Nickel exposure enhances the susceptibility of lichens Usnea amblyoclada and Ramalina celastri to urban atmospheric pollutants

In the present study, the effect of nickel incorporation on the chemical response of Ramalina celastri (Spreng.) Krog & Swinsc. and Usnea amblyoclada (Mull. Arg.) Zahlbr. exposed to urban atmospheric pollutants was assessed. Lichen thalli were treated with Ni solutions and then transplanted to two areas of the city of Cordoba with different levels of pollution. After exposure, the concentration of chlorophyll a, chlorophyll b, phaeophytin a, hydroperoxy conjugated dienes, malondialdehyde, sulphur content, electric conductivity of the immersion water, and nickel content were measured. Also, a Pollution Index was calculated for each lichen species. The exposure to Ni altered the physiological response to atmospheric pollutants in both lichen species, making them more sensitive to any damage caused by them. When the species were compared, it was observed that R. celastri accumulated more sulphur than U. amblyoclada.