Oxidative stress induced by fluorine in Xanthoria parietina (L.) Th. Fr.

In our work we were interested in the toxicity of fluorine on the various parameters of stress: chlorophyll, proteins, and antioxidant system in the lichen Xanthoria parietina (L.) Th. Fr., and for this purpose, lichen thalli were treated by sodium fluoride (NaF) at concentrations of 0, 0.5, 1.0, 5.0 and 10.0 mM, for time scale 0, 24, 48 and 96 h. The analysis results obtained revealed that all the parameters evaluated showed significant variations compared to those of the controls. From the analysis results obtained, it was noted that chlorophyll a (Ca), chlorophyll b (Cb) and total chlorophyll (Ca+b) decreased correlating with exposure times to NaF (r = -0.785, p < 0.001; r = -0.955, p < 0.001; r = -0.899, p < 0.001, respectively), with a significant increase of Ca/b ratio (p = 0.00572**) showing that Cb was more affected than Ca. However, hydrogen peroxide (H2O2) increased (r = 0.949, p < 0.001). In correlation with NaF concentrations, Glutathione (GSH) increased (r = 0.969, p < 0.001), while proteins decreased (r = -0.872, p < 0.001). Furthermore, results showed that catalase activity (CAT) increased correlating with increasing exposure time of X. parietina to increasing concentrations of NaF. Long-term exposure (48 h -96 h) caused a significant decrease in GSH content (p = 0.02*) followed by total destruction at time 96 h.