A lichen is a symbiotic community between one or more fungi , the so-called mycobionts , and one or more photosynthetic partners. These photobionts are green algae or cyanobacteria . In the symbiosis , the green algae are also called phycobionts , the cyanobacteria also as cyanobionts . The properties of lichens are clearly different from those of the organisms that make them up. The typical growth forms of the lichens only develop in the symbiosis, and the mycobionts only form the characteristic lichen acids in cohabitation with a photobiont . The science of the lichen is the lichen customer or Lichenologie .
There are around 25,000 species of lichen worldwide. About 2000 of them occur in Central Europe. The proportion of endemic species is much lower in lichens than in flowering plants. Lichen are always named after the fungus that forms the lichen, as it is usually this that gives it its shape and structure. Several photobionts can be present in one lichen. Recent research has shown that more than one species of fungus can be found in a lichen. In the biological system , lichens are assigned to the fungi , among which they occupy a special position as their own form of life; so they are not plants .
Structure and growth habit
Lichen exist in a wide range of colors, ranging from white to bright yellow, various shades of brown, strong orange, deep red, pink, olive green, blue-green and gray to deep black.
The fungus almost always forms the actual vegetation body of the lichen, a network of fungal threads (hyphae), the so-called camp ; enclosed in it is a population of photobionts. Most lichens are made up of several layers.
In most foliage lichens, the outer layer of dense, braided mushroom threads is formed on the side facing away from the substrate, called the upper bark (a). Below is the layer of algae, in which the algae are stored in a loose fungal network (b). This is followed by the medullary layer, which consists of a loose fungal network without algae (c). This is followed by the lower bark facing the substrate (d), which is anchored by rhizines (e), root-like fungal threads that lie close to the substrate or penetrate it. Such lichen bodies, in which the photobionts are only in one layer, are called heteromeric. If, on the other hand, the phototrophic partner is more or less randomly scattered in the mushroom body, one speaks of a homeomeric thallus .
- Crusty lichen : A crusty lichen consists of beds called areoles. These do not always close closely together. They can sit on a prothallus individually or in groups. Granular, varnish-like or scabbed coatings can also be formed on plant residues, moss , bark and soil. A pseudo-cortex is created by the death of the outermost layer of the bed and by the mucilage of the cell remains. The growth of the thallus is reproduced by this necral layer from the mucous, dying cells.
- Deciduous or leaf lichen : The lichen is flat (folios) and lies more or less loosely on the substrate. Morphologically, the leaf lichens are very diverse and colonize different habitats such as on mosses, but also on rock. As with plant leaves, the leaf-like growth optimizes the light yield for photosynthesis by the photobiont. The growth zone is on the "leaf margins".
- Shrub lichen : The thallus is shrub-shaped and grows as an upright lawn on earth or rock or hangs from trees, dead wood or rocks ( beard or ribbon lichen). The growth zone is at the end of the individual branches.
- Gelatinous lichens: These are lichens with cyanobacteria as partners, which swell gelatinously when moistened and are usually blackish to dark olive in color.
The division into growth forms does not correspond to the phylogenetic relationships.
Mycobiont, photobiont and their symbiosis
The mushrooms are among 98 percent of the department of hose mushrooms on, very few species are stand mushrooms . Some lichen fungi that are only known to be sterile are formally assigned to the Deuteromycota or Fungi imperfecti . Over 20 percent of the mushrooms known today live in a lichen symbiosis.
In 85 percent of the cases, the photobiont is a one- or few-cell green algae ; so far over 80 species from around 30 genera are known. The most important of these is undoubtedly Trebouxia , which can be found in lichens of the genera Cladonia , Parmelia , Ramalina , Umbilicaria and Xanthoria . Other important green algae are Coccomyxa , Myrmecia and the filamentous genus Trentepohlia .
There are also lichens in which the partner comes from the bacterial Phylum of the Cyanobacteria . Its only class, Cyanobacteria, contains over 2000 species in five orders. With the exception of the order Oscillatoriales , all have representatives in lichen symbioses. The most important genus of cyanobacteria with lichen symbionts is Nostoc .
Sometimes green algae and cyanobacteria also appear together in one lichen. While all photobionts can live without their fungal partner, mycobionts cannot be found in nature without their domesticated partner; however, most of them can be kept in culture without photobionts.
The symbiosis between fungi and photobionts can occur in different forms of contact. The fungal threads can only lie loosely next to the partner, one then speaks of contact hyphae , they can enclose them tightly (bracket hyphae) or even penetrate them ( haustorium ).
The benefits of symbiosis are heavily on the side of the mycobiont, and the community is probably best described as controlled parasitism . This is also shown by the fact that the fungus controls the growth and the rate of cell division of the algae. Because of the long development time of this probiotic relationship, a balance has been established between fungus and algae. The advantage for the fungus is that it is supplied with nutrients by the photobionts, which the algae forms through photosynthesis . The fungus, in turn, protects the partner from drying out too quickly, as the humidity in the hyphae does not fluctuate as much; in addition, it shields its photobiont from ultraviolet radiation . In locations where the algae on the ground would be exposed to pH values between 3.5 and 6.5, living in association with the mycobiont helps to absorb phosphate . The common multiplication strategy of fungus and alga also results in an advantage for both symbionts.
Green algae produce sugar alcohols such as ribitol , erythritol or sorbitol , which are more digestible for the fungus than carbohydrates . With cyanobacteria as a partner, however, glucose is transported. With the nitrogen-fixing cyanobacteria, reduced nitrogen is also supplied to the mycobionts. Material flows of the primary metabolism from the fungus to the photobiont are not known.
Lichens have no way of regulating their water balance because they have no real roots for active water absorption and no protection against evaporation . Only over the surface of the lichen bed can they soak up water in a relatively short time like a sponge, either in liquid form or as water vapor. When it is dry, they lose the water they need to maintain their metabolism relatively quickly and switch to a photosynthetically inactive “lifeless” state, in which the water content can be less than ten percent of the dry weight. There is strong evidence that the sugar trehalose plays a major role in protecting vital macromolecules such as enzymes , membrane components or the genetic material DNA itself, as is the case with tardigrade confronted with similar problems .
Contrary to what was assumed for a long time, the mycobiont does not protect the photobiont from dehydration, but at most extends the time that is available for this process. Rather, the almost complete loss of moisture is part of the survival strategy of lichens: only when they are dried out are they able to withstand temperature extremes or high light intensities, especially from ultraviolet radiation ; Artificially moistened lichens, on the other hand, quickly lose their vitality under these circumstances. In many species, drying out is accompanied by a thickening of the bark layer, which becomes more opaque.
The ability to rigid still is very important, especially in cold areas, as frozen water is not available for metabolism. The time that a lichen can survive in such a stage varies depending on the species; However, the case of a desert lichen is known, which after 40 years in a dried-out state could be "revived" by moistening.
The metabolism is only reactivated when water is absorbed again, through rain, dew or humidity. With a water content of 65 to 90 percent of the maximum storage capacity, it reaches its highest efficiency.
Because the humidity is subject to strong fluctuations in the course of a day, the photosynthesis rate of the lichens also varies accordingly; it is usually highest in the early morning, when the lichen bed is wetted by dew.
The rhythm of life described above is also a reason for the extremely slow growth of some lichens. Crusty lichens sometimes only grow a few tenths of a millimeter per year, leaf lichens usually less than an inch. However, the uneven symbiosis also contributes to slow growth, in which the photobiont, which often only takes up ten percent of the lichen volume, has to take care of the mycobiont's nutrition alone.
On the other hand, the most luxuriant growth is found mainly in subtropical cloud forests and near the sea coasts, where only slight fluctuations in humidity ensure optimal growth conditions.
The primary (intracellular) products such as proteins , amino acids , polysaccharides , lipids , vitamins, etc. are formed by both the photo and mycobionts and are not lichen specific. The so-called lichen substances are secondary products of metabolism and are formed exclusively by the fungus and deposited extracellularly on the hyphae .
Today over 600 substances are known, the main groups being divided according to their biosynthetic origin into acetyl polymalonates (such as usnic acid ), shikimic acids and mevalonic acids . These are also the most important color pigments such as yellow vulpic acid or yellow-orange parietin . Chemical reagents that trigger a color reaction are used to detect lichen acids. The most important are calcium or sodium hypochlorite (“C”), potassium hydroxide (“K”) and p-phenylenediamine (“P” or “Pd”).
distribution and habitat
Many lichens grow only very slowly, usually only a few millimeters per year, some species even only a fraction of a millimeter. Therefore, they can only survive in locations where they are not overgrown by plants and prevented from photosynthesis. In damp locations, they often cannot prevail against mosses . Under suitable conditions, such as permanent moisture and suitable temperatures, such as in the rainforest or cloud forest , lichens grow a few centimeters a year.
Similar growth forms in partially matching habitats occur in air algae (aerophytes), which also grow on exposed surfaces such as tree trunks or rocks and can color them with bright colors. The genus Trentepohlia occurs in Central Europe .
Lichens usually have modest metabolic requirements and are content with small amounts of minerals from dust that is blown in the air or nutrients that are contained in rainwater or are dissolved from the subsoil.
Many species are able to develop extreme habitats. Some lichens can grow on bare rock, while others have been found at an altitude of almost 5000 meters in the Himalayan mountains. They occur in the desert as well as in heathland , in moors as well as in permafrost areas and can withstand temperatures of −47 degrees Celsius to +80 degrees Celsius in rigidity. About 200 species of lichen can be found in the Antarctic ; even at 86 degrees south latitude, six species of lichen can be found in the Horlick Mountains . There are also amphibious species, such as Verrucaria serpuloides , that live permanently in the water.
Lichen colonize a wide variety of locations such as tree bark, rocks, soil and even rusted metal, paint or plastics; some robust species can even be found on busy roads. Many types of lichen are substrate-specific, which means that they only thrive on basic rock such as limestone or dolomite or acidic, lime-free silicate rock such as quartz , gneiss or basalt .
Lichen that grows as an epiphyte on trees are not parasites ; they take no nutrients or water from the plant, only photosynthesis is somewhat hindered by the cover. They show clear preferences for certain conditions such as the acidic bark of spruce , birch or alder or the base-rich bark of walnut , norway maple or elder . These features are often valuable identification aids. A number of lichens themselves serve as substrates for other lichens. Typical sequences often form in which different types of lichen are layered in a characteristic order.
On rock, lichens are important pioneering organisms that either sit on the rock or even penetrate the stone. In the case of endolithic lichens, the bed is developed inside the rock and can only be recognized from the outside by discoloration of the rock. In the case of representatives of the genus Verrucaria on limestone , only the fruiting bodies called perithecia are visible as black depressions. After the camp died out, the rock was littered with small pits. Only after the stone has been scratched does the green layer of alga appear. Despite their inconspicuousness, these species play an important role in the chemical and physical weathering and soil formation , all the more so because they often cover the rocks over the whole area.
Since lichens naturally make no distinction between substrates in natural and artificial environments, they are often found on walls, roofs, fences or tombstones. The latter can be used to date lichen growth.
The most extreme habitat in which lichens have so far been able to demonstrate their ability to survive is without a doubt space. Experiments carried out in May 2005 on the lichen maple lichen ( Rhizocarpon geographicum ) and the delicate yellow lichen ( Xanthoria elegans ) showed that these species are able to withstand the hostile conditions outside of the earth's atmosphere, such as strong, for at least a period of about two weeks To withstand temperature fluctuations and high UV radiation intensity. Scientists at the Senckenberg Research Institute have found in a current study (as of 2017) that some types of lichen develop differently depending on the respective climatic conditions and can also select different algae for symbiosis. The lichen-forming fungi Lasallia pustula and Lasallia hispanica live together with various green algae of the Trebouxia genus, depending on the altitude . Both combinations were found in the middle altitude range. Based on DNA analyzes, it was found that the lichen-forming fungi can theoretically live together with seven different Trebouxia species.
As with flowering plants , species of lichen occur with each other or with plant species. The naming of such societies follows rules that are recorded in a code of the plant-sociological nomenclature.
An example of an association determined by lichens is the Cladonio-Pinetum - the lichen-pine forest. It is the least interesting from a forestry point of view, but in terms of nature conservation it is particularly valuable and rare form of pine forest with the most nutrient-poor locations. This society in Central Europe is severely threatened by diffuse, widespread inputs of pollutants and nutrients ( eutrophication ). When benefiting from the nutrients succession it is mainly through Drahtschmielen displaced -Kiefernwald.
As long as they live in a lichen community, the photobionts only reproduce vegetatively, so they do not form gametes . The mushroom partner, on the other hand, can reproduce sexually like other mushrooms.
All spores are only a few thousandths of a millimeter in size. The sexual spores are formed, depending on whether the mycobiont belongs to the tubular or stand fungi, in so-called "tubes" (asci) or on so-called "stands" (basidia) and are accordingly referred to as asco- or basidiospores .
- Apothecia are usually sharply demarcated from the lichen bed, rounded to disk-shaped or bowl-shaped. A layer consisting of parallel asci and non-spore-forming hyphae ends, the so-called hymenium, lies open on top of it or in it.
- Perithecia are more or less spherical, almost closed structures in which the asci are located and the ascospores are formed, which can only emerge through a pore.
The fungus can also reproduce asexually through pycnospores, which are formed in pycnidia . These are spherical to pear-shaped containers that are embedded in the bearing. In these, pycnospores are separated by special hyphae . Pycnidia are usually recognizable as very small blackish spots on the bed.
The spores spread through the air and, if they reach higher layers of air, can be transported over long distances, sometimes worldwide. For example, isolated monuments or tombstones are also colonized, even if the nearest lichen deposit is far away.
The way in which the lichen synthesis takes place, i.e. how the community of mycobiont and photobiont arises, is not yet fully understood. The fungal partner must first track down a suitable free-living algae or bacterial partner and then take control of it. Both apparently only happen when both the fungus and the algae or bacterium are in a "starved" state that is urgently dependent on nutrients. Even in the laboratory, it is only then possible to form the lichen from the two individual organisms. The typical growth form of the respective lichen species only emerges after the fungal partner has established its dominance over the photobiont.
Many lichens are not dependent on such favorable circumstances and have developed special vegetative reproductive organs with which fungus and algae can be spread simultaneously:
- Isidia are outgrowths in the form of pins, buttons, leaves or small branches that have a predetermined breaking point at the base. Wind, water or light contact break them off and form a new lichen on a suitable surface.
- Sorals are dusty breakouts of the lichens, from which granules of a few intertwined fungal threads and algae emerge (soredia). By spreading these granules, new lichens can also be formed.
|Lichen species ( shrub , leaf and crusty flora )||Speed in mm / year|
Lichen is one of the longest living creatures and can reach an age of several hundred years, in individual cases even more than 4,500 years, as is the case with a map lichen ( Rhizocarpon geographicum ) from Greenland . Due to their constant growth rate after an initial period, they can be used to determine the age of exposed stones (glacier retreat or newly erected structures). Most studies refer to the yellow clans of the genus Rhizocarpon , whereby the diameter of the lichen bed is directly related to the age of the subsoil. This age dating based on lichens is also known as lichenometry and was introduced in 1957 by the Austrian botanist Roland Beschel . In 1965, Gerhard Follmann determined the age of the 500-year-old monumental figures on Easter Island based on the lichen growth. The method is, however, controversial because of the not always uniform growth and is only used where, for example, the radiocarbon method cannot be used.
Lichens and animals
Especially in the far north, where the vegetation is sparse, lichens are about 90 percent of the main diet for reindeer during the winter months . Mostly it is reindeer lichens ( Cladonia ), which they expose with their hooves under a blanket of snow and can utilize them with the help of the enzyme lichenase . Also Elche use this food source.
Incidentally, it is mainly invertebrates such as snails, insects and mites, to whose diet lichens contribute to different degrees. These also include dust lice (Psocoptera), sometimes also called wattle, to which the book lice ( Liposcelis simulans ) belongs. The larva of the horn mite Mycobates parmeliae is also worth mentioning , with its bright orange color it has adapted to its habitat in the common yellow lichen .
In addition to food, the lichen vegetation also provides a habitat and camouflage from predators for many animals. Mites and insects live in large numbers between lichen beds; lichens are also an important habitat for the tardigrade , which is also resistant to drought . The caterpillars of various moths camouflage themselves with pieces of lichen, others imitate a lichen-covered branch ( mimicry ).
Many birds use lichens, especially leaf- and shrub-shaped species, for building nests , such as the plover , which builds its bottom nest from around 250 thalli of the corpse lichen and other members of the genus Cladonia and Cetraria .
|Concentration in µg / m 3||Lichen species|
|> 170||no lichen|
|~ 150||Lecanora conizaeoides|
|~ 70||Xanthoria parietina|
|~ 60||Ramalina farinacea|
|~ 40||Anaptychia ciliaris|
Lichen are considered to be pointer organisms for certain environmental conditions, especially air quality. This is because the coexistence between fungus and alga can easily be disrupted. The nutrients and pollutants contained in the air and rain are absorbed almost unfiltered, as lichens have no special organs for absorbing water from the soil and absorb moisture over the entire thallus. Therefore, they are particularly sensitive to air pollution. The first reports of a massive impoverishment of lichen vegetation in the area of industrialized cities date from the second half of the 19th century, long before forest dieback and acid rain came into the public eye. The main cause could be identified as the increased sulfur dioxide content in the air. In the meantime, sulfur filters in industrial plants and catalytic converters in motor vehicles have helped to improve the quality of the air, so that today lichens can again be found more frequently in large cities.
With "passive monitoring", conclusions are drawn about the air quality based on distribution and frequency ( lichen mapping ). In “active monitoring”, several thalli of a certain type, usually the bladder lichen, are exposed at a contaminated site and reactions such as loss of vitality, discoloration of the thallus or even the death of the organisms are observed ( lichen exposure ). The bioindication with lichen, however, is designed for a long time. In Germany, passive and active monitoring have been standardized in the VDI series of guidelines 3799 and 3957 since 1991 .
In areas with intensive agriculture, fertilizers containing nitrogen compounds react weakly basic with the rain. Above all, this leads to the disappearance of the lichen species that prefer acidic locations.
Finally, lichens also store radioactive substances. In particular, they can be used to monitor radioactive precipitation following atmospheric nuclear weapons tests. After the Chernobyl accident , large amounts of radioactive isotopes reached Finland and were ingested by reindeer lichens ( Cladonia ). In reindeer, which mainly feed on these lichens, they accumulated further and finally found their way into the human body as food via the animals' milk and the cheese made from it.
The oldest paleontological evidence of a symbiosis of fungus and algae is evidence of fossils from southern China that are around 600 million years old and thus date from the geological epoch of the Ediacarium . They still contain lichens that live in the water. Until then, fossils from the early Devonian , some 400 million years ago, were considered the oldest lichen fossils . Recently, Prototaxites from Devon discussed as possible "Riesenflechte". It is not clear whether this species living on land is descended from the species found in China, as lichens have arisen independently several times. From a taxonomic point of view, lichens are a so-called polyphyletic group of fungi, which means that the individual species do not go back to a lichen parent species. Considerations that this form of organization populated the land before the vascular plants , as only frugal, occasionally moist organisms could take their first steps on bare rock , also speak for a high phylogenetic age . It is also possible that the first lichens appeared after the vascular plants.
Lichens and humans
History of lichens
The Greek botanist Theophrastos , a pupil of Aristotle , describes for the first time in his work "History of Plants" two types of lichen, a bearded lichen ( Usnea ) and a lichen on coastal rocks ( Rocella ). At that time, they were not recognized as independent organisms, but rather thought to be outgrowths of trees or algae ( seaweed ).
It was not until the 17th century that interest developed again and the name “Lichen” began to be used. This is derived from the Greek λειχην (leichän, Latin Lichen) and means "wart", which indicates the shape of the fruiting body. The number of the previously known species increased to only 28. The French doctor and botanist Joseph Pitton de Tournefort divided the lichens as a separate department "Lichen" from the mosses in a new system . Although more than 170 species were known by 1753, Carl von Linné only described 80 species and called them the “poorest farming people” of the vegetation.
With the publication of the writing Methodus, qua omnes detectos lichenes ad genera redigere tentavit , Erik Acharius founded scientific lichenology in 1803. He created a system based on the structure of the fruiting bodies and compiled a list of all 906 types of lichen known at the time.
The doctor and mycologist Heinrich Anton de Bary first recognized the symbiosis in a certain type of gelatinous lichen in 1866. The assumption that lichens are double organisms of algae and fungus was taken up in 1869 by the Swiss botanist Simon Schwendener , who applied it to the other lichen species.
The oldest use of lichens is as food. The best known is the controversial view whether the biblical manna could have been the desert lichen Sphaerothallia esculenta .
Certain lichens, e.g. B. Cetraria islandica and Lecanora esculenta , were mainly cooked in times of need or used as flour additive. Some participants in difficult expeditions, such as John Franklin's search for the Northwest Passage , only survived thanks to lichen. In Canada , some lichens were known as “tripes de roche” (rock tripe). In the Indian region of Bellary , the curry dish “rathapu” is prepared from a type of Parmelia . In Japan , the umbilical lichen Iwatake ( Umbilicaria esculenta ) is a delicacy and is used as a soup or salad. In North America , Bryoria species are prepared as food.
- “ And the moss that grows on certain trees has healing powers in it. And that which grows on rotten wood has almost no healing power, because it is present in stinky sap from the roofs and rotten wood and in stones, breaks out and grows out in the moss, so it is almost useless. "
According to the doctrine of signatures , the real lung lichen ( Lobaria pulmonaria ) was used against lung diseases in the past and is still used in homeopathy today . In the 17th and 18th centuries, the common lung lichen that grew on pines was used in a monastery on the Ussolka in Siberia as a bitter substance (instead of hops ) in beer brewing. Honey beer is flavored with the species Parmelia hottentotta , which is endemic to Africa .
In the Middle Ages, lichens that grew on exposed skulls were used as "Muscus cranii humani" or "Muscus ex cranio humano" against epilepsy .
Lichen often contains a wide variety of ingredients that make them interesting for the pharmaceutical industry. The Icelandic moss ( Cetraria islandica ) is added to cough suppressants. The antibiotic usnic acid was discovered in the tree beard ( Usnea ). Certain polysaccharides (sarcoma-180) have recently become of interest in cancer treatment.
Some species are used for alcohol production (e.g. Bryoria spp. , Cladonia spp. , Cetraria islandica ).
For a long time the purple orseille , a valuable dye, was obtained from the lichens of the genus Roccella and the species Pertusaria corallina that occur on coastal rocks . Litmus is also a lichen pigment obtained from Roccella species. Other types of lichen, such as Evernia or Parmelia , can also be used to dye wool and fabrics, which in Europe was mainly practiced in Scandinavia and Scotland . In particular, pleasant yellow and brown tones can be achieved. In the south of Chile , beard braids of the genus Usnea are still used for dyeing wool . The Swedish natural scientist Carl von Linné mentions six dye lichens in his Plantae tinctoriae .
The Alpine reindeer lichen ( Cladonia stellaris ) is finally imported in large quantities from Scandinavia and is used as model trees in architectural models or in wreaths.
At the Wilde Mändle dance of the Alpine region, which is still performed every five years in Oberstdorf, the performers are adorned all over their bodies with long, shaggy beards that are sewn onto the linen garment. Only the eye area remains free. They dance to original, rhythmic music.
An unusual use of a lichen is known by the Waorani, a tribe of Amazonian Indians in eastern Ecuador . The Waorani shamans used the lichen Dictyonema huaorani for their rituals , formed by the rare symbiosis between a mushroom and a cyanobacterium. According to recent studies, the lichen contains various tryptamines , such as 5-MeO-DMT , 5-MeO-NMT and psilocybin, as psychoactive components .
Braiding in literature
Of course, lichens are also mentioned in many places in reports about northern Europe, for example in Alfred Andersch's travel stories "High latitudes" and "Nordic walks".
By Hans Magnus Enzensberger 's poem comes weave customer (from the band Braille , 1969).
Concrete walls that are darkly colored by lichen growth are a popular basis for reverse graffiti , as areas not covered by a stencil are cleaned of lichen with the water jet of a high-pressure cleaner.
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- Bernhard Marbach, Christian Kainz: Moose, Farne and Lichen. Recognize and identify common and conspicuous species . BLV Verlagsgesellschaft, Munich 2002, ISBN 3-405-16323-4 , p. 17.
- Guido B. Feige, Bruno B. Kremer: Flechten. Double creatures made from mushrooms and algae. Occurrence, way of life, purpose. Franckh, Stuttgart 1979, ISBN 3-440-00302-7 , p. 33.
- Willfried Nobel, Heike Beismann, Jürgen Franzaring, Reinhard Kostka-Rick, Gerhard Wagner, Walter Erhardt: Standardized biological measurement methods for determining and evaluating the effects of air pollution on plants (bioindication) in Germany. In: Hazardous substances - cleanliness. Air . 65, No. 11/12, 2005, , pp. 478-484.
- Archive link ( Memento of the original from January 11, 2007 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- Matthew P. Nelsen, Robert Lücking a. a .: No support for the emergence of lichens prior to the evolution of vascular plants. In: Geobiology. 2019, doi : 10.1111 / gbi.12369 .
- Heribert Schöller: Lichen - history, biology, systematics, ecology, nature conservation and cultural significance . Schweizerbartsche Verlagsbuchhandlung, Frankfurt am Main 1997, ISBN 3-7829-1151-2 , pp. 3–10.
- Heribert Schöller: Lichen - history, biology, systematics, ecology, nature conservation and cultural significance . Schweizerbartsche Verlagsbuchhandlung, Frankfurt am Main 1997, ISBN 3-7829-1151-2 , pp. 185–186.
- Werner-Christian Simonis: The lower medicinal plants. Mushrooms - algae - lichens. Heidelberg 1970.
- Heribert Schöller: Lichen - history, biology, systematics, ecology, nature conservation and cultural significance . Schweizerbartsche Verlagbuchhandlung, Frankfurt am Main 1997, ISBN 3-7829-1151-2 , p. 189.
- A. Tacón, J. Palma: La comercialización de los productos forestales no madereros: una oportunidad para el manejo comunitario y la valorización del bosque nativo . In: R. Catalán, P. Wilken, A. Kandzor, D. Tecklin, H. Burschel. Bosques y comunidades del Sur de Chile. Editorial Universitaria, Santiago de Chile 2006, ISBN 956-11-1829-7 , pp. 253-266.
- New psychedelic species of lichen discovered: Dictyonema huaorani , Psychedelic Frontier of February 3, 2015
- See: Alwin Binder : Lesson model for the treatment of Enzensberger's poem "lichenskunde" in the 13th grade of the grammar school. In: German lessons. 23, 1971, No. 1, pp. 100-120.