Wednesday 31 July 2019
Tuesday 30 July 2019
Sunday 28 July 2019
Friday 26 July 2019
Ex.No. 1 GENERAL CHARACTERS OF FUNGI
Fungus is a Latin word which means
mushroom. Fungi are achlorophyllous, nucleated, branched, unicellular or
multicellular microorganisms that may reproduce by sexually or asexual and
eukaryotic organisms. Fungus cell wall is made up of chitin and Oomycetes
fungus cell wall is made up of cellulose.
Morphology of fungi
1. Thallus – Vegetative/ somatic body of the fungus.
a. Unicellular - singe celled (E.g.. Yeast)
b. Filamentous– thread form of fungi ( E.g. Eumycota)
c. Holocarpic thallus – Entire thallus is converted into reproductive
structure (Yeast)
d. Eucarpic thallus – The thallus is differentiated into vegetative
part which absorbs nutrients and a reproductive part which forms reproductive
structure. (Pythium)
2. Hyphae – It is a tubular
filament thin tube with the layer of protoplasm and cytoplasm.
3. Mycelium – Mass of hyphae are collectively called as Mycelium.
a. Septate mycelium – Presence of cross walls (Higher fungi)
b. Aseptate mycelium or Coenocytic mycelium – Without cross walls
(Oomycetes, Zygomycetes)
c. Monokaryotic – Contains single nucleus
d. Dikaryotic – Contains pair of nuclei
e. Intercellular mycelium – In between the cells
f.
Intracellular mycelium – Inside
the host
4. Septal pore – Septa have pores that allow cytoplasm, organelles and
some time nuclei pass through the body of the fungus
a. Simple pore septum – A septum having circular pore in the middle.
(Ascomycetes)
b. Dolipore or complex pore septum – A septum having a central pore is
swollen and forming a barrel shaped structure with open ends which is
surrounded by a thin membrane is called parenthesome. (Basidiomycetes)
5. Flagella – The motile cells in the lower fungi responsible for
locomotion.
a. Whiplash type – flagellum with a smooth continuous surface
b. Tinsel type – flagellum with a surface covered hair like structure
Aggregation
and Modification of fungal hyphae
In
most fungi, during certain stages of its life cycle the mycelium become
organised into loosely or compactly woven tissues which are distinguishable
from the normal hyphae composing a thallus.
1. Plectenchyma – It’s a false tissue are formed by aggregation of
hyphae. It is two types.
a. Prosenchyma – Parallel to one another forming a loose tissue (E.g..
Stromata)
b. Pseudoparaenchyma – Hyphal elements are oval or isometric shape and
closely packed. Eg. Pycnidium)
2. Rhizomorph – Root like structure of compact masses. (E.g.. Armillariella mellea, Ganoderma)
3. Sclerotia – It is a compact, hard resting structure made up of
pseudo parenchymal tissues.
|
Disease name
|
Causal organism
|
Sclerotia structure
and colour
|
|
Rice sheath blight
|
Rhizoctonia solani
|
Brown colour and irregular structure
|
|
Pulses root rot
|
Rhizoctonia bataticola
|
Black colour
|
|
Ground nut collar rot
|
Sclerotium rolfsii
|
Brown colour and
mustard shaped
|
|
Ergot or sugary disease
of cumbu
|
Claviceps fusiformis
|
Black colour, the
grains are replaced by sclerotia and look like a grain structure (false
grain).
|
4. Chlamydospore – Fusarium
produces resting structure is known as Chlamydospore. They are produced either
singly or in chains and may be terminal or intercalary in the hyphae.
5. Appressorium – It is a special structure for attachment on host
surface at the tip of germ tube.
6. Haustoria – It is a knob like structure of the hyphae present in the
host cells and absorbs nutrients from the host.
Thursday 25 July 2019
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