Absorption of the natural radioactive gas 222Rn and its progeny 210pb by Spanish moss Tillandsia usneoides and its response to radiation

Radon is the most abundant radioactive gas in natural air and the major contributor to human exposure. However, few attempts have been made to directly measure the relationship between radon and plants. Epiphytic Tillandsia usneoides was chosen as a model to investigate whether it can absorb Rn-222 and its daughter Pb-210 and to determine the physiological and genetic effects of radon on plants. The results showed that T. usneoides was effective in reducing airborne radon because radon concentrations in the chamber after plant treatment decreased faster than those in the natural situation, and activity concentrations of Pb-210 in the plant increased significantly with an increase in radon concentration. The changes in the parameters of genetic damage, including tail DNA, tail length, tail moment and olive tail moment in T. usneoides also increased significantly with the increase of radon concentrations, suggesting that DNA was unavoidably affected by radioactive radon. In contrast, the physiological responses of T. usneoides exposed to radon suggest that this plant can resist radon stress because there was no difference in MDA, soluble proteins and leaf relative electronic conductivity, and increasing SOD may play a role in the tolerance to oxidative stress. Therefore, parameters of genetic damage have the potential to be used as biomarkers to monitor the concentrations of airborne radon.