Introduction, Features, Unique Characters and Life Cycle of Oedogonium. This File Is best For Your Presentation.

1. PHYCOLOGY AND
BRYOLOGY

2. DEPARTMENT OF BOTANY
MUHAMMAD MUBASHIR ALI
BBOF19E001
BS BOTANY 5th (S.S)

3. ASSIGNMENT TOPIC
OEDOGONIUM

4. Habitat
• The Oedogonium (Gr. oedos =
swelling + gonos = reproductive
bodies) is an exclusively fresh-
water alga usually found in
ponds, pools, lakes and rivers.
• They attach to various
substrates such as wood, stone
or growing as an epiphyte on
stems or leaves of aquatic
plants.

5. Plant body
Thallus structure
The thallus is multicellular, green
and filamentous. The filaments are
narrow, unbranched and are formed
of end to end joining of cylindrical
cells of three different kinds.

6. Cylindrical cells
1. The lowermost basal colourless cells which may be simple,
lobed, disc-like or finger shaped and serve as attaching organs or
holdfast.
2. The uppermost or apical cells which may be rounded or in the
form of a fine, hair-like process (Oedogonium ciliata).
3. The intercalary green cells forming the main bulk of the
filament.

8. CAP CELLS
Some cells of the filament
have ring-like structures called
apical caps at their anterior
ends. These cells are known as
cap cells.

9. Cell structure
• The protoplast is surrounded by a three-layered thick and rigid
cell wall. The outer layer is formed of chitin, the middle of
pectose and the inner of cellulose.
• Inner to cell wall plasmalemma is present that encloses the
cytoplasm and the nucleus.
• In mature cells the center of the cell is occupied by a large
central vacuole filled with cell sap.
• A single nucleus is generally located in the center of the cell
embedded in the cytoplasm just within the chloroplasts.

10. • A single large reticulate chloroplast is present in each cell. It is
parietal in position and extends from one end of the cell to the
other. It appears to be made up of hollow cylindrical network
with narrow meshes.
• Many pyrenoids are present in the chloroplast. Mitochondria,
Golgi bodies, endoplasmic reticulum and other cell organelles
are present in each cell.

12. Life cycle-reproduction
Oedogonium reproduces vegetatively, asexually and sexually.
Vegetative Reproduction
Fragmentation
• During which the filaments divide into small parts of
fragments by disintegration of intercalary cells in which the
gametes or zoospores are produced.
• By accidental breakage of the filaments. Each fragment
grows into new filaments by cell division.

14. Akinetes
• The thick-walled, reddish-brown, oval or rounded spores
produced in chains during periods unfavourable for growth.
• The akinete is the long cell between two vegetative cells. It
is filled with spores for long term survival.
• Each germinates into new filament when the conditions
become favourable for growth.

16. Asexual Reproduction
• The asexual reproduction
takes place by zoospores
produced in zoosporangium.
• A cap cell acts as a
zoosporangium. A single
zoospore develops per
zoosporangium.

17. Mechanism of Zoospore Formation
• The nucleus of the zoosporangium moves towards one side and
the entire protoplast contracts into a rounded or oval mass.
• A colourless, beak-like area develops at one side of the mass
just close to the nucleus.
• Around this area blepharoplast granules develop in the form a
circular ring. Each granule give rise to a flagellum which form a
crown around this colourless area.
• The cell wall of the zoosporangium ruptures at the cap region
and the zoospore is released enveloped in a mucilaginous
vesicle.

18. • This vesicle dissolves soon and the zoospore is set free.

19. Structure and germination of zoospore
• Each zoospore is spherical or pear-shaped, uninucleate, deep
green in colour due to presence of chloroplast and have a
crown of flagella at its anterior beak-like end.
• The zoospore after coming in contact with a substratum
attaches itself to it through its anterior end, withdraws its
flagella and elongates.
• The lower part develops into holdfast and the upper part
divides and redivides transversely to produce a new filament.

21. Sexual Reproduction
The sexual reproduction is an advanced type of oogamy. The two
basic factors that promote the sexual reproduction are deficiency
of nitrogen and alkaline pH. The male and female gametes differ
morphologically as well as physiologically and develop in highly
differentiated male and female sex organs, the antheridia and
oogonia. Some species are homothallic or monoecious, while the
others are heterothallic or dioecious.

22. Antheridia
• The antheridia develop in any cap cell of the filament which acts
as antheridial mother-cell.
• It divides by repeated transverse divisions into a row of flat,
compartment-like, uninucleate cells known as antheridia.
• The nucleus of each antheridium divides mitotically into two
daughter nuclei. Each daughter nucleus becomes surrounded by
a mass of cytoplasm and metamorphose into unicellular,
uninucleate, multiflagellate antherozoid or male sperm.
• The sperms liberate by the rupturing cell wall and swim towards
the oogonium to fertilize the egg.

23. • The male sperms can be differentiated from zoospores in having
less amount of chlorophyll, fewer flagella and their smaller size.

24. Oogonium
• The oogonium develops in an actively growing cap cell known
an oogonial mother cell.
• It divides transversely into a basal supporting or suffultory cell
and an upper oogonium proper cell.
• The oogonium proper cell enlarges into a spherical, Ellipsoidal
or oval oogonium.
• The entire protoplast of the oogonium is transformed into a
single non-motile egg which is green in color due to presence of
chlorophyll.

25. • The nucleus migrates towards the periphery in a mature egg.
• At the anterior end of the egg a colourless patch known as
receptive spot develops.
• Just opposite the receptive spot a small pore or transverse slit
develops in the oogonial wall for the entry of male sperms.
• These suffultory cell may or may not divide further. In case of
farther division, it develops a new oogonium.

27. Development of Dwarf Male or Nannandrium
A dwarf male develops from specialized spores, the androspores
produced in androsporangia. The androsporangia may develop
on the same filament in which the oogonium is present
(gynandrospory) or in a special filament in which only the
androspores are formed (idioandrospory).
• The androsporangia are uninucleate, flat, discoid cells that by
repeated transverse divisions in a cap cell.
• The protoplast of the each androsporangium metamorphose
into a single uninucleate, multiflagellate -androspore.
• The androspores are smaller in size than the antherozoids.

28. • The androspores liberate by the formation of a slit in the
wall of androsporangium and are enveloped in a
mucilaginous sheath that dissolves soon and the androspore
starts swimming freely.
• After swimming for some time, it settles either on the
oogonium or its supporting cell and secretes a wall,
elongates and cuts off one or more flat cells which act as
antheridia.
• This short filament with antheridia is the dwarf male or
nannandrium.
• The nucleus of each antheridium divides mitotically into

29. two daughter nuclei and each nucleus is surrounded by cytoplasm
and metamorphose into a uninucleate, multiflagellate antherozoid.
• The antherozoids liberated by a break in the wall of the
antheridium, swim for some time and fertilize the eggs.
• The mature oogonia secretes a substance which attracts the
free swimming antherozoids chemotactically.
• In some species the oogonium secretes a mucilaginous
substance through the pore present in its wall which entangles
the antherozoids in it.
• Only one antherozoids enters the oogonium and penetrates the
egg membrane through the receptive spot to bring about
fertilization that results in formation of zygote.

31. Germination of Oospore
• The zygote secretes a three-layered thick wall around it and often
develops red colour.
• The outermost layer is ornamented and these are important
taxonomically.
• The zygote germinates after a long period of rest when the
conditions become favorable for growth. But in some species, it
germinates immediately.
• The zygote nucleus divides meiotically to produce four haploid
nuclei.

32. • The protoplast also divides into four segments and each segment
develops a crown of flagella to become a meioszoospore (the
zoospore formed as a result of meiosis).
• These zoospores liberate by break in the wall of the oospore
enveloped in a vesicle which dissolves soon.
• The zoospores swim for some time and then settle on some
substratum, withdraw their flagella and germinate into new
filaments.

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