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内容記述 |
It is well established that radiation effects on wild organisms from nuclear power plant accidents primarily depend on the dose received at the accident; however, impacts of prolonged low-dose exposure remain poorly understood. In this study, oxidative DNA damage in Pinus densiflora, assessed via 8-OHdG levels, was compared between inside (0.87–7.74 μSv/h) and outside (0.094–0.16 μSv/h) the difficult-to-return zone 10 years after the Fukushima accident. Leaf 8-OHdG levels varied among the sites but were unrelated to the absorbed dose. In buds, 8-OHdG levels were very low. An irradiation experiment on 2-year seedlings using Cs-137 at three dose rates (44.8, 461, 1738 mGy/h) also found no association between dose rate and 8-OHdG levels; only sampling points correlated with 8-OHdG levels. In contrast, both dose rate and 8-OHdG levels negatively affected seedling survival after the irradiation experiment. Even without irradiation, samples with >0.04% 8-OHdG did not survive. These results suggest 8-OHdG status indicates seedling health and that environmental stress induces oxidative stress via photosynthesis disruption. Additionally, microsatellite mutation rate in megagametophytes was assessed in 1136 seeds using nine markers, detecting only one mutation in contaminated areas, not statistically significant. This mutation rate was too low for sufficient statistical power. In this study, no evidence was found that low-dose chronic exposure affects oxidative DNA damage or mutation rate in P. densiflora. To understand the impact of low-dose chronic radiation exposure on wild plants, further studies incorporating environmental stress and using endpoints other than mutations, such as genome methylation levels and/or responses to oxidative stress, are necessary. |
