Presentation on theme: "What is a lichen ? Where do they live ? Different sorts of lichen Classify and recognize lichens How do lichen reproduce ? Lichens as air quality indicators."— Presentation transcript:
What is a lichen ? Where do they live ? Different sorts of lichen Classify and recognize lichens How do lichen reproduce ? Lichens as air quality indicators
What is a lichen ? A lichen is a living organism formed by a durable association of a fungus and an algae named « symbiosis » This association is usefull for both partners : the algae gives to the fungus nutriments from photosynthesis and the fungus gives a surface to the algae, minerals and protection against dehydration Some other examples or symbiosis : orchids, bacteria in cows'stomac or alfalfa
Lichens are very special in vegetal wildlife since they have no leaves, no root, nor trunk. The structure's name is « thalle ». Rhizocarpon geographicum Ramalina sp and Xanthoria parietina
- The algi gives vitamins, proteins, sugars - The fungi protects and stocks water in its membrane, it can transfer water to the algi. - Minerals come from dusts et solved salts in water
Growth of lichens is very slow, from 0,1 to 10 mm per year. In a very few case centimeters in a year. Growth is slower in winter than in summer, and faster on rich substratum. Lichens can be about tens years old for foliated lichens to centuries for big one. Some years for this one on the left, but tens of years for this big lichen on the right
Algae fungus Symbiotic discovery was made by a swiss botanist Simon Schwendener ; his ideas were rejected, as well as those of the english writer and drawer Béatrix Potter.
Where do they live ? Because of this symbiotic association, lichens are able to live in every environments even the most unlikely. They also are able to put up with the most extremely conditions. Besides, they do not need a ground to grow Be careful since you could think that this old chewing-gum on the left is a lichen !
Old walls and trees (specially fruit trees) can be covered by lichens Chapelle Notre-Dame in Châteaulin
Lichens are the first plants in every environment, from forests to cities, and in every climates or latitude. Lichen distribution varies with several condition factors : - Water - Light - Temperature - Wind conditions - Ground nature
Some lichens are epiphytal and live in only one kind of bark, depending of physical and chemical conditions such as pH (mesure of acidity). Beech bark covered by lichen. Cladonia on an old stump.
Different sorts of lichen trier et classer les lichens d'après leur morphologie It is possible to sort out and classify lichens depending of their morphology Thalle joined On all the surface Thalle not joined on all the surface Lichen crustacé Thalle with branches Thalle with leaves Lichen fruticuleux Lichen foliacé
Classify and name lichen lichens crustacés: sticked to the rock or the tree specie n°1 specie n°2 specie n°3 specie n°4 specie n°5
Lichens fruticuleux: they look like trees with small branches
Lichens foliacés : they are sticked to the rock or the tree with several points but we can take them off
lichens foliacés can be identify by their colour : Grey
How do the lichen reproduce ? Two ways : - Scattering of small pieces of lichen - Scattering of fungus ’ spores Lichen crustacé in reproducing period
Only the fugus is able to reproduce sexually. Fungus’spores come from apothecies, often very coloured. Spores are scattered by the wind, they will germinate if they meet the right algae and the good conditions.
Lichens : air quality indicators Lichens take all their nutriments form the air et by this way they are very sensitive to air pollution. Because they live during a very long time, they can help us to know and follow air pollution for a long period... The most sensitive to air pollution are fructiculeux, the less sensitive are the crustacés. So, if you find fructiculeux in your area, that means that the air of your place is not polluted.
. Usnées growing on trees are the most sensitive to air pollution. If you find so many lichens, that means that the air is very good and not polluted.
Lichens are very usefull to know more about acids pollution (nitrogen dioxydes and sulfur dioxydes) Sulfur dioxydes can give acid rains that are responsible of lichen disparition. Near the roads, there are not a lot of lichens and only a few sorts of lichens.
Lichens are also able to accumulate some products such as heavy metals, pesticides and all organics polluants, which come from human activities
Number of species (presence) 01 to 23 to 45 to 78 and + No one or crustacés only Very important pollution important Pollution Evernia prunastri or Pseudevernia furfuracea average Pollution Genus Ramalina Low Pollution Genus Usnea Almost No Pollution The presence, the absence or abundance level of some species allow us to evaluate the air quality even in very small areas.
Lichens play a very important part in ecosystems, some insects feed with them (like plecopters which are very good water quality indicators !) A lot of insects use lichens, such as this butterfly using it to hide from predators
As well as a lot of other species, animals or plants, lichens are very good bio- indicators and they give us information about a fundamental life indicator : the air It ‘s up to us to look at them and react if they disappear !!
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