Morphology, anatomy and economic importance of Lichens for under graduate students.

1. LICHENS
Dr. A. SASIKALA,
MSc. PhD.
Lecturer in Botany,
PVKN Govt. College,
Chittoor.

2. LICHENS
Schwender (1867-68) first studied and described the
relationship as helotism
Anton Von DeBary (1887) described the association as
symbiosis
Reinke (1896) described the association as mutualism or
consortium
Elenkin (1902) described it as endosaprophytism
Awasthi described it as polysymbiosis or parasymbiosis
Ahmedjian (1962) treated the relationship as symbiosis

3. LICHENS
Mycobiont: Fungal hphae , thallus of lichens, mostly belong to
discomycetes or loculoascomycetes
Phycobiont or photobiont: Algae, randomly distributed or in a
separate zone, belongs to either chlorophyceae or cyanophyceae
Chlorophycophilous lichen: only one phycobiont belonging to
chlorophyceae
Diphycophilous lichen: one chlorophycean and one
cyanophycean algae

4. OCCURRENCE
Distributed in all hospitable habitats except in chemically polluted
areas (lichen deserts)
Depending on the substrate lichens are of various types:
1. Corticolous lichens: Grow on tree trunks. Ex. Usnea, Parmelia
2. Lignicolous lichens: Grow on wood. Ex. Calicium, Chanetheca
3. Terricolous lichens: Grow on ground. Ex. Cladonia, Lecidea
4. Saxicolous lichens: Grow on rocks. Ex. Dermatocarpon,
Verrucaria

9. MORPHOLOGY
Crustose lichens: Thin and flat strongly attached to the
substratum. Grow on bark of trees, ground and surface of rocks. Ex.
Grahis, Leconora, Verrucaria, Rhizocarpon etc.,
Foliose lichens: Possess small leaf like branches parallel to the
substratum, rhizenes are produced from the lower surface. Ex.
Parmelia, Pyxis etc.,
Fruiticose lichens: Extremely branched like a bush, branches are
cylindrical may grow upto 5 to 10 feet. Rhizenes are absent. Ex.
Usnea, Cladonia, Ramalina etc.,
Squammulose lichens: Thallus covered with number of scales or
squammules. Some species of Cladonia

14. ANATOMY
Upper cortex: upper layer of fungal hyphae, like multiple epidermis,
forms a special tissue called prosenchyma
Algal zone: i. Heteromerous lichens: clear zone of algal cells
ii. Homiomerous lichens: randomly distributed algal cells
Medulla: Middle part of loosely owen fungal hyphae, help in
translocation of water and minerals
Lower cortex: only in foliose lichens, tightly owen fungal hyphae
with absorptive rhizenes

20. NUTRITION AND GROWTH
Algal partner helps the fungal partner in nutrition
In some lichens fungal hyphae sends in haustoria into algal cells
Carbohydrates and vitamins are transferred to fungal partner
from algal cells
Fungal hyphae absorb water and minerals through upper cortex
and rhizenes and supply them to algal partner
Growth is very slow due to the slow growing nature of its fungal
partner (about 1 mm to 1cm in a year)

21. REPRODUCTION
Vegetative reproduction:
Fragmentation: When the central part of the thallus disintigrates,
the peripheral parts dissociate and form new lichen thalli
Soridia: bud like structures with net work of fungal hyphae,
formed in groups called soralium, break through upper cortex and
appear as distinct pustules
Isidia: Cylindrical root like structures growing upwards with a
basal constriction
Cephalodia: Gall like structures with different algal members
(diphycophyllus)

23. REPRODUCTION
Asexual reproduction:
Occurs only in mycobiont
Flask shaped pycnidium with an ostiole is
formed
Pycnidiophores with spores are formed lining
the inner surface of pycnidium
Spores after dispersal form individual fungal
colonies
When come in contact with suitable algal
partner form lichens

24. REPRODUCTION
Sexual reproduction: It also occurs only in mycobiont
Ascolichens: Produce ascocarps (apothecium)
Female gametangium: Ascogonium with globose basal region and
a long narrow trichogyne which penetrates the upper cortx and
exposes on the surface
Male gametangium: Antheridium or spermagonium with male
nucleus
Trichogyne receives male nucleus which pairs with female nucleus
forming a dikaryon
Then ascigenous hyphae develop, produce the asci and ascocarp
is formed as in normal apothecial fungi
Asci produce ascospores

25. APOTHECIUM

26. REPRODUCTION
Basidiolichens: Basidiocarps are formed
Corticoid lichens produce bracket like fruit bodies on tree trunks
Clavarioid lichens produce erect, branching fruit bodies on wood
The agaricoid lichens rarely produce fruit bodies
The basidiospores disperse and produce primary mycelium,
secondary mycelium and tertiary mycelium as in normal fungi
Sexual reproduction is absent in deuterolichens

28. REPRODUCTION
Reproduction in phycobiont: Algal partner normally do not
reproduce, but can be induced to reproduce in laboratory
conditions
Show cell division, aplanospore formation, heterocysts, akinites
under laboratory conditions

29. CLASSIFICATION
Hensen and Jahns (1924),Poelt (1973) classified lichens along
with fungi
Alexopoulos and Mims followed poelt in classification of lichens
According to this system lichens are classified into three divisions
Ascolichens: Ascomycotina mycobiont, fruit bodies are either
apothecium or pseudothecium
Basidiolichens: Basidiomycotina mycobiont, fruit bodies are
basidiocarps
Deuterolichens: Do not produce any spores either asexual or
sexual

30. IMPORTANCE OF LICHENS
Ecological importance: In xerosere plant succession, saxicolous
lichens play the role of primary colonizers. They carryout weathering
of rocks (biogeophysical and biogeochemical)
Lichens as food: Eskimos, people of Alaska and Greenland
Rein deer mass – Cladonia and other lichens
Braeria and Usnea – palatable for animals
Lichenin: carbohydrate, reserve food material
Rock flower – Parmelia species

31. CLADONIA PARMELIA

32. IMPORTANCE OF LICHENS
Drug preparations: lobaria pulmonaria – pulmonary diseases
Parmelia sulcata – barain infections
Peltigera canina – rabies
Parmelia saxatilis – epilepsy
Usnea, Cladonia – Usnic acid – antibiotic
Sodium usnate – tomato canker
Leconoric acid – tobaco mosaic
Usnic acid – tobaco mosaic
Other extracts of lichens – wood rotting fungi

33. IMPORTANCE OF LICHENS
Preparation of dyes:
1. Orchil (a dye) – Rosella, Leconora – dying silk and wool garments
2. Orcinol – staining chromosomes in biology laboratories
3. Litmus dyes – Rosella tinctoria, R. montagnii
Preparation of perfumes: species of Ramalina and Cladonia
As pollution indicators: detect pollution due to SO2 , heavy metals
and other pollutants
For tanning in leather industry: Lobaria pulmonaria, Cetraria
islandica
Production of alcohol: species of Cladonia, Usnea, Ramalina and
other lichens
To detect copper and lime deposits: Species of Cetraria and
leconora

34. IMPORTANCE OF LICHENS
Harmful activities: Cedar poisoning – skin rash to wood cutters
Some times interfere with physiology of host plant
Spoil the stone carvings in temples
Forest fires – old mans beard – Usnea species – highly
inflammable

37. THE END

38. LICHENS