Spirogyra

Here i made a detailed ppt on Spirogyra

3. Spirogyra

4. Occurrence:
•Spirogyra is a large genus. It is widely distributed and found throughout
the world. It has of about 300 species. It is found in fresh water. It
grows as free floating mass. Therefore, it is commonly calledpond
scum.
•It commonly grows in fresh water stagnant reservoirs. It also grows in
slow running streams and rivers. It looks like a mass of long shining
silky filaments in running water. That is why it is also calledpond silk.
•Suitable season for its growth is winter. But it grows well throughout
the year. It develops reproductive stage if temperature rises. It
develops vegetative stage if temperature lowers.

5. Common species
•S. crassata, S. elongata, S. microspora, S
indicaand S. cqmmunis.Vegetative structure
Plant Body
•The plant body consists of filaments. These filaments
are cylindrical and unbranched. The young filaments
have modified basal cells
calledhapteronorholdfast.
•Hapteronis used for attachment to some object at
the bottom. Rhizoids also grow on hapteronin S.
rhizoidesand S. dubia. But rhizoids are absent in
other plants. The adult plants are always free floating.

6. Cell Structure
Each filament consists of a single row of cylindrical cells. These cells have
following structures:
I.Cell wall: Each cell is enclosed by a firm cell wall. Cell wall is composed of two
layered. The inner layer is composed of cellulose. The outer layer is composed of
pecticsubstances. Water makes the pecticsubstance gelatinous. It gives the
plant a slimy touch.
II.Protoplast: Their protoplast consists of a single nucleus, a mass of cytoplasm,
chloroplast and a large central vacuole.
•a)Nucleus:The nucleus is present in the center. It is suspended by strands of
cytoplasm. In some cases, it may parietal in position. it has a complex nucleolus.
•b)Cytoplasm:A large central vacuole is present. Therefore, its cytoplasm is
peripheral in position. Cytoplasm is traversed by severalcytoplasmic strands.

7. •Chloroplasts:Chloroplasts are present in cytoplasm. Their number is
variable.Thenumber of the chloroplast is the characteristic feature of this
alga. Their number may be 1 to 12 30111e times 24.
•d)Cytoplasmic organelles:Golgi bodieg, mitochondria and
endoplasmic reticulum are present in the cytoplasm.
REPRODUCTION
•Spirogyra reproduces by vegetative and sexual methods. However, some
workers have also reported asexual reproduction in Spirogyra. Asexual
reproduction occurs through akinetesand aplanosporeformation.

8. Vegetative Reproduction
•Fragmentation is the common method of vegetative
reproduction in Spirogyra. Accidental breaking or injury
may occur. It breaks the filament into 2-3 cell portions.
Each portion germinates to produce a new plant. In
some cases, cross walls are produced by invagination.
This cross wall separates two cells apart and two
fragments are formed.
Sexual Reproduction
•Sexual reproduction is isogamous. It takes place by conjugation of non-flagellated
gametes. Conjugations may be of two types: the scalariformconjugation and the
lateral conjugation. Simultaneous scalarifortnand lateral conjugation may occur in
S. gratiana. But it occurs rarely.

9. (A) Scalariformconjugation
•It is of most common type of conjugation. In this case, two
parallel lying filaments take part. Most of the cells of the
filaments participate in conjugation at the same time.
Therefore, both the filaments appear as adder-like. Hence
it is called scalarifonnor ladder-like conjugation.
a)Gamete formation:All cells of a filament can
producegametangia.A single gamete is formed from
eachgametangium.Acontinuousconjugation tubeis formed
between ale two cells of different filaments. The protoplasmic
contents of the cells change into a single elliptical gamete.

10. b)Fertilization:There are two methods of fertilization.
•Dioecious filaments:In this case, during fusion, one gamete passes
through the conjugation tube. It reaches the apposite cell. It fuses with the
gametes of the other filament. As a result,zygosporeis formed in one cell.
The other stands remain empty. The motile cell is called male gamete and
other is female gamete. Zygosporeis formed in a cell of the filament.
Therefore, the two filaments are dioecious.
•Monoecious filaments:In this case, gametes of both the
•filaments move. The zygosporeis formed in the conjugation tube.
Therefore, sex distinction is not possible. Therefore, neither one can be
called male or female. Such filaments are Mr oecious

11. (B) Lateral conjugation
Lateral conjugation occurs between the two adjacent cells of the same filament. Therefore, such
plants are bisexual and monoecious. There are two types of lateral conjugations: direct late
,
II
conjugation indirect lateral conjugation.
a. Direct lateral conjugation
•It reursbetween the two adjacent cells. In this case, pppercell functions asmale
gametangium.The lower cell acts asfemale gametangium.The lower cell increases in size.
The upper cell remains smaller. The protoplast of male cell forms an outgrowth. This
outgrowth elongates. This outgrowth comes in contact with transverse wall in between male
and female cells. Later, it passes through it by forming an opening in it. Thus conjugation tube
is not formed and the contents of male cell pass into the female cell. As a result,zygosporeis
formed.

12. b. Indirect lateral conjugation
•It occurs rarely. It is reported inS. affinis.In this case, a
papilla like outgrowth is formed in the transverse
septum. This outgrowth grows and breaks the septum.
Thus a side passage is formed between the two cells.
The upper cell behaves asmale gametangium.The
lower cell acts asfemale gametangium.The male
gamete passes through this side passage. It fuses with
female gamete and zygosporeis formed. This type of
lateral conjugation is also calledchainconjugation.
Gametes
Fig: Germination
of Zygospore

13. Formation and germination of zygospore
•Zygote is formed by the fusion of male and female
gametes. It soon develops a thick wall and becomes
zygospore. Zygosporeis composed of three layered
wall. The gametangialwall decay and the zygospore
come out. It settles down to the bottom of water
body. It undergoes a resting period. Before
germination the zygosporenucleus divides
meiotically. It produces four nuclei. Three nuclei
degenerate. Only one nucleus germinates to develop
a new haploid plant. Fig:
Germination
of Zygospore

14. Parthenogenesis
•In some rare cases, the gametes fail to fuse. These gametes become
rounded and secrete a cell wall around them. Now they behave as spores.
Such spores are calledparthenospores.These spores germinate directly
into new haploid plants.
Fig:
Germination
of Zygospore

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