Symbiosis in lichens - Wikipedia
The fungus benefits from the symbiotic relation because algae or cyanobacteria produce food by photosynthesis, which is utilized by fungus. Discusses parasitic and mutualistic relationships of fungi. (fungi and plant roots ) and lichen (fungi and either cyanobacteria or green algae). Commensalism: An association in which one species, usually the smaller, benefits from A mycorrhiza is defined as a symbiotic relationship between the roots of plants and fungi. From fabula-fantasia.info fabula-fantasia.info .. Although the lichen thallus is composed of an algal and fungal component.
Peltigera canina, the dog lichen is used as medicine for hydrophobia in ancient days. Lobaria pulmonaria, lungwort are used for the diseases of lungs respiratory diseases and T. Parmelia is useful against epilepsy. Usnea species are good against urinary diseases. Xanthoria sp is used in jaundice etc Some lichens possess anticarcinogenic properties.
The lungwort lichen is used in tanning, in perfumery.
Symbiosis: Mycorrhizae and Lichens
The cell walls of the fungi of certain lichens contain colouring matters. Species of Rocella and Lecanora yield a most important colouring matter known as Orchil or Cudbear. This is used in colouring woolen and silk fabrics. It is also used for manufacturing litmus papers which are used in laboratories for acid and base identification. It is obtained from Roccella montagnei.
In Russia and Sweden, lichens are used for the production of alcohol. Some lichens are harmful to industrial products because they cause considerable damage to glass surfaces and marble stones due to etching. Ecological Importance of Lichens: Lichens Contribute to Soil Formation: Lichens thrive in undisturbed sites where nothing else will grow. They grow on rocks, barren soil and the bark of dead or live trees.
They are not parasitic when they grow on trees, they just use the tree bark as a home. They enrich the soil by trapping water, dust, and silt. When lichens die they contribute organic matter to the soil, improving the soil so that other plants can grow there.
In the picture V. On parts of the rock that have dried it is harder to see but you may notice that it is slightly green, revealing the presence of the photobiont. The red spots are the alga Hildenbrandia polytypa, similar is size and growth habit to V. The last picture again shows Verrucaria mucosa, this time growing under water at high tide. Note that even this lichen has its limits; most of the rocks in the picture have no lichens at all. This may be because the rocks are too small and may be moved by currents as the tide ebbs and flows or it may be that their surfaces are unsuitable for lichens.
Another problem that lichens face is being eaten by animals. Many contain acids and other compounds that make them unpalatable to animals but V.
Notice the large rock above the one with lichens on it. On its surface is a small snail called a periwinkle. Some periwinkles, notably the rough periwinkle, eat V. This has not happened here yet but there are in fact several periwinkles present, as well as the white barnacles and a mussel. How many periwinkles are here? Not many at first glance, but you might be surprised.
Click on the picture to get an enlarged view and see how many periwinkles you can count. One of the more intriguing mutualisms found in our region is the one between the brown alga Ascophyllum nodosum and the fungus Mycophycias ascophylli. Ascophyllum nodosum, commonly called rockweed, occurs in the intertidal zone where it is left exposed to the air when the tide goes out. Mycophycias ascophylli, a member of the lichen-forming order of fungi Verrucarialesgrows within the body thallus of A.
In return the fungus has access to carbohydrates and other nutrients within its protective environment. Garbary and colleagues at St. Francis Xavier University in Nova Scotia have studied this mutualism in detail and have shown that the fungus not only forms relationships with the rockweed but also seems to form a mutualism with Polysiphonia lanosa, a common epiphyte found attached to the A. At far left is a thallus of A.
You may wish to look further back on this page to see the habitat photo of A. The next picture shows a detail from the first panel.
The small almond-shaped structures along the stem are receptacles. Each receptacle bears a number of conceptacles, structures that release sperm and egg into the ocean each spring. These are seen as bumpy areas in the second photo but in the third more highly magnified panel they can be seen more easily and reveal the pores through which the sperm and egg escape.
The next panel is even further magnified and the conceptacles are even clearer. In this panel it is also possible to see tiny black dots, resembling grains of pepper; these are the perithecia fruiting bodies of Mycophycias ascophylli. The blue box drawn on around one of these leads to the next photograph, taken with a compound microscope, showing a detailed view of one perithecium partially submerged in the receptacle. The perithecia contain asci and ascospores.
The last panel shows one ascus containing eight 2-celled ascospores. The ascospores are not very clear in this picture but are nevertheless nearly mature. In our region Ascophyllum nodosum releases its sperm and eggs in late May. On a warm day at low tide these tiny cells ooze out of the conceptacles like toothpaste out of a tube. When the tide comes in they are released into the water.
The sperm, released in numbers large enough to colour the water orange, swim activly in search of eggs and attach to them when they find one. Eggs can be observed spinning wildly, powered by hundreds of sperm attached to their surface.Lichen: Two Living Things In One - Biology for Kids
Prior toorganisms such as algae, bacteria and fungi, were included in the plant kingdom. InWhitaker, proposed a five kingdom system that was used for many years, but may soon also become outdated. Although, this term is antiquated, it is still used to describe the "bodies" of algae, fungi and of course lichens. The only group of plants, in which we still use the term thallus, to refer to the plant body, are the bryophytes.
MUTUALISMS BETWEEN FUNGI AND ALGAE
Although the lichen thallus is composed of an algal and fungal component, lichens are not studied in mycology or phycology that part of botany that studies algae. Instead, they are studied in their own discipline, lichenology. There are relatively few lichen researchers. Of these most are systematists. As a result, there are still some basic questions concerning this symbiosis that are unanswered or at least up for debate. One of the most basic questions, that has been asked since the discovery of the lichen symbiosis, concerns whether lichens represent a true mutualistic symbiosis or nothing more than a variation of a host-parasite relationship.
There is evidence supporting both sides. That it represented a mutualistic symbiosis, in which the alga was believed to contribute the food supply through photosynthesis, and the fungus protected the alga from desiccation, harmful solar radiation and provided the alga with water and inorganic nutrients, was postulated by Beatrix Potter, the writer and illustrator of Peter Rabbit, soon after Schwendener had determined the true nature of the lichen thallus.
In order to understand both sides of the issue, lets look at the morphology and anatomy of lichens. The Lichen Thallus In the traditional sense of lichens, their thallus can be artificially divided into four forms: Foliose Lichens Lichen thallus which is generally "leaf-like", in appearance and attached to the substrate at various points by root-like structures called rhizines.
Because of their loose attachment, they can easily be removed. These are the lichens which can generally be mistaken for bryophytes, specifically liverworts. It is possible, or even probable, that herbaria still contain lichens that have been mistakenly identified as liverworts.
If we look at these a foliose lichen in longitudinal section, from top to bottom, we would be able to distinguished the following layers: Often composed of tightly interwoven mycelium, which gives it a cellular appearance.
This cellular appearance is referred to as pseudoparenchymatous. Composed of interwoven hyphae with the host algal cells. This is the ideal location for the algal cells.
Mutualisms between fungi and algae
Beneath the upper cortex so that it receives the optimal amount of solar radiation, for photosynthesis, but not direct solar radiation which would be harmful. Composed of loosely interwoven mycelium. Layer is entirely fungal. Usually same composition as the upper cortex and attached to the substrate by root-like structures called rhizines. The rhizines are entirely fungal, in origin, and serve to anchor it to the substrate.
Thus, the foliose lichens also have what is referred to as a dorsiventral thallus, i. Sectional views, illustrating how the three thallus types of lichens differ. The entire lower surface is attached to the substrate. These lichens are so thin that they often appear to be part of the substrate on which they are growing. The following link shows an image of several lichen thalli. Crustose species that are brightly colored often give the substrate a "spray-painted" appearance. The thallus has the upper cortex, algal and medullary layers in common with the foliose lichens, but does not have a lower cortex.
The medullary layer attached directly to the substrate and the margins are attached by the upper cortex. This type of lichen is tightly flattened to its substrate and the entire lower surface medulla is attached, making it impossible to remove the thallus from its substrate.
Fruticose Lichens The thallus is often composed of pendulous "hair-like or less commonly upright branches finger-like.
The thallus is attached at a single point by a holdfast. In cross section, the thallus can usually be seen to be radially symmetrical, i. The layers that can be recognized are the cortex, algal layer, medullary layer, and in some species the center has a "cord" which is composed of tightly interwoven mycelium. Other species have a hollow center that lack this central cord. Fructicose lichen thallus is attached to its substrate at a single point, but finding that point is not that easy!
Biology of Lichens In looking at the anatomy of the lichen, it is obvious that there is interaction between the phycobiont and mycobiont, but what kind of interaction is occurring. One school of thou0ght is that the alga produces the food material and that the fungus protects alga from desiccation, high light intensities, mechanical injuries and provides it with water and minerals. This is the reasoning that many introductory text books have adopted and they define a lichen as a mutualistic symbiosis.
However, in studies that have been done that examines the alga-fungus interface, it can be clearly seen that haustoria, specialized feeding structures present in parasitic fungi, penetrate the alga cells. Thus, many lichenologist have defined this relationship as a controlled form of parasitism.
There is more evidence and I would like to go over some of these. Illustration of haustoria penetrating algal cells give evidence that the lichen symbiosis is really a controlled form of parasitism.
- Introduces relationships fungi have with other organisms, including mycorrhizae and lichen.
- Navigation menu
Conditions outside these parameters will usually be fatal for most species of fungi and algae. However, lichens occur all over the world. They even occur in arctic and hot, dry desert areas where few organisms can live or even survive. Thus, the lichen is able to exploit habitats that few other organisms are able to utilize that seem likely to be the result of their mutualistic, symbiotic relationship. Another experiment that demonstrates that lichens represent a mutualistic symbiotic relationship was carried out in the laboratory by Vernon Ahmadjian.
Although, it is not difficult to separate the myco- and phycobiont components of the lichen, and grow them separately in the laboratory, putting the component back together is another story. For many years it was not possible to put the two together to reform the lichen thallus.
The reason for this was the method that was used in attempting to reform the lichen thallus. These types of media did not work. Ahmadjian reasoned that if the lichen represents a symbiosis, the reason that the relationship formed was because, in nature, neither one could obtain all the nutrients necessary for survival and that only after the two organisms interacted was it possible.
Thus, Ahmadjian created a minimal medium, which would not support the growth of either the myco- or phycobiont, and inoculated them into that medium. This method successfully reformed the lichen thallus, in the laboratory, for the first time. Although, it would appear that there is a great deal more evidence supporting the lichen thallus as a product of mutualistic symbiosis, there are still many who believe that the relationship is that of a balance parasitism that favors the mycobiont.
A Few Words on The Lichen Component Although there are approximately 13, species of lichens recognized, the number of taxonomic groups of fungi and algae that produce the lichen thallus are few. Mycobionts In the traditional sense of lichens, which is how we are defining lichens, the fungal components are always in the Ascomycota, specifically in those groups that form their asci and ascospores in fruiting bodies.
The fungi involved in the lichen symbiosis are never found to be free-living in nature. Phycobiont Regardless of whether we are using the traditional or expanded definition of lichens, the algae involved in the association are the same. Of all the different species of algae that are known, only the divisions Chlorophyta "green" algae and Cyanophyta "blue-green" algae or Cyanobacteria are involved in lichen formation.
The latter are actually bacteria rather than algae although they were classified as such once upon a time. Furthermore, within these divisions, only a few genera are involved in the lichen symbiosis.
Some genera, such as Trebouxia, are known to only occur in lichens and are not free-living, but there are also examples that are free-living. Economic Relevance Economically, lichens have little significance. Perhaps this is why there is so little interest in this group of organisms. One way that they have been utilized is in the extraction of blue, red, brown or yellow dyes in the garment industry. Also, the indicator pigments used in litmus paper was also derived from lichens.
Previously, we briefly mentioned lichens as a source of pharmaceutical compounds. You can include some "folk" remedies in this category as well. They are also used in the cosmetic industry, in the making of perfumes and essential. Finally, some species have been used as food. One species, Lecanora esculenta, is a species that grows in the mountains near Israel and are typically blown free from their substrate. Desert tribes grind up the lichen, dry it and mix it with dry meal to form a flour.
It is postulated that this is the species lichen that is referred to as "Manna from Heaven" when Moses led the Hebrews across the desert during biblical time. One species, Cladonia rangiferina reindeer mossis fed upon by reindeers and cattle. This has led to the discovery that lichens readily absorb radioactive elements. After open-air, atomic testing, both Alaskan Eskimos and Scandinavian Laplanders were found to have high levels of radioactive contamination, which they had absorbed from eating reindeer, which in turn ate lichens.
Other Significant Uses for Lichens Lichens are conspicuously absent in and surrounding cities because many species are sensitive to pollution, especially to sulfur dioxide and flourine, which are common pollutants. For this reason, they have been commonly used as indicators of pollutants. In urban areas, where lichen surveys have been carried out, the absence of certain indicator species is used as early warnings of decrease in air quality.
Lichens also play a very significant role in nature. They are the pioneers in rocky substrates, where there is no soil.
Sloth fur has symbiotic relationship with green algae
Lichens break down the rocky substrate into soil and their decomposing thallus fertilize the newly produced soil, making it possible for the plant habitation. Reproduction Reproduction of the lichen is entirely asexual.
It may occur by soredia sing.: This is best seen in a sectioned lichen. The other means of asexual reproduction is by isidia sing.: Ascospores and conidia also form, but these will only reproduce the fungus.
It is assumed that these structures will come in contact with a suitable algal host and resynthesis the lichen thallus. However, the latter are not thought to be significant in lichen reproduction. From left to right: Clusters of soralia, two soredia, as seen through the microscope, isidia and section through soredium.