Lichens

[BenR]

In response to the request/suggestion of His Hamaness this may hopefully grow into a useful resource for anyone interested in lichens.

 

Lichens are a symbiotic relationship between fungi (mycobiont) and algae (photobiont). The fungus provide the home for the alga and the alga provides the food, via photosynthesis for itself and the fungus.

 

The body of the lichen is called a thallus (thalli plural) and they reproduce with spores similar to fungi.

 

Lichens provide masses of biodiversity! They can cover most surfaces and can also be present under the surface of rock in extreme cases (endolithic lichens).

They contribute to soil formation by weathering rocks.

 

Low lichen biodiversity values are strongly correlated with high levels of respiratory problems, meaning they are a good indicator of pollutants.

 

Evernia prunastri is used a fixative in the perfume industry.

 

The list goes on. They are truly interesting and complex things! But then I am a geek!

 

First picture shows Xanthoria parietina and Physcia tenella Both are tolerant to pollution by nitrogen oxides, sulphur dioxide and various other atmospheric pollutants. Therefore they are good bio-indicators of polluted air.

 

Second picture shows a range of lichens that are not tolerant to pollution. Therefore indicators of very clean air.

 

Sadly I don't have a very good camera, but I am sure Hama will post some better photos of lichens:thumbup:

[BenR]

Oops second picture is not the one I intended. It is a clean air lichen though!

 

Here is the one I intended to post.

[mrtree]

Oh the complexities. To make it even more difficult.

 

Can't the photobiont be a cyanobacteria or in about 5% of known lichen species (the cephalodiates) be both? Lichens with cyanobacteria need liquid water while those only containing algae can adsorb water vapour from the air.

 

Reproduction is not necesarily by spores, many lichens reproduce by vegetative propugales (such as isidia, soredia or blastidia) or thallis fragments. Lichen-forming ascomyscetes may reproduce sexually (via ascospores) but these spores must meet a photosynthetic partner and relichenize.

 

Your endoliths are common in deserts and are about the only visible life in the dry valleys of Antarctica. Remarkable creatures.

[David Humphries]

Fine thread Ben,

 

if you don't mind I'm going to move it into the Ecology forum.

 

 

Will try an add some shots, if I can track them down.

 

 

 

 

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[Tony Croft aka hamadryad]

You see my man, I told you you had it in you! Great thread this will be, I promise you.

 

i will dig out my photos later (gotta work today)

 

as for the geeks, it is my dream to see our force dominate the rebels in here! One day we will see threads like this outwieghing the "take down" threads by 50-1!

 

whoop whooop its the sound of the tree police!

[Andy Collins]

I've learned more in the opening posts than I ever knew on this topic, keep it coming, very interesting

[mrtree]

Hamadryad will be interested I am sure

 

The bulk of the mycobionts are ascomycetes with only a few species of basidiomycetes.

 

About one in five fungi species are lichenized. This lichenization has occurred at least three seperate times in evolutionary history and has also been lost so we see species of fungi today that were once lichenized.

[BenR]

Oh the complexities. To make it even more difficult.

 

Can't the photobiont be a cyanobacteria or in about 5% of known lichen species (the cephalodiates) be both? Lichens with cyanobacteria need liquid water while those only containing algae can adsorb water vapour from the air.

 

Reproduction is not necesarily by spores, many lichens reproduce by vegetative propugales (such as isidia, soredia or blastidia) or thallis fragments. Lichen-forming ascomyscetes may reproduce sexually (via ascospores) but these spores must meet a photosynthetic partner and relichenize.

 

Your endoliths are common in deserts and are about the only visible life in the dry valleys of Antarctica. Remarkable creatures.

 

Very true mrtree! I was trying to give a simple introduction/overview. But yes complexity Also, I think I am right in saying that some fungi can exist as a mycobiont with algae/cyanobacterium, or they can exist in their own right as fungi

Edited March 5, 2011 by BenR

[mrtree]

I think that the current view is that all species of lichenizing fungi cannot survive in a free state in any form other than as a spore, thus they do not grow into mycelium or fruiting body. The phtosynthezing organism can be in a free state and many are extrememly common in nature.

[BenR]

Some more pictures for the thread. All on Oak.