The first in a symbiotic nature in 1866, for example, one of the types specified by the physician and mycologist Anton de Bari. In 1869 botanist Simon Slenderer spread these ideas to all types.[1] In the same year, Russian botanists Andrew S. Famintsyn and Osip Vasilevich Baranetsky found that the green cells in the lichen — celled algae. This was perceived by contemporaries as "astonishing".
Today lichenology is a self-discipline related with the Mycology and botany.
Traditional systematics of lichens is largely conditional and reflects the peculiarities of their structure and environment than the relationships within the group, especially because it is based only on mycobiont and photobiont retains its taxonomic independence. Klassificeret lichens in different ways, but currently consider them as an environmental group, not giving them the status of the taxon since the independence of origin of different groups of lichens is not in doubt, and the groups that are included with lichens, placed there that and related mycobiont fungi that do not form lichens. To refer to lichen species using binomial nomenclature, the names correspond to the name of mycobiont.
Lichens are very sensitive to air pollution, especially to sulfur dioxide (sulfurous gas). The degree of sensitivity varies for different types, so they are used as bioindicators of the degree of contamination of the environment.
The lichen Usnea filipendula grows only in areas with very high air quality.
Lichens are organisms-indicators (bio-indicators) to determine the environmental conditions, particularly air quality (lichen-indications). The high sensitivity of lichens to pollution caused by the interaction of its components easy to break. From the air or from the rain do that without any obstacles in the lichen with nutrients and toxic substances, this is because lichens have no special organs for the extraction of moisture from the substrate, and swallow her whole thallus. Therefore, they are especially vulnerable to air pollution.
The first reports of mass death of lichens in the areas of industrial developed cities appeared in the second half of the nineteenth century. The main reason was the increase in the content of sulfur dioxide in the air. Meanwhile, the use of sulfur filters for industrial equipment and catalytic converters in cars has helped to improve air quality, so that today the lichens in large cities are frequent.
In the "passive monitoring" takes into account the frequency of occurrence of lichens in an area, on which the conclusion about the air quality here. Under "active monitoring" watch a particular kind of lichen (Hypogymnia physodes often is), which is planted in the studied location and the impact on the environment (reduction in viability, discoloration of taloma, death) to judge its quality. Lichen-indications intended for long-term studies.
In areas with intensive agriculture, large fertilizing, nitrogen compounds of which are distributed by water, making the soil reaction is weakly basic. This leads to the disappearance of lichen species that prefer acidic soil. Lichens serve as indicators of the presence in the air of toxic heavy metals accumulated in the tissues, which eventually can lead to death of the lichen. Accumulate lichens and radioactive substances. They can therefore be used to monitor fallout from atmospheric nuclear tests.