LICHEN

INTRODUCTION ::

Study of lichen called lichenology.

Lichens are composite thalloid structure containing algae and fungi.

Lichens are distinct group of plant having two components i.e. algal components called Phycobiont and

fungal component called Mycobiont.

Algal component of lichen synthesize carbohydrates by photosynthesis and provides nutrition of fungi

and themselves while fungal component helps in water absorption and water retention. Hence lichen is

an example symbiosis.

The term "Lichen" was first given by Theopharastus for superficial growth on bark of Olea europea

(olive) tree.

Erik Acharius – father of Lichenology.

De Bary – gave this association the name Symbiosis.

Crombie – gave the master-slave hypothesis for this association (also called husband-wife relation

ship). It is also called helotism (Most accepted association now a days).

In this association, the fungal component shows predominance over algal component and the later is a

subordinate partner. Such type of association is known as helotism.

HABIT & HABITAT ::

The lichen are mostly perennial, aerial, slow growing and long lived plant.

Lichens are cosmopolitan. Lichens are even in areas which appear unsuitable for normal plant like bare

hard rock and cold arctic region.

Lichens are most sensitive to air pollution specially SO2-pollution.

In India lichen are most common in eastern Himalaya as compare to western Himalaya Lichens are

absent in planes.

On the basis of habitat, lichen are of following type :

1. Saxicolous – Lichens growing on rocks. eg. – Dermatocarpon, Pornia

2. Corticolous – Lichens growing on tree bark eg. – Parmelia, Usnea

3. Terricolous – Lichens growing on soil eg. Cladonia, Collema.

4. Lignicolous – Lichens growing on wood eg. – Cyphelium.

The lichen may also occur in fresh water eg. – "Hymenelia lacustris"

Few marine species eg. "Caloplaca marina"

CLASSIFICATION ::

Major part of lichens thalli are composed of fungal component.

I. ON THE BASIS OF THEIR FUNGAL COMPONENT -

A. Ascolichen : - Fungal partner is the member of ascomycetes.

• Algal partner is mostly member of green algae and rarely blue green algae.

• Most of the lichens are Ascolichen

B. Basidiolichen : Fungal partner belongs to basidiomycetes.

• In basidiolichen, algal partner is always a member of Myxophyceae (B.G.A.).

Example – Cora pavonia

POINTS TO BE REMEMBERED ::

1. In 80% cases of lichen algal partner is member of green algae or chlorophyceae and in 20% cases

blue green algae.

2. 80% Lichen have Ascomycetes Fungus and 20% is Basidiomycetes.

3. Important member of green algae in lichens is Trebouxia [most common unicellular green alga],

Pleurococcus, Cladophora.

Blue green algae – Nostoc, Scytonema, Anabaena, Gloeocapsa, Rivularia etc.

II. CLASSIFICATION OF THE BASIS OF TYPES OF THALLUS -

Lichens are of three types -

1. Crustose lichen -

• Thallus are flat. The thallus is closely adhered

to the substratum and provides a crust like

appearance.

• These lichens are partially or completely

embedded in to substratum.

• These can't be separated from the substratum

without breaking them.

• Fruiting bodies are visible above the surface

of the substratum.

e.g – Rhizocarpon, Graphis, Lecanora,

Verrucaria, Haemotomma.

2. Foliose lichen –

• Thallus are flat leaf-like and lobed.

• They are attached to the substratum with the help of rhizoid like rhizines.

• These hariy structures are developed from lower side of thallus e.g. Parmelia, Peltiger, physcia

and collema.

3. Fruiticose lichen –

• Thallus is well developed, shrub like, cylindrical and branched thallus.

• They grow erect (Ex. Cladonia) or hang from substratum (Ex. Usnea).

• They are attached to the substratum by their basal mucilagenous disc.

INTERNAL STRUCTURES OF LICHEN ::

V.S. of foliose lichen -

a. Upper cortex – It is made up of compactly interwoven fungal hyphae. Intercellular spaces are

absent. If present then filled with gelatinous substance.

• In some lichens (Parmelia) breathing pores are present on upper cortex.

b. Algal layer – It occurs just below the upper cortex. This layer forms photosynthetic zone of

thallus.

• In this layer algal cells are present and some fungal hyphae are randomly oriented. This layer also

called "gonidial layer".

Cortex

c. Medulla – Beneath the algal zone there occurs medulla. It is made up of loosely interwoven

fungal hyphae with large spaces between them which are randomly oriented.

d. Lower cortex – It is made up of compactly interwoven fungal hyphae some of these hyphae

become specialized and extend downward from the lower surface of the cortex and helps in the

attachment of thallus to the substratum. These specialized hyphae are known as rhizines.

• Internal structure of curstose lichens is also more or less similar to foliose lichens.

• The lower cortex does not occur in fruiticose lichens due to their cylindrical structure and

medulla forms the central part of the axis.

POINTS :

(i) Breathing pores – The upper surface of some lichen have loosely arranged areas called breathing pores.

They help in gaseous exchange. eg. Parmelia

(ii) Cyphellae – These are small, almost circular depression on the lower side of thallus (In foliose lichen).

They are meant for exchange of gases.

•Cyphellae [cyphella-singular] are analogous to stomata of higher plants.

REPRODUCTION ::

These are of following type -

VEGETATIVE REPRODUCTION ::

(a) Fragmentation : The main thallus breaks into small pieces and each piece grows to form new lichen

thallus.

(b) Soredium : Some small bud-like outgrowths, known as soredia, develop on the surface the thallus.

• A soredium contains one or few algal cells closely enveloped by a weft of fungal hyphae.

• They are detached from the thallus by the impact of wind or rain. The soredia germinate on suitable

substratum and form new thalli.

(c) Isidium : Isidia are small, stalked, greyish-black coral-like outgrowths which develop on the upper

surface of the thallus.

• The isidium has an outer cortical layer enclosing the algal and fungal components.

• It is usually constricted at the base and is easily detachable from the parent thallus. It germinates

under favourable conditions and forms new thallus.

• In addition to propagation, isidia also help in increasing the photosynthetic surface of the thallus.

• They vary in shape may be rod like (e.g. Parmelia), coral-like (e.g. Peltigera), scale-like (e.g.

Collema) or cigar like (e.g. Usnea).

(D) Cephalodium : These are small wart-like structures formed on the surface or inside of the thallus.

• One of the characteristic feature of cephalodium is that its algal and fungal components differ

from that of the thallus.

• It is due to the fact that cephalodia develop on the younger parts of the thallus from soredia of some

other species. Hence, the cephlodium may be regarded as sterile thallus of some other lichen.

They retain moisture.

• In some species, the cephalodium contains the same fungal hyphae as in thallus but the algal

component is always different.

ASEXUAL REPRODUCTION ::

(a) Oidia : The fungal hyphae form small thin walled bodies called oidia.

• On coming in contact with suitable algal component they form new lichen thallus.

(b) Conidia : In several lichens, the fungal component form conidia. Conidia produced on conidiophores.

(c) Pycnidiospores : These spores are formed in flask shaped structures, called Pycnidium.

• Pycnidiospores form new fungal mycelium and Mycelium form new lichen in contact with suitable

algal component.

SEXUAL REPRODUCTION ::

Sexual reproduction is the function

of fungal component.

The fungal component of most of

the lichens belongs to the class

ascomycetes.

Female sex organ is called

"Carpogonium".

Carpogonium differentiated into

two parts – lower coiled part is

called "ascogonium" and upper

straight part is called

"trichogyne".

The ascogonium remains embedded

with in the algal layer of the

thallus, whereas the trichogyne

projects over the surface of the

thallus.

Male sex organ is called

"Spermogonium"

It is flask shaped. It open out side

by ostiole.

Inside spermogonium non motile

sperms or spermatia are formed.

The spermatia are ooze out

through ostiole in the form of

slimy mass and attach with the

trichogyne and wall of both soon

dissolves.

Nucleus of spermatia reaches in

ascogonium.

Many "Ascogenous hyphae" arises from the fertilized ascogonium.

These cells are uni or binucleated and the terminal or penultimate (sub-terminal) binucleate cell of the

ascogenous hyphe develops into an ascus. In ascus both nuclei fuse to form a diploid nucleus.

In ascus one meiosis and one mitotic division take place and 8-ascospores are formed in each ascus by

paraphysis.

Asci (Ascogenous hyphae, ascus mother cells, ascospores) and some sterile hyphae form fruiting body

called "apothecium" eg. Parmelia or Perithecium eg. Dermatocarpon, Verrucaria.

Ascospores are liberated from ascus and on coming in contact with suitable algae form new lichen

thallus.

ECONOMIC IMPORTANCE OF LICHEN ::

1. Ecological importance :

• The lichens are pioneer of vegetation in lithosere (succession on rocky surface).

In Lithosere – sequence of different stages is –

Crustose lichen (pioneer) → Foliose lichen → Fruiticose lichen → Moss stage

Tree (climax) Shrub stage Herb stage

• Lichen initiates biological weathering of rocks by forming acids like Carbonic acid, Oxalic acid.

• Biological weathering of rocks leads to the formation of soil i.e. helpful in pedogenesis. So Lichens

are farmer of nature.

2. As Food & Fooder : -

• Cladonia rangiferina (reindeer moss) in tundra region (adapted to low temperature habitat).

• Cetraria icelandica (iceland moss) used in iceland.

• Umbillicaria is used as food in Japan.

• Endocarpon miniatum is used as vegetable in Japan.

• Lecanora esculenta is used as delicious food in Israel

• Evernia used in bakery products by Egypt.

• Species of parmelia are called "rock flower" and used as food in South India.

3. Lichen as a source of dye :

• Litmus (acid-base indicator) is obtained from Rochella montagnei, Lasallia pustulata and

Rochella tinctoria.

• An orchil (blue dye) is obtained from Rochella and Lecanora and Purified form of orchil is

"orcein" and used as biological stain (Histological studies).

4. Lichen as source of medicine :

• "Usnic acid" is important broad specturm antibiotic and it is obtained from Usnea and Cladonia.

• Parmelia saxatilis is used against curing epilepsy.

• Peltigera canina is used aganist hydrophobia.

• Xanthoria parientina is used aganist jaundice.

• Loberia pulmonaria is used against lung infection.

• Cetraria is used as Laxative.

• The "protolichesterinic acid" obtained from some lichen. This acid have anticarcinogenic

properties.

5. Brewing and distillation :

• The lichen contains carbohydrate in the form of "lichenin". So some lichen like Cetraria and

Lecanora are used for alcoholic fermentation.

6. In cosmetics and perfumes :

• Some lichens have aromatic substance like Evernia, Ramalina are used for manufacturing soap.

7. Poisonous lichen :

• Cetraria juniperina and Letharia vulpina (wolf moss) are used as poison.

8. Indicator of air pollution :

• Lichens are very sensitive to SO2 and die at higher level of SO2.

• So lichens are not found in industrial areas where atmosphere is polluted by smoke (specially

SO2), So lichens are biological indicator of air pollution.

9. Forest fire :

• Usnea, popularly known as "old man's beard", is of inflammable nature. They are responsible for

fires in the forests during summer season.

MYCORRHIZA

Mycorrhiza is the symbiotic relationship between roots of higher plants (Seed plant) and fungus.

Mycorrhiza is an example of symbiosis. Fungus obtain food and shelter from root and it helps to root in

absorption of water & minerals.

Mycorrhiza name was given by "Frank" (1885).

Mycorrhiza are of two types

(a) Ectomycorrhiza -

• In this type of mycorrhiza surface of root completely covered by pseudo parenchymatous sheath

formed by fungal hyphae.

• Fungal hyphae enter intercellulary in cortical cell of root.

• Fungal hyphae which arises from pseudo parenchymatous sheath limited up to outer cortical cell

and form a net called "Hartig net".

• Ectomycorrhiza occurs in Pinus, Fagus, Abies, Oak, Eucalyptus etc.

• Fungus mainly members of class basidiomycetes. eg. Clavatia, Amanita, etc.

• Root hair are absent on root.

• Fungus helpful in absorption of water and minerals.

• Due to presence of fungus absorptive surface of root increses. In return fungus gets carbohydrates

from the root.

Note : Amanita is found in Pinus roots where as Russula is found in Fagus roots.

(b) Endomycorrhiza :

• In this type of mycorrhiza fungus does not form pseudo parenchymatous sheath.

• Fungal hyphae enter intracellularly in cortical cell of root.

• Intracellular fungal hyphae form baranched structures in cells of roots called "arbuscule". Due to

same reason endomycorrhiza is called Vesicular arbuscular mycorrhiza (VAM).

• VAM increases fertility of soil.

• VAM is important in phosphate nutrition of plant.

• Endomycorrhiza occurs in orchid.

• Fungus mainly member of class "zygomyctes". e.g., Corticium, Rhizoctonia etc.

Note : - The angiospermic saprophytes in which root system are poorly developed, survive only

because of their mycorrhizal fungi. (Armillaria fungi mainly found in orchid's roots).

Special point :

Ectomycorrhizal genera → Hebeloma, Laccaria, Pisolithus.

Endomycorrhizal genera : Glomus, Gigaspora, Sclerocystis.

Lichen & Mycorrhiza Exercise

Q.1 Lichen show

(1) Parasitic relation of fungi on algae

(2) Mycorrhizal relationship of algae & Fungi

(3) Symbiosis of algae & Fungi

(4) Commensalism

Q.2 Litmus is obtained from lichen

(1) Lecanora esculenta

(2) Rochella tinctoria

(3) Cladonia rangiferina

(4) Cetaria islandica

Q.3 A Semi parasite relationship between the

algal and fungal components of a lichen is

termed as

(1) Helotism (2) Epiphytism

(3) Parasitism (4) Predation

Q.4 In majority of lichens the algal and Fungal

partner belong to

(1) Green algae and ascomycetes

(2) Blue green algae and Basidiomycetes

(3) Green algae and any fungi

(4) Green algae and deuteromycetes

Q.5 Lichen is a pioneer vegetation of

(1) Hydrosere (2) Psammosere

(3) Lithosere (4) Halosere

Q.6 When a group of algal cells are imprisoned

in fungal mycelium & whole of this group

is then used for vegetative multiplication

of a lichen, it is called -

(1) Isidium (2) Soredium

(3) Cephalodium (4) Helotism

Q.7 Most common phycobiont in a lichen is :

(1) Microcystis (2) Trebouxia

(3) Ulothrix (4) Spirogyra

Q.8 Lichen are best indicators of

(1) Air pollution

(2) Water pollution

(3) Soil pollution

(4) All type of pollution

Q.9 Lichen do not like to grow in cities

because of the

(1) Absence of the right type of algae and

fungi

(2) Lack of moisture

(3) SO2 pollution

(4) Absence of natural habitats

Q.10 Mycorrhiza is an association between roots

of higher plant and fungus. It is an example

of

(1) Symbiosis (2) Myremecophilly

(3) Helotism (4) Parasitism

Q.11 "Old man's beard" is the common name of : -

(1) Funaria (2) Cladonia

(3) Usnea (4) Rocella tinctoria

Q.12 Reindeer moss is common name of : -

(1) Usnea comosa

(2) Cladonia rangiferina

(3) Funaria hygrometrica

(4) Sphagnum aceutifolium

Q.13 These exists a close association between the

algae and the fungus within a lichen. The

fungus :]

(1) fixes the atmospheric nitrogen for the

algae

(2) releases oxygen for the algae

(3) provides protection, anchorage and

absorption for the algae

(4) provides food for the algae

Q.14 Lichens are -

(1) Slowest growing plants

(2) Grow faster than their components

(3) Faster growing plants

(4) Grow with normal rate

Q.15 A lichen having much branched system of

cylindrical or ribbon-like branches but a

small thallus is called as

(1) Foliose lichen (2) Fruticose lichen

(3) Crsutos lichen (4) Thallose lichen

Q.16 Lichens are ecologically important because -

(1) They are associated with mycorrhizal

roots

(2) They are association of algae and fungi

(3) They are pioneers (earliest settlers on

barren rocks) and pass xeric conditions

successfully

(4) They can grow in greatly polluted area

Q.17 Mycorrhiza is the -

(1) Symbiotic association between fungus

and the roots of seed plants

(2) Parasitic association between fungus

and the roots of seed plants

(3) Saprophytic association between fungus

and roots of seed plants

(4) All of these

Q.18 Fungus which is found in Pinus root -

(1) Amanita/Boletus (2) Armillaria

(3) Fomes (4) Corticium

LICHEN & MYCORRHIZAQues. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Ans. 3 2 1 1 3 2 2 1 3 1 3 2 3 1 2

Ques. 16 17 18

Ans. 3 1 1

EXERCISE

Answer Key

STATE PMT EXAMS EXERCISE

Q.1 Zygote of Spirogyra produces four haploid

nuclei in which,

[UTTARANCHAL PMT]

(1) One functional

(2) Resolution occur

(3) Magnification occur

(4) Resolving power present

Q.2 Branched conidiophores are present in :

[UTTARANCHAL PMT]

(1) Rhizopus (2) Penicillium

(3) Ustilago (4) Aspegrillus

Q.3 Sexual reproduction in Spirogyra is

morphologically characterised by :

[C.G. PMT]

(1) Oogamy

(2) Anisogamy

(3) Isogamy

(4) Isogamy and oogamy both

Q.4 Zygospores are formed in ?

[C.G. PMT]

(1) Puccinia

(2) Pencillium

(3) Alterneria

(4) Mucor

Q.5 Common bread mould is :

[C.G. PMT]

(1) Yest (2) Mucor

(3) Bacteria (4) Virus

Q.6 Mycorrhiza is a : [C.G. PMT]

(1) Parasitic relation between fungus and

algae

(2) Symbiotic relation between fungus and

algae

(3) Symbiotic relation between fungus and

roots

(4) Parasitic relation between fungus and

roots

Q.7 Earliest settelers on barren land and rocks

are : [C.G. PMT]

(1) Mosses (2) Lichens

(3) Fern (4) None

Q.8 In Ulothrix meiosis occurs in :

[JHARKHAND]

(1) Gamete (2) Zygospore

(3) Zoospore (4) Thallus

Q.9 Lichens are : [JHARKHAND]

(1) Sporophyte (2) Parasite

(3) Symbionts (4) Saprophyte

Q.10 VAM is useful for : [JHARKHAND]

(1) Phosphate nutrition

(2) Breaking of dormancy

(3) Decrease in diseases

(4) Retarding flowering

Q.11 Pigments present in chloroplast of Ulothrix :

[JHARKHAND]

(1) chl-a, chl-b and fucoxanfhin

(2) chl-a, chl-b, chl-c, c-phycocyanin, c-

phycoerythrin

(3) chl-a, chl-b, -carotene, xanthophyll

(4) chal-a, chl-b, r-phycocyanine, r-phycoerythrin

95

Q.12 Which of the following algae shows

physiological anisogamy ?

[JHARKHAND]

(1) Spirogyra (2) Ulothrix

(3) Volvox (4) All of these

Q.13 Yeast is different from penicillium and

Rhizopus in being [JHARKHAND]

(1) Acellular (2) Unicellular

(3) Having unseptate hyphae

(4) multicellualr

Q.14 Which of the following is known as pond

silk ? [BIHAR]

(1) Spirogyra (2) Ulothrix

(3) Nostoc (4) Anabanea

Q.15 Chloroplasts of Spirogrya have :

[BIHAR]

(1) Spiral margin

(2) Smooth or wavy margin

(3) Smooth margin

(4) None of the above

Q.16 The symbiotic association of fungi and

algae is called [UP CPMT]

(1) Lichen (2) Mycorrhiza

(3) Rhizome (4) Endomycorrhiza

Q.17 Zygote of Spirogyra produces four haploid

nuclei in which [UP CPMT]

(1) One is functional

(2) Two are functional

(3) Three are functional

(4) All four are functional

Q.18 A place was rocky and barren but now

there is a green forest, the sequence of

origin is [UP CPMT]

(1) Lichen, moss, herbs, shrubs

(2) Moss, lichen, herbs, shrubs

(3) Lichen, moss shrubs, herbs

(4) Shurbs, herbs, moss, lichen

Q.19 Mycorrhiza helps in [UP CPMT]

(1) Nutrition uptaking

(2) Food manufacturing

(3) Disease resistance

(4) Disease prevention

Q.20 Mycorrhiza promotes plant growth by :

[UP CPMT]

(1) Absorbing inorganic ions from soil

(2) Helping the plant in utilizing

atmospheric nitrogen

(3) Protecting the plant from infection

(4) Serving as plant growth regulator

Q.21 Lichens show [UP CPMT]

(1) Symbiosis (2) Commensalism

(3) Parasitism (4) Cooperation

Q.22 Mycrorrhiza in higher plants helps in

[UP CPMT]

(1) Absorption of phosphates and water

from soil

(2) N2 fixation

(3) Water supply

(4) Resistance against disease

96

Q.23 In which 'torula condition' is found ?

[MP PMT]

(1) Spirogyra (2) Mucor

(3) Riccia (4) Ulothrix

Q.24 The zygospore in spirogyra is

[MP PMT]

(1) One-layered (2) Two-layered

(3) Three-layered (4) Multi-layered

Q.25 Sexual reproduction in spirogyra is :

[MP PMT]

(1) Isogamous

(2) Anisogamous

(3) Physiological anisogamous

(4) Oogamous

Q.26 Cell wall Mucor is made up of :

[MP PMT]

(1) Chitin (2) Cellulose

(3) Pectin (4) Mucilage

Q.27 Which one of the following shows

haplontic life cycle ? [MP PMT]

(1) Ulothrix (2) Funaria

(3) Selaginella (4) Pinus

Q.28 Sporangiospores of Mucor are :

[MP PMT]

(1) Haploid (2) Diploid

(3) Triploid (4) Polyploid

Q.29 In Ulothrix, meiosis takes place during :

[MP PMT]

(1) Zoo spore formation

(2) Gamete formation

(3) Zygote germination

(4) Zoospore germination

Q.30 Mucor shows [MP PMT]

(1) Isogamy

(2) Anisogamy

(3) Oogamy

(4) None of the above

Q.31 The life cycle of Spirogyra is :

[MP PMT]

(1) Haplontic (2) Diplo-haplontic

(3) Haplo-diplontic (4) Diplontic

Ques. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

Ans. 1 2 3 4 2 3 2 2 3 1 3 1 2 1 2 1 1

Ques. 18 19 20 21 22 23 24 25 26 27 28 29 30 31

Ans. 1 1 1 1 1 2 3 3 1 1 1 3 1 1

STATE PMT EXAMS EXERCISE

Answer Key