Two parameters were applied to estimate the degree of stress
induced by exposure of the lichen Ramalina duriaei
(De Not.) Bagl. to air pollution in urban-industrial sites in Israel.
Changes in the spectral reflectance response of
the thallus and in the production of stress-ethylene, 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 of the lichen.
The concentrations of Cu, Mg, Fe, Ni, Pb, V, Cr, Mn and sulphate-S in
in situ thalli collected in a nature reserve
in an industrial town (Ashdod, SW Israel) were higher than those detected
in in situ thalli collected in a forest
(HaZorea Forest) in the north-east of Israel. The high concentrations
of these mineral elements in R. duriaei from
the nature reserve coincided with a high rate of production of
stress-ethylene and with a low normalized difference
vegetation index (NDVI) indicating that changes in the spectral
reflectance response relate to damage to the chlorophyll.
Lichens collected in the unpolluted forest in February 1994, either
resuspended in the same site or transplanted
in nine sites in the Ashdod region, and retrieved in November 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 rural localities. Statistical
analysis revealed a positive correlation between the amount of
ethylene produced by R. duriaei and the
concentration of V and Ni in the same thalli.
To test the integrity of the ethylene-producing system, lichens
were soaked in either 5 mM or 10 mM FeCl2 at
pH 3·7. Thalli exposed to a very polluted environment produced
less ethylene after this treatment. The NDVI
correlated positively with the concentration of K in the thallus but
negatively with the concentration of Mn, Ni,
Pb and sulphate-S in the same material.
It may be concluded that the in situ thalli of
R. duriaei in the nature reserve are 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.