Mutualisms between fungi and algae
The tiny lichen is a critical part of the food chain, but how do algae and fungi work together to form these What are these strange, plant-like green things?. Mutualistic Relationships Between Algae and Fungi (Excluding Lichens) Interactions between fungi and green algae have already been described for the . Algal-fungal relationships in lichens: Recognition, synthesis and development. In Algal symbiosis. Edited by L.J. Goff. Cambridge University.
The photographs above illustrate two other types you may encounter.
The first are structures called lyrellae. These are similar to apothecia but are greatly elongated. In the case of Graphis scripta, shown in the photo, the lyrellae are highly branched and may resemble some kind of mysterious writing.
Fungi Symbiosis ( Read ) | Biology | CK Foundation
The second photograph, of Calicium trabinellum, illustrates a mazaedium, a kind of stalked apothecium in which the asci dissolve and leave the ascospores to pile up in a powdery mass. A few basidiomycetes are also capable of forming lichens. These are not generally considered to be highly-developed relationships yet there is no doubt they function as lichens. The first of the two photos above shows Multiclavula mucida.
- MUTUALISMS BETWEEN FUNGI AND ALGAE
- Lichens : Symbiotic Relation Between Algae and Fungi
In this species the basidia and basidiospores line the surface of the upright "fingers" and under cool moist conditions release the spores to drift in the wind. The photobiont, a green alga, forms a thick crust of the the substrate, in this case rotten wood.
The algae are enclosed by the hyphae of the mycobiont. In the second picture the mycobiont is Lichenomphalia umbellifera, a mushroom. The photobiont and its relationship with the phytobiont are the same as in M.
Since these sexual structures reproduce only the fungus, the resulting spores must be fortunate enough to land on an appropriate alga, or perish.
However, there is another way. If the lichen can disperse propagules containing both myco- and photobionts then it will be able to develop in any suitable habitat.
However, this type of reproduction is strictly clonal and does not allow for the kind of genetic recombination that occurs during sexual reproduction.
Clonal reproduction of lichens can occur in several ways. The simplest of these is simply to separate a piece of the thallus containing both alga and fungus and send it off by wind or water to develop in a new place.
This kind of reproduction is common among lichens and generally effective. There are more highly developed forms of clonal reproduction, two of which are represented in the photographs above.
In the first the lichen has produced soredia. Soredia are small bundles of algae held together by fungal hyphae. They are small enough to be carried by wind yet guarantee the presence of both partners. The illustration above left shows a young thallus of the foliose lichen Peltigera didactyla. In this species the upper surface becomes dotted with soralia, special structures for the production of soredia. In the photograph, the soralia have released granular masses of soredia.
Symbiosis in lichens
The other photograph above is a highly magnified view of isidia, small coral-like branches containing both mutualists that can break off and drift to a new habitat. The lichen in the picture is Xanthoparmelia conspersa, a common lichen on exposed rock in New Brunswick. Lichen habitats One of the fascinating aspects of lichen biology is the ability of these organisms to occupy habitats that would be totally in inhospitable to other organisms.
Thus we can find them growing on the ground in deserts, on the sides of dry rock, hanging from the branches of trees and and even growing on the backs of turtles. They are nearly as easy to find and study in the middle of winter as during the warmer months. The first of the three photographs above was taken in Saskatchewan, out in an open prairie. The rock in the forground is the highest point in the immediate area; animals sitting there get a panoramic view of the grassland and all that is taking place there.
It is a favourite place for birds, especially birds of prey waiting for a mouse or vole that might be moving through the grass. The orange lichen is a species of Xanthoria that thrives on nitrogen-rich bird droppings left on the rock. Similar species of Xanthoria, as well as members of the related genus Caloplaca, can be found on our seacoast on rocks frequented by gulls and cormorants. The second of the two pictures above is of White Horse Island, a small island in the Bay of Fundy supporting large colonies of nesting birds.
Lichens are known in which there is one fungus associated with two or even three algal species. Rarely, the reverse can occur, and two or more fungal species can interact to form the same lichen. Chlorococcales is now a relatively small order and may no longer include any lichen photobionts.
Algae that resemble members of the Trebouxia are presumed to be in the class Trebouxiophyceae and go by the same descriptive name Trebouxioid.
Cyanolichens[ edit ] Although the photobionts are almost always green algae chlorophytasometimes the lichen contains a blue-green alga instead cyanobacterianot really an algaand sometimes both types of photobionts are found in the same lichen.
A cyanolichen is a lichen with a cyanobacterium as its main photosynthetic component photobiont. Another cyanolichen group, the jelly lichens e. These lichen species are grey-blue, especially when dampened or wet. They usually grow on the barks of trees, dry logs of wood, bare rocks. They are xerophytes in nature and can withstand a long period of drought. On the basis of fungal components: The fungal partner belongs to Ascomycetes Basidiolichens: The fungal partner belongs to Basidiomycetes Deuterolichens: The fungal partner belongs to deuteromycetes On the basis of Thallus: In this case, the thallus form crust like structure.
It closely adheres to the substrate. They are found on bark or rock. Graphis, Lecanora, Haematomma In this case, thallus has leaf-like lobes.lichens : Symbiotic Association between Algae and Fungi
They are fixed from the substrate by hairy rhizoids like structure called rhizines. They are attached only at central points. Parmellia, Collema, Peltigera Their thalli are cylindrical ribbon-like and branched. It is attached only at the base by basal mucilagenous disc. They are commonly called as shrubby lichens. Two species of Lecanora have been used as food in the barren plains and mountains of Western Asia and Northern Africa.
Certain classes of East Siberian inhabitants use lichens as vegetable diet. It is also used for the preparation of chocolates and pastries. It is a food for reindeer and cattle. Species of Cladonia, Citraria, Evernia, Parmelia are used as fodder.