004 and 97 +/- 8 mGyh(-1). After seven days of exposure, root fresh weight showed a dose dependent decrease starting from a dose rate of 9.4 +/- 0.5 mGyh(-1). Based on these data, an EDR10 value of 1.5 +/- 0.4 mGyh(-1) was estimated for root fresh weight and 52 +/- 17 mGyh(-1) for frond fresh weight. Different antioxidative enzymes and metabolites were further examined to analyze if -radiation induces oxidative stress in L. minor.