MORE IMPORTANT THAN YOU THINK
1- Biological indicators Lichens being very susceptible to air pollution (SO2) are biological indicators of their environment. Since lichens lack the organs like root, stem and leaf as found in higher plants, the pollutants together with humidity and rainwater enter in their thallus surface. The pollutants negatively affecting their growth cause certain species (especially the foliose and the fruticose ones more susceptible) immediately disappear in the region. Therefore, it's possible to measure the degree of pollution in an area by observing the diversity and distribution of the lichens there. 2- Lichen Chemistry and Important Application Areas Lichens produce about 600 different type of secondary compounds unique to these organisms, only as a result of physiological association of the algal and the fungal partners (not produced by any single of them). These secondary lichen substances which are so characteristic of lichens are of fungal origin. For the detection of lichen substances, TLC (Thin-Layer Chromatography) method has been applied commonly. Uses of lichen's secondary metabolites starts from the lichen systematic and extends to the industrial areas such as dying, perfume, pharmacology and medicine. For example, red and purple dyes were produced from Roccella species, which were used for the production of turnusol paper. Cladonia rangiformis provided ethyl alcohol. Antibacterial effect of Usnea species was found significantly for Gram-positive bacteria. Usnic acid is utilized commercially for producing antiseptic creams. Usnic acid is reported to be more effective than Penicillin in the treatment of wounds and burns. Lichen secondary metabolites especially the Usnic acid, have also been found to exhibit antiviral, antifungal, antihistamine, spasmolytic and antitumor properties. In the Northern European countries Cetraria islandica (Iceland moss) is used for treating lung diseases and preparations from this species are still sold in Europe, usually as pastilles. In France and Yugoslavia, tons of Evernia prunastri and Pseudevernia furfuracea are harvested to use their sweet "mossy-smelling" extractions in some perfumes. Lecanora esculenta being rich in mannite, has been used as flour and food for camels in S. Arabia and Asian contries. 3- Old Uses of Lichens It is known that Xanthoria parietina with its yellow-orange color have been used for treatment of jaundice, Lobaria pulmonaria having alveole-like depressions on its surface for treatment of tuberculosis. In old Egypt, Pseudevernia furfuracea is utilized for the mummify. |