The document discusses the structure and types of lichens. Lichens are a symbiotic relationship between fungi and algae or cyanobacteria. They have three main structural forms - crustose, foliose, and fruticose. Lichens reproduce both sexually, through the fusion of male and female gametes, and asexually, through fragmentation or the formation of structures like isidia, soredia, and cephalodia. Lichens have various economic uses including nitrogen fixation, use as food and dyes, roles in biodegradation and producing antibiotic compounds, and use in traditional medicine.

2. PRESENTED BY : AQIL QURESHI
UNIVERSITY OF EDUCATION TOWNSHIP
CAMPUS

3.  Introduction
 Structure of Lichens
 Forms of Lichens
 Classification of Lichens
 Species and Common Naming of Lichens
 Vegetative Reproduction
 Asexual and Sexual Reproduction
 Economic Importance of Lichens

4.  Order : Lechano Rales
 Kingdom : Fungi
 Genus : Lichens
 The intimate symbiotic association of fungi and algae is
called lichens.
 The algae of lichens mostly belong to chlorophyta and
cynobacteria.
 Lichens are abundant growing on bark, leaves and
mosses.
 The fungus is called mycobiont. The
photosynthesizing organism is called a photobiont.

5.  The part of lichen that is not involved in reproduction is
called Thallus.
 Thallus is composed of following parts:
 Upper Cortex
 Algal Zone
 Medulla
 Lower Cortex
 Upper Cortex: Cortex is a protective skin of densely
packed fungal filaments. Upper cortex present on the
top side.

7.  Algal Zone: These are often enclosing algae within
complex fungal tissues.

9.  Algal Zone: These are often enclosing algae within
complex fungal tissues.
 Medulla: It is the central part of the thallus. It forms
the main part of thallus. These are the conductiong
cells.

11.  Algal Zone: These are often enclosing algae within
complex fungal tissues.
 Medulla: It is the central part of the thallus. It forms
the main part of thallus. These are the conductiong
cells.
 Lower Cortex: It is present below the medulla. It is a
narrow layer of compactly arranged hyphae.

13.  The lichens are divided into three groups on the basis
of thallus.
 Crustose Lichens:The thallus from crust like structure.
It is closely adhere to the substrate.
 Example: Graphics
 Foliose Lichens: In this case, thallus has leaf like
lobes. They are free from the substrate.
 Example: Physcia, Permellia.
 Fructicose Lichens: The thallus are cylindrical ribbon
like and branched.
 Example: Cladonia, Usnea

15.  There are two groups of lichens:
 Ascolichens: In this case, lichens belong to
Ascomycota. Majority of the lichens belongs to this
group.
 Basidiolichens: In this case, lichens belong to
Basidomycota.

16.  There are about 20,000 known species of lichens.
 Some lichens have lost the ability to reproduce
sexually. But they are still taken as specie.
 Common names for lichens may contain the word moss
like Reindeer moss and Iceland moss.

17.  Vegetative reproduction occurs by different methods:
 Fragmentation: It is most effective way of
reproduction.
 It is found in foliose and fruticose lichens.
 Mechanical stress or death of some cells breaks the
thallus into fragments.
 Each fragment has growing areas.
 There growing areas grow to form new thallus.
 Isidia:These are small papilla like outgrowths.
 These are present on the upper surface of thallus.

18.  Each isidium is composed of algal cells and fungal
hyphae.
 Isidia detach from the body. Isidia are found in
Permellia etc.
 Soredia: Soredia are small bud like outgrowths formed
on the surface of thallus.
 Soredia are composed of many algal cells with few
fungal hyphae.

20.  Cephalodia: They are external or internal gall like
outgrowths.
 They are dark in colour.
 They consist of fungal hyphae enclosed in algal cells.

22.  Asexual reproduction takes place by pycnidiospores,
conidia oidia formation.
 In some cases, hyphae break down into small pieces
known as oidia.
 While pycniospores are produced within the flask
shaped structures known as pycnidia.
 Sexual reproduction is oogamous, Ascogonium and
spermatia are formed.
 Oogamous characterized by fusion of a small actively
motile male gamete and a large immobile female
gamete.

23.  Ascogonium
 The female sex organ in ascomycetous fungi.
 The hyphae, in fungi of the Ascomycota, that grow
from the ascogonium after it has fused with the
antheridium.
 Spermatia
 A nonmotile male gamete, as in red algae and certain
fungi.
 Colorless cell of certain fungi and lichens, developed
within spermagonia.

24.  Role in nitrogen fixation
 Food
 Biodegradation
 As dyes
 Antibiotic metabolites
 Traditional medicine

25.  Role in Nitogen Fixation: Cynobacteria are involved
in nitrogen fixation.This nitrogen increases the fertility
of soil.
 Food: some used as a staple food.It was cooked as a
bread, pudding, soup, or salad.
 Biodegradation:Lichens can degrade polyester resins.
 As dyes: Many lichens produce secondary compounds
and pigments.

26.  Antibiotic Metabolites: Lichens produce metabolites.
These are useful in the medical community.
 A few are associated to antiseptic.
 Traditional Medicine: Lichens are also used in
nonscientific traditional medicine practices of many
cultures.