3. Lichens
A lichen is not a single organism. Rather, it is a symbiosis
between different organisms - a fungus and an alga or
cyanobacterium.
Cyanobacteria are sometimes still referred to as 'blue-greenCyanobacteria are sometimes still referred to as 'blue-green
algae', though they are quite distinct from the algae.
The non-fungal partner contains chlorophyll and is called the
photobiont.
#15,000-20,000 species.
4. Lichens are small, non vascular plant found on bark of tree,
ground, rock, fences, roofs and other man made objects.
Lichen on stone Lichen covered
tree,Tresco
5. Xanthoria sp. lichen
on volcanic rock in
Craters of the Moon
National Monument
(Idaho, USA)
Xanthoria sp. With oval
thallus On tree
6. Cladonia fimbiata found
on moist environment
Pine forest with
lichen ground-cover
7. Lichens may be of varied colour
- Grey, Greyish green, yellow, brown,
orange or red.
16. Soredia:
» Greyish, minute rounded bud-like
outgrowths.
» Developed on surface of thallus
» Fall on suitable substratum to germinate
17. Isidia:
Coral like outgrowth, develop from thallus
Help in photosynthesis
Like Soredia, they are easily dispersed.
The isidia on the foliose lichen----Xanthoparmelia
australasica.
18. Found only in Mycobionts
Fertilization organs- Spermagonia
&Ascogonia
Reproduction called Spermatization.
Ascocarp may be Apothecium or
Perithecium or an Ascostroma
Ascospore
Hyphal
branches
Free living
alga
+ =
19.
20. Soil formation and growth of new
Vegetation – Enrich by forming humus
Food – Contain Lichenin carbohydrate
compound.
In ireland,sweden and norway Cetraria In ireland,sweden and norway Cetraria
Islandica is taken as food.
Cetraria Islandica
21. South India species of Paramelia is use in
making delicious curry
Reindeer moss - the only fodder for reindeer and
cattle during winter.
22. Medicine –
Pelligera caniana is used for
hydrophobia
Species of Cladonia, Cetraria for
intermittent fever and as laxatives.
Lobaria pulmonare for lung diseases. Lobaria pulmonare for lung diseases.
Cladonia
Lobaria pulmonare
23. Dyes and Perfumes –
Rocella tinctoria yields litmus commonly used
as indicators
Rocella sp. Give ‘orchil’ used in dyeing wollen
and fabrics.
Contain Cleoresinous substance used in
perfumery.perfumery. E.g- Evernia prunastris.
A sampling of lichen-dyed yarns
Evernia prunastris
24. As pollution indicators –
Lichens are killed by low level of Sulphur
dioxide.
Accumulate SO2 within their thalli.
Geological estimation –Geological estimation –
Lichens with known, slow growth
rates, like Rhizocarpon geographicum,
have been used to estimate the
dates of geological events such
as the retreat of glaciers.
