Lichens are sensitive in varying degrees to man-induced pollutants such as sulphur dioxide. This fact is widely used as an indicator of air quality.
Several studies, led by Prof. Yaacov Garty
from Tel Aviv University, were designed to determine the environmental impact of pollutants emitted by combustion of heavy fuel oil in Ashdod and Haifa vicinities, in Israel. For this purpose, thalli of Ramalina duriaei
lichen (in the picture) were transplanted from a clean environment to the suspected polluted one.
At the end of each experiment the photosynthetic activity, chlorophyll integrity, electric conductivity, spectral reflectance, as well as chemical content of different elements of the thalli were analyzed. It was found that the normalized difference vegetation index (NDVI), indicative of the spectral reflectance response of the thallus, correlated with photosynthetic rate, chlorophyll, K, and P content, and inversely correlated with amounts of Al, Ba, Cr, Cu, Fe, Ni, Pb, Pe, Sulfat-S, V, and Zn. The results are summarized in the following table. The NDVI appears to enable the detection of early signs of pollutant induced stress before changes in other physiological parameters become apparent.