THE INFLUENCE OF AIR-POLLUTION ON THE CONCENTRATION OF MINERAL ELEMENTS, ON THE SPECTRAL REFLECTANCE RESPONSE AND ON THE PRODUCTION OF STRESS-ETHYLENE IN THE LICHEN RAMALINA-DURIAEI

Two parameters were applied to estimate the degree of stress induced b y exposure of the lichen Ramalina duriaei (De Not.) Bagl. to air pollu tion in urban-industrial sites in Israel. Changes in the spectral refl ectance response of the thallus and in the production of stress-ethyle ne, were compared with the concentration of sulphate-S, V, Ni, K, Pb, P, Cu, Cr, Fe, Mn and Mg in either in situ or in transplanted thalli o f the lichen. The concentrations of Cu, Mg, Fe, Ni, Pb, Si, Cr, Mn and sulphate-S in in situ thalli collected in a nature reserve in an indu strial town (Ashdod, SW Israel) were higher than those detected in in situ thalli collected in a forest (HaZorea Forest) in the north-east o f Israel. The high concentrations of these mineral elements in R. duri aei from the nature reserve coincided with a high rate of production o f stress-ethylene and with a low normalized difference vegetation inde x (NDVI) indicating that changes in the spectral reflectance response relate to damage to the chlorophyll. Lichens collected in the unpollut ed forest in February 1994, either resuspended in the same site or tra nsplanted in nine sites in the Ashdod region, and retrieved in Novembe r of the same year, contained a higher concentration of sulphate-S, Pb , Cu, Ni, V and Cr in the urban-industrial sites than in most of the r ural localities. Statistical analysis revealed a positive correlation between the amount of ethylene produced by R. duriaei and the concentr ation of V and Ni in the same thalli. To test the integrity of the eth ylene-producing system, lichens were soaked in either 5 mM or 10 mM Fe Cl2 at pH 3.7. Thalli exposed to a very polluted environment produced less ethylene after this treatment. The NDVI correlated positively wit h the concentration of K in the thallus but negatively with the concen tration of Mn, Ni, Pb and sulphate-S in the same material. It may be c oncluded that the in situ thalli of R. duriaei in the nature reserve a re severely stressed and possibly endangered by the pollution produced by the combustion of heavy fuel oil in the local power plant and oil refineries and by acid rain.