General characters of fungi

which includes study materials general characters of fungi a

1. General characters of fungi
The branch of biology that deals with fungi is called‘Mycology’
Fungusis a Latin word which means ‘Mushroom’
Fungi(definition)-Fungi iseukaryotic, achlorophyllsspore bearing organisms that can
reproduce by both sexual and asexualmanner and can obtain nutrients through haustoria
Eg–Yeast, mould, rusts, smuts and mushrooms
Morphological characters of fungi
Thallus–Entire body of fungus is called thallus(mass of hyphae constitute to form
thallus). Vegetative/ somatic thallus gives rise to reproductive structures, from which
spores are produced either sexuall or sexually
Holocarpic–whole thallus is converted into one are more reproductive
structures
Eg–SynchytriumandOlphidium
Eucarpic–only a portion of thallus become reproductive
Eg–Oomycota,AscomycotaandBasidiomycota
Mycelium–filamentous vegetative body of the fungus is called mycelium/ Single
thread of hyphae
(or)
The hyphal mass or network of hyphae constituting the body (thallus) of the fungus is
called as mycelium
Hypha-Individual branch of mycelium which are generally uniform in thickness,
usually about 2-10 μm in diameter. The hyphae may be septate or aseptate
Coenocytic hyphae-The aseptate or non-septate hyphae having the nuclei
scattered in the cytoplasm(obscene of septa/ cross walls).
Septate hyphae-The hyphae have septa having perforations through which
cytoplasmic strands, containing nuclei can migrate from one cell to the
other.(presence of septa)
Doipore septa
It is a complex type septa with barrel shaped central pore and hemi spherical
cap is calledparenthosome/pore cap
Dolipore septum is formed inAgaricomycotinacertain basidiomycetes.
Plasmodium–Naked,motilemultinucleated mass of protoplasm is called plasmodium
Rhizomorphs:Thicker root like aggregates.Also called mycelial cords
Sclerotium:It is a hard and compact vegetative resting structure resistant to
unfavourable conditions. It is mostly made up of pseudoparenchymatous cells
Eg–Sclerotium,Rhizoctonia,Sclerotinia,Claviceps
Septa–The cross walls which divide the hypha into cellsare calledsepta

2. Stroma:some fungi also develop mat like structures which contain the fruiting
bodies.
Fungal cell structure
Fungal cell wall is made up ofChitin + glucan, whereas
Oomycotacell wall is made up ofcellulose
Zycomycota cell wallis made up ofChitosan chitin
Special somatic structures
Appresorium–It is the anchoring organ/ attachment organ of fungi
Haustorium–It is absorbing organ, which absorb nutrients from host.
Rhizoid–short root like filamentous outgrowth devoid of nuclei
Eg-Rhizopus
Hyphal modifications
Mycelium of higher fungi is organised into loosely or compactly woven tissues,
called fungal tissues/ plectenchyma. They are of two types
Prosenchyma–loosely woven fungal tissues in which the individual hypha
lie parallel to one another
Pseudoparenchyma:compactly woven fungal tissue with more or less
isometric resembling parenchyma of higher plants
Stromata–Compact matters like structure made upof parenchyma and
pseudoparenchyma usually form fruiting bodies off fungi of various shapes and
sizes
Eg–Acervuli (Colletotrichum), Sporodochia (Fusarium)
Reproduction in fungi
Spore–minute, simple and basic reproductive unit of fungus, which are
capable of growing into a new thallus. The process of formation of spores
are calledSporogenesis/Sporulation
Sporangia–It is a sac like structure in which spores are formed
Sporangiphore–sporangia are produced at the end of the of the
undifferentiated or on specialized spore bearing structure are called
Sporangiphone
1.Asexual reproduction–It does not involve the union of nuclei or gametes
and hence called assomaticorvegetative reproduction
Spores are produced by asexual are production are celled
mitospores/asexualspores
A.Fission–parent cell divides into two daughter cells by constriction. The
nucleus is divided into two halves b formation of transverse septum
Eg–Yeast
B.Budding–Small outgrowth or bud produced from the parent cell
enlarges graduallyand nuclei migrates into the growing bud an then bud
eventually breaks off to form the new thallus

3. C.Fragmentation–Small fragment of hyphae detached from the parent
mycelium to grow into new thallus. These small fragments/spores are
calledarthrospores/Oidia
Eg–Powdery mildew
Flagellum–Hair like structure that serves a motile cell (locomotoryorgan)
Anterior(episthocont)–
Posterior(opisthocont)-
Axoneme–feather like a central rachis, the hair of flagella is calledflimmers
hairs/mastogoneme
Conidia-a spore produced asexually by various fungi at the tip of a specialized
hypha.
Conidiophore–The conidiophore may befree or aggregation of aggregated to
form compound conidiophore/ fruiting bodies on which conidia
are produced
Zoospores–Motile asexual spores ofOomycotaproduced with in zoosporngium.
They arealways naked (without cell wall)
Planospores= motilespores = Swarm spores
Aplanospores= non motile spores
Chlamydopsores-Thickwalled resting spore formed either single or in chains from
terminal or intercalary cells o the hyphaeeg–Fusarium,Saprolegnia
It is thick walled and contains reserve food materials to withstand
unfoavorble conditions
Gemmae–Chlamydospores dispersed inn water currents is called gemmae

4. 2.Sexual reproduction–
Three typical phases occurs in sequence during sexual reproduction
A.Plasmogamy-Union of protoplasts bringing their nuclei togeather
within the same cell
B.Karyogamy–Fusion oftwo nuclei result in the formation of zygote/
diploid nuclei. The organ in which karyogamy takes place is celled
Zeugites
C.Meiosis–Fused diploid nucleus undergoes meiosis, which reduced
the number of chromosomesto haploid.The organ in which meiosis
takes place is celledGonotoconts
Types of plasmogamy
i.Planogametic copulation/ Gametogamy
a)Isogamy/ isogamous fertilization–fusion of isogametes of
same size and shape
Eg–OlphidiumandSynchytrium
b)Anisogamy/anisogamous fertilization-fusion of
anisogametes in which gametes are morphologically similar
but differ in size
Eg–Allomyces
c)Heterogamy/ ooplanogametic copultion–fusion ofmotile
male gametes withnon-motilefemalegametes
Asexual fruiting bodies–
A.Pycnidium–It is a hallow , flask shaped or globose fruiting bodies with
narrow circular mouth calledostiole.It has a wall made up of multilayer
pseudoparenchymatous sterile tissue, calledperidium. The inner wall of
the fruiting body is lined with numerous short conidia called
pycnidiospores
Eg–Macrophominaphaseolina,Diplodianatalensis,Botrydiplodia
theobromae
B.Spordachium–It is a hemispherical, barrel shaped compound conidiophore
produced byFusarium,TuberculariaandEpicoccum.Itconsistsof cushion
shapedaggregation ofhyphae in the lower part and expresses the conidia
on the upper part.
C.Acervuli–It is asaucer shaped depressed pseudoparenchymatous
aggregation of hyphae which develops beneath thesurface of the host with
a bed of closely packed parallel simple conidiophores
Eg–Colletotrichum,Pestalotia
D.Synemma–loose aggregation of branched or unbranched erect
conidiophore to form dene fascicle, similar to mycelial strands
Eg–Ceratocystis,Graphium
E.Sori–Spore bearing hyphaeeg–Smut sori, Rust sori

5. Eg-Monoblephariales
ii.Gametangialcontact/ Gametangiogamy–
Fusion of two morphologically distinguishable gametangia with
undifferentiated protoplasm and nuclei. The gametes pass either
through pore dissolved at the point of contact calledFertilization
tube/ trichogyne
iii.Gametangial copulation/ Aplanogametic copulation/ Gametangy
a)Hologamy–entire content of one gametangium passes into
another through pore developed in the gametangial wall at
the point of contact
Eg–Yeast
b)Direct fusion/ isogamous copulation–two morphologically
similar gametangia fuse and to become a single cell
Eg-MucorandRhizopus
c)Anisogametangial copulation-fusion between unequal
gametangia
Eg-Zygorhyncus
iv.Spermatization–some fungi produce numerous, non-motile minute,
sphericaluninucleate spores are calledspermatia,whichare
produced from the flask like sexual apparatus calledspermagonium
v.Somatogamy–no sex organs are produced,but theundifferentiated
somatic cells functions as gamtes
Homothallic-Fungi in which every thallus is sexually self-fertile.
The male gametes fertilize the female gametes of the same
mycelium
Eg-common inAscomycotaand rare inBasidiomycota
Heterothallic–The fungal thallusis sexually self-sterile and
requires another compatible thallus of different mating types for
sexual reproduction. The male gametes fertilize the female
gametes of another sexually compatible mycelium.
The phenomenon of heterothallism was reported by
A. F. Blakeslee(1904) inMucor
Eg–Oomycota,ZygomycotaandBasidiomycota
Typesofsexual spores–
Oospore–globose, yellow to dark brown with two layer wall and a
central oil globule in the form of lipids as food material
Zygospore-thick walled resting diploid sexual spore
Ascospore-haploid sexual resting spore
Basidiospore-exogenous sexual spore

6. Parasexual reproduction–Plasmogamy, karyogmy and meiosis takes place in
sequence but not at specified points in life cycle. The phenomenon of parasexuality
was first discovered byPontecarvo and Roperin 1952 inAspergillusnidulans