botany - Do green algae form obligate symbioses with fungi? - Biology Stack Exchange
Newest Questions. Science; 5 points; 5 minutes ago. The india sepoy posted at barrackpore who had to sacrifice his life for raising his voice. The tiny lichen is a critical part of the food chain, but how do algae and fungi work together to form these symbiotic organisms?. interact to form long-lasting relationships remains one of the central questions in The symbiosis between the filamentous fungus Cladonia grayi and the and algal genes upregulated in vitro in early lichen development.
Neither of these organisms is a plant, so the lichen isn't a plant either. Different species of lichens can look very different from each other. Thorsten Lumbsch, a lichenologist at The Field Museum in Chicago, took photographs of two varieties of lichens—a rock lichen above and a spot lichen below —during a recent Thorsten Lumbsch Thorsten Lumbsch Through photosynthesis, the alga harvests the sun's energy to make food for the fungus, which provides a place for the alga to live.
But the relationship is lopsided, Schmitt says, with algae caged like prisoners—even slaves—inside their fungal hosts. Around the world, scientists have identified tens of thousands of types of lichens. At least as many probably still await discovery, says Thorsten Lumbsch, a lichenologist at the Field Museum in Chicago. By putting together a lichen family tree, they hope to understand why so many different types of lichens have evolved in so many places around the world. Most research involves attempts to understand basic facts about the organisms and their interrelationships.
But researchers are also teaming up with lichens to monitor the health of the environment, among other applications. Tough work Studying lichens is rarely easy. Most species depend on very specific conditions, and scientists can rarely get them to grow in laboratories.
This provides lichenologists a great excuse to travel around the world, scouting new specimens and insights. Lumbsch, for one, makes several trips to Australia and South America each year. In the field, he searches for a group of crusty lichens that tends to be quite tiny—usually less than a few millimeters long. Finding samples takes patience and a trained eye. So, I go there and crawl on my knees on the forest floor with a hand lens.
posavski-obzor.info: Microorganisms: Lichen
This photograph was taken on a research trip to India in January Thorsten Lumbsch Spotting lichens is challenging enough. Identifying them is even harder. Many species look exactly alike, even when they are only distant cousins. The most commonly occurring genus of symbiotic cyanobacteria is Nostoc. Depending on context, the taxonomic name can be meant to refer to the entire lichen, or just the fungus that is part of the lichen.
What Are Lichens?
The alga or cyanobacterim bears its own scientific name, which bears no relationship to either the name of the lichen or the fungus. The fungal partner may be an Ascomycete or Basidiomycete.
Next to the Ascomycota, the largest number of lichenized fungi occur in the unassigned fungi imperfecti. Comparatively few Basidiomycetes are lichenized, but these include agaricssuch as species of Lichenomphaliaclavarioid fungisuch as species of Multiclavulaand corticioid fungisuch as species of Dictyonema.
Other lichen fungi occur in only five orders in which all members are engaged in this habit Orders GraphidalesGyalectalesPeltigeralesPertusarialesand Teloschistales.
Lichenized and nonlichenized fungi can even be found in the same genus or species. But when wet, they are completely transformed. This is because the fungal cells in the upper cortex become transparent and the colors of the algal or cyanobacterial layers can shine through. Green algae bestow lichens with a bright green color, while cyanobacteria give hues of dark green, brown, or black, according to the Forest Service. Photosymbiodeme with green [algal] lobes growing from cyanobacterial ones.
It actively seeks out the photobiont by chemical recognition. Acceptance occurs when the two lichen partners interact without negatively influencing one another. He notes that fitness and how the lichen partners work together are dependent on environmental conditions.
Usually, once a lichen association has been established the mycobiont does not switch partners. In this case the fungus associates with a cyanobacterium in shady, humid conditions to form small, shrub-like thalli. However in drier or more exposed conditions, the fungus associates instead with green algae to form large, flat lobes. Mosses are also not lichensaccording to the Forest Service. Though at first glance some may superficially resemble a lichen, mosses are actually primitive versions of plants and are capable of independent photosynthesis.
Importance Lichens are key players in a variety of environmental processes. For example, cyanobacterial photobionts participate in nitrogen fixation.
Lichens also contribute to a phenomenon known as biological weathering. The lichen mycobionts can break down rocks and release minerals by producing certain chemicals.
Lichens can also disrupt rock surfaces simply by physically attaching to them, and by the expansion and contraction of their thalli, according to a article published in the journal Catena.
Weathering can lead to the eventual disintegration of rocks, according to the article. While this is a disadvantage, especially when lichens grow on building stones, it is also an essential step for the formation of primitive soils. When lichens decompose, the organic matter that is left behind, along with particles of rock and dust trapped by thalli provide material for the development of primitive soils.